In the cardiac cycle, ventricular repolarization is represented by which wave on an ECG?
Answer: C
The T wave represents ventricular repolarization. The QRS complex represents ventricular depolarization, while P wave represents atrial depolarization.
Q.22Medium
Which hormone is essential for the regulation of calcium and phosphate homeostasis?
Answer: C
Both PTH and calcitonin regulate calcium-phosphate balance. PTH increases blood calcium while calcitonin decreases it through opposing mechanisms.
Q.23Medium
A person exposed to high altitude experiences increased erythropoietin (EPO) secretion. This is an example of:
Answer: A
Low oxygen at high altitude stimulates EPO release, which increases RBC production, restoring oxygen levels and decreasing EPO secretion—a classic negative feedback loop.
Q.24Medium
Which of the following accurately describes the absolute refractory period?
Answer: B
During absolute refractory period, inactivated sodium channels cannot open regardless of stimulus strength, making another action potential impossible.
Q.25Medium
In the renin-angiotensin-aldosterone system (RAAS), which enzyme converts angiotensinogen to angiotensin I?
Answer: B
Renin, secreted by juxtaglomerular cells, cleaves angiotensinogen to form angiotensin I, which is then converted to angiotensin II by ACE.
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Q.26Medium
A patient suffers from myasthenia gravis. Which of the following is most likely affected?
Answer: B
Myasthenia gravis is an autoimmune disorder where antibodies attack acetylcholine receptors at the neuromuscular junction, reducing muscle contraction capability.
Q.27Medium
How does the parasympathetic nervous system affect heart rate and cardiac output?
Answer: B
The parasympathetic nervous system (via vagus nerve) releases acetylcholine, which decreases heart rate and force of contraction through M2 receptors.
Q.28Medium
In the process of blood clotting, what is the primary function of thrombin?
Answer: B
Thrombin is a serine protease that cleaves fibrinogen into fibrin monomers, which polymerize to form the structural basis of blood clots.
Q.29Medium
A 45-year-old patient has abnormally high blood glucose despite insulin administration. Which condition is most likely?
Answer: B
Type 2 diabetes involves insulin resistance where cells don't respond properly to insulin, maintaining elevated blood glucose despite insulin presence.
Q.30Medium
Which of the following correctly describes the role of the cerebellum in motor control?
Answer: B
The cerebellum compares intended movements with actual movements, providing real-time corrections for coordination, balance, and fine motor control.
Q.31Medium
In the cardiac cycle, what occurs during the isovolumetric contraction phase?
Answer: B
During isovolumetric contraction, ventricular volume stays constant while pressure rapidly increases as both AV and semilunar valves are closed.
Q.32Medium
A marathon runner experiences 'hitting the wall' around 20km. This is primarily due to:
Answer: B
Glycogen depletion in muscles and liver reduces glucose availability for ATP production, causing sudden fatigue despite continued oxygen availability.
Q.33Medium
In synaptic transmission, what is the role of monoamine oxidase (MAO)?
Answer: B
MAO degrades monoamines (dopamine, serotonin, norepinephrine) in mitochondria of presynaptic terminals, regulating neurotransmitter levels.
Q.34Medium
In the auditory system, how does the cochlea convert sound vibrations into neural signals?
Answer: B
Stapes vibrations move perilymph in the cochlea, causing basilar membrane displacement and stereocilia bending on hair cells, generating action potentials.
Q.35Medium
Which statement accurately describes the relationship between respiratory rate and blood CO2 levels?
Answer: B
Central and peripheral chemoreceptors detect increased CO2 (and decreased pH), sending signals to respiratory centers to increase ventilation rate.
Q.36Medium
A patient with severe dehydration experiences increased blood osmolarity. Which hormone is primarily released to counteract this condition?
Answer: B
ADH (vasopressin) is released in response to increased blood osmolarity, increases aquaporin-2 channels in collecting ducts, and promotes water reabsorption.
Q.37Medium
During the refractory period following an action potential, why is it difficult to generate another action potential?
Answer: B
During the refractory period, sodium channels enter an inactivated state (unable to reopen immediately) while potassium channels remain open, hyperpolarizing the membrane.
Q.38Medium
A student experiences increased heart rate and dilated pupils during an exam. Which division of the autonomic nervous system is responsible?
Answer: B
The sympathetic nervous system triggers 'fight or flight' responses including increased heart rate and pupil dilation via norepinephrine and epinephrine.
Q.39Medium
The countercurrent multiplier mechanism in the Loop of Henle is essential for:
Answer: B
The countercurrent multiplier creates an osmotic gradient allowing the production of concentrated urine by establishing osmolarity differences in the medulla.
Q.40Medium
During inspiration, which of the following occurs?
Answer: B
During inspiration, external intercostal muscles contract, increasing thoracic volume, decreasing intrapleural pressure, and allowing air to flow into lungs.
