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Question 1
Correct
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Antidiuretic hormone (ADH) levels are found to be increased in a young lady with unexplained hyponatraemia.
In a healthy patient under normal circumstances, in which of the following conditions would ADH not be released?Your Answer: Increased alcohol intake
Explanation:Antidiuretic hormone (ADH) is produced in the hypothalamus’s supraoptic nucleus and then released into the blood via axonal projections from the hypothalamus to the posterior pituitary.
It is carried down axonal extensions from the hypothalamus (the neurohypophysial capillaries) to the posterior pituitary, where it is kept until it is released, after being synthesized in the hypothalamus.
The secretion of ADH from the posterior pituitary is regulated by numerous mechanisms:
Increased plasma osmolality: Osmoreceptors in the hypothalamus detect an increase in osmolality and trigger ADH release.Hypovolaemia causes a drop in atrial pressure, which stretch receptors in the atrial walls and big veins detect (cardiopulmonary baroreceptors). ADH release is generally inhibited by atrial receptor firing, but when the atrial receptors are stretched, the firing reduces and ADH release is promoted.
Hypotension causes baroreceptor firing to diminish, resulting in increased sympathetic activity and ADH release.
An increase in angiotensin II stimulates angiotensin II receptors in the hypothalamus, causing ADH production to increase.Nicotine, Sleep, Fright, and Exercise are some of the other elements that might cause ADH to be released.
Alcohol (which partly explains the diuretic impact of alcohol) and elevated levels of ANP/BNP limit ADH release. -
This question is part of the following fields:
- Physiology
- Renal Physiology
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Question 2
Incorrect
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A patient with a high potassium level is at risk of going into cardiac arrest. What changes in the ECG may indicate the incident of cardiac arrest in this patient?
Your Answer:
Correct Answer: Peaked T waves and broad QRS complex
Explanation:Severe hyperkalaemia can result in a heart attack or a life-threatening arrhythmia.
T waves become narrow-based, pointed, and tall if hyperkalaemia is not treated.
The QRS complex widens and eventually merges with the T wave, resulting in a classic sine-wave electrocardiogram. Ventricular fibrillation and asystole are likely to follow.
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This question is part of the following fields:
- Physiology
- Renal
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Question 3
Incorrect
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Angiotensin II is part of the RAAS system. One of its effects is the constriction of efferent arterioles. Which of the following best describes the effect of angiotensin II- mediated constriction of efferent arterioles?
Your Answer:
Correct Answer: Decreased renal plasma flow, increased filtration fraction, increased GFR
Explanation:The Renin-Angiotensin-Aldosterone System (RAAS) is a hormone system composed of renin, angiotensin, and aldosterone. Those hormones are essential for the regulation of blood pressure and fluid balance.
Cases of hypotension, sympathetic stimulation, or hyponatremia can activate the Renin-angiotensin-aldosterone system (RAAS). The following process will then increase the blood volume and blood pressure as a response.
When renin is released it will convert the circulating angiotensinogen to angiotensin I. The ACE or angiotensin-converting enzyme will then catalyst its conversion to angiotensin II, which is a potent vasoconstrictor. Angiotensin II can constrict the vascular smooth muscles and the efferent arteriole of the glomerulus.
The efferent arteriole is a blood vessel that delivers blood away from the capillaries of the kidney. The angiotensin II-mediated constriction of efferent arterioles increases GFR, reduces renal blood flow and peritubular capillary hydrostatic pressure, and increases peritubular colloid osmotic pressure, as a response to its action of increasing the filtration fraction.
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This question is part of the following fields:
- Physiology
- Renal Physiology
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Question 4
Incorrect
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Fenestrated capillaries are typically found where in the body:
Your Answer:
Correct Answer: Renal glomeruli
Explanation:Fenestrated capillaries, found in renal glomeruli, endocrine glands and intestinal villi, are more permeable than continuous capillaries with less tight junctions, and the endothelial cells are also punctured by pores which allow large amounts of fluids or metabolites to pass.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 5
Incorrect
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Arterial baroreceptors are located primarily in which of the following:
Your Answer:
Correct Answer: Carotid sinus and aortic arch
Explanation:Arterial baroreceptors are located in the carotid sinus and aortic arch, and detect the mean arterial pressure (MAP). A decrease in MAP (such as in postural hypotension, or haemorrhage) reduces arterial stretch and decreases baroreceptor activity, resulting in decreased firing in afferent nerves travelling via the glossopharyngeal nerve (carotid sinus) and vagus nerve (aortic arch) to the medulla where the activity of the autonomic nervous system is coordinated. Sympathetic nerve activity consequently increases, causing an increase in heart rate and cardiac contractility, peripheral vasoconstriction with an increase in TPR, and venoconstriction with an increase in CVP and thus an increase in cardiac output and blood pressure. Parasympathetic activity (vagal tone) decreases, contributing to the rise in heart rate.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 6
Incorrect
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Regarding dynamic compression of the airways, which of the following statements is CORRECT:
Your Answer:
Correct Answer: It occurs during forced expiration.
Explanation:Dynamic compression occurs because as the expiratory muscles contract during forced expiration, all the structures within the lungs, including the airways, are compressed by the positive intrapleural pressure. Consequently the smaller airways collapse before the alveoli empty completely and some air remains within the lungs (the residual volume). Physiologically this is important as a completely deflated lung with collapsed alveoli requires significantly more energy to inflate. Dynamic compression does not occur in normal expiration because the intrapleural pressure is negative throughout the whole cycle.
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 7
Incorrect
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Which of these is NOT a naturally occurring anticoagulant:
Your Answer:
Correct Answer: Factor V Leiden
Explanation:It’s crucial that thrombin’s impact is restricted to the injured site. Tissue factor pathway inhibitor (TFPI), which is produced by endothelial cells and found in plasma and platelets, is the first inhibitor to function. It accumulates near the site of harm induced by local platelet activation. Xa and VIIa, as well as tissue factor, are inhibited by TFPI. Other circulating inhibitors, the most potent of which is antithrombin, can also inactivate thrombin and other protease factors directly. Coagulation cofactors V and VIII are inhibited by protein C and protein S. Tissue plasminogen activator (TPA) from endothelial cells facilitates fibrinolysis by promoting the conversion of plasminogen to plasmin.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 8
Incorrect
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Regarding bile acids, which of the following statements is INCORRECT:
Your Answer:
Correct Answer: The main primary bile acids are deoxycholic acid and lithocholic acid.
Explanation:Bile acids have a hydrophobic and a hydrophilic end and in aqueous solution, bile salts orient themselves around droplets of lipid forming micelles to keep the lipid droplets dispersed. The principal primary bile acids are cholic acid and chenodeoxycholic acid. They are made more soluble by conjugation with taurine or glycine in the liver. Of the bile acids excreted into the intestine, about 95% are reabsorbed into the portal circulation by active transport mechanisms in the distal ileum and recycled by the liver.
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 9
Incorrect
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A 32-year-old woman diagnosed with hyperthyroidism has her T 4 levels grossly elevated and she is started on carbimazole.
A release of which of the following from the hypothalamus is inhibited by increase in T4 levels?Your Answer:
Correct Answer: Thyrotropin-releasing hormone
Explanation:A negative feedback mechanism involving the hypothalamic-pituitary-thyroid axis controls the release of T3 and T4 into the bloodstream.
When metabolic rate is low or serum T3 and/or T4 levels are decrease, this triggers the secretion of thyrotropin-releasing hormone (TRH) from the hypothalamus.
TRH goes to the anterior pituitary gland and stimulates secretion of thyroid-stimulating hormone (TSH).
An increased serum level of T3 and T4 inhibits the release of TRH.
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This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 10
Incorrect
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Which of the following statements is correct regarding flow through the cardiovascular system?
Your Answer:
Correct Answer: Turbulent blood flow may be caused by increased cardiac output.
Explanation:Frictional forces at the sides of a vessel cause a drag force on the fluid touching them in laminar blood flow, which creates a velocity gradient where the flow is greatest at the centre. Laminar blood flow may become disrupted and flow may become turbulent at high velocities, especially in large arteries or where the velocity increases sharply at points of sudden narrowing in the vessels, or across valves. There is increased tendency for thrombi formation when there is turbulent blood flow. Clinically, turbulence may be heard as a murmur or a bruit. As a result of elevated cardiac output, there may be turbulent blood flow, even when the cardiac valves are anatomically normal, and as a result, a physiological murmur can be heard. One such example is pregnancy.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 11
Incorrect
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From which of the following cell types are platelets derived?
Your Answer:
Correct Answer: Megakaryocytes
Explanation:Synthesis of platelets occurs in the bone marrow by fragmentation of megakaryocytes cytoplasm, derived from the common myeloid progenitor cell. The average time for differentiation of the human stem cell to the production of platelets is about 10 days. The major regulator of platelet formation is thrombopoietin and 95% of this is produced by the liver. Normal platelet count is 150 – 450 x 109/L and the normal lifespan of a platelet is about 10 days. Usually about one-third of the marrow output of platelets may be trapped at any one time in the normal spleen.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 12
Incorrect
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Regarding cardiac excitation-contraction coupling, which of the following statements is CORRECT:
Your Answer:
Correct Answer: In relaxation, Ca 2+ is transported out of the cell using energy from a Na + gradient.
