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  • Question 1 - Which of the following options is correct regarding the coagulation pathway? ...

    Correct

    • Which of the following options is correct regarding the coagulation pathway?

      Your Answer: Tissue factor released by damaged tissue initiates the extrinsic pathway

      Explanation:

      The extrinsic pathway is considered as the main pathway of coagulation cascade.

      Heparin is known to inhibit the activation of coagulation factors 2,9,10, and 11.

      The extrinsic and intrinsic pathways meet at the activation of coagulation factor 10.

      Fibrinogen is converted into Fibrin in the presence of Thrombin. Plasminogen is converted into plasmin during fibrinolysis to breakdown fibrin clot.

    • This question is part of the following fields:

      • Physiology And Biochemistry
      71
      Seconds
  • Question 2 - A 60-year old male has anaemia and is being investigated. The most common...

    Correct

    • A 60-year old male has anaemia and is being investigated. The most common combination of globin chains in a normal adult is:

      Your Answer: ?2?2

      Explanation:

      There are 4 different types of globin chains which surround 4 heme molecules in haemoglobin (Hb) – ?, ?, ? and ?.
      ? chains are essential.
      ?2?2 and ?2?2 are not found in a healthy adult.
      97% of the Hb in a healthy adult is made of ?2?2 (2 ? chains and 2 ? chains).
      ?2?2 accounts for around 1.5-3% of the adult Hb.
      ?2?2 accounts for less than 1%.

      With respect to oxygen transport in cells, almost all oxygen is transported within erythrocytes. There is limited solubility and only 1% is carried as solution. Thus, the amount of oxygen transported depends upon haemoglobin concentration and its degree of saturation.

      Haemoglobin is a globular protein composed of 4 subunits. Haem is made up of a protoporphyrin ring surrounding an iron atom in its ferrous state. The iron can form two additional bonds – one is with oxygen and the other with a polypeptide chain.
      There are two alpha and two beta subunits to this polypeptide chain in an adult and together these form globin. Globin cannot bind oxygen but can bind to CO2 and hydrogen ions.
      The beta chains are able to bind to 2,3 diphosphoglycerate. The oxygenation of haemoglobin is a reversible reaction. The molecular shape of haemoglobin is such that binding of one oxygen molecule facilitates the binding of subsequent molecules.

      The oxygen dissociation curve (ODC) describes the relationship between the percentage of saturated haemoglobin and partial pressure of oxygen in the blood.
      Of note, it is not affected by haemoglobin concentration.

      Chronic anaemia causes 2, 3 DPG levels to increase, hence shifting the curve to the right

      Haldane effect – Causes the ODC to shift to the left. For a given oxygen tension there is increased saturation of Hb with oxygen i.e. Decreased oxygen delivery to tissues.
      This can be caused by:
      -HbF, methaemoglobin, carboxyhaemoglobin
      -low [H+] (alkali)
      -low pCO2
      -ow 2,3-DPG
      -ow temperature

      Bohr effect – causes the ODC to shifts to the right = for given oxygen tension there is reduced saturation of Hb with oxygen i.e. Enhanced oxygen delivery to tissues. This can be caused by:
      – raised [H+] (acidic)
      – raised pCO2
      -raised 2,3-DPG
      -raised temperature

    • This question is part of the following fields:

      • Physiology And Biochemistry
      16.9
      Seconds
  • Question 3 - A 30-year old male has Von Willebrand's disease and attends the hospital to...

    Incorrect

    • A 30-year old male has Von Willebrand's disease and attends the hospital to get an infusion of desmopressin acetate. The way this works is by stimulating the release of von Willebrand factor from cells, which in turn increases factor VIII and platelet plug formation in clotting.

      In patients that have no clotting abnormalities, the substance that keeps the blood soluble and prevents platelet activation normally is which of these?

      Your Answer: Thromboxane

      Correct Answer: Prostacyclin

      Explanation:

      Even though aprotinin reduces fibrinolysis and therefore bleeding, there is an associated increased risk of death. It was withdrawn in 2007.
      Protein C is dependent upon vitamin K and this may paradoxically increase the risk of thrombosis during the early phases of warfarin treatment.

      The coagulation cascade include two pathways which lead to fibrin formation:
      1. Intrinsic pathway – these components are already present in the blood
      Minor role in clotting
      Subendothelial damage e.g. collagen
      Formation of the primary complex on collagen by high-molecular-weight kininogen (HMWK), prekallikrein, and Factor 12
      Prekallikrein is converted to kallikrein and Factor 12 becomes activated
      Factor 12 activates Factor 11
      Factor 11 activates Factor 9, which with its co-factor Factor 8a form the tenase complex which activates Factor 10

      2. Extrinsic pathway – needs tissue factor that is released by damaged tissue)
      In tissue damage:
      Factor 7 binds to Tissue factor – this complex activates Factor 9
      Activated Factor 9 works with Factor 8 to activate Factor 10

      3. Common pathway
      Activated Factor 10 causes the conversion of prothrombin to thrombin and this hydrolyses fibrinogen peptide bonds to form fibrin. It also activates factor 8 to form links between fibrin molecules.

      4. Fibrinolysis
      Plasminogen is converted to plasmin to facilitate clot resorption

    • This question is part of the following fields:

      • Physiology And Biochemistry
      56.2
      Seconds
  • Question 4 - A 63-year old male who has heart failure has peripheral oedema and goes...

    Incorrect

    • A 63-year old male who has heart failure has peripheral oedema and goes to the GP's office. The GP notes that he is fluid-overloaded. This causes his atrial myocytes to release atrial natriuretic peptide (ANP). ANP's main action is by which of these mechanisms?

      Your Answer: Promote sodium reabsorption

      Correct Answer: Antagonist of angiotensin II

      Explanation:

      Atrial natriuretic peptide (ANP) is secreted mainly from myocytes of right atrium and ventricle in response to increased blood volume.
      It is secreted by both the right and left atria (right >> left).

      It is a 28 amino acid peptide hormone, which acts via cGMP
      degraded by endopeptidases.

      It serves to promote the excretion of sodium, lowers blood pressure, and antagonise the actions of angiotensin II and aldosterone.

    • This question is part of the following fields:

      • Physiology And Biochemistry
      35.8
      Seconds
  • Question 5 - All of the following are causes of hypalbuminaemia except: ...

