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Question 1
Correct
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Regarding airway resistance, which of the following statements is CORRECT:
Your 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 2
Correct
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Regarding hepatitis B, which of the following statements is CORRECT:
Your Answer: Chronic hepatitis B infection is indicated by the persistence of HBsAg for more than 6 months.
Explanation:Chronic hepatitis B infection is indicated by the persistence of HBsAg for more than 6 months. Hepatitis B has a long incubation period of about 2 – 6 months. Hepatitis B vaccine has recently been introduced to the routine childhood immunisation schedule – given at 2, 3 and 4 months. It is also given to babies born to hepatitis B infected mothers at birth, four weeks and 12 months old. Treatment of acute hepatitis is supportive. Treatment with antivirals should be considered in chronic infection as responders have a reduced risk of liver damage and liver cancer in the long term.
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This question is part of the following fields:
- Microbiology
- Pathogens
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Question 3
Incorrect
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An analytical study is conducted to compare the risk of stroke between Ticagrelor therapy and Warfarin therapy among patients with atrial fibrillation. The following is obtained from the study:
No. of patients who took Ticagrelor: 300
No. of patients who took Ticagrelor and suffered a stroke: 30
No. of patients who took Warfarin: 500
No. of patients who took Warfarin and suffered a stroke: 20
Compute for the absolute risk reduction of a stroke, with Warfarin as the standard of treatment.Your Answer: 0.1
Correct Answer: -0.06
Explanation:Absolute risk reduction (ARR) is computed as the difference between the absolute risk in the control group (ARC) and the absolute risk in the treatment group (ART).
Since Warfarin is the standard of treatment, Warfarin is considered as the control group.
ARR = ARC-ART
ARR = (20/500) – (30/300)
ARR = -0.06This means that there is increased risk of stroke in the treatment group, which is the Ticagrelor group.
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This question is part of the following fields:
- Evidence Based Medicine
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Question 4
Incorrect
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The cutaneous circulation is responsible for the skin's blood supply. Because the skin is not a highly metabolically active tissue with low energy requirements, its blood supply differs from that of other tissues. Instead of capillaries, some of the circulating blood volume in the skin passes through arteriovenous anastomoses (AVAs).
Which of the following statements regarding arteriovenous anastomoses is correct?
Your Answer:
Correct Answer: AVAs are innervated by sympathetic fibres originating from the hypothalamus
Explanation:Short vessels called arteriovenous anastomoses (AVAs) link tiny arteries and veins. They have a large lumen diameter. The strong and muscular walls allow AVAs to completely clog the vascular lumen, preventing blood flow from artery to vein (acting like a sphincter). When the AVAs open, they create a low-resistance connection between arteries and veins, allowing blood to flow into the limbs’ superficial venous plexuses. There is no diffusion of solutes or fluid into the interstitium due to their strong muscle walls.
AVAs are densely innervated by adrenergic fibres from the hypothalamic temperature-regulation centre. High sympathetic output occurs at normal core temperatures, inducing vasoconstriction of the AVAs and blood flow through the capillary networks and deep plexuses. When the temperature rises, sympathetic output decreases, producing AVA vasodilation and blood shunting from the artery to the superficial venous plexus. Heat is lost to the environment as hot blood rushes near to the skin’s surface.
AVAs are a specialized anatomical adaptation that can only be found in large quantities in the fingers, palms, soles, lips, and pinna of the ear. -
This question is part of the following fields:
- Cardiovascular Physiology
- Physiology
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Question 5
Incorrect
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Which of the following side effects is most likely caused by erythromycin:
Your Answer:
Correct Answer: QT - prolongation
Explanation:The side effects of erythromycin include abdominal pain, anaphylaxis,
cholestatic hepatitis, confusion,
diarrhoea, dyspepsia, fever, flatulence, hallucinations, hearing loss,
headache, hypertrophic pyloric stenosis, hypotension, Interstitial
nephritis, mild allergic reactions, nausea, nervous system effects,
including seizures, pain, pruritus, pseudomembranous colitis,
QT prolongation, rash, skin eruptions, tinnitus, urticaria,
ventricular arrhythmias, ventricular tachycardia, vertigo, vomiting -
This question is part of the following fields:
- Infections
- Pharmacology
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Question 6
Incorrect
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Which of the following statements is false regarding the biceps brachii muscle?
Your Answer:
Correct Answer: It pronates the radioulnar joint in the forearm
Explanation:The biceps brachii muscle is one of the chief muscles of the arm. The origin at the scapula and the insertion into the radius of the biceps brachii means it can act on both the shoulder joint and the elbow joint, which is why this muscle participates in a few movements of the arm. It derives its name from its two heads which merge in one unique distal body, defining the unusual structure of the muscle.
The biceps brachii muscle is supplied by the musculocutaneous nerve (C5-C6), a branch of the brachial plexus.
Arterial supply to the biceps brachii muscle varies considerably, coming from up to eight vessels originating from the brachial artery in the middle third of the arm.