Explanation:During the AP plateau, Ca2+enters the cell and activates Ca2+sensitive Ca2+release channels in the sarcoplasmic reticulum allowing stored Ca2+to flood into the cytosol; this is called Ca2+-induced Ca2+release. In relaxation, about 80% of Ca2+is rapidly pumped back into the SR (sequestered) by Ca2+ATPase pumps. The Ca2+that entered the cell during the AP is transported out of the cell primarily by the Na+/Ca2+exchanger in the membrane which pumps one Ca2+ion out in exchange for three Na+ions in, using the Na+electrochemical gradient as an energy source. Increased heart rate increases the force of contraction in a stepwise fashion as intracellular [Ca2+] increases cumulatively over several beats; this is the Treppe effect. Factors that affect intracellular [Ca2+] and hence cardiac contractility are called inotropes.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 13
Incorrect
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Which of the following is required for vitamin B12 absorption:
Your Answer:
Correct Answer: Intrinsic factor
Explanation:Intrinsic factor is essential for the absorption of the small amounts of vitamin B12 normally present in the diet from the terminal ileum. The parietal cells of the stomach produce intrinsic factor, and following a gastrectomy, the absorption of vitamin B12 will be markedly reduced, and a deficiency state will exist.
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 14
Incorrect
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Which of the following represents ventricular repolarisation on the ECG:
Your Answer:
Correct Answer: T wave
Explanation:P wave = Atrial depolarisation
QRS complex = Ventricular depolarisation
T wave = Ventricular repolarisation -
This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 15
Incorrect
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On which of the following is preload primarily dependent?
Your Answer:
Correct Answer: End-diastolic volume
Explanation:Preload refers to the initial stretching of the cardiac myocytes before contraction. It is therefore related to muscle sarcomere length. The sarcomere length cannot be determined in the intact heart, and so, other indices of preload are used, like ventricular end-diastolic volume or pressure. The end-diastolic pressure and volume of the ventricles increase when venous return to the heart is increased, and this stretches the sarcomeres, which increase their preload.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 16
Incorrect
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Continuous capillaries are typically found where in the body:
Your Answer:
Correct Answer: Blood-brain barrier
Explanation:Continuous capillaries, found in the skin, lungs, muscles and CNS, are the most selective with low permeability, as junctions between the endothelial cells are very tight, restricting the flow of molecules with MW > 10,000.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 17
Incorrect
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Regarding fat digestion, which of the following statements is CORRECT:
Your Answer:
Correct Answer: Chylomicrons consist of a cholesterol and triglyceride core with a phospholipid coat studded with apolipoproteins.
Explanation:Dietary fat is chiefly composed of triglycerides. In the duodenum fat is emulsified by bile acids, a process where larger lipid droplets are broken down into much smaller droplets providing a greater surface area for enzymatic digestion. Once inside the epithelial cell, lipid is taken into the smooth endoplasmic reticulum where much of it is re esterified. Dietary and synthesised lipids are then incorporated into chylomicrons in the Golgi body, which are exocytosed from the basolateral membrane to enter lacteals. Chylomicrons consist mainly of triglyceride with small amounts of cholesterol and cholesteryl esters in the centre with a phospholipid coat studded with apolipoproteins. Fat-soluble are absorbed into enterocytes from micelles by simple diffusion together with the products of fat digestion.
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 18
Incorrect
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A 19-year-old with a longstanding history of asthma presents to the ED with worsening symptoms of cough and wheeze and a peak expiratory flow rate (PEFR) measurement is taken.
Which statement concerning PEFR is true?Your Answer:
Correct Answer: PEFR is dependent upon the patient's height
Explanation:The maximum flow rate generated during a forceful exhalation, after maximal inspiration is the peak expiratory flow rate (PEFR).
PEFR is dependent upon initial lung volume. It is, therefore, dependant on patient’s age, sex and height.
PEFR is dependent on voluntary effort and muscular strength of the patient.
PEFR is decreased with increasing airway resistance, e.g. in asthma, and it correlates well with the forced expiratory volume in one second (FEV1) value measured in spirometry. This correlation decreases in patients with asthma as airflow decreases.
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This question is part of the following fields:
- Physiology
- Respiratory Physiology
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Question 19
Incorrect
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A possible diagnosis of Cushing's illness is being investigated in an overweight patient with resistant hypertension. A CRH (corticotropin-releasing hormone) test is scheduled.
Which of the following statements about corticotropin-releasing hormone is correct?Your Answer:
Correct Answer: It is produced by cells within the paraventricular nucleus of the hypothalamus
Explanation:Corticotropin-releasing hormone (CRH) is a neurotransmitter and peptide hormone. It is generated by cells in the hypothalamic paraventricular nucleus (PVN) and released into the hypothalamo-hypophyseal portal system at the median eminence through neurosecretory terminals of these neurons. Stress causes the release of CRH.
The CRH is carried to the anterior pituitary through the hypothalamo-hypophyseal portal system, where it activates corticotrophs to release adrenocorticotropic hormone (ACTH). Cortisol, glucocorticoids, mineralocorticoids, and DHEA are all produced in response to ACTH.
Excessive CRH production causes the size and quantity of corticotrophs in the anterior pituitary to expand, which can lead to the creation of a corticotrope tumour that generates too much ACTH.
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This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 20
Incorrect
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A 59-year-old woman presents with a history of tiredness and weight gain and a diagnosis of hypothyroidism is suspected.
Which of these changes is likely to appear first in primary hypothyroidism?Your Answer:
Correct Answer: Increased thyroid-stimulating hormone (TSH)
Explanation:The earliest biochemical change seen in hypothyroidism is an increase in thyroid-stimulating hormone (TSH) levels.
Triiodothyronine (T3) and thyroxine (T4) levels are normal in the early stages.
TBG levels are generally unchanged in primary hypothyroidism.
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This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 21
Incorrect
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Which of the following does NOT predispose to digoxin toxicity in a patient taking digoxin:
Your Answer:
Correct Answer: Hyponatraemia
Explanation:Hypoxia, hypercalcaemia, hypokalaemia and hypomagnesaemia predispose to digoxin toxicity. Care should also be taken in the elderly who are particularly susceptible to digoxin toxicity. Hypokalaemia may be precipitated by use of diuretics. Although hyponatremia can result in the development of other pathological disturbances, it does not potentiate digoxin toxicity.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 22
Incorrect
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Which statement accurately describes the osmolality in the various parts of the Henle Loop?
Your Answer:
Correct Answer: The osmolality of fluid in the descending loop equals that of the peritubular fluid
Explanation:The Loop of Henle connects the proximal tubule to the distal convoluted tubule and lies parallel to the collecting ducts. It consists of three major segments, including the descending thin limb, the ascending thin limb, and the ascending thick limb. These segments are differentiated based on structure, anatomic location, and function.
The main function of the loop of Henle is to recover water and sodium chloride from urine. When fluid enters the loop of Henle, it has an osmolality of approximately 300 mOsm, and the main solute is sodium.
The thin descending limb has a high water permeability but a low ion permeability. Because it lacks solute transporters, it cannot reabsorb sodium. Aquaporin 1 (AQP1) channels are used to passively absorb water in this area. The peritubular fluid becomes increasingly concentrated as the loop descends into the medulla, causing water to osmose out of the tubule. The tubular fluid in this area now equalizes to the osmolality of the peritubular fluid, to a maximum of approximately 1200 mOsm in a long medullary loop of Henle and 600 mOsm in a short cortical loop of Henle.
The thin ascending limb is highly permeable to ions and impermeable to water. It allows the passive movement of sodium, chloride, and urea down their concentration gradients, so urea enters the tubule and sodium and chloride leave. Reabsorption occurs paracellularly due to the difference in osmolarity between the tubule and the interstitium.
The thick ascending limb is also impermeable to water but actively transports sodium, potassium, and chloride out of the tubular fluid. The osmolality of the tubular fluid is lower compared to the surrounding peritubular fluid. This area is water impermeable. This results in tubular fluid leaving the loop of Henle with an osmolality of approximately 100 mOsm, which is lower than the osmolality of the fluid entering the loop, and urea being the solute.
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This question is part of the following fields:
- Physiology
- Renal Physiology
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Question 23
Incorrect
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Which statement regarding skeletal muscle is true?
Your Answer:
Correct Answer: Myosin is the major constituent of the thick filament
Explanation:Myosin is the major constituent of the thick filament.
Actin is the major constituent of the THIN filament.
Thin filaments consist of actin, tropomyosin and troponin in the ratio 7:1:1.
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This question is part of the following fields:
- Basic Cellular Physiology
- Physiology
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Question 24
Incorrect
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Regarding bile, which of the following statements is CORRECT:
Your Answer:
Correct Answer: Bile passes into the duodenum through the ampulla of Vater.
Explanation:Bile is synthesised in the liver. Bile functions to eliminate endogenous and exogenous substances from the liver, to neutralise gastric acid in the small intestine, and to emulsify fats in the small intestine and facilitate their digestion and absorption. Bile is stored and concentrated in the gallbladder. Bile passes out of the gallbladder via the cystic duct. Bile passes into the duodenum through the ampulla of Vater regulated by the sphincter of Oddi.
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 25
Incorrect
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Which of the following is NOT a typical side effect of digoxin:
Your Answer:
Correct Answer: Hypokalaemia
Explanation:Digoxin does not cause hypokalaemia, but hypokalaemia does potentiate digoxin toxicity. The adverse effects of digoxin are frequently due to its narrow therapeutic window and include:
Cardiac adverse effects – Sinoatrial and atrioventricular block, Premature ventricular contractions, PR prolongation and ST-segment depression
Nausea, vomiting and diarrhoea
Blurred or yellow vision
CNS effects – weakness, dizziness, confusion, apathy, malaise, headache, depression, psychosis
Thrombocytopenia and agranulocytosis (rare)
Gynaecomastia in men in prolonged administration -
This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 26
Incorrect
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You are reviewing a patient with hypocalcaemia secondary to hypoparathyroidism. Parathyroid hormone (PTH) acts to increased calcium reabsorption at which of the following sites in the nephron:
Your Answer:
Correct Answer: Distal convoluted tubule
Explanation:Parathyroid hormone (PTH) is a peptide hormone synthesised by the chief cells of the parathyroid glands, located immediately behind the thyroid gland. PTH is primarily released in response to decreasing plasma [Ca2+] concentration. PTH acts to increase plasma calcium levels and decrease plasma phosphate levels.