    Incorrect

    • All of the following are causes of hypalbuminaemia except:

      Your Answer: Major surgery

      Correct Answer: Starvation

      Explanation:

      Major surgery induces the systemic inflammatory response and this causes endothelial leakage and a low albumin level.

      Albumin is a single polypeptide which is made but not stored in the liver. Therefore, levels are a reflection of synthetic activity. It is negatively charged and very soluble.

      Only 40% of albumin is intravascular, and the rest in the in interstitial compartment.

      If there was normal liver function during starvation, albumin will be maintained and proteolysis will occur elsewhere.
      It is not catabolised during starvation.
      Starvation and malnutrition may, however, present as part of other disease processes that are associated with hypalbuminaemia.

      Causes of low albumin are

      1. Decreased production (hepatic dysfunction)
      2. Increased loss (renal dysfunction)
      3. Redistribution (endothelial leak/damage)
      4. Increased catabolism (very rare)

    • This question is part of the following fields:

      • Physiology And Biochemistry
      32.5
      Seconds
  • Question 6 - The main action of atrial natriuretic peptide is: ...

    Incorrect

    • The main action of atrial natriuretic peptide is:

      Your Answer: Vasoconstriction

      Correct Answer: Vasodilation

      Explanation:

      Atrial natriuretic peptide (ANP) is secreted mainly from myocytes of right atrium and ventricle in response to increased blood volume.
      It is secreted by both the right and left atria (right >> left).

      It is a 28 amino acid peptide hormone, which acts via cGMP
      degraded by endopeptidases.

      It serves to promote the excretion of sodium, lowers blood pressure, and antagonise the actions of angiotensin II and aldosterone.

    • This question is part of the following fields:

      • Physiology And Biochemistry
      75
      Seconds
  • Question 7 - A 40-year old gentleman has palpitations and has gone to the emergency department....

    Correct

    • A 40-year old gentleman has palpitations and has gone to the emergency department. He is found to have monomorphic ventricular tachycardia. The resting potential of ventricular monocytes is maintained by which electrolyte?

      Your Answer: Potassium

      Explanation:

      Potassium maintains the resting potential of cardiac myocytes, with depolarization triggered by a rapid influx of sodium ions, and repolarization due to efflux of potassium. A slow influx of calcium is responsible for the longer duration of a cardiac action potential compared with skeletal muscle.

      The cardiac action potential has several phases which have different mechanisms of action as seen below:

      Phase 0: Rapid depolarisation – caused by a rapid sodium influx.
      These channels automatically deactivate after a few ms.

      Phase 1: caused by early repolarisation and an efflux of potassium.

      Phase 2: Plateau – caused by a slow influx of calcium.

      Phase 3 – Final repolarisation – caused by an efflux of potassium.

      Phase 4 – Restoration of ionic concentrations – The resting potential is restored by Na+/K+ATPase.
      There is slow entry of Na+into the cell which decreases the potential difference until the threshold potential is reached. This then triggers a new action potential

      Of note, cardiac muscle remains contracted 10-15 times longer than skeletal muscle.

      Different sites have different conduction velocities:
      1. Atrial conduction – Spreads along ordinary atrial myocardial fibres at 1 m/sec

      2. AV node conduction – 0.05 m/sec

      3. Ventricular conduction – Purkinje fibres are of large diameter and achieve velocities of 2-4 m/sec, the fastest conduction in the heart. This allows a rapid and coordinated contraction of the ventricles

    • This question is part of the following fields:

      • Physiology And Biochemistry
      22.1
      Seconds
  • Question 8 - A normal woman at term, not in labour, has her arterial blood gas...

    Correct

    • A normal woman at term, not in labour, has her arterial blood gas analysed.

      Which set of results is most likely her own?

      Option - pH - PaCO2 - HCO3 - PaO2
      A - 7.35 - 28 mmHg (3.73 kPa) - 27 mmol/L - 104 mmHg (13.8kPa)
      B - 7.43 - 32 mmHg (4.27 kPa) - 21 mmol/L - 104 mmHg (13.8kPa)
      C - 7.44 - 36 mmHg (4.8 kPa) - 27 mmol/L - 104 mmHg (13.8kPa)
      D - 7.45 - 40 mmHg (5.33 kPa) - 21 mmol/L - 104 mmHg (13.8kPa)
      E - 7.46 - 44 mmHg (5.87kPa) - 21 mmol/L - 104 mmHg (13.8kPa)

      Your Answer: B

      Explanation:

      Due to an increased tidal volume with little change or slight increase in respiratory rate, Minute ventilation at term is increased by about 50%. Hypothalamic function are thought to influence by Progesterone, oestradiol and prostaglandins. This causes a mild compensated respiratory alkalosis.

      Maternal PaCO2 is usually decreased to about 32 mmHg (4.27 kPa) as a result of this increased alveolar ventilation at term . A compensatory decrease in serum bicarbonate from 27 to 21 mmol/L by renal excretion lessens the impact of maternal alkalosis.

    • This question is part of the following fields:

      • Physiology And Biochemistry
      126.4
      Seconds
  • Question 9 - All of the following are true when describing the autonomic nervous system except:...

    Incorrect

    • All of the following are true when describing the autonomic nervous system except:

      Your Answer: The sympathetic trunk begins at the base of the skull and extends to the coccyx

      Correct Answer: Juxta glomerular apparatus, piloerector muscles and adipose tissue are all organs under sole parasympathetic control

      Explanation:

      With regards to the autonomic nervous system (ANS)

      1. It is not under voluntary control
      2. It uses reflex pathways and different to the somatic nervous system.
      3. The hypothalamus is the central point of integration of the ANS. However, the gut can coordinate some secretions and information from the baroreceptors which are processed in the medulla.

      With regards to the central nervous system (CNS)
      1. There are myelinated preganglionic fibres which lead to the
      ganglion where the nerve cell bodies of the non-myelinated post ganglionic nerves are organised.
      2. From the ganglion, the post ganglionic nerves then lead on to the innervated organ.

      Most organs are under control of both systems although one system normally predominates.

      The nerves of the sympathetic nervous system (SNS) originate from the lateral horns of the spinal cord, pass into the anterior primary rami and then pass via the white rami communicates into the ganglia from T1-L2.

