Physiology MCQs
Physiology MCQs help medical and dental students master body functions across cardiovascular, respiratory, renal, digestive, endocrine, and neurophysiology systems. Ideal for MDCAT, NTS, USMLE, and FCPS, these quizzes boost retention and exam success.
Q: The majority of carbon dioxide is transported in blood as
A) Carbaminohemoglobin
B) Dissolved gas
C) Carbonic acid
D) Bicarbonate
✅ Correct Answer: D
Explanation: CO₂ is primarily carried as bicarbonate ions in the plasma after conversion by carbonic anhydrase.
Q: Smooth muscle in blood vessels is primarily controlled by
A) Somatic nervous system
B) Sensory nerves
C) Central nervous system
D) Autonomic nervous system
✅ Correct Answer: D
Explanation: The autonomic nervous system regulates the contraction and relaxation of vascular smooth muscle.
Q: The hormone responsible for regulating circadian rhythms is
A) Melatonin
B) Cortisol
C) Insulin
D) Serotonin
✅ Correct Answer: A
Explanation: Melatonin, secreted by the pineal gland, controls the sleep-wake cycle.
Q: The refractory period ensures unidirectional propagation of
A) Blood flow
B) Hormone release
C) Muscle contraction
D) Action potential
✅ Correct Answer: D
Explanation: It prevents a nerve impulse from traveling backward along the axon.
Q: The fluid portion of blood without clotting factors is called
A) Lymph
B) Plasma
C) Interstitial fluid
D) Serum
✅ Correct Answer: D
Explanation: Serum is plasma minus fibrinogen and other clotting proteins.
Q: The adrenal medulla secretes hormones that act as
A) Sympathetic neurotransmitters
B) Growth inhibitors
C) Antioxidants
D) Digestive enzymes
✅ Correct Answer: A
Explanation: Epinephrine and norepinephrine mimic sympathetic nervous system activity.
Q: Aldosterone increases sodium reabsorption in the
A) Distal tubule
B) Loop of Henle
C) Proximal tubule
D) Collecting duct
✅ Correct Answer: A
Explanation: Aldosterone targets cells in the distal tubule to enhance sodium retention.
Q: The hormone responsible for uterine contractions during labor is
A) Progesterone
B) FSH
C) Estrogen
D) Oxytocin
✅ Correct Answer: D
Explanation: Oxytocin stimulates strong contractions of the uterine muscles during childbirth.
Q: The process of heat loss through direct contact is called
A) Evaporation
B) Radiation
C) Conduction
D) Convection
✅ Correct Answer: C
Explanation: Conduction transfers heat directly between surfaces in contact.
Q: The hormone that raises blood calcium levels is
A) Parathyroid hormone
B) Glucagon
C) Insulin
D) Calcitonin
✅ Correct Answer: A
Explanation: Parathyroid hormone stimulates bone resorption and calcium reabsorption in kidneys.