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.62Medium
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.63Easy
Which of the following best describes the role of surfactant in respiratory physiology?
Answer: B
Pulmonary surfactant (lipid + protein) reduces surface tension in alveoli, preventing their collapse during expiration and reducing work of breathing.
Q.64Medium
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.65Easy
Which hormone primarily regulates sodium reabsorption in the distal convoluted tubule and collecting duct?
Answer: B
Aldosterone, released by the adrenal cortex, increases sodium reabsorption via mineralocorticoid receptors in the DCT and collecting duct.
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Q.66Easy
During gastric digestion, what is the primary function of pepsin?
Answer: B
Pepsin is a protease activated in the acidic stomach environment, cleaving peptide bonds in proteins to form polypeptides and oligopeptides.
Q.67Hard
A patient with spinal cord injury at T5 level loses pain sensation below the waist. Which spinal tract is likely damaged?
Answer: B
The spinothalamic tract carries pain and temperature sensation, crossing at the spinal cord level. Damage results in contralateral loss of pain sensation below the injury.
Q.68Medium
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.69Medium
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.70Medium
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.71Hard
Which mechanism explains how the kidney maintains blood pH around 7.35-7.45?
Answer: A
Kidneys reabsorb filtered HCO3- and secrete H+ ions, regulate ammonia production, and adjust acid-base balance through selective reabsorption and secretion.
Q.72Medium
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.73Hard
A patient develops Cushing's syndrome due to excessive cortisol. Which feedback mechanism is disrupted?
Answer: B
In Cushing's syndrome, elevated cortisol fails to inhibit CRH and ACTH secretion, disrupting the normal negative feedback loop of the HPA axis.
Q.74Hard
Which of the following best explains oxygen-hemoglobin dissociation curve shift to the RIGHT?
Answer: B
Right shift (Bohr effect) occurs with decreased pH, increased CO2, increased temperature, and elevated 2,3-DPG, facilitating oxygen release to tissues.
Q.75Medium
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.76Easy
A person experiences tremors and rigidity due to dopamine deficiency in the basal ganglia. What is this condition?
Answer: B
Parkinson's disease results from loss of dopaminergic neurons in the substantia nigra, causing dopamine deficiency and characteristic motor symptoms.
Q.77Medium
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.78Easy
Which of the following hormones is primarily responsible for regulating blood glucose levels during fasting?
Answer: A
Glucagon is secreted by alpha cells of pancreatic islets during fasting and increases blood glucose by promoting glycogenolysis and gluconeogenesis.
Q.79Easy
The functional unit of the kidney responsible for ultrafiltration is:
Answer: C
The glomerulus with Bowman's capsule forms the renal corpuscle, which is the site of ultrafiltration where small molecules are filtered from blood.
Q.80Easy
During muscle contraction, which protein binds to myosin heads to allow cross-bridge cycling?
Answer: B
Myosin heads bind to specific sites on actin filaments, forming cross-bridges that enable muscle contraction through the sliding filament mechanism.