      There are short pre-ganglionic and long post ganglionic fibres.
      Pre-ganglionic synapses use acetylcholine (ACh) as a neurotransmitter on nicotinic receptors.
      Post ganglionic synapses uses adrenoceptors with norepinephrine / epinephrine as the neurotransmitter.
      However, in sweat glands, piloerector muscles and few blood vessels, ACh is still used as a neurotransmitter with nicotinic receptors.

      The ganglia form the sympathetic trunk – this is a collection of nerves that begin at the base of the skull and travel 2-3 cm lateral to the vertebrae, extending to the coccyx.

      There are cervical, thoracic, lumbar and sacral ganglia and visceral sympathetic innervation is by cardiac, coeliac and hypogastric plexi.

      Juxta glomerular apparatus, piloerector muscles and adipose tissue are all organs under sole sympathetic control.

      The PNS has a craniosacral outflow. It causes reduced arousal and cardiovascular stimulation and increases visceral activity.

      The cranial outflow consists of
      1. The oculomotor nerve (CN III) to the eye via the ciliary ganglion,
      2. Facial nerve (CN VII) to the submandibular, sublingual and lacrimal glands via the pterygopalatine and submandibular ganglions
      3. Glossopharyngeal (CN IX) to lungs, larynx and tracheobronchial tree via otic ganglion
      4. The vagus nerve (CN X), the largest contributor and carries ¾ of fibres covering innervation of the heart, lungs, larynx, tracheobronchial tree parotid gland and proximal gut to the splenic flexure, liver and pancreas

      The sacral outflow (S2 to S4) innervates the bladder, distal gut and genitalia.

      The PNS has long preganglionic and short post ganglionic fibres.
      Preganglionic synapses, like in the SNS, use ACh as the neuro transmitter with nicotinic receptors.
      Post ganglionic synapses also use ACh as the neurotransmitter but have muscarinic receptors.

      Different types of these muscarinic receptors are present in different organs:
      There are:
      M1 = pupillary constriction, gastric acid secretion stimulation
      M2 = inhibition of cardiac stimulation
      M3 = visceral vasodilation, coronary artery constriction, increased secretions in salivary, lacrimal glands and pancreas
      M4 = brain and adrenal medulla
      M5 = brain

      The lacrimal glands are solely under parasympathetic control.

    • This question is part of the following fields:

      • Physiology And Biochemistry
      179.5
      Seconds
  • Question 10 - Which statement regarding the cardiac action potential is correct? ...

    Incorrect

    • Which statement regarding the cardiac action potential is correct?

      Your Answer:

      Correct Answer:

      Explanation:

      Cardiac conduction

      Phase 0 – Rapid depolarization. Opening of fast sodium channels with large influx of sodium

      Phase 1 – Rapid partial depolarization. Opening of potassium channels and efflux of potassium ions. Sodium channels close and influx of sodium ions stop

      Phase 2 – Plateau phase with large influx of calcium ions. Offsets action of potassium channels. The absolute refractory period

      Phase 3 – Repolarization due to potassium efflux after calcium channels close. Relative refractory period

      Phase 4 – Repolarization continues as sodium/potassium pump restores the ionic gradient by pumping out 3 sodium ions in exchange for 2 potassium ions coming into the cell. Relative refractory period

    • This question is part of the following fields:

      • Physiology And Biochemistry
      0
      Seconds
  • Question 11 - A patient's ECG is abnormal, with an abnormal broad complex QRS complexes. This...

    Incorrect

    • A patient's ECG is abnormal, with an abnormal broad complex QRS complexes. This means either a ventricular origin problem or aberrant conduction. The normal resting membrane potential of the heart's ventricular contractile fibres is which of the following?

      Your Answer:

      Correct Answer: -90mV

      Explanation:

      The cardiac muscle’s contractile fibres have a much more stable resting potential than its conductive fibres. In the ventricular fibres it is -90mV and in the atrial fibres it is -80mV.

      The cardiac action potential has several phases which have different mechanisms of action as seen below:

      Phase 0: Rapid depolarisation – caused by a rapid sodium influx.
      These channels automatically deactivate after a few ms. (QRS complex)

      Phase 1: caused by early repolarisation and an efflux of potassium.

      Phase 2: Plateau – caused by a slow influx of calcium.

      Phase 3 – Final repolarisation – caused by an efflux of potassium.

      Phase 4 – Restoration of ionic concentrations – The resting potential is restored by Na+/K+ATPase.
      There is slow entry of Na+into the cell which decreases the potential difference until the threshold potential is reached. This then triggers a new action potential

      Of note, cardiac muscle remains contracted 10-15 times longer than skeletal muscle.

      Different sites have different conduction velocities:
      1. Atrial conduction – Spreads along ordinary atrial myocardial fibres at 1 m/sec

      2. AV node conduction – 0.05 m/sec

      3. Ventricular conduction – Purkinje fibres are of large diameter and achieve velocities of 2-4 m/sec, the fastest conduction in the heart. This allows a rapid and coordinated contraction of the ventricles

    • This question is part of the following fields:

      • Physiology And Biochemistry
      0
      Seconds
  • Question 12 - Which of the following causes the right-sided shift of the oxygen haemoglobin dissociation...

    Incorrect

    • Which of the following causes the right-sided shift of the oxygen haemoglobin dissociation curve?

      Your Answer:

      Correct Answer: Chronic iron deficiency anaemia

      Explanation:

      With respect to oxygen transport in cells, almost all oxygen is transported within erythrocytes. There is limited solubility and only 1% is carried as solution. Thus, the amount of oxygen transported depends upon haemoglobin concentration and its degree of saturation.

      Haemoglobin is a globular protein composed of 4 subunits. Haem is made up of a protoporphyrin ring surrounding an iron atom in its ferrous state. The iron can form two additional bonds – one is with oxygen and the other with a polypeptide chain.
      There are two alpha and two beta subunits to this polypeptide chain in an adult and together these form globin. Globin cannot bind oxygen but can bind to CO2 and hydrogen ions.
      The beta chains are able to bind to 2,3 diphosphoglycerate. The oxygenation of haemoglobin is a reversible reaction. The molecular shape of haemoglobin is such that binding of one oxygen molecule facilitates the binding of subsequent molecules.