In the shoulder joint both muscle heads partially enforce opposite movements. The long head pulls the arm away from the trunk (abduction) and turns it inwards (inward rotation) whereas the short head pulls the arm back towards the trunk (adduction). When both heads contract simultaneously it leads to an arm bend (flexion). In the elbow joint the muscle bends the forearm (flexion) and rotates it outwards (supination). The supination is most powerful in a flexed elbow. In addition to the movement functions, the biceps has the important task to support the humeral head within the shoulder joint. Its antagonist is the triceps brachii in the posterior compartment of the arm.
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This question is part of the following fields:
- Anatomy
- Upper Limb
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Question 7
Incorrect
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A patient who has a nerve injury has sparing of the upper half of the orbicularis oculi muscle but not the lower half. Which branch of the facial nerve supplies the lower half of the orbicularis oculi?
Your Answer:
Correct Answer: Zygomatic branch
Explanation:The facial nerve divides into five terminal branches once in the parotid gland.
1. The temporal branch innervates muscles in the temple, forehead and supraorbital areas.
2. The zygomatic branch innervates muscles in the infraorbital area, the lateral nasal area and the upper lip.
3. The buccal branch innervates muscles in the cheek, the upper lip and the corner of the mouth.
4. The marginal mandibular branch innervates muscles of the lower lip and chin.
5. The cervical branch innervates the platysma muscle. -
This question is part of the following fields:
- Anatomy
- Cranial Nerve Lesions
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Question 8
Incorrect
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In a VF arrest, a 6-year-old child is brought to your Emergency Department resuscitation area. He weighs 16 kilogrammes. He's had three DC shocks, but he's still in VF and doesn't have an output.
What amiodarone dose should he get now, according to the most recent APLS guidelines?Your Answer:
Correct Answer: 80 mg
Explanation:In a shockable (Vf/pVT) paediatric cardiac arrest, amiodarone should be administered after the third and fifth shocks. The dose is 5 mg/kg (maximum 300 mg) and should be administered over a three-minute period. If at all possible, administration via a central line is recommended.
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This question is part of the following fields:
- Cardiovascular Pharmacology
- Pharmacology
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Question 9
Incorrect
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A 30-year-old man suffers from an open fracture of his forearm. As a consequence of his injury, the nerve that innervates the pronator quadratus muscle was severed.
Which of the following statements regarding the pronator quadratus muscle is considered correct?Your Answer:
Correct Answer: Its deep fibres bind the radius and ulna together
Explanation:Pronator quadratus is a deep-seated, short, flat, and quadrilateral muscle with fibres running in a parallel direction.
It arises from the oblique ridge on the anterior surface of the distal fourth of the Ulna. It is inserted in lateral border and anterior surface of the distal fourth of the radius. It is innervated by the anterior interosseous nerve, a branch of the median nerve (C8-T1). It is vascularized by the anterior interosseous artery.
The action of the pronator quadratus muscle along with the pronator teres result in the pronation of the radioulnar joint. Contraction of this muscle pulls the distal end of the radius over the ulna, resulting in the pronation of the radioulnar joint
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This question is part of the following fields:
- Anatomy
- Upper Limb
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Question 10
Incorrect
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Vitamin D is a group of secosteroids that play a role in calcium and phosphate control. Vitamin D's hormonally active metabolite is 1,25-dihydroxycholecalciferol.
Which enzyme hydroxylates 25-hydroxycholecalciferol to form 1,25-dihydroxycholecalciferol?Your Answer:
Correct Answer: 1-alpha-hydroxylase
Explanation:The hormone-active metabolite of vitamin D is 1,25-dihydroxycholecalciferol (commonly known as calcitriol). Its activities raise calcium and phosphate levels in the bloodstream.
In the presence of UVB light, 7-dehydrocholesterol is converted to cholecalciferol in the epidermal layer of the skin, resulting in 1,25-dihydroxycholecalciferol.
Cholecalciferol is then converted to 25-hydroxycholecalciferol in the endoplasmic reticulum of liver hepatocytes by 25-hydroxylase (calcifediol).
Finally, 1-alpha-hydroxylase converts 25-hydroxycholecalciferol to 1,25-dihydroxycholecalciferol in the kidney. The key regulatory point in the formation of 1,25-dihydroxycholecalciferol is 1-alpha-hydroxylase, which is induced by parathyroid hormone or hypophosphatemia.
The following are the primary effects of 1,25-dihydroxycholecalciferol:
Calcium and phosphate absorption in the small intestine is increased.
Calcium reabsorption in the kidneys is increased.
Increases phosphate reabsorption in the kidneys.
Increases the action of osteoclastic bacteria (increasing calcium and phosphate resorption from bone)
Inhibits the action of 1-alpha-hydroxylase in the kidneys (negative feedback) -
This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 11
Incorrect
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A 20-year-old male patient lives in a travelling community and has never received any vaccinations. He presents to you with fever.
Which of these statements concerning indications and contraindications for vaccination is FALSE?