Parathyroid hormone (PTH) acts to increase calcium reabsorption in the distal tubule of the nephron (by activating Ca2+entry channels in the apical membrane and the Ca2+ATPase pump in the basolateral membrane) and increase phosphate excretion by inhibiting reabsorption in the proximal tubule of the nephron. -
This question is part of the following fields:
- Endocrine
- Physiology
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Question 27
Incorrect
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Many of the chemical digestion and absorption takes place in the small intestine. Most digestive enzymes in the small intestine are secreted by the pancreas and enter the small intestine through the pancreatic duct.
Which of these digestive enzymes is responsible for breaking down lipids into fatty acid and glycerol?Your Answer:
Correct Answer: Pancreatic lipase
Explanation:The principal enzyme involved in lipid digestion is pancreatic lipase. It breaks down triglycerides into free fatty acids and monoglycerides. Pancreatic lipase works with the help of emulsifying agents secreted by the liver and the gallbladder. The main emulsifying agents are the bile acids, cholic acid and chenodeoxycholic acid. These are conjugated with the amino acids glycine and taurine to form bile salts. Bile salts are more soluble than bile acids and act as detergents to emulsify lipids. The free fatty acids and monoglycerides form tiny particles with these bile salts called micelles. The outer region of the micelle is water-attracting (hydrophilic), whereas the inner core is water-repelling (hydrophobic). This arrangement allows the micelles to enter the aqueous layers surrounding the microvilli and free fatty acids and monoglycerides to diffuse passively into the small intestinal cells.
Pancreatic amylase breaks down some carbohydrates (notably starch) into oligosaccharides.
Chymotrypsin is a proteolytic enzyme that aids in digestion of protein
Carboxypeptidase hydrolyses the first peptide or amide bond at the carboxyl or C-terminal end of proteins and peptides
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This question is part of the following fields:
- Gastrointestinal Physiology
- Physiology
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Question 28
Incorrect
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Regarding chemical control of respiration, which of the following statements is INCORRECT:
Your Answer:
Correct Answer: The blood-brain barrier is freely permeable to HCO3 - ions.
Explanation:CSF is separated from the blood by the blood-brain barrier. This barrier is impermeable to polar molecules such as H+and HCO3-but CO2can diffuse across it easily. The pH of CSF is therefore determined by the arterial PCO2and the CSF HCO3-and is not affected by blood pH.
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 29
Incorrect
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Na+ is reabsorbed via the Na+/K+/2Cl-symporter in which part of the loop of Henle?
Your Answer:
Correct Answer: Thick ascending limb
Explanation:In the thick ascending limb is the part of the loop of Henle in which there is active reabsorption of Na+and Cl- ions from the tubular fluid. This occurs via the Na+/K+/2Cl-symporter on the apical membrane.
This mechanism is by:
1. Na+ions are transported across the basolateral membrane by Na+pumps and the Cl-ions by diffusion.
2. K+leaks back into the tubular fluid via apical ROMK K+channels which creates a positive charge.
3. This positive charge drives the reabsorption of cations (Na+, K+, Ca2+, Mg2+) through paracellular pathways.
4. Due to the thick ascending limb being impermeable to water, the tubular fluid osmolality is reduced by ion reabsorption, the interstitial fluid osmolality is increased, and an osmotic difference is created. -
This question is part of the following fields:
- Physiology
- Renal
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Question 30
Incorrect
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A lung function test is being performed on a male patient. For this patient, which of the following volumes for functional residual capacity is considered a normal result?
Your Answer:
Correct Answer: 2.0 L
Explanation:The volume of air that remains in the lungs after a single breath is known as functional residual capacity (FRC). It is calculated by combining the expiratory reserve volume and residual volume. In a 70 kg, average-sized male, a normal functional residual capacity is approximately 2100 mL.
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This question is part of the following fields:
- Physiology
- Respiratory Physiology
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Question 31
Incorrect
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As a response to low blood pressure, the baroreceptor reflex will facilitate vasoconstriction by activating which receptor?
Your Answer:
Correct Answer: Alpha1
Explanation:The rate of baroreceptor firing slows down when blood pressure falls too low. This causes an increase in sympathetic stimulation of the heart, resulting in an increase in cardiac output. It also causes vasoconstriction by activating alpha 1 receptors in smooth muscle, which causes sympathetic stimulation of peripheral vessels.
Alpha2 receptors can be found in both the brain and the peripheral nervous system. They control sympathetic outflow in the brain stem.
Beta1 receptors, which are found on the cell membrane of cardiac muscle cells, stimulate heart rate and myocardial contractility. The smooth muscle cell membrane contains beta2 receptors, which promote smooth muscle relaxation in the lungs causing bronchodilation, GI tract, and peripheral blood vessels.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 32
Incorrect
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Urine flow rate = 2 ml/min
Urine concentration of creatinine = 18 mg/ml
Plasma concentration of creatinine = 0.25 mg/ml
What is the estimated glomerular filtration rate (eGFR)?
Your Answer:
Correct Answer: 144 ml/min
Explanation:GFR can be estimated by:
GFR = UCr x V / PCr
Where:
UCr = urine concentration of creatinine
PCr = plasma concentration of creatinine
V = rate of urine flowIn this case GFR = (18 x 2) / 0.25 = 144 ml/min
Note: Creatinine is used to estimate GFR because it is an organic base naturally produced by muscle breakdown, it is freely filtered at the glomerulus, it is not reabsorbed from the nephron, it is not produced by the kidney, it is not toxic, and it doesn’t alter GFR.
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This question is part of the following fields:
- Physiology
- Renal Physiology
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Question 33
Incorrect
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A 57-year-old woman receives vitamin B12 injections following a gastrectomy.
Which of the following cell types, if absent, is responsible for her vitamin B12 deficiency?Your Answer:
Correct Answer: Parietal cells
Explanation:Intrinsic factor, produced by the parietal cells of the stomach, is essential for the absorption of vitamin B12 from the terminal ileum.
After a gastrectomy, the absorption of vitamin B12 is markedly reduced, and a deficiency will occur. -
This question is part of the following fields:
- Gastrointestinal Physiology
- Physiology
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Question 34
Incorrect
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Question 35
Incorrect
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Which of the following is the site of secretion of intrinsic factor:
Your Answer:
Correct Answer: Stomach
Explanation:Intrinsic factor is essential for the absorption of the small amounts of vitamin B12 normally present in the diet from the terminal ileum. The parietal cells of the stomach produce intrinsic factor, and following a gastrectomy, the absorption of vitamin B12 will be markedly reduced, and a deficiency state will exist.
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 36
Incorrect
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Depolarisation of a neuron begins with which of the following:
Your Answer:
Correct Answer: Opening of ligand-gated Na + channels
Explanation:Action potentials are initiated in nerves by activation of ligand-gated Na+channels by neurotransmitters. Opening of these Na+channels results in a small influx of sodium and depolarisation of the negative resting membrane potential (-70 mV). If the stimulus is sufficiently strong, the resting membrane depolarises enough to reach threshold potential (generally around -55 mV), at which point an action potential can occur. Voltage-gated Na+channels open, causing further depolarisation and activating more voltage-gated Na+channels and there is a sudden and massive sodium influx, driving the cell membrane potential to about +40 mV.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 37
Incorrect
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A 54-year-old woman presents with polyuria and polydipsia. She is known to suffer from bipolar disorder, which has been well controlled by the use of lithium for many years.
What is the SINGLE most likely diagnosis?Your Answer:
Correct Answer: Nephrogenic diabetes insipidus
Explanation:Diabetes insipidus is the inability to produce concentrated urine. It is characterised by the presence of excessive thirst, polyuria and polydipsia. There are two distinct types of diabetes insipidus:
Cranial (central) diabetes insipidus and;
Nephrogenic diabetes insipidus
Cranial diabetes insipidus is caused by a deficiency of vasopressin (anti-diuretic hormone). Patients with cranial diabetes insipidus can have a urine output as high as 10-15 litres per 24 hours, but adequate fluid intake allows most patients to maintain normonatraemia. 30% of cases are idiopathic, and a further 30% are secondary to head injuries. Other causes include neurosurgery, brain tumours, meningitis, granulomatous disease (e.g. sarcoidosis) and drugs, such as naloxone and phenytoin. A very rare inherited form also exists that is associated with diabetes mellitus, optic atrophy, nerve deafness and bladder atonia.
Nephrogenic diabetes insipidus is caused by renal resistance to the action of vasopressin. As with cranial diabetes insipidus, urine output is markedly elevated. Serum sodium levels can be maintained by secondary polydipsia or can be elevated. Causes of nephrogenic diabetes insipidus include chronic renal disease, metabolic disorders (e.g. hypercalcaemia and hypokalaemia) and drugs, including long-term lithium usage and demeclocycline.
In view of the history of long-term lithium use, in this case, nephrogenic diabetes insipidus is the most likely diagnosis. -
This question is part of the following fields:
- Physiology
- Renal Physiology
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Question 38
Incorrect
-
At rest, skeletal muscle accounts for between 15-20% of cardiac output and accounts for around 50% of body weight. This can increase to nearly 80% of cardiac output during exercise. Skeletal muscle circulation is highly controlled and has a number of specialized adaptations as a result of this high degree of disparity during exercise, in combination with the diversity in the size of skeletal muscle around the body.
What is the primary mechanism for boosting skeletal muscle blood flow during exercise?