      The oxygen dissociation curve (ODC) describes the relationship between the percentage of saturated haemoglobin and partial pressure of oxygen in the blood.
      Of note, it is not affected by haemoglobin concentration.

      Chronic anaemia causes 2, 3 DPG levels to increase, hence shifting the curve to the right

      Haldane effect – Causes the ODC to shift to the left. For a given oxygen tension there is increased saturation of Hb with oxygen i.e. Decreased oxygen delivery to tissues.
      This can be caused by:
      -HbF, methaemoglobin, carboxyhaemoglobin
      -low [H+] (alkali)
      -low pCO2
      -ow 2,3-DPG
      -ow temperature

      Bohr effect – causes the ODC to shifts to the right = for given oxygen tension there is reduced saturation of Hb with oxygen i.e. Enhanced oxygen delivery to tissues. This can be caused by:
      – raised [H+] (acidic)
      – raised pCO2
      -raised 2,3-DPG
      -raised temperature

    • This question is part of the following fields:

      • Physiology And Biochemistry
      0
      Seconds
  • Question 13 - With regards to oxygen delivery in the body, which of these statements is...

    Incorrect

    • With regards to oxygen delivery in the body, which of these statements is true?

      Your Answer:

      Correct Answer: Anaemia will reduce oxygen delivery

      Explanation:

      Oxygen delivery depends on 2 variables.
      1) Content of oxygen in blood
      2) Cardiac output

      Oxygen content (arterial) = (Hb (g/dL) x 1.39 x SaO2 (%) ) + (0.023 x PaO2 (kPa))

      Oxygen content (mixed venous) = (Hb (g/dL) x 1.39 x mixed venous saturation) + (0.023 x mixed venous partial pressure of oxygen in kPA)

      Huffner’s constant = 1.39 = 1g of Hb binds to 1.39 ml of O2

      Oxygen delivery DO2 (ml/min) = 10 x Cardiac output (L/min) x Oxygen content
      Normally 1000ml/min

      Oxygen consumption VO2 (ml/min) = 10 x Cardiac output (L/min) x Difference in arterial and mixed venous oxygen content
      Normally 250 ml/min

      Oxygen extraction ratio (OER) = VO2/DO2
      Normally approximately 25%

    • This question is part of the following fields:

      • Physiology And Biochemistry
      0
      Seconds
  • Question 14 - A 89-year old male has hypertension, with a blood pressure of 170/68 mmHg...

    Incorrect

    • A 89-year old male has hypertension, with a blood pressure of 170/68 mmHg and has been admitted to the hospital. He is on no regular medications. His large pulse pressure can be accounted for by which of the following?

      Your Answer:

      Correct Answer: Reduced aortic compliance

      Explanation:

      Cardiac output = stroke volume x heart rate

      Left ventricular ejection fraction = (stroke volume / end diastolic LV volume ) x 100%

      Stroke volume = end diastolic LV volume – end systolic LV volume

      Pulse pressure = Systolic Pressure – Diastolic Pressure

      Systemic vascular resistance = mean arterial pressure / cardiac output
      Factors that increase pulse pressure include:
      -a less compliant aorta (this tends to occur with advancing age)
      -increased stroke volume

    • This question is part of the following fields:

      • Physiology And Biochemistry
      0
      Seconds
  • Question 15 - Prophylactic antibiotics are required for which of the following procedures? ...

    Incorrect

    • Prophylactic antibiotics are required for which of the following procedures?

      Your Answer:

      Correct Answer: Caesarean section

      Explanation:

      Staphylococcus aureus infection is the most likely cause.

      Surgical site infections (SSI) occur when there is a breach in tissue surfaces and allow normal commensals and other pathogens to initiate infection. They are a major cause of morbidity and mortality.

      SSI comprise up to 20% of healthcare associated infections and approximately 5% of patients undergoing surgery will develop an SSI as a result.
      The organisms are usually derived from the patient’s own body.

      Measures that may increase the risk of SSI include:
      -Shaving the wound using a single use electrical razor with a disposable head
      -Using a non iodine impregnated surgical drape if one is needed
      -Tissue hypoxia
      -Delayed prophylactic antibiotics administration in tourniquet surgery, patients with a prosthesis or valve, in clean-contaminated surgery of in contaminated surgery.

      Measures that may decrease the risk of SSI include:
      1. Intraoperatively
      – Prepare the skin with alcoholic chlorhexidine (Lowest incidence of SSI)
      -Cover surgical site with dressing

      In contrast to previous individual RCT’s, a recent meta analysis has confirmed that administration of supplementary oxygen does not reduce the risk of wound infection and wound edge protectors do not appear to confer benefit.

      2. Post operatively
      Tissue viability advice for management of surgical wounds healing by secondary intention

      Use of diathermy for skin incisions
      In the NICE guidelines the use of diathermy for skin incisions is not advocated. Several randomised controlled trials have been undertaken and demonstrated no increase in risk of SSI when diathermy is used.

    • This question is part of the following fields:

      • Physiology And Biochemistry
      0
      Seconds
  • Question 16 - A 45-year old male who was involved in a road traffic accident has...

    Incorrect

    • A 45-year old male who was involved in a road traffic accident has had to receive a large blood transfusion of whole blood which is two weeks old. Which of these best describes the oxygen carrying capacity of this blood?

      Your Answer:

      Correct Answer: It will have an increased affinity for oxygen

      Explanation:

      With respect to oxygen transport in cells, almost all oxygen is transported within erythrocytes. There is limited solubility and only 1% is carried as solution. Thus, the amount of oxygen transported depends upon haemoglobin concentration and its degree of saturation.

      Haemoglobin is a globular protein composed of 4 subunits. Haem is made up of a protoporphyrin ring surrounding an iron atom in its ferrous state. The iron can form two additional bonds – one is with oxygen and the other with a polypeptide chain.
      There are two alpha and two beta subunits to this polypeptide chain in an adult and together these form globin. Globin cannot bind oxygen but can bind to CO2 and hydrogen ions.
      The beta chains are able to bind to 2,3 diphosphoglycerate. The oxygenation of haemoglobin is a reversible reaction. The molecular shape of haemoglobin is such that binding of one oxygen molecule facilitates the binding of subsequent molecules.