Your Answer:
Correct Answer: Premature infants should have the their immunisation schedule adjusted for gestational age
Explanation:All vaccines are contraindicated in individuals with:
A confirmed anaphylactic reaction to a previous dose of the vaccine or a vaccine containing the same antigens.
A confirmed anaphylactic reaction to a component in the vaccine e.g. neomycinLive attenuated vaccines are contraindicated in pregnancy except in cases where risk of infection is more than the risks of vaccination.
During times of acute febrile illness, vaccination should be avoided.
12 weeks should elapse after a dose of human immunoglobulin before a live vaccine is administered.
The normal times recommended for immunization of full-term babies should also be applied to premature infants and correction for gestational age should NOT be implemented.
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This question is part of the following fields:
- Microbiology
- Principles Of Microbiology
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Question 12
Incorrect
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A patient suffers a stab wound to the neck. The entry point of the blade is situated within the posterior triangle of the neck.
Which of the following muscles is most likely to be involved? Select ONE answer only.Your Answer:
Correct Answer: Anterior scalene
Explanation:The anterior triangle is the triangular area of the neck found anteriorly to the sternocleidomastoid muscle. It is formed by the anterior border of sternocleidomastoid laterally, the median line of the neck medially and by the inferior border of the mandible superiorly. The apex of the anterior triangle extends towards the manubrium sterni. The anterior triangle contains:
Muscles: thyrohyoid, sternothyroid, sternohyoid muscles
Organs: thyroid gland, parathyroid glands, larynx, trachea, esophagus, submandibular gland, caudal part of the parotid gland
Arteries: superior and inferior thyroid, common carotid, external carotid, internal carotid artery (and sinus), facial, submental, lingual arteries
Veins: anterior jugular veins, internal jugular, common facial, lingual, superior thyroid, middle thyroid veins, facial vein, submental vein, lingual veins
Nerves: vagus nerve (CN X), hypoglossal nerve (CN XII), part of sympathetic trunk, mylohyoid nerveThe posterior triangle is a triangular area found posteriorly to the sternocleidomastoid muscle. It has three borders; anterior, posterior and inferior borders. The anterior border is the posterior margin of the sternocleidomastoid muscle. The posterior border is the anterior margin of the trapezius muscle, while the inferior border is the middle one-third of the clavicle. The investing layer of deep cervical fascia and integument forms the roof of the space, while the floor is covered with the prevertebral fascia along with levator scapulae, splenius capitis and the scalene muscles. The inferior belly of omohyoid subdivides the posterior triangle into a small supraclavicular, and a large occipital, triangle.
Contents:
Vessels: the third part of the subclavian artery, suprascapular and transverse cervical branches of the thyrocervical trunk, external jugular vein, lymph nodes
Nerves: accessory nerve (CN XI), the trunks of the brachial plexus, fibers of the cervical plexus
Of the muscles listed in the options, only the anterior scalene is situated within the posterior triangle of the neck. -
This question is part of the following fields:
- Anatomy
- Head And Neck
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Question 13
Incorrect
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A 30-year old male is taken to the emergency room after suffering a blunt trauma to the abdomen. He is complaining of severe abdominal pain, however all his other vital signs remain stable. A FAST scan is performed to assess for hemoperitoneum.
If hemoperitoneum is present, it is most likely to be observed in which of the following areas?Your Answer:
Correct Answer: Liver
Explanation:The Focused Assessment with Sonography in Trauma (FAST) is an ultrasound protocol developed to assess for hemoperitoneum and hemopericardium. Numerous studies have demonstrated sensitivities between 85% to 96% and specificities exceeding 98%.
The FAST exam evaluates four regions for pathologic fluid: (1) the right upper quadrant, (2) the subxiphoid (or subcostal) view, (3) the left upper quadrant, and (4) the suprapubic region.
The right upper quadrant (RUQ) visualizes the hepatorenal recess, also known as Morrison’s pouch, the right paracolic gutter, the hepato-diaphragmatic area, and the caudal edge of the left liver lobe. The probe is positioned in the sagittal orientation along the patient’s flank at the level of the 8 to 11 rib spaces. The hand is placed against the bed to ensure visualization of the retroperitoneal kidney. The RUQ view is the most likely to detect free fluid with an overall sensitivity of 66%. Recent retrospective evidence suggests the area along the caudal edge of the left lobe of the liver has the highest sensitivity, exceeding 93%.
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This question is part of the following fields:
- Abdomen And Pelvis
- Anatomy
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Question 14
Incorrect
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A 45-old woman is on several medications and being treated for epilepsy and bipolar disorder. In the ward rounds, you are asked to examine her in detail and discover she has a noticeable tremor. You believe that one of her medications may be responsible for this new onset tremor.
Which of the following medications is least likely to be responsible for this tremor?Your Answer:
Correct Answer: Carbamazepine
Explanation:The only medication that does not commonly cause tremors is carbamazepine.
The other drugs present with the following types of tremors as a side effect to their usage:
1. Sodium valproate – Postural tremor is most common, but a resting tremor can also occur. Approximately 25% of patients taking sodium valproate are found to develop a tremor within 12 months of starting therapy.