Your Answer:
Correct Answer: Metabolic hyperaemia
Explanation:In skeletal muscle, blood flow is closely related to metabolic rate. Due to the contraction of precapillary sphincters, most capillaries are blocked off from the rest of the circulation at rest and are not perfused. This causes an increase in vascular tone and vessel constriction. As metabolic activity rises, this develops redundancy in the system, allowing it to cope with greater demand. During exercise, metabolic hyperaemia, which is induced by the release of K+, CO2, and adenosine, recruits capillaries. Sympathetic vasoconstriction in the active muscles is overridden by this. Simultaneously, blood flow in non-working muscles is restricted, preserving cardiac output. During exercise, muscle contractions pump blood through the venous system, raising the pressure differential between arterioles and venules and boosting blood flow via capillaries.
Capillary angiogenesis is evident when muscles are used repeatedly (e.g. endurance training). It is a long-term effect, not a quick fix for increased blood flow.
The local partial pressure of alveolar oxygen is the primary intrinsic control of pulmonary blood flow (pAO2). Low pAO2 promotes arteriole vasoconstriction and vice versa. The hypoxic pulmonary vasoconstriction (HPV) reflex allows blood flow to be diverted away from poorly ventilated alveoli and towards well-ventilated alveoli in order to maximize gaseous exchange.
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This question is part of the following fields:
- Cardiovascular Physiology
- Physiology
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Question 39
Incorrect
-
A patient in the Emergency Department had a diagnosis of diabetic ketoacidosis (DKA) and you commence an insulin infusion. Which of these statements concerning endogenous insulin is true?
Your Answer:
Correct Answer: Insulin has a short half-life of around 5-10 minutes
Explanation:Insulin, a peptide hormone, is produced in the pancreas by the beta-cells of the islets of Langerhans.
The beta-cells first synthesise an inactive precursor called preproinsulin which is converted to proinsulin by signal peptidases, which remove a signal peptide from the N-terminus.
Proinsulin is converted to insulin by the removal of the C-peptide.
Insulin has a short half-life in the circulation of about 5-10 minutes.
Glucagon and parasympathetic stimulation stimulates insulin release. -
This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 40
Incorrect
-
Which of the following ions normally has the highest concentration in intracellular fluid:
Your Answer:
Correct Answer: K +
Explanation:Potassium (K+) is the principal intracellular ion; approximately 4 mmol/L is extracellular (3%) and 140 mmol/L intracellular (97%).
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 41
Incorrect
-
In the foetus at 4 months gestation, where does haematopoiesis mainly occur?
Your Answer:
Correct Answer: Liver and spleen
Explanation:The first place that haematopoiesis occurs in the foetus is in the yolk sac. Later on, it occurs in the liver and spleen, which are the major hematopoietic organs from about 6 weeks until 6 – 7 months gestation. At this point, the bone marrow becomes the most important site. Haemopoiesis is restricted to the bone marrow in normal childhood and adult life.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 42
Incorrect
-
Stimulation of J receptors located on alveolar and bronchial walls results in all of the following EXCEPT for:
Your Answer:
Correct Answer: Tachycardia
Explanation:Juxtapulmonary or ‘J’ receptors are located on alveolar and bronchial walls close to the capillaries. Their afferents are small unmyelinated C-fibres or myelinated nerves in the vagus nerve. Activation causes depression of somatic and visceral activity by producing apnoea or rapid shallow breathing, a fall in heart rate and blood pressure, laryngeal constriction and relaxation of skeletal muscles via spinal neurones. J receptors are stimulated by increased alveolar wall fluid, pulmonary congestion and oedema, microembolism and inflammatory mediators. J receptors are thought to be involved in the sensation of dyspnoea in lung disease.
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 43
Incorrect
-
Regarding fluid balance, which of the following statements is CORRECT:
Your Answer:
Correct Answer: About three-quarters of extracellular fluid is interstitial.
Explanation:An ‘average’ person (70 kg male) contains about 40 litres of water in total, separated into different fluid compartments by biological semipermeable membranes; plasma cell membranes between extracellular and intracellular fluid, and capillary walls between interstitial and intravascular fluid. Around two-thirds of the total fluid (27 L) is intracellular fluid (ICF) and one-third of this (13 L) is extracellular fluid (ECF). The ECF can be further divided into intravascular fluid (3.5 L) and interstitial fluid (9.5 L).
Transcellular fluid refers to any fluid that does not contribute to any of the main compartments but which are derived from them e.g. gastrointestinal secretions and cerebrospinal fluid, and has a collective volume of approximately 2 L.
Osmosis is the passive movement of water across a semipermeable membrane from regions of low solute concentration to those of higher solute concentration. -
This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 44
Incorrect
-
An arterial blood gas test is performed to a 25-year-old students who presents with confusion, headache, nausea and malaise. The results show that carbon monoxide levels are significantly high. Which of the following carbon monoxide poisoning assertions is true?
Your Answer:
Correct Answer: The PO 2 of the blood in CO poisoning can be normal
Explanation:By combining with haemoglobin to form carboxyhaemoglobin, carbon monoxide (CO) disrupts the blood’s oxygen transport function. CO binds to haemoglobin with a 240-fold higher affinity than oxygen. As a result, even small amounts of CO can bind a large portion of the blood’s haemoglobin, making it unavailable for oxygen transport.
During a suspected carbon monoxide poisoning, the blood PO2 and haemoglobin concentrations will be normal, but the oxygen concentration will be drastically reduced. The oxygen dissociation curve will also shift to the left in the presence of Carboxyhaemoglobin ( haemoglobin and carbon monoxide combination), interfering with oxygen unloading.
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This question is part of the following fields:
- Physiology
- Respiratory Physiology
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Question 45
Incorrect
-
You've been asked to give a discussion to a group of medical students about skeletal muscle physiology and its use in clinical medicine. They pose a series of difficult questions to you.
Which of the following definitions for the A-band of the sarcomere is correct?
Your Answer:
Correct Answer: A band that contains the entire length of a single thick filament (myosin)
Explanation:Myofibrils, which are around 1 m in diameter, make up each myofiber. The cytoplasm separates them and arranges them in a parallel pattern along the cell’s long axis. These myofibrils are made up of actin and myosin filaments that are repeated in sarcomeres, which are the myofiber’s basic functional units.
Myofilaments are the filaments that make up myofibrils, and they’re made mostly of proteins. Myofilaments are divided into three categories:
Myosin filaments are thick filaments made up mostly of the protein myosin.
Actin filaments are thin filaments made up mostly of the protein actin.
Elastic filaments are mostly made up of the protein titin.
The sarcomere is a Z-line segment that connects two adjacent Z-lines.
The I-bands are thin filament zones that run from either side of the Z-lines to the thick filament’s beginning.
Between the I-bands is the A-band, which spans the length of a single thick filament.
The H-zone is a zone of thick filaments that is not overlaid by thin filaments in the sarcomere’s centre. The H-zone keeps the myosin filaments in place by surrounding them with six actin filaments each.
The M-band (or M-line) is a disc of cross-connecting cytoskeleton elements in the centre of the H-zone.
The thick filament is primarily made up of myosin. The thin filament is primarily made up of actin. Actin, tropomyosin, and troponin are found in a 7:1:1 ratio in thin filaments. -
This question is part of the following fields:
- Basic Cellular Physiology
- Physiology
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Question 46
Incorrect
-
Which of the following is NOT a function of bile:
Your Answer:
Correct Answer: Digestion of fats into monoglycerides and fatty acids.
Explanation:Bile functions to eliminate endogenous and exogenous substances from the liver (including bilirubin), to neutralise gastric acid in the small intestine, and to emulsify fats in the small intestine and facilitate their digestion and absorption. Bile salts also act as bactericides, destroying many of the microbes that may be present in the food. Bile doesn’t contain digestive enzymes for digestion of lipids into monoglycerides and fatty acids; this is performed mainly by pancreatic lipase.
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 47
Incorrect
-
What is the correct adrenaline dose for a patient with pulseless ventricular tachycardia?
Your Answer:
Correct Answer: 10 ml of 1 in 10,000 adrenaline solution
Explanation:Ventricular fibrillation or pulseless ventricular tachycardia (VF/VT) are referred to as shockable rhythm.
IV adrenaline 1 mg (10 mL of 1:10,000 solution) should be administered after 3 shocks and every 3 – 5 minutes/after alternate shocks thereafter for a shockable rhythm.
For a non-shockable rhythm, 1 mg IV adrenaline should be administered as soon as IV access is obtained, and then every 3 – 5 minutes/after alternate shocks thereafter.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 48
Incorrect
-
Question 49
Incorrect
-
If the ejection fraction increases, there will be a decrease in:
Your Answer:
Correct Answer: End-systolic volume
Explanation:An increase in ejection fraction means that a higher fraction of the end-diastolic volume is ejected in the stroke volume (e.g. because of the administration of a positive inotropic agent). When this situation occurs, the volume remaining in the ventricle after systole, the end-systolic volume, will be reduced. Cardiac output, stroke volume, and mean arterial pressure will be increased.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 50
Incorrect
-
Regarding fat digestion, which of the following statements is CORRECT:
Your Answer:
Correct Answer: Lipids are reesterified in the smooth endoplasmic reticulum of the enterocyte.
Explanation:Fats are digested almost entirely in the small intestine and are only released from the stomach into the duodenum at the rate at which they can be digested (the presence of fatty acids and monoglycerides in the duodenum inhibits gastric emptying). In the duodenum fat is emulsified by bile acids, a process where larger lipid droplets are broken down into much smaller droplets providing a greater surface area for enzymatic digestion. Pancreatic lipase digests triglyceride into monoglycerides and free fatty acids. The products of fat digestion (fatty acids and monoglycerides), cholesterol and fat-soluble vitamins diffuse passively into the enterocytes. Once inside the epithelial cell, lipid is taken into the smooth endoplasmic reticulum where much of it is re esterified. Dietary and synthesised lipids are then incorporated into chylomicrons in the Golgi body, which are exocytosed from the basolateral membrane to enter lacteals.