      The oxygen dissociation curve (ODC) describes the relationship between the percentage of saturated haemoglobin and partial pressure of oxygen in the blood.
      Of note, it is not affected by haemoglobin concentration.

      Chronic anaemia causes 2, 3 DPG levels to increase, hence shifting the curve to the right

      Haldane effect – Causes the ODC to shift to the left. For a given oxygen tension there is increased saturation of Hb with oxygen i.e. Decreased oxygen delivery to tissues.
      This can be caused by:
      -HbF, methaemoglobin, carboxyhaemoglobin
      -low [H+] (alkali)
      -low pCO2
      -ow 2,3-DPG
      -ow temperature

      Bohr effect – causes the ODC to shifts to the right = for given oxygen tension there is reduced saturation of Hb with oxygen i.e. Enhanced oxygen delivery to tissues. This can be caused by:
      – raised [H+] (acidic)
      – raised pCO2
      -raised 2,3-DPG
      -raised temperature

    • This question is part of the following fields:

      • Physiology And Biochemistry
      0
      Seconds
  • Question 17 - The plateau phase of the myocardial action potential is as a result of:...

    Incorrect

    • The plateau phase of the myocardial action potential is as a result of:

      Your Answer:

      Correct Answer: Slow influx of calcium

      Explanation:

      Cardiac conduction

      Phase 0 – Rapid depolarization. Opening of fast sodium channels with large influx of sodium

      Phase 1 – Rapid partial depolarization. Opening of potassium channels and efflux of potassium ions. Sodium channels close and influx of sodium ions stop

      Phase 2 – Plateau phase with large influx of calcium ions. Offsets action of potassium channels. The absolute refractory period

      Phase 3 – Repolarization due to potassium efflux after calcium channels close. Relative refractory period

      Phase 4 – Repolarization continues as sodium/potassium pump restores the ionic gradient by pumping out 3 sodium ions in exchange for 2 potassium ions coming into the cell. Relative refractory period

    • This question is part of the following fields:

      • Physiology And Biochemistry
      0
      Seconds
  • Question 18 - The tip of a pulmonary artery flotation catheter becomes wedged when threaded through...

    Incorrect

    • The tip of a pulmonary artery flotation catheter becomes wedged when threaded through the chambers of the heart and the pulmonary artery.

      Which of the following options best describes the sequence of pressures measured at the catheter's tip during its passage through a normal patient's pulmonary artery?

      Your Answer:

      Correct Answer: 0-12 mmHg, 2-25 mmHg, 12-25 mmHg and 8-12 mmHg

      Explanation:

      The tricuspid valve allows the tip of a pulmonary artery catheter to pass through the right atrium and into the right ventricle.

      The balloon will be inflated before crossing the pulmonary valve and entering the pulmonary artery, where it will eventually wedge or occlude the artery, providing an indirect measure of left atrial pressure.

      0-12 mmHg in the right atrium
      2-25 mmHg in the right ventricle
      12-25 mmHg in the pulmonary artery
      8-12 mmHg is the occlusion pressure

    • This question is part of the following fields:

      • Physiology And Biochemistry
      0
      Seconds
  • Question 19 - Seven days after undergoing an inguinal hernia repair, a 24-year old male presents...

    Incorrect

    • Seven days after undergoing an inguinal hernia repair, a 24-year old male presents with a wound that is erythematous, tender and has a purulent discharge. The most likely cause of this is which of the following?

      Your Answer:

      Correct Answer: Infection with Staphylococcus aureus

      Explanation:

      Staphylococcus aureus infection is the most likely cause.

      Surgical site infections (SSI) occur when there is a breach in tissue surfaces and allow normal commensals and other pathogens to initiate infection. They are a major cause of morbidity and mortality.

      SSI comprise up to 20% of healthcare associated infections and approximately 5% of patients undergoing surgery will develop an SSI as a result.
      The organisms are usually derived from the patient’s own body.

      Measures that may increase the risk of SSI include:
      -Shaving the wound using a single use electrical razor with a disposable head
      -Using a non iodine impregnated surgical drape if one is needed
      -Tissue hypoxia
      -Delayed prophylactic antibiotics administration in tourniquet surgery, patients with a prosthesis or valve, in clean-contaminated surgery of in contaminated surgery.

      Measures that may decrease the risk of SSI include:
      1. Intraoperatively
      – Prepare the skin with alcoholic chlorhexidine (Lowest incidence of SSI)
      -Cover surgical site with dressing

      In contrast to previous individual RCT’s, a recent meta analysis has confirmed that administration of supplementary oxygen does not reduce the risk of wound infection and wound edge protectors do not appear to confer benefit.

      2. Post operatively
      Tissue viability advice for management of surgical wounds healing by secondary intention

      Use of diathermy for skin incisions
      In the NICE guidelines the use of diathermy for skin incisions is not advocated. Several randomised controlled trials have been undertaken and demonstrated no increase in risk of SSI when diathermy is used.

    • This question is part of the following fields:

      • Physiology And Biochemistry
      0
      Seconds
  • Question 20 - All of the following statements are true about blood clotting except: ...

    Incorrect

    • All of the following statements are true about blood clotting except:

      Your Answer:

      Correct Answer: Administration of aprotinin during liver transplantation surgery prolongs survival

      Explanation:

      Even though aprotinin reduces fibrinolysis and therefore bleeding, there is an associated increased risk of death. It was withdrawn in 2007.
      Protein C is dependent upon vitamin K and this may paradoxically increase the risk of thrombosis during the early phases of warfarin treatment.

      The coagulation cascade include two pathways which lead to fibrin formation:
      1. Intrinsic pathway – these components are already present in the blood
      Minor role in clotting
      Subendothelial damage e.g. collagen
      Formation of the primary complex on collagen by high-molecular-weight kininogen (HMWK), prekallikrein, and Factor 12
      Prekallikrein is converted to kallikrein and Factor 12 becomes activated
      Factor 12 activates Factor 11
      Factor 11 activates Factor 9, which with its co-factor Factor 8a form the tenase complex which activates Factor 10

      2. Extrinsic pathway – needs tissue factor that is released by damaged tissue)
      In tissue damage:
      Factor 7 binds to Tissue factor – this complex activates Factor 9
      Activated Factor 9 works with Factor 8 to activate Factor 10

      3. Common pathway
      Activated Factor 10 causes the conversion of prothrombin to thrombin and this hydrolyses fibrinogen peptide bonds to form fibrin. It also activates factor 8 to form links between fibrin molecules.