2. Lithium – fine hand tremor is very commonly seen and reported in as many as 50% of patients during the first week of therapy. The tremor tends to reduce with time and is only present in around 5% of patients taking the medication two years or longer.
3. Atypical antipsychotics, such as olanzapine and quetiapine – tremor and limb shakiness. -
This question is part of the following fields:
- CNS Pharmacology
- Pharmacology
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Question 15
Incorrect
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Regarding penicillin antibiotics, which of the following statements is CORRECT:
Your Answer:
Correct Answer: Patients with a history of atopy are at higher risk of hypersensitivity reactions.
Explanation:Allergic reactions to penicillins occur in 1 – 10% of exposed individuals; anaphylactic reactions occur in fewer than 0.05% of treated patients. Patients with a history of atopic allergy are at higher risk of anaphylactic reactions to penicillins. Patients with a history of anaphylaxis, urticaria, or rash immediately after penicillin use should not receive a penicillin or other beta-lactam antibiotics; about 0.5 – 6.5 % of penicillin-sensitive patients will also be allergic to the cephalosporins.
Patients with a history of a more minor rash (i.e. non-confluent, non-pruritic rash restricted to a small area of the body) or delayed reaction (rash occurring more than 72 hours after penicillin administration), may not be truly allergic and may be considered for penicillin or beta-lactam treatment in severe infection (although possibility of allergy should be borne in mind). Other beta-lactam antibiotics (including cephalosporins) can be used in these patients.
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This question is part of the following fields:
- Infections
- Pharmacology
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Question 16
Incorrect
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A 30-year-old male presents with easy bruising and bleeding gums, feeling very tired lately, and recurrent chest infections over the past few months. He had glandular fever approximately 6 months ago and feels that his symptoms started after that.
His full blood count today is as follows:
Hb 6.3 g/dl (11.5-14 g/dl)
MCV 90 fl (80-100 fl)
WCC 2.0 x 10 9 /l (4-11 x 10 9 /l)
Platelets 15 x 10 9 /l (150-450 x 10 9 /l)
The SINGLE most likely diagnosis is?Your Answer:
Correct Answer: Aplastic anaemia
Explanation:Aplastic anaemia is a life-threatening failure of haemopoiesis characterised by pancytopenia and hypocellular bone marrow. It is rare and patients present with features of recurrent infections secondary to (leukocytopenia), increased bleeding tendency (secondary to thrombocytopenia) and anaemia. In aplastic anaemia, there is damage to the bone marrow and the haematopoietic stems cells leading to pancytopenia.
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This question is part of the following fields:
- Haematology
- Pathology
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Question 17
Incorrect
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You intend to suture a hand wound with plain 1 percent lidocaine.
In 1 mL of plain 1 percent lidocaine solution, how much lidocaine hydrochloride is there?Your Answer:
Correct Answer: 10 mg lidocaine hydrochloride
Explanation:10 mg of lidocaine hydrochloride is contained in each 1 mL of plain 1 percent lidocaine solution.
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This question is part of the following fields:
- Anaesthesia
- Pharmacology
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Question 18
Incorrect
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Regarding the trachea, which of the following statements is INCORRECT:
Your Answer:
Correct Answer: A cricothyrotomy involves making an opening in the neck inferior to the cricoid cartilage.
Explanation:A cricothyrotomy involves making an opening in the median cricothyroid ligament (the medial part of the cricothyroid membrane), between the cricoid cartilage below and the thyroid cartilage above.
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This question is part of the following fields:
- Anatomy
- Head And Neck
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Question 19
Incorrect
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Which of the following clinical features is a feature of a chronic extravascular haemolytic anaemia:
Your Answer:
Correct Answer: Gallstones
Explanation:Clinical features of haemolytic anaemia include:
Anaemia
Jaundice (caused by unconjugated bilirubin in plasma, bilirubin is absent from urine)
Pigment gallstones
Splenomegaly
Ankle ulcers
Expansion of marrow with, in children, bone expansion e.g. frontal bossing in beta-thalassaemia major
Aplastic crisis caused by parvovirus -
This question is part of the following fields:
- Haematology
- Pathology
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Question 20
Incorrect
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Atrial natriuretic peptide (ANP) acts to cause all of the following effects EXCEPT for:
Your Answer:
Correct Answer: Vasoconstricts the afferent arteriole
Explanation:ANP acts to:
Inhibit Na+ reabsorption in the distal nephron (through inhibition of ENaC in principal cells)
Suppress the production of renin
Suppress the production of aldosterone
Suppress the production of ADH
Cause renal vasodilation, increasing the glomerular filtration rate -
This question is part of the following fields:
- Physiology
- Renal
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Question 21
Incorrect
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In the United Kingdom, which of the following is the most often used intravenous aesthetic:
Your Answer:
Correct Answer: Propofol
Explanation:In the United Kingdom, propofol is the most widely used intravenous anaesthetic. In adults and children, it can be used to induce or maintain anaesthesia, although it is not commonly used in newborns. It can also be used to sedate individuals in intensive care and for sedation during operations.