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 51
Incorrect
-
A 70 year old man who has a previous history of small cell lung cancer was found to have severe hyponatraemia on a recent blood test and he is sent to the emergency room. In the nephron, where is the likely cause of this abnormality?
Your Answer:
Correct Answer: Distal nephron
Explanation:In the cancer patient, hyponatremia is usually caused by the syndrome of inappropriate antidiuretic hormone (SIADH). This develops more frequently with small cell lung cancer (SCLC) than with other malignancies. The pathogenesis of this is as a result of the process whereby ADH binds V2 receptors on renal principal cells in the late distal tubule and collecting ducts, resulting in elevation of cAMP levels. Increased cAMP levels cause fusion of intracellular vesicles with the apical membrane. There are water channels called aquaporins in their membranes of these vesicles, and these increase the water permeability, thus facilitating increased water reabsorption and urine concentration. Thus, by increasing water retention, ADH causes blood to be diluted, which then decreases the concentration of solutes like sodium.
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This question is part of the following fields:
- Endocrine
- Physiology
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Question 52
Incorrect
-
In adult advanced life support, which of the following best describes the correct administration of adrenaline for a non-shockable rhythm:
Your Answer:
Correct Answer: Give 1 mg of adrenaline as soon as intravenous access is achieved and every 3 - 5 minutes thereafter
Explanation:IV adrenaline 1 mg (10 mL of 1:10,000 solution) should be given after 3 shocks and every 3 – 5 minutes/after alternate shocks thereafter.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 53
Incorrect
-
Regarding alteplase, which of the following statements is INCORRECT:
Your Answer:
Correct Answer: Alteplase is commonly associated with hypotensive effects.
Explanation:Alteplase is a recombinant tissue-type plasminogen activator (tPA), a naturally occurring fibrin-specific enzyme that has selectivity for activation of fibrin-bound plasminogen. It has a short half-life of 3 – 4 minutes and must be given by continuous intravenous infusion but is not associated with antigenic or hypotensive effects, and can be used in patients when recent streptococcal infections or recent use of streptokinase contraindicates the use of streptokinase.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 54
Incorrect
-
Oedema can occur as a result of any of the following WITH THE EXCEPTION OF:
Your Answer:
Correct Answer: Increased interstitial hydrostatic pressure
Explanation:Oedema is defined as a palpable swelling produced by the expansion of the interstitial fluid volume. A variety of clinical conditions are associated with the development of oedema, including heart failure, cirrhosis, and nephrotic syndrome. The development of oedema requires an alteration in capillary dynamics in a direction that favours an increase in net filtration and also inadequate removal of the additional filtered fluid by lymphatic drainage. Oedema may form in response to an elevation in capillary hydraulic pressure (which increases the delta hydraulic pressure) or increased capillary permeability, or it can be due to disruption of the endothelial glycocalyx, decreased interstitial compliance, a lower plasma oncotic pressure (which reduces the delta oncotic pressure), or a combination of these changes. Oedema can also be induced by lymphatic obstruction since the fluid that is normally filtered is not returned to the systemic circulation.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 55
Incorrect
-
Regarding cellular respiration, which of the following statements is CORRECT:
Your Answer:
Correct Answer: When fats are used as the primary energy source, an excess of acetyl-CoA is produced.
Explanation:Cellular respiration is the process by which cells obtain energy in the form of adenosine triphosphate (ATP). ATP transfers chemical energy from the energy rich substances in the cell to the cell’s energy requiring reactions e.g. active transport, DNA replication and muscle contraction.Cellular respiration is essentially a three step process: 1) Glycolysis, 2)The Krebs cycle, 3)The electron transfer system.The main respiratory substrate used by cells is 6-carbon glucose. Fats and proteins can also be used as respiratory substrates. When fats are being used as the primary energy source, in the absence of glucose, an excess amount of acetyl-CoA is produced, and is converted into acetone and ketone bodies. This can occur in starvation, fasting or in diabetic ketoacidosis. Proteins are used as an energy source only if protein intake is very high, or if glucose and fat sources are depleted.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 56
Incorrect
-
Carbon dioxide is transported in the blood approximately:
Your Answer:
Correct Answer: 60% as bicarbonate ions, 30% as carbamino compounds and 10% dissolved in plasma.
Explanation:Carbon dioxide is transported in the blood from tissues to the lungs in three ways as bicarbonate ions (60%), as carbamino compounds with proteins (30%) or simply dissolved in plasma (10%).
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 57
Incorrect
-
Atrial natriuretic peptide (ANP) is primarily produced in response to:
Your Answer:
Correct Answer: An increase in intravascular fluid volume
Explanation:Atrial natriuretic peptide (ANP) is released from cardiac atrial muscle cells in response to atrial stretch caused by an increase in intravascular fluid volume and is also produced in collecting duct cells.
Atrial natriuretic peptide acts to inhibit sodium reabsorption in the distal nephron. -
This question is part of the following fields:
- Physiology
- Renal
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Question 58
Incorrect
-
Which of the following cell types in the stomach secretes histamine?
Your Answer:
Correct Answer: Enterochromaffin-like cells
Explanation:The parietal cells operate in close association with another type of cell called enterochromaffin-like cells (ECL cells), the primary function of which is to secrete histamine. The ECL cells lie in the deep recesses of the oxyntic glands and therefore release histamine indirect contact with the parietal cells of the glands.
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 59
Incorrect
-
Noradrenaline exhibits its positive inotropic effect by which of the following mechanisms:
Your Answer:
Correct Answer: Binds to beta1-receptors and causes increased Ca2+ entry via L-type channels during the action potential
Explanation:Noradrenaline (the sympathetic neurotransmitter) is a positive inotrope; it binds to β1-adrenoceptors on the membrane and causes increased Ca2+entry via L-type channels during the AP and thus increases Ca2+release from the SR. Noradrenaline also increases Ca2+sequestration into the SR and thus more Ca2+is available for the next contraction. Cardiac glycosides (e.g. digoxin) slow the removal of Ca2+from the cell by inhibiting the membrane Na+pump which generates the Na+gradient required for driving the export of Ca2+; consequently the removal of Ca2+from the myocyte is slowed and more Ca2+is available for the next contraction. Acidosis is negatively inotropic, largely because H+competes for Ca2+binding sites.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 60
Incorrect
-
A patient who was put on low molecular weight heparin for suspected DVT and was scheduled for an ultrasound after the weekend, arrives at the emergency department with significant hematemesis. Which of the following medications can be used as a heparin reversal agent:
Your Answer:
Correct Answer: Protamine sulfate
Explanation:The management of bleeding in a patient receiving heparin depends upon the location and severity of bleeding, the underlying thromboembolic risk, and the current aPTT (for heparin) or anti-factor Xa activity (for LMW heparin). As an example, a patient with minor skin bleeding in the setting of a mechanical heart valve (high thromboembolic risk) and a therapeutic aPTT may continue heparin therapy, whereas a patient with major intracerebral bleeding in the setting of venous thromboembolism several months prior who is receiving heparin bridging perioperatively may require immediate heparin discontinuation and reversal with protamine sulphate. If haemorrhage occurs it is usually sufficient to withdraw unfractionated or low molecular weight heparin, but if rapid reversal of the effects of the heparin is required, protamine sulphate is a specific antidote (but only partially reverses the effects of low molecular weight heparins). Clinician judgment and early involvement of the appropriate consulting specialists is advised.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 61
Incorrect
-
A patient is referred for lung function tests on account of a history of breathlessness and cough.
Which statement about lung volumes is correct?
Your Answer:
Correct Answer: The tidal volume is the volume of air drawn in and out of the lungs during normal breathing
Explanation:The tidal volume(TV) is the amount of air that moves in and out of the lungs with each respiratory cycle. In a healthy male, the usual volume is 0.5 L (,7 ml/kg body mass).
The vital capacity(VC) is the maximum amount of air that can be exhaled following maximal inspiration. The usual volume in a healthy male is 4.5 L.
The residual volume(RV) is the amount of air remaining in the lungs after maximum expiration. The usual volume in a healthy male is 1.0 L.
The inspiratory reserve volume(IRV) is the maximum amount of air that can be breathed in forcibly after normal inspiration. The usual volume in a healthy male is 3.0 L.
The expiratory reserve volume(ERV) is the volume of air that can be breathed out forcibly after normal expiration. The usual volume in a healthy male is 1.0 L.
Total lung capacity(TLC) is the volume of air the lungs can accommodate. TLC = RV+VC. The usual volume in a healthy male is 5.5 L.
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This question is part of the following fields:
- Physiology
- Respiratory Physiology
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Question 62
Incorrect
-
Regarding V/Q mismatch, which of the following statements is CORRECT:
Your Answer:
Correct Answer: In a true shunt, increasing inspired oxygen has no effect on improving hypoxaemia.
Explanation:Both ventilation and perfusion increase towards the lung base, because of the effects of gravity, but the gravitational effects are greater on perfusion than ventilation and therefore there is a regional variation in V/Q ratio from lung apex (high V/Q) to lung base (low V/Q). In a pure shunt, there is normal perfusion but absent ventilation and the V/Q ratio = 0. In a true shunt increasing oxygen fraction has no effect because the oxygen-enriched air fails to reach the shunted blood. An increased A-a gradient is seen in V/Q mismatch.
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 63
Incorrect
-
A patient with a history of worsening chronic breathlessness on exertion undergoes lung function testing. The results demonstrate an FEV 1 that is 58% predicted and an FEV 1 /FVC ratio less than 0.7.