      4. Fibrinolysis
      Plasminogen is converted to plasmin to facilitate clot resorption

    • This question is part of the following fields:

      • Physiology And Biochemistry
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  • Question 21 - A 63-year old man has palpitations and goes to the emergency room. An...

    Incorrect

    • A 63-year old man has palpitations and goes to the emergency room. An ECG shows tall tented T waves, which corresponds to phase 3 of the cardiac action potential.
      The shape of the T wave is as a result of which of the following?

      Your Answer:

      Correct Answer: Repolarisation due to efflux of potassium

      Explanation:

      Cardiac conduction

      Phase 0 – Rapid depolarization. Opening of fast sodium channels with large influx of sodium

      Phase 1 – Rapid partial depolarization. Opening of potassium channels and efflux of potassium ions. Sodium channels close and influx of sodium ions stop

      Phase 2 – Plateau phase with large influx of calcium ions. Offsets action of potassium channels. The absolute refractory period

      Phase 3 – Repolarization due to potassium efflux after calcium channels close. Relative refractory period

      Phase 4 – Repolarization continues as sodium/potassium pump restores the ionic gradient by pumping out 3 sodium ions in exchange for 2 potassium ions coming into the cell. Relative refractory period

    • This question is part of the following fields:

      • Physiology And Biochemistry
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  • Question 22 - All of the following are responses to massive haemorrhage except which of the...

    Incorrect

    • All of the following are responses to massive haemorrhage except which of the following?

      Your Answer:

      Correct Answer: Decreased cardiac output by increased direct parasympathetic stimulation

      Explanation:

      With regards to compensatory response to blood loss, the following sequence of events take place:

      1. Decrease in venous return, right atrial pressure and cardiac output
      2. Baroreceptor reflexes (carotid sinus and aortic arch) are immediately activated
      3. There is decreased afferent input to the cardiovascular centre in medulla. This inhibits parasympathetic reflexes and increases sympathetic response
      4. This results in an increased cardiac output and increased SVR by direct sympathetic stimulation. There is increased circulating catecholamines and local tissue mediators (adenosine, potassium, NO2)
      5. Fluid moves into the intravascular space as a result of decreased capillary hydrostatic pressure absorbing interstitial fluid.

      A slower response is mounted by the hypothalamus-pituitary-adrenal axis.
      6. Reduced renal blood flow is sensed by the intra renal baroreceptors and this stimulates release of renin by the juxta-glomerular apparatus.
      7. There is cleavage of circulating Angiotensinogen to Angiotensin I, which is converted to Angiotensin II in the lungs (by Angiotensin Converting Enzyme ACE)

      Angiotensin II is a powerful vasoconstrictor that sets off other endocrine pathways.
      8. The adrenal cortex releases Aldosterone
      9. There is antidiuretic hormone release from posterior pituitary (also in response to hypovolaemia being sensed by atrial stretch receptors)
      10. This leads to sodium and water retention in the distal convoluted renal tubule to conserve fluid
      Fluid conservation is also aided by an increased amount of cortisol which is secreted in response to the increase in circulating catecholamines and sympathetic stimulation.

    • This question is part of the following fields:

      • Physiology And Biochemistry
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  • Question 23 - A 74-year old male who has a history of heart failure has an...

    Incorrect

    • A 74-year old male who has a history of heart failure has an exacerbation of his symptoms and goes to the ED. An ultrasound scan is done which shows that there is a decrease in his stroke volume. Which of these choices would one expect to increase his stroke volume0

      Your Answer:

      Correct Answer: Respiratory inspiration

      Explanation:

      Respiratory inspiration causes a decreased pressure in the thoracic cavity, which in turn causes more blood to flow into the atrium.

      Sitting up decreases venous because of the action of gravity on blood in the venous system.
      Hypotension also decreases venous return.
      A less compliant aorta, like in aortic stenosis increases end systolic left ventricular volume which decreases stroke volume.

      Systemic vascular resistance = mean arterial pressure / cardiac output. Increased vascular resistance impedes the flow of blood back to the heart.

      Increased venous return increases end diastolic LV volume as there is more blood returning to the ventricles.

    • This question is part of the following fields:

      • Physiology And Biochemistry
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  • Question 24 - A 25-year old male with palpitations and dizziness presents to the emergency room....

    Incorrect

    • A 25-year old male with palpitations and dizziness presents to the emergency room. In the triage process, cardiac monitoring shows supraventricular tachycardia with a heart rate of 200 beats per minute. This high heart rate arises as a result of different specialised cells and nerve fibres in the heart which are responsible for conducting that action potential which is generated in the event of systole.
      The fastest conduction velocity is carried out by which of the following?

      Your Answer:

      Correct Answer: Purkinje fibres

      Explanation:

      The correct answer is the Purkinje fibres, which conducts at a velocity of about 4m/sec.

      The electrical conduction system of the heart starts with the SA node which generates spontaneous action potentials.

      This is conducted across both atria by cell to cell conduction, and occurs at around 1 m/s. The only pathway for the action potential to enter the ventricles is through the AV node in a normal heart.
      At this site, conduction is very slow at 0.05ms, which allows for the atria to completely contract and fill the ventricles with blood before the ventricles depolarise and contract.

      The action potentials are conducted through the Bundle of His from the AV node which then splits into the left and right bundle branches. This conduction is very fast, (,2m/s), and brings the action potential to the Purkinje fibres.

      Purkinje fibres are specialised conducting cells which allow for a faster conduction speed of the action potential (,2-4m/s). This allows for a strong synchronized contraction from the ventricle and thus efficient generation of pressure in systole.

    • This question is part of the following fields:

      • Physiology And Biochemistry
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  • Question 25 - All of the following statements about that parasympathetic nervous system (PNS) are true...