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This question is part of the following fields:
- Anaesthesia
- Pharmacology
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Question 22
Incorrect
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Question 23
Incorrect
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Which one of these equations best defines lung compliance?
Your Answer:
Correct Answer: Change in volume / change in pressure
Explanation:Lung compliance is defined as change in volume per unit change in distending pressure.
Lung compliance is calculated using the equation:
Lung compliance = ΔV / ΔP
Where:
ΔV is the change in volume
ΔP is the change in pleural pressure.Static compliance is lung compliance in periods without gas flow, and is calculated using the equation:
Static compliance = VT / Pplat − PEEP
Where:
VT = tidal volume
Pplat = plateau pressure
PEEP = positive end-expiratory pressure -
This question is part of the following fields:
- Physiology
- Respiratory Physiology
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Question 24
Incorrect
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The fluid in contact with a tube is dragged by frictional forces to the tube's sidewalls. This creates a velocity gradient in which the fluid flow is greatest in the tube's centre.
Which of the following terms most accurately characterizes this flow pattern?Your Answer:
Correct Answer: Laminar flow
Explanation:The fluid in contact with a tube is dragged by frictional forces at the tube’s sidewalls. This creates a velocity gradient in which the fluid flow is greatest in the tube’s centre.
This is known as laminar flow, and it characterizes the flow in most circulatory and respiratory systems when they are at rest.The velocity of the fluid flow can fluctuate erratically at high velocities, particularly within big arteries and airways, disrupting laminar flow. As a result, resistance increases significantly.
This is known as turbulent flow, and symptoms include heart murmurs and asthmatic wheeze. -
This question is part of the following fields:
- Basic Cellular Physiology
- Physiology
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Question 25
Incorrect
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What is the mechanism of action of penicillin antibiotics:
Your Answer:
Correct Answer: Inhibition of bacterial cell wall synthesis
Explanation:Penicillins and the other ß-lactam antibiotics are bactericidal. They produce their antimicrobial action by preventing cross-linkage between the linear peptidoglycan polymer chains that make up the bacterial cell wall. They, therefore, inhibit cell wall synthesis.
The integrity of the ß-lactam ring is essential for antimicrobial activity. Many bacteria (including most Staphylococci) are resistant to benzylpenicillin and phenoxymethylpenicillin because they produce enzymes (penicillinases, ß-lactamases) that open the ß-lactam ring. -
This question is part of the following fields:
- Infections
- Pharmacology
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Question 26
Incorrect
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A 36-year-old man presented to the emergency room with a two-week history of shortness of breath, fevers, and malaise. A chest X-ray was ordered and the results confirmed the diagnosis of a right middle lobe pneumonia.
Which of the following structures of the heart lies closest to the consolidation?Your Answer:
Correct Answer: Right atrium
Explanation:In its typical anatomical orientation, the heart has 5 surfaces formed by different internal divisions of the heart:
Anterior (or sternocostal) – Right ventricle
Posterior (or base) – Left atrium
Inferior (or diaphragmatic) – Left and right ventricles
Right pulmonary – Right atrium
Left pulmonary – Left ventricleThe silhouette sign of Felson is with respect to the right middle lobe. The right heart border should have a distinct appearance due to the right atrium abutting aerated right middle lobe. The consolidation in the right middle lobe has resulted in loss of this silhouette.
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This question is part of the following fields:
- Anatomy
- Thorax
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Question 27
Incorrect
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A 33-year-old woman demonstrates right-sided superior homonymous quadrantanopia upon visual field testing. A diagnosis of a brain tumour has been established.
Which of the following anatomical points in the visual pathway has the lesion occurred?Your Answer:
Correct Answer: Lower optic radiation
Explanation:Homonymous quadrantanopia is not a disease; it is a clinical finding that points towards a lesion of the optic radiations coursing through the temporal lobe.
Homonymous superior quadrantanopia is caused by damage to the contralateral inferior parts of the posterior visual pathway: the inferior optic radiation (temporal Meyer loop), or the inferior part of the occipital visual cortex below the calcarine fissure. -
This question is part of the following fields:
- Anatomy
- Central Nervous System
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Question 28
Incorrect
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Intravenous glucose solutions are typically used in the treatment of all of the following situations except:
Your Answer:
Correct Answer: Hypokalaemia
Explanation:In hypokalaemia, initial potassium replacement therapy should not involve glucose infusions, as glucose may cause a further decrease in the plasma-potassium concentration. Glucose infusions are used for the other indications like diabetic ketoacidosis, hypoglycaemia, routine fluid maintenance in patients who are nil by mouth (very important in children), and in hyperkalaemia.
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This question is part of the following fields:
- Fluids And Electrolytes
- Pharmacology
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Question 29
Incorrect
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Regarding chronic idiopathic thrombocytopaenic purpura (ITP), which of the following statements is INCORRECT:
Your Answer:
Correct Answer: ITP is classically associated with massive splenomegaly.