Which of the following is the most likely diagnosis? Select ONE answer only.Your Answer:
Correct Answer: COPD
Explanation:Obstructive lung disorders are characterised by airway obstruction. Many obstructive diseases of the lung result from narrowing of the smaller bronchi and larger bronchioles, often because of excessive contraction of the smooth muscle itself.
In obstructive lung disease, FEV1is reduced to <80% of normal and FVC is usually reduced but to a lesser extent than FEV1. The FEV1/FVC ratio is reduced to <0.7.
Types of obstructive lung disorders include:
Chronic obstructive pulmonary disease (COPD)
Asthma
Bronchiectasis -
This question is part of the following fields:
- Physiology
- Respiratory Physiology
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Question 64
Incorrect
-
Antidiuretic hormone (ADH) levels are found to be increased in a young lady with unexplained hyponatraemia.
Which of the following is a result of the release of ADH?Your Answer:
Correct Answer: Small volumes of concentrated urine
Explanation:ADH, or antidiuretic hormone, is a hormone that regulates water and electrolyte balance. It is released in response to a variety of events, the most important of which are higher plasma osmolality or lower blood pressure. ADH increases plasma volume and blood pressure via acting on the kidneys and peripheral vasculature.
ADH causes extensive vasoconstriction by acting on peripheral V1 Receptors.ADH binds to B2 Receptors in the terminal distal convoluted tubule and collecting duct of the kidney, increasing transcription and aquaporin insertion in the cells that line the lumen. Aquaporins are water channels that allow water to pass through the tubule and into the interstitial fluid via osmosis, lowering urine losses.
The permeability of the distal collecting duct (the section within the inner medulla) to urea is likewise increased by ADH. More urea travels out of the tubule and into the peritubular fluid, contributing to the counter current multiplier, which improves the Loop of Henle’s concentrating power.Overall, there is enhanced urea and water reabsorption in the presence of ADH, resulting in modest amounts of concentrated urine. There is minimal urea and water reabsorption in the absence of ADH, resulting in huge amounts of dilute urine.
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This question is part of the following fields:
- Physiology
- Renal Physiology
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Question 65
Incorrect
-
A 53 year old women presents to the emergency room with a chronic cough. The pulmonary receptors likely to be involved in causing her cough are:
Your Answer:
Correct Answer: Irritant receptors
Explanation:Throughout the airways, there are irritant receptors which are located between epithelial cells which are made of rapidly adapting afferent myelinated fibres in the vagus nerve. A cough is as a result of receptor stimulation located in the trachea, hyperpnoea is as a result of receptor stimulation in the lower airway. Stimulation may also result in reflex bronchial and laryngeal constriction. Many factors can stimulate irritant receptors. These include irritant gases, smoke and dust, airway deformation, pulmonary congestion, rapid inflation/deflation and inflammation. Deep augmented breaths or sighs seen every 5 – 20 minutes at rest are due to stimulation of these irritant receptors. This reverses the slow lung collapse that occurs in quiet breathing.
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 66
Incorrect
-
A 60 -year-old man is tested to have low calcium levels . After additional questioning, it becomes clear that he has a calcium-deficient diet.
What is the daily calcium intake recommendation for a healthy adult?Your Answer:
Correct Answer: 1300 mg
Explanation:A daily calcium intake of 1,000 to 1,300 mg is advised for adults. Women have a slightly higher calcium need than men and are at a higher risk of developing osteoporosis as they age.
Calcium-rich foods include the following:
Milk, cheese, and butter as dairy products.
Broccoli, spinach, and green beans as green veggies.
Bread, rice, and cereals as whole grain foods.
Sardines, salmon, and other bony fish
Eggs
Nuts
The following foods have the least calcium:
Carrot
Fruits such as kiwis, raspberries, oranges, and papaya
Chicken and pork in meats. -
This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 67
Incorrect
-
Following a decrease in extracellular volume, which of the following is a reaction to enhanced sympathetic innervation of the kidney:
Your Answer:
Correct Answer: Release of renin
Explanation:The RAS pathway begins with renin cleaving its substrate, angiotensinogen (AGT), to produce the inactive peptide, angiotensin I, which is then converted to angiotensin II by endothelial angiotensin-converting enzyme (ACE). ACE activation of angiotensin II occurs most extensively in the lung. Angiotensin II mediates vasoconstriction as well as aldosterone release from the adrenal gland, resulting in sodium retention and increased blood pressure.
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This question is part of the following fields:
- Physiology
- Renal
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Question 68
Incorrect
-
Regarding the refractory period, which of the following statements is INCORRECT:
Your Answer:
Correct Answer: Action potentials can occur in the relative refractory period but the amplitude of the action potential is smaller.
Explanation:Following the action potential, Na+channels remain inactive for a time in a period known as the absolute refractory period where they cannot be opened by any amount of depolarisation. Following this there is a relative refractory period where the temporary hyperpolarisation (due to delayed closure of rectifier K+channels) makes the cell more difficult to depolarise and an action potential can be generated only in response to a larger than normal stimulus. The refractory period limits the frequency at which action potentials can be generated, and ensures that, once initiated, an action potential can travel only in one direction. An action potential is an all or nothing response so the amplitude of the action potential cannot be smaller.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 69
Incorrect
-
Cystic fibrosis patients have a weakened lung surfactant system. Which of the following cell types is in charge of surfactant secretion?
Your Answer:
Correct Answer: Type II pneumocytes
Explanation:Alveolar type II cells are responsible for four primary functions: surfactant synthesis and secretion, xenobiotic metabolism, water transepithelial transport, and alveolar epithelium regeneration following lung injury.
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 70
Incorrect
-
Regarding water and electrolyte absorption in the small intestine, which of the following statements is INCORRECT:
Your Answer:
Correct Answer: Na+ enters the cell across the apical membrane against its concentration gradient by both membrane channels and transporter protein mechanisms.
Explanation:As the contents of the intestine are isotonic with body fluids and mostly have the same concentration of the major electrolytes, their absorption is active. Water cannot be moved directly, but follows osmotic gradients set up by the transport of ions, primarily mediated by the sodium pump.Na+/K+ ATPase located on the basolateral membrane of the epithelial cells pumps three Na+ ions from the cell in exchange for two K+ ions, against their respective concentration gradients. This leads to a low intracellular concentration of Na+ and a high intracellular concentration of K+. The low intracellular concentration of Na+ ensures a movement of Na+ from the intestinal contents into the cell down its concentration gradient by both membrane channels and transporter protein mechanisms. Na+ is then rapidly pumped again by the basolateral sodium pump. K+ leaves the cell across the basolateral membrane down its concentration gradient linked to an outward movement of Cl- against its concentration gradient (Cl- having entered the cell across the luminal membrane down its concentration gradient).
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 71
Incorrect
-
During swallowing, which of the following structures primarily closes the tracheal opening:
Your Answer:
Correct Answer: Epiglottis
Explanation:The vocal cords of the larynx are strongly
approximated, and the larynx is pulled upward
and anteriorly by the neck muscles. These actions,
combined with the presence of ligaments that
prevent upward movement of the epiglottis, cause
the epiglottis to swing back over the opening
of the larynx. All these effects acting together
prevent the passage of food into the nose and
trachea. Most essential is the tight approximation
of the vocal cords, but the epiglottis helps to
prevent food from ever getting as far as the vocal
cords. Destruction of the vocal cords or of the
muscles that approximate them can cause
strangulation. -
This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 72
Incorrect
-
Which of the following does not increase renal phosphate excretion?
Your Answer:
Correct Answer: Vitamin D
Explanation:PO43-renal excretion is regulated several mechanisms. These include:
-parathyroid hormone – increases excretion by inhibiting reabsorption in the proximal tubule
-acidosis – increases excretion
-glucocorticoids – increases excretion
-calcitonin – increases excretion
-activated vitamin D – decreases excretion by increasing reabsorption in the distal tubule -
This question is part of the following fields:
- Physiology
- Renal
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Question 73
Incorrect
-
All of the following cause bronchoconstriction, EXCEPT for:
Your Answer:
Correct Answer: Adrenaline
Explanation:Factors causing bronchoconstriction:
- Via muscarinic receptors
- Parasympathetic stimulation
- Stimulation of irritant receptors
- Inflammatory mediators e.g. histamine, prostaglandins, leukotrienes
- Beta-blockers
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 74
Incorrect
-
Regarding the partial pressure of gases, which of the following statements is INCORRECT:
Your Answer:
Correct Answer: At high altitude, the oxygen fraction is reduced.
Explanation:At altitude, the oxygen fraction is unaltered but the barometric pressure and thus partial pressure of oxygen is reduced.
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 75
Incorrect
-
Foetal haemoglobin (HbF) comprises about how much of the total haemoglobin in adults:
Your Answer:
Correct Answer: 0.5 - 0.8%
Explanation:Foetal haemoglobin (HbF) makes up about 0.5 – 0.8 % of total adult haemoglobin and consists of two α and two gamma (γ) globin chains.
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This question is part of the following fields:
- Basic Cellular
- Physiology
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Question 76
Incorrect
-
What is the main mechanism of action of dopamine as an inotropic sympathomimetic:
Your Answer:
Correct Answer: Beta1-receptor agonist
Explanation:Dopamine is a neurotransmitter and a metabolic precursor of the catecholamines. It acts on beta1-receptors in cardiac muscle increasing cardiac contractility, and increases renal perfusion by stimulating dopamine receptors in the renal vasculature. This is of benefit in cardiogenic shock where deterioration of renal function is common.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 77
Incorrect
-
What is the mechanism of action of captopril:
Your Answer:
Correct Answer: Inhibition of the conversion of angiotensin I to angiotensin II
Explanation:Angiotensin-converting enzyme inhibitors (ACE inhibitors) e.g. captopril inhibit the conversion of angiotensin I to angiotensin II, and thus have a vasodilatory effect, lowering both arterial and venous resistance. The cardiac output increases and, because the renovascular resistance falls, there is an increase in renal blood flow. This latter effect, together with reduced aldosterone release, increases Na+ and H2O excretion, contracting the blood volume and reducing venous return to the heart.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 78
Incorrect
-
Which of the following is most true of the sinoatrial node:
Your Answer:
Correct Answer: Frequency of depolarisation is increased by sympathetic stimulation.