    Incorrect

    • All of the following statements about that parasympathetic nervous system (PNS) are true except:

      Your Answer:

      Correct Answer: The PNS has nicotinic receptors throughout the system

      Explanation:

      With regards to the autonomic nervous system (ANS)

      1. It is not under voluntary control
      2. It uses reflex pathways and different to the somatic nervous system.
      3. The hypothalamus is the central point of integration of the ANS. However, the gut can coordinate some secretions and information from the baroreceptors which are processed in the medulla.

      With regards to the central nervous system (CNS)
      1. There are myelinated preganglionic fibres which lead to the
      ganglion where the nerve cell bodies of the non-myelinated post ganglionic nerves are organised.
      2. From the ganglion, the post ganglionic nerves then lead on to the innervated organ.

      Most organs are under control of both systems although one system normally predominates.

      The nerves of the sympathetic nervous system (SNS) originate from the lateral horns of the spinal cord, pass into the anterior primary rami and then pass via the white rami communicates into the ganglia from T1-L2.

      There are short pre-ganglionic and long post ganglionic fibres.
      Pre-ganglionic synapses use acetylcholine (ACh) as a neurotransmitter on nicotinic receptors.
      Post ganglionic synapses uses adrenoceptors with norepinephrine / epinephrine as the neurotransmitter.
      However, in sweat glands, piloerector muscles and few blood vessels, ACh is still used as a neurotransmitter with nicotinic receptors.

      The ganglia form the sympathetic trunk – this is a collection of nerves that begin at the base of the skull and travel 2-3 cm lateral to the vertebrae, extending to the coccyx.

      There are cervical, thoracic, lumbar and sacral ganglia and visceral sympathetic innervation is by cardiac, coeliac and hypogastric plexi.

      Juxta glomerular apparatus, piloerector muscles and adipose tissue are all organs under sole sympathetic control.

      The PNS has a craniosacral outflow. It causes reduced arousal and cardiovascular stimulation and increases visceral activity.

      The cranial outflow consists of
      1. The oculomotor nerve (CN III) to the eye via the ciliary ganglion,
      2. Facial nerve (CN VII) to the submandibular, sublingual and lacrimal glands via the pterygopalatine and submandibular ganglions
      3. Glossopharyngeal (CN IX) to lungs, larynx and tracheobronchial tree via otic ganglion
      4. The vagus nerve (CN X), the largest contributor and carries ¾ of fibres covering innervation of the heart, lungs, larynx, tracheobronchial tree parotid gland and proximal gut to the splenic flexure, liver and pancreas

      The sacral outflow (S2 to S4) innervates the bladder, distal gut and genitalia.

      The PNS has long preganglionic and short post ganglionic fibres.
      Preganglionic synapses, like in the SNS, use ACh as the neuro transmitter with nicotinic receptors.
      Post ganglionic synapses also use ACh as the neurotransmitter but have muscarinic receptors.

      Different types of these muscarinic receptors are present in different organs:
      There are:
      M1 = pupillary constriction, gastric acid secretion stimulation
      M2 = inhibition of cardiac stimulation
      M3 = visceral vasodilation, coronary artery constriction, increased secretions in salivary, lacrimal glands and pancreas
      M4 = brain and adrenal medulla
      M5 = brain

      The lacrimal glands are solely under parasympathetic control.

    • This question is part of the following fields:

      • Physiology And Biochemistry
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  • Question 26 - The rapid depolarisation phase of the myocardial action potential is caused by: ...

    Incorrect

    • The rapid depolarisation phase of the myocardial action potential is caused by:

      Your Answer:

      Correct Answer: Rapid sodium influx

      Explanation:

      The cardiac action potential has several phases which have different mechanisms of action as seen below:
      Phase 0: Rapid depolarisation – caused by a rapid sodium influx.
      These channels automatically deactivate after a few ms

      Phase 1: caused by early repolarisation and an efflux of potassium.

      Phase 2: Plateau – caused by a slow influx of calcium.

      Phase 3 – Final repolarisation – caused by an efflux of potassium.

      Phase 4 – Restoration of ionic concentrations – The resting potential is restored by Na+/K+ATPase.
      There is slow entry of Na+into the cell which decreases the potential difference until the threshold potential is reached. This then triggers a new action potential

      Of note, cardiac muscle remains contracted 10-15 times longer than skeletal muscle.

      Different sites have different conduction velocities:
      1. Atrial conduction – Spreads along ordinary atrial myocardial fibres at 1 m/sec

      2. AV node conduction – 0.05 m/sec

      3. Ventricular conduction – Purkinje fibres are of large diameter and achieve velocities of 2-4 m/sec, the fastest conduction in the heart. This allows a rapid and coordinated contraction of the ventricles

    • This question is part of the following fields:

      • Physiology And Biochemistry
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  • Question 27 - Which statement is true about the autonomic nervous system? ...

    Incorrect

    • Which statement is true about the autonomic nervous system?

      Your Answer:

      Correct Answer: Preganglionic synapse utilise Acetylcholine as the neurotransmitter in both parasympathetic and sympathetic systems

      Explanation:

      With regards to the autonomic nervous system (ANS)

      1. It is not under voluntary control
      2. It uses reflex pathways and different to the somatic nervous system.
      3. The hypothalamus is the central point of integration of the ANS. However, the gut can coordinate some secretions and information from the baroreceptors which are processed in the medulla.

      With regards to the central nervous system (CNS)
      1. There are myelinated preganglionic fibres which lead to the
      ganglion where the nerve cell bodies of the non-myelinated post ganglionic nerves are organised.
      2. From the ganglion, the post ganglionic nerves then lead on to the innervated organ.

      Most organs are under control of both systems although one system normally predominates.

      The nerves of the sympathetic nervous system (SNS) originate from the lateral horns of the spinal cord, pass into the anterior primary rami and then pass via the white rami communicates into the ganglia from T1-L2.

      There are short pre-ganglionic and long post ganglionic fibres.
      Pre-ganglionic synapses use acetylcholine (ACh) as a neurotransmitter on nicotinic receptors.
      Post ganglionic synapses uses adrenoceptors with norepinephrine / epinephrine as the neurotransmitter.
      However, in sweat glands, piloerector muscles and few blood vessels, ACh is still used as a neurotransmitter with nicotinic receptors.

      The ganglia form the sympathetic trunk – this is a collection of nerves that begin at the base of the skull and travel 2-3 cm lateral to the vertebrae, extending to the coccyx.