Explanation:Chronic ITP is a relatively common disorder. The highest incidence is in women aged 15 – 50 years. It is the most common cause of thrombocytopaenia without anaemia or neutropaenia. It is usually idiopathic but it may been seen in association with other conditions. Platelet autoantibodies (usually IgG) result in the premature removal of platelets from the circulation by macrophages of the reticuloendothelial system. In many causes the antibody is directed against the glycoprotein IIb/IIIa or Ib complex. The normal platelet lifespan of 10 days is reduced to a few hours. Total megakaryocyte mass and platelet turnover are increased to approximately five times normal. Despite the destruction of platelets by splenic macrophages, the spleen is normally not enlarged. In fact, an enlarged spleen should lead to a search for other possible causes for the thrombocytopenia.
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This question is part of the following fields:
- Haematology
- Pathology
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Question 30
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 31
Incorrect
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A patient with a diagnosis of HIV presents with a fever, sore throat, and general malaise and you are concerned the patient may have an AIDS defining illness.
Which one of these, according to the CDC definition, would mean a patient infected with HIV has AIDS?
Your Answer:
Correct Answer: CD4 T-cell percentage of total lymphocytes of less than 15%
Explanation:According to the CDC definition, a patient co-infected with HIV can be diagnosed with AIDS if he or she has:
A CD4 T-cell count of less than 200 cells/mm3 or;
A CD4 T-cell percentage of total lymphocytes of less than 15% or;
An AIDS defining infectionA Streptococcal throat infection is not an AIDS defining infection.
A normal CD4 count ranges from 500-1000 cells/mm3. A CD4 (not CD8) count of less than 200 cells/mm3 is AIDS defining.
The CD4 count can vary from day to day and depending upon the time that the blood test is taken. It can also be affected by the presence of other infections or illnesses. Treatment with anti-retroviral therapy should be considered at CD4 count of less than 350 cells/mm3.
Serum concentrations of the p24 antigen (the viral protein that makes up most of the core of the HIV) are usually high in the first few weeks after human immunodeficiency virus (HIV) infection and testing for p24 antigen is therefore a useful way of diagnosing very early infection.
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This question is part of the following fields:
- Microbiology
- Specific Pathogen Groups
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Question 32
Incorrect
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A 70-year-old man presents with right-sided hemiplegia and loss of joint position sense, vibratory sense, and discriminatory touch. Upon further physical examination, it was observed that her tongue deviates to the left-hand side. An MRI and CT scan was ordered and results showed that he was suffering a left-sided stroke.
Branches of which of the following arteries are most likely implicated in the case?Your Answer:
Correct Answer: Anterior spinal artery
Explanation:Medial medullary syndrome is a form of stroke that affects the medial medulla of the brain. It is caused by a lesion in the medial part of the medulla, which is due to an infraction of vertebral arteries and/or paramedian branches of the anterior spinal artery.
It is characterized by contralateral paralysis of the upper and lower limb of the body, a contralateral decrease in proprioception, vibration, and/or fine touch sensation, paresthesias or less commonly dysesthesias in the contralateral trunk and lower limb, and loss of position and vibration sense with proprioceptive dysfunction. Ipsilateral deviation of the tongue due to ipsilateral hypoglossal nerve damage can also be seen.
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This question is part of the following fields:
- Anatomy
- Central Nervous System
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Question 33
Incorrect
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You are giving a teaching session to a group of final year medical students regarding lower limb neurology. Which of the following clinical features would be expected in an obturator nerve palsy:
Your Answer:
Correct Answer: Weakness of hip adduction
Explanation:Damage to the obturator nerve results in weak adduction of the hip with lateral swinging of the limb during walking due to unopposed abduction.
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This question is part of the following fields:
- Anatomy
- Lower Limb
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Question 34
Incorrect
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The cutaneous circulation's principal role is thermoregulation. This process is aided by the existence of arteriovenous anastomoses.
Which of the following anatomical areas has the greatest number of arteriovenous anastomoses?Your Answer:
Correct Answer: Pinna of the ear
Explanation:Short vessels called arteriovenous anastomoses (AVAs) link tiny arteries and veins. They have a large lumen diameter. The strong and muscular walls allow AVAs to completely clog the vascular lumen, preventing blood flow from artery to vein (acting like a sphincter). When the AVAs open, they create a low-resistance connection between arteries and veins, allowing blood to flow into the limbs’ superficial venous plexuses. There is no diffusion of solutes or fluid into the interstitium due to their strong muscle walls.
AVAs are densely innervated by adrenergic fibres from the hypothalamic temperature-regulation centre. High sympathetic output occurs at normal core temperatures, inducing vasoconstriction of the AVAs and blood flow through the capillary networks and deep plexuses. When the temperature rises, sympathetic output decreases, producing AVA vasodilation and blood shunting from the artery to the superficial venous plexus. Heat is lost to the environment as hot blood rushes near to the skin’s surface.
