Which of the following represents the correct sequence of blood flow through the heart?
Answer: A
Deoxygenated blood returns to right atrium, passes to right ventricle, pumped to lungs, oxygenated blood returns to left atrium, then left ventricle, and exits via aorta.
Q.82Easy
The resting membrane potential of a neuron is approximately:
Answer: B
The typical resting membrane potential is -70 mV, maintained by the Na+/K+ ATPase pump and selective membrane permeability.
Q.83Medium
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.84Medium
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.85Easy
Which of the following is the primary site of digestion of carbohydrates?
Answer: A
Carbohydrate digestion begins in the mouth with salivary amylase and continues in the small intestine with pancreatic amylase and brush border enzymes.
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Q.86Medium
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.87Medium
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.88Medium
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.
Q.89Medium
A mutation in the genes encoding dystrophin protein leads to:
Answer: B
Dystrophin is a structural protein that stabilizes muscle cell membranes; its absence causes Duchenne muscular dystrophy with progressive muscle weakness.
Q.90Easy
In the visual pathway, the structure responsible for focusing light onto the retina is:
Answer: C
The lens adjusts its shape (accommodation) through ciliary muscle contraction to focus light precisely on the retina for clear vision.
Q.91Medium
Which of the following best explains how the human body maintains stable internal temperature despite environmental changes?
Answer: B
The hypothalamus acts as the body's thermostat, detecting temperature changes and triggering responses (sweating, vasoconstriction) through negative feedback mechanisms.
Q.92Hard
A person injures their spinal cord at the cervical level. Which of the following would NOT be affected?
Answer: D
Taste is mediated by cranial nerves (VII, IX, X) which are not affected by cervical spinal cord injury. Cervical injury affects arms, legs, and potentially breathing.
Q.93Medium
During exercise, what is the primary mechanism by which muscles obtain additional oxygen?
Answer: A
Exercise triggers increased respiratory and heart rates, enhancing oxygen delivery to muscles through elevated blood flow and ventilation.
Q.94Medium
Which hormone is essential for maintaining calcium homeostasis and is activated by low blood calcium levels?
Answer: B
PTH is secreted by parathyroid glands in response to hypocalcemia, increases calcium reabsorption in kidneys, and promotes calcium mobilization from bones.
Q.95Hard
A researcher observes that blocking acetylcholinesterase leads to prolonged muscle contraction. This demonstrates that acetylcholinesterase's role is to:
Answer: C
Acetylcholinesterase breaks down acetylcholine in the synaptic cleft, terminating signal transmission; its inhibition causes acetylcholine accumulation and sustained contraction.
Q.96Hard
In a diabetic patient with hyperglycemia, which of the following best explains why glucose appears in urine?
Answer: B
Glucose is normally filtered and reabsorbed via active transport. When blood glucose exceeds ~180 mg/dL, the reabsorptive capacity is saturated, causing glycosuria.
Q.97Hard
Which neural pathway transmits pain and temperature sensation from the body to the brain?
Answer: B
The spinothalamic tract carries pain and temperature information from the spinal cord to the thalamus and sensory cortex via crossed fibers.
Q.98Medium
A patient exhibits symptoms of excessive thirst, frequent urination, and fatigue. Blood tests reveal elevated glucose levels and reduced insulin secretion. Which pancreatic cells are primarily affected in this condition?
Answer: B
The symptoms (polydipsia, polyuria, fatigue) along with elevated blood glucose and reduced insulin indicate Type 1 diabetes mellitus, where autoimmune destruction of pancreatic beta cells occurs, reducing insulin production.
Q.99Medium
Which of the following statements about the human kidney's counter-current multiplier system is correct?
Answer: B
The counter-current multiplier system in the loop of Henle (particularly the thick ascending limb) creates an osmotic gradient that enables water reabsorption in the collecting duct, essential for urine concentration.
Q.100Hard
A marathon runner experiences muscle cramps after 2 hours of intense exercise despite adequate hydration. Analysis shows normal blood glucose and electrolyte levels. Which physiological mechanism most likely explains this condition?
Answer: A
Despite normal glucose and electrolytes, prolonged high-intensity exercise causes lactate accumulation and acidosis beyond the muscle buffer system's capacity, leading to involuntary muscle cramps through disrupted calcium regulation in muscle fibers.