      There are cervical, thoracic, lumbar and sacral ganglia and visceral sympathetic innervation is by cardiac, coeliac and hypogastric plexi.

      Juxta glomerular apparatus, piloerector muscles and adipose tissue are all organs under sole sympathetic control.

      The PNS has a craniosacral outflow. It causes reduced arousal and cardiovascular stimulation and increases visceral activity.

      The cranial outflow consists of
      1. The oculomotor nerve (CN III) to the eye via the ciliary ganglion,
      2. Facial nerve (CN VII) to the submandibular, sublingual and lacrimal glands via the pterygopalatine and submandibular ganglions
      3. Glossopharyngeal (CN IX) to lungs, larynx and tracheobronchial tree via otic ganglion
      4. The vagus nerve (CN X), the largest contributor and carries ¾ of fibres covering innervation of the heart, lungs, larynx, tracheobronchial tree parotid gland and proximal gut to the splenic flexure, liver and pancreas

      The sacral outflow (S2 to S4) innervates the bladder, distal gut and genitalia.

      The PNS has long preganglionic and short post ganglionic fibres.
      Preganglionic synapses, like in the SNS, use ACh as the neuro transmitter with nicotinic receptors.
      Post ganglionic synapses also use ACh as the neurotransmitter but have muscarinic receptors.

      Different types of these muscarinic receptors are present in different organs:
      There are:
      M1 = pupillary constriction, gastric acid secretion stimulation
      M2 = inhibition of cardiac stimulation
      M3 = visceral vasodilation, coronary artery constriction, increased secretions in salivary, lacrimal glands and pancreas
      M4 = brain and adrenal medulla
      M5 = brain

      The lacrimal glands are solely under parasympathetic control.

    • This question is part of the following fields:

      • Physiology And Biochemistry
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  • Question 28 - While on the ward, you notice a patient that is lying down supine...

    Incorrect

    • While on the ward, you notice a patient that is lying down supine and attached to a monitor is hypotensive with a blood pressure of 90/70mmHg and he is also tachycardic with a pulse of 120 beats/minute. After adjusting the bed with the patient's legs raised by 45 degrees, you reassess the blood pressure after 1 minute and his blood pressure has increased to 100/75mmHg. You then prescribe IV fluids and ask for 500ml of normal saline to be given intravenously over 15 minutes.
      The increase in the blood pressure can be explained by which physiological association?

      Your Answer:

      Correct Answer: Venous return is proportional to stroke volume

      Explanation:

      Cardiac muscle contraction strength is dependent on the action of adrenaline and noradrenaline, but these hormones contribute to cardiac contractility, not to Starling’s law.

      Stroke volume (via a cardiac monitor) and/or pulse pressure (via an arterial line) should be measured to assess the effects of a passive leg raise. An increase in stroke volume by 9% or in pulse pressure by 10% are considered indicative of fluid responsiveness.

      A passive leg raise can lead to transient increases in blood pressure and stroke volume as it increased the amount of venous return to the heart. Venous return increases in this situation as it transfers a larger volume of blood from the lower limbs to the right heart. It therefore mimics a fluid challenge. However its effects are short lasting and often lead to minimal increases in blood pressure. It therefore should not be used to treat shock in isolation. The passive leg raise is useful in determining the likelihood that a patient with shock will respond to fluid resuscitation.

      Sarcomeres, which can be in cardiac, smooth or skeletal muscle, function optimally when stretched to a specific point.
      Blood that enters the ventricles during diastole causing stretching of sarcomeres within cardiac muscle. The extent to which they stretch is proportional to the strength of ventricular muscle contraction. Therefore, the venous return (amount of blood returned to the heart) is proportional to stroke volume. The end diastolic volume is determined by venous return and is also proportional to stroke volume.

    • This question is part of the following fields:

      • Physiology And Biochemistry
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  • Question 29 - A 5-year old male has ingested a peanut and has developed urticaria, vomiting...

    Incorrect

    • A 5-year old male has ingested a peanut and has developed urticaria, vomiting and hypotension. The pathogenesis of this condition is derived from predominant cells of which cell line?

      Your Answer:

      Correct Answer: Common myeloid progenitor

      Explanation:

      A is correct. Common myeloid progenitor cells are involved in the anaphylaxis reaction.
      B is incorrect. The common lymphoid lineage gives rise to T-cells, B-cell and NK cells.
      C is incorrect as megakaryocytes give rise to platelets.
      D is incorrect – Neural crest cells give rise to various cells throughout the body, including melanocytes, enterochromaffin cells and Schwann cells. However, they do not give rise to mast cells.
      E is incorrect. Reticulocytes give rise to erythrocytes.

      This is a classic case of anaphylaxis. In this situation, IgE previously raised against antigens (in this case peanut antigen) bind to mast cells, and this causes them to degranulate.
      There is release of vasoactive substances like histamine into the blood, and this is responsible for the symptoms seen. Therefore, the main type of cells involved in the pathogenesis of the disease is mast cells.

    • This question is part of the following fields:

      • Physiology And Biochemistry
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  • Question 30 - A 20-year old lady has been having excessive bruising and bleeding of her...

    Incorrect

    • A 20-year old lady has been having excessive bruising and bleeding of her gums. She is under investigation for the extrinsic pathway of coagulation. Which is the best investigation to order?

      Your Answer:

      Correct Answer: Prothrombin time (PT)

      Explanation:

      The extrinsic pathway is best assessed by the PT time.

      D-dimer is a fibrin degradation product which is raised in the presence of blood clots.

      A 50:50 mixing study is used to assess if a prolonged PT or aPTT is due to factor deficiency or a factor inhibitor.

      The thrombin time is a test used to assess fibrin formation from fibrinogen in plasma. Factors that prolong the thrombin time include heparin, fibrin degradation products, and fibrinogen deficiency.

      Intrinsic pathway – Best assessed by APTT. Factors 8,9,11,12 are involved. Prolonged aPTT can be seen in haemophilia and use of heparin.

      Extrinsic pathway – Best assessed by Increased PT. Factor 7 involved.

      Common pathway – Best assessed by APTT & PT. Factors 2,5,10 involved.

      Vitamin K dependent factors are factors 2,7,9,10

    • This question is part of the following fields:

      • Physiology And Biochemistry
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