AVAs are a specialized anatomical adaptation that can only be found in large quantities in the fingers, palms, soles, lips, and pinna of the ear. -
This question is part of the following fields:
- Cardiovascular Physiology
- Physiology
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Question 35
Incorrect
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The following statements concerning lung compliance is true EXCEPT?
Your Answer:
Correct Answer: Lung compliance is described by the equation: C = ∆ P/ ∆V, where C = compliance, P = pressure, and V = volume
Explanation:Lung compliance is the change in volume per unit change in distending pressure.
It is calculated using the equation:
Lung compliance = ΔV / ΔP
Where:
ΔV is the change in volume
ΔP is the change in pleural pressure.Lung compliance is inversely proportional to stiffness and elastance.
It comprises static (no airflow) and dynamic (during continuous breathing) components.
It is the slope of the pressure-volume curve.
Lung compliance describes the distensibility of the lungs and the chest wall.
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This question is part of the following fields:
- Physiology
- Respiratory Physiology
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Question 36
Incorrect
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A patient suffers an injury to his thigh that damages the nerve that innervates pectineus.
Which of the following nerves has been damaged in this case? Select ONE answer only.Your Answer:
Correct Answer: Femoral nerve
Explanation:Pectineus is innervated by the femoral nerve. It may also receive a branch from the obturator nerve.
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This question is part of the following fields:
- Anatomy
- Lower Limb
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Question 37
Incorrect
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If a lesion is observed in Broca's area, which function is expected to become affected?
Your Answer:
Correct Answer: Formation of words
Explanation:The primary functions of the Broca area are both language production and comprehension. While the exact role in the production is still unclear, many believe that it directly impacts the motor movements to allow for speech. Although originally thought to only aid in speech production, lesions in the area can rarely be related to impairments in the comprehension of language. Different regions of the Broca area specialize in various aspects of comprehension. The anterior portion helps with semantics, or word meaning, while the posterior is associated with phonology, or how words sound. The Broca area is also necessary for language repetition, gesture production, sentence grammar and fluidity, and the interpretation of others’ actions.
Broca’s aphasia is a non-fluent aphasia in which the output of spontaneous speech is markedly diminished and there is a loss of normal grammatical structure. Specifically, small linking words, conjunctions, such as and, or, and but, and the use of prepositions are lost. Patients may exhibit interjectional speech where there is a long latency, and the words that are expressed are produced as if under pressure. The ability to repeat phrases is also impaired in patients with Broca’s aphasia. Despite these impairments, the words that are produced are often intelligible and contextually correct. In pure Broca’s aphasia, comprehension is intact.
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This question is part of the following fields:
- Anatomy
- Central Nervous System
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Question 38
Incorrect
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You examine a 43-year-old woman who was referred to you by a friend. She suffers from a variety of medical conditions and takes a variety of medications, including amitriptyline.
Which of the following is NOT a contraindication to amitriptyline treatment?Your Answer:
Correct Answer: Breastfeeding
Explanation:Amitriptyline is a tricyclic antidepressant (TCA) that is most commonly used to treat depression, but it can also be used to treat anxiety disorders, chronic pain, and attention deficit hyperactivity disorder (ADHD). It inhibits reuptake, raising serotonin and noradrenaline levels while also inhibiting acetylcholine action.
TCAs have a number of drawbacks, including:
Acute Porphyria
Arrhythmias
During bipolar disorder’s manic phase
Heart block
After a myocardial infarction, there is an immediate recovery period.TCA levels in breast milk are too low to be harmful, and use can be continued while breastfeeding.
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This question is part of the following fields:
- CNS Pharmacology
- Pharmacology
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Question 39
Incorrect
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Which of the following states that the total pressure exerted by a mixture of gases is equal to the sum of the partial pressures of each of the gases in the mixture:
Your Answer:
Correct Answer: Dalton's law
Explanation:Dalton’s law states that when two or more gases, which do not react chemically, are present in the same container, the total pressure is the sum of the partial pressures of each gas.
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 40
Incorrect
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The following all cause a right shift in the oxygen dissociation curve EXCEPT for:
Your Answer:
Correct Answer: Foetal haemoglobin
Explanation:A decreased affinity of haemoglobin for oxygen (and hence increased ease of dissociation), shown by a right shift in the oxygen dissociation curve, is caused by a fall in pH, a rise in PCO2(the Bohr effect) and an increase in temperature. These changes occur in metabolically active tissues such as in exercise, and encourage oxygen release. The metabolic by-product 2,3-diphosphoglycerate (2,3 -DPG) also causes a right shift; 2, 3 -DPG may also be raised in chronic anaemia, chronic lung disease, or at high altitude. Foetal haemoglobin (HbF) binds 2, 3 -DPG less strongly than does adult haemoglobin (HbA), and so the HbF dissociation curve lies to the left of that for HbA, reflecting its higher oxygen affinity. This helps transfer oxygen from mother to foetus.
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This question is part of the following fields:
- Physiology
- Respiratory
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Question 41
Incorrect
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A blood test of a 7-year-old child with a 6-day history of bloody diarrhoea reveals a low platelet count, anaemia, and impaired kidney function. What bacteria is suspected of causing such a condition?