Explanation:Cardiac myocyte contraction is not dependent on an external nerve supply but instead the heart generates its own rhythm, demonstrating inherent rhythmicity. The heartbeat is initiated by spontaneous depolarisation of the sinoatrial node (SAN), a region of specialised myocytes in the right atrium close to the coronary sinus, at a rate of 100-110 beats/min. This intrinsic rhythm is primarily influenced by autonomic nerves, with vagal influences being dominant over sympathetic influences at rest. This vagal tone reduces the resting heart rate down to 60-80 beats/min. To increase heart rate, the autonomic nervous system increases sympathetic outflow to the SAN, with concurrent inhibition of vagal tone. These changes mean the pacemaker potential more rapidly reaches the threshold for action potential generation.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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Question 79
Incorrect
-
If the afferent arteriole's diameter is smaller than the efferent arteriole's diameter in the glomerulus:
Your Answer:
Correct Answer: The net filtration pressure will decrease
Explanation:The relative resistance of the afferent and efferent arterioles substantially influences glomerular capillary hydrostatic pressure and consequently GFR. Filtration is forced through the filtration barrier due to high pressure in the glomerular capillaries. Afferent arteriolar constriction lowers this pressure while efferent arteriolar constriction raises it.
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This question is part of the following fields:
- Physiology
- Renal
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Question 80
Incorrect
-
A 70-year-old patient diagnosed with Cushing's syndrome and has a history of weight gain, hypertension, and easy bruising.
Which of these assertions about Cushing's syndrome is correct?Your Answer:
Correct Answer: Diagnosis can be confirmed by a dexamethasone suppression test
Explanation:Cushing’s syndrome is a group of symptoms and signs brought on by long-term exposure to high amounts of endogenous or exogenous glucocorticoids.
Iatrogenic corticosteroid injection is the most prevalent cause of Cushing’s syndrome. Cushing’s illness is the second most prevalent cause of Cushing’s syndrome. Cushing’s disease is distinct from Cushing’s syndrome in that it refers to a single cause of the illness, a pituitary adenoma that secretes high quantities of ACTH, which raises cortisol levels.
Because cortisol enhances the vasoconstrictive impact of endogenous adrenaline, patients with Cushing’s syndrome are usually hypertensive.
Hyperglycaemia (due to insulin resistance) rather than hypoglycaemia is a common symptom.
Cortisol levels fluctuate throughout the day, with the greatest levels occurring around 0900 hours and the lowest occurring at 2400 hrs during sleep. The diurnal swing of cortisol levels is lost in Cushing’s syndrome, and levels are greater throughout the 24-hour period. In the morning, levels may be normal, but they may be high at night-time, when they are generally repressed.A dexamethasone suppression test or a 24-hour urine free cortisol collection can both be used to establish the existence of Cushing’s syndrome.
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This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 81
Incorrect
-
Which law describes the rate of diffusion in a solution?
Your Answer:
Correct Answer: Fick’s law
Explanation:Fick’s law describes the rate of diffusion in a solution. Fick’s law states that:
Jx = -D A (ΔC / Δx)
Where:
Jx = The amount of substance transferred per unit time
D = Diffusion coefficient of that particular substance
A = Surface area over which diffusion occurs
ΔC = Concentration difference across the membrane
Δx = Distance over which diffusion occurs
The negative sign reflects movement down the concentration gradient -
This question is part of the following fields:
- Basic Cellular Physiology
- Physiology
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Question 82
Incorrect
-
Intrinsic factor is secreted by which of the following cell types in the stomach:
Your Answer:
Correct Answer: Parietal cells
Explanation:Intrinsic factor is essential for the absorption of the small amounts of vitamin B12 normally present in the diet from the terminal ileum. The parietal cells of the stomach produce intrinsic factor, and following a gastrectomy, the absorption of vitamin B12 will be markedly reduced, and a deficiency state will exist.
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 83
Incorrect
-
The correct statement about the glomerular filtration barrier is which of the following?
Your Answer:
Correct Answer: The basement membrane is negatively charged, restricting filtration of negatively charged molecules.
Explanation:The main factor in determining whether a substance is filtered or not is molecular weight. Molecules < 7 kDa in molecular weight e.g. glucose, amino acids, urea, ions are filtered freely, but larger molecules are increasingly restricted up to 70 kDa, and there is very little filtration for anything above this.
There is further restriction of negatively charged molecules because they are repelled by negative charges, particularly in the basement membrane. Albumin, which has a molecular weight of 69 kDa and is negatively charged, is filtered but only in very small amounts. All of the filtered albumin is reabsorbed in the proximal tubule. Small molecules such as ions, glucose, amino acids and urea pass the filter without hindrance. Other than the ultrafiltrate being essentially protein free, it has an otherwise identical composition of plasma. Bowman’s capsule consists of:
– an epithelial lining which consists of a single layer of cells called podocytes
– endothelium which is perforated by pores or fenestrations – this allows plasma components with a molecular weight of < 70 kDa to pass freely. -
This question is part of the following fields:
- Physiology
- Renal
-
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Question 84
Incorrect
-
Regarding carbohydrate, which of the following statements is INCORRECT:
Your Answer:
Correct Answer: Most dietary carbohydrate is in the form of disaccharides.
Explanation:Carbohydrates are the main energy source of most diets. They provide 17 kJ (4 kcal) of energy per gram. Most dietary carbohydrate is in the form of polysaccharides. The principal ingested polysaccharides are starch which is derived from plant sources and glycogen which is derived from animal sources. Dietary fibre consists of indigestible carbohydrate (found in plant foods) such as cellulose, lignin and pectin.
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This question is part of the following fields:
- Gastrointestinal
- Physiology
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Question 85
Incorrect
-
The transport of oxygen from maternal to fetal circulation is made possible by fetal haemoglobin. Which of the statements about fetal haemoglobin (HbF) is also correct?
Your Answer:
Correct Answer: The oxygen dissociation curve for foetal haemoglobin is shifted to the left of that of adult haemoglobin
Explanation:Fetal haemoglobin is the most common type of haemoglobin found in the foetus during pregnancy. It transports oxygen from the maternal circulation to the fetal circulation. It can easily bind to oxygen from the maternal circulation because it has a high affinity for oxygen. From 10 to 12 weeks of pregnancy to the first six months after birth, the erythroid precursor cells produce fetal haemoglobin. In comparison to adult haemoglobin, fetal haemoglobin has two alpha and two gamma subunits, whereas adult haemoglobin has two alpha and two beta subunits in its major form.
And, unlike adult haemoglobin, the oxygen dissociation curve of fetal haemoglobin is left-shifted. Myoglobin is an oxygen storage molecule with a very high affinity for oxygen. Only when the partial pressure of oxygen is exceeded does it release oxygen.
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This question is part of the following fields:
- Physiology
- Respiratory Physiology
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Question 86
Incorrect
-
In adult basic life support, chest compressions should be performed at which of the following rates:
Your Answer:
Correct Answer: 100 - 120 per minute
Explanation:Chest compressions should be performed at a rate of 100 – 120 per minute.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 87
Incorrect
-
Loop diuretics primarily act on which Na+ transporter?
Your Answer:
Correct Answer: Na + /K + /2Cl - symporter
Explanation:The most potent diuretics are loop diuretics e.g. furosemide. They work by inhibiting the Na+/K+/2Cl-symporter in the thick ascending limb of the loop of Henle, which inhibits sodium, potassium, and chloride reabsorption. As a result, there is diuresis with loss of these electrolytes. There is a reduction in transcellular voltage difference, paracellular calcium and magnesium reabsorption.
The medullary interstitium becomes more concentrated by salt reabsorption in the ascending limb. Loop diuretics block this process and reduce the ability of the kidney to concentrate urine. In the collecting duct, there is increased sodium delivery to the principal cells, which increases potassium secretion in return for sodium reabsorption. -
This question is part of the following fields:
- Physiology
- Renal
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Question 88
Incorrect
-
Regarding diuretics, which of the following statements is CORRECT:
Your Answer:
Correct Answer: Carbonic anhydrase inhibitors have their effect by inhibiting bicarbonate reabsorption.
Explanation:Carbonic anhydrase inhibitors e.g. acetazolamide block the reaction of carbon dioxide and water and so prevent Na+/H+exchange and bicarbonate reabsorption. The increased bicarbonate levels in the filtrate oppose water reabsorption. Proximal tubule sodium reabsorption is also reduced because it is partly dependent on bicarbonate reabsorption.
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This question is part of the following fields:
- Physiology
- Renal
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Question 89
Incorrect
-
An 82 year old man taking warfarin as a maintenance medication comes in to your clinic because of an infection. Which antibiotic is the safest choice for this patient?
Your Answer:
Correct Answer: Cefalexin
Explanation:Alterations in the international normalized ratio (INR) brought about by the concurrent use of antibiotics and warfarin may result in either excessive clotting or excessive bleeding if they are deemed to have a high risk for interaction. As such, there should be careful consideration of the class of antibiotic to be used.
Antibiotics from the following drug classes should generally be avoided as they have a high risk for interaction with warfarin, possible enhancing the anticoagulant effects of warfarin resulting in bleeding: Fluoroquinolones (e.g. ciprofloxacin, levofloxacin), Macrolides (e.g. clarithromycin, erythromycin, azithromycin), Nitroimidazoles (e.g. metronidazole), Sulphonamides (e.g. co-trimoxazole, a combination of trimethoprim and sulfamethoxazole), Trimethoprim, Tetracyclines (e.g. doxycycline).