Your Answer:
Correct Answer: Escherichia coli
Explanation:Escherichia coli produces shiga toxin that causes diarrhoea, hemorrhagic colitis, and haemolytic uremic syndrome.
Haemolytic uremic syndrome is characterized by anaemia, thrombocytopenia, and acute renal failure. Transmission of E. coli is possible after consuming contaminated, undercooked drinks and foods. E. coli enters the body via the faecal-oral pathway.
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This question is part of the following fields:
- Microbiology
- Pathogens
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Question 42
Incorrect
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You see a patient in the Emergency Department with features consistent with a diagnosis of type I diabetes mellitus.
Which of these is MOST suggestive of type I diabetes mellitus?
Your Answer:
Correct Answer: History of recent weight loss
Explanation:A history of recent weight loss is very suggestive of an absolute deficiency of insulin seen in type I diabetes mellitus.
An age of onset of less than 20 years makes a diagnosis of type I diabetes mellitus more likely. However, an increasing number of obese children and young people are being diagnosed with type II diabetes.
Microalbuminuria, peripheral neuropathy, and retinopathy all occur in both type I and type II diabetes mellitus. They are not more suggestive of type I DM.
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This question is part of the following fields:
- Endocrine Physiology
- Physiology
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Question 43
Incorrect
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When a child has mumps, how long should he or she be off from school?
Your Answer:
Correct Answer: 5 days from onset of swelling
Explanation:To avoid the spread of infection, infected patients should be isolated. Patients should avoid going to school, childcare, or job for five days after the swelling has occurred.
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This question is part of the following fields:
- Microbiology
- Pathogens
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Question 44
Incorrect
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A 26-year-old man is involved in a motorcycle accident that results in an open fracture of his tibia and fibula. The nerve that innervates peroneus tertius is damaged as a consequence of his injuries.
Peroneus tertius receives its innervation from which of the following nerves? Select ONE answer only.Your Answer:
Correct Answer: Deep peroneal nerve
Explanation:Peroneus brevis is innervated by the superficial peroneal nerve.
Peroneus longus is innervated by the superficial peroneal nerve.
Peroneus tertius is innervated by the deep peroneal nerve. -
This question is part of the following fields:
- Anatomy
- Lower Limb
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Question 45
Incorrect
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In the treatment of bradyarrhythmias with adverse characteristics or risk of asystole, what is the initial suggested dose of atropine?
Your Answer:
Correct Answer: 500 micrograms
Explanation:Atropine 500 mcg IV bolus should be administered if there are any adverse features or risk of asystole. If the reaction is not adequate, repeat the steps every 3 to 5 minutes up to a maximum dose of 3 mg. In the case of acute myocardial ischemia or myocardial infarction, atropine should be taken with caution since the increased heart rate may aggravate the ischemia or increase the size of the infarct.
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This question is part of the following fields:
- Cardiovascular
- Pharmacology
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Question 46
Incorrect
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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 47
Incorrect
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Which of the following is a contraindication for aspirin?
Your Answer:
Correct Answer: Children under 16 years
Explanation:Aspirin contraindications include: hypersensitivity to NSAIDs; asthma, rhinitis, and nasal polyps; and usage in children or teens.
There is little evidence of allergic cross-reactivity for salicylates. However, due to similarities in chemical structure and/or pharmacologic activities, the possibility of cross-sensitivity cannot be completely ruled out. -
This question is part of the following fields:
- Central Nervous System
- Pharmacology
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Question 48
Incorrect
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A 62-year-old man complains of chest pain and goes to the emergency room. You diagnose him with an acute coronary syndrome and prescribe enoxaparin as part of his treatment plan.
Enoxaparin inactivates which of the following?Your Answer:
Correct Answer: Thrombin
Explanation:Enoxaparin is a low molecular weight heparin (LMWH) that works in the same way as heparin by binding to and activating the enzyme inhibitor antithrombin III. Antithrombin III inactivates thrombin by forming a 1:1 complex with it. Factor Xa and a few other clotting proteases are also inhibited by the heparin-antithrombin III complex.
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This question is part of the following fields:
- Cardiovascular Pharmacology
- Pharmacology
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Question 49
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 50
Incorrect
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What is the interquartile range of the following data set: 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70
Your Answer:
Correct Answer: 30
Explanation:5, 10, 15 /20, 25, 30 /35, 40, 45 /50, 60, 70
Sample size (n) = 12
Median = [(n+1)/2]th value
= (12+1)/2 = 6.5
= halfway between 6th and 7th value
= (30 +35)/2 = 32.5
The lower (first) quartile = halfway between 15 and 20
= 17.5
The upper (third) quartile = halfway between 45 and 50
= 47.5
The interquartile range is the difference between the upper quartile and lower quartile
= 47.5 – 17.5 = 30 -
This question is part of the following fields:
- Evidence Based Medicine
- Statistics
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SESSION STATS - PERFORMANCE PER SPECIALTY