Low risk antibiotics that have low risk for interaction with warfarin includes cephalexin, from the cephalosporin class, and clindamycin which is a lincomycin.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 90
Incorrect
-
A 34-year-old woman was diagnosed with multiple sclerosis two years ago. Her symptoms have been steadily deteriorating, with no intervals of remission in sight.
Which of the following aspects of nerve conduction is disrupted by multiple sclerosis?
Your Answer:
Correct Answer: Saltatory conduction
Explanation:Local currents propagate action potentials down the axons of neurons. This local current flow following depolarisation results in the depolarisation of the neighbouring axonal membrane, and when this region approaches the threshold, more action potentials are generated and so forth. Due to the refractory period, portions of the membrane that have recently depolarized will not depolarize again, resulting in the action potential only being able to go in one direction.
The square root of axonal diameter determines the velocity of the action potential; the axons with the biggest diameter have the quickest conduction velocities. When a neuron is myelinated, the speed of the action potential rises as well.
The myelin sheath is an insulating coating that surrounds certain neural axons. By increasing membrane resistance and decreasing membrane capacitance, the myelin sheath improves conduction. This enables faster electrical signal transmission via a neuron, making them more energy-efficient than non-myelinated neuronal axons.
Electrical impulses are quickly transmitted from one node to the next, causing depolarization of the membrane above the threshold and triggering another action potential, which is then transmitted to the next node. An action potential is rapidly conducted down a neuron in this manner. Saltatory conduction is the term for this.
Multiple sclerosis is an example of a clinical disorder in which the myelin sheath is affected. It is an immune-mediated disorder in which certain nerve cells in the brain and spinal cord become demyelinated. The ability of some areas of the nervous system to properly transmit action potentials is disrupted by demyelination, resulting in a variety of neurological symptoms and indications. -
This question is part of the following fields:
- Basic Cellular Physiology
- Physiology
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Question 91
Incorrect
-
The proximal convoluted tubule (PCT) is the first part of the renal tubule and lies in the renal cortex. The bulk of reabsorption of solute occurs is the PCT and 100% of glucose is reabsorbed here.
Which of the following is the mechanism of glucose reabsorption in the PCT?Your Answer:
Correct Answer: Secondary active transport
Explanation:Glucose reabsorption occurs exclusively in the proximal convoluted tubule by secondary active transport through the Na.Glu co-transporters, driven by the electrochemical gradient for sodium.
The co-transporters transport two sodium ions and one glucose molecule across the apical membrane, and the glucose subsequently crosses the basolateral membrane by facilitated diffusion. -
This question is part of the following fields:
- Physiology
- Renal Physiology
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Question 92
Incorrect
-
Regarding loop diuretics, which of the following statements is INCORRECT:
Your Answer:
Correct Answer: The risk of hypokalaemia is greater with loop diuretics than with an equipotent dose of a thiazide diuretic.
Explanation:Hypokalaemia can occur with both thiazide and loop diuretics. The risk of hypokalaemia depends on the duration of action as well as the potency and is thus greater with thiazides than with an equipotent dose of a loop diuretic. Hypokalaemia is dangerous in severe cardiovascular disease and in patients also being treated with cardiac glycosides. Often the use of potassium-sparing diuretics avoids the need to take potassium supplements. In hepatic failure, hypokalaemia caused by diuretics can precipitate encephalopathy, particularly in alcoholic cirrhosis.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
-
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Question 93
Incorrect
-
What is the mechanism of action of captopril:
Your Answer:
Correct Answer: Angiotensin-converting enzyme inhibitor
Explanation:Captopril is an angiotensin-converting enzyme (ACE) inhibitor, which inhibits the conversion of angiotensin I to angiotensin II.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
-
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Question 94
Incorrect
-
Which of the following is not true regarding the structure and function of glomerular filtration membrane?
Your Answer:
Correct Answer: The absence of a basement membrane reduces impedance to filtration
Explanation:The glomerular filtration membrane is composed of fenestrated capillary endothelium, basement membrane, and filtration slits. It is an organized, semipermeable membrane preventing the passage of most of the proteins into the urine.
The anatomical arrangement of the glomerular filtration membrane maximizes the surface area available for filtration. The arrangement of its arterioles results in high hydrostatic pressures and facilitates filtration.
Fenestrated capillary endothelium of the glomerular filtration membrane is with relatively large pores. It allows the free movement of plasma proteins and solutes but still restricts the movement of blood cells.
Filtration slits are the smallest filters and restrict the movement of plasma proteins but still allow free movement of ions and nutrients.
The glomerular basement membrane (GBM) is a critical component of the glomerular filtration membrane. Thus, it is not true that its absence will reduce the resistance of flow. The basement membrane is true to be more selective and contains negatively charged glycoproteins. However, it still allows free passage of water, nutrients, and ions. Severe structural abnormalities of the GBM can result in protein (albumin) leakage.
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This question is part of the following fields:
- Physiology
- Renal Physiology
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Question 95
Incorrect
-
A 17-year-old male patient diagnosed with cystic fibrosis is experiencing shortness of breath, coughing, and flu-like symptoms. His X-ray results shows atelectasis, or collapsed lung, specifically in his lower right lung. All of the following statements are true regarding collapsed lungs, except for which one.
Your Answer:
Correct Answer: Atelectasis is an example of a perfusion defect
Explanation:Atelectasis is a complete or partial collapse of the lung. It occurs when the alveoli deflate or are filled with alveolar fluid. It is considered a ventilation defect of the alveoli due to cystic fibrosis. It is not a perfusion defect. A perfusion defect will produce pathological dead space in which the lung alveoli are ventilated adequately but are not perfused, and there is no gas exchange. While with atelectasis, the alveoli remain perfused. However, there is impaired oxygen delivery and intrapulmonary shunting of blood will be present in the collapsed area. Since there is no exchange of gas at the capillary-alveolar interface of the collapsed segments, the pulmonary capillary blood will have similar PO2 and PCO2.
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This question is part of the following fields:
- Physiology
- Respiratory Physiology
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Question 96
Incorrect
-
How is filtered K+mainly reabsorbed in the thick ascending limb of the loop of Henle:
Your Answer:
Correct Answer: Secondary active transport via Na + /K + /2Cl - cotransporter
Explanation:Around 30% of filtered K+is reabsorbed in the thick ascending limb of the loop of Henle, primarily via the luminal Na+/K+/2Cl-cotransporter, but there is also significant paracellular reabsorption, encouraged by the positive potential in the tubular lumen.
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This question is part of the following fields:
- Physiology
- Renal
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Question 97
Incorrect
-
Mannitol is primarily indicated for which of the following:
Your Answer:
Correct Answer: Cerebral oedema
Explanation:Mannitol is an osmotic diuretic that can be used to treat cerebral oedema and raised intraocular pressure. Mannitol is a low molecular weight compound and is, therefore, freely filtered at the glomerulus and is not reabsorbed. It, therefore, increases the osmolality of the glomerular filtrate and tubular fluid, increasing urinary volume by an osmotic effect. It also does not cross the blood-brain-barrier (BBB).
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
-
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Question 98
Incorrect
-
Regarding hypernatraemia, which of the following statements is INCORRECT:
Your Answer:
Correct Answer: In acute severe hypernatraemia, seizures and intracranial vascular haemorrhage can occur as a result of brain cell lysis.
Explanation:Acute severe hypernatraemia is a medical emergency and requires inpatient management in a high dependency setting. Seizures and intracranial vascular haemorrhage as a result of brain cell crenation can occur. The cause is most commonly excessive water loss and the key aspect of treatment is aggressive fluid replacement (typically with normal saline as this is relatively hypotonic). If urine osmolality is low, diabetes insipidus (DI )should be considered and a trial of synthetic ADH given. In patients with known DI, it is essential to ensure synthetic ADH is given parenterally and that close fluid balance is observed.
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This question is part of the following fields:
- Endocrine
- Physiology
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Question 99
Incorrect
-
Regarding airway resistance, which of the following statements is CORRECT:
Your Answer:
Correct Answer: Airway resistance is predominantly determined by the radius of the airway as described by Poiseuille's law.
Explanation:Flow through airways is described by Darcy’s law which states that flow is directly proportional to the mouth-alveolar pressure gradient and inversely proportional to airway resistance. Airway resistance is primarily determined by the airway radius according to Poiseuille’s law, and whether the flow is laminar or turbulent. Parasympathetic stimulation causes bronchoconstriction and sympathetic stimulation causes bronchodilation, but mediated by beta2-adrenoceptors. Muscarinic antagonists e.g. ipratropium bromide cause bronchodilation.
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 100
Incorrect
-
All of the following statement about the microcirculation are correct except:
Your Answer:
Correct Answer: Over the capillary bed, there is a net absorption of fluid.
Explanation:The hydrostatic pressure along the length of the capillary is usually greater than plasma oncotic pressure. As a result, there is a small net filtration of fluid from the capillary into the interstitial space. The regulation of blood flow into the microcirculation is via the vasoconstriction of small arterioles, which is activated by the sympathetic nervous system through numerous nerve endings in their walls. Unlike proteins, most ions and small molecules diffuse easily across capillary walls and thus the crystalloid osmotic pressure they exert is roughly the same on either side of the capillary wall. Because the plasma colloid osmotic pressure is higher than interstitial colloid osmotic, fluid is drawn intravascularly. A reduction of hydrostatic capillary pressure and transient increase in absorption of fluid is a result of arteriolar constriction.
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This question is part of the following fields:
- Cardiovascular
- Physiology
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SESSION STATS - PERFORMANCE PER SPECIALTY
