✨ Introduction
Physiology is the backbone of nursing and medical sciences, as it explains how the human body functions. For NCLEX preparation, mastering physiology concepts is essential to answer patient care and clinical scenario-based questions. This set of 50 carefully designed NCLEX Physiology MCQs covers vital topics such as the cardiovascular, respiratory, nervous, renal, and endocrine systems. Each question is provided with the correct answer and a brief explanation to strengthen your concepts. These practice questions are perfect for nursing students and medical aspirants aiming to succeed in high-stakes exams like NCLEX, NLE, and other nursing board tests.
1. Which organ is primarily responsible for maintaining homeostasis in blood glucose levels?
A. Liver
B. Kidney
C. Pancreas
D. Heart
✅ Answer: C. Pancreas
💡 Explanation: The pancreas regulates blood glucose by releasing insulin (lowers glucose) and glucagon (raises glucose). This balance is crucial for maintaining homeostasis.
2. What is the primary function of hemoglobin in red blood cells?
A. Transport nutrients
B. Carry oxygen
C. Maintain blood pressure
D. Regulate body temperature
✅ Answer: B. Carry oxygen
💡 Explanation: Hemoglobin binds oxygen in the lungs and delivers it to tissues. It also helps in transporting a small amount of carbon dioxide back to the lungs.
3. Which part of the nephron is responsible for the majority of water reabsorption?
A. Distal convoluted tubule
B. Proximal convoluted tubule
C. Loop of Henle
D. Collecting duct
✅ Answer: B. Proximal convoluted tubule
💡 Explanation: About 65–70% of filtered water and electrolytes are reabsorbed in the proximal convoluted tubule, making it the main site of reabsorption.
4. The sinoatrial (SA) node is also known as the:
A. Pacemaker of the heart
B. AV node regulator
C. Conduction pathway
D. Bundle of His
✅ Answer: A. Pacemaker of the heart
💡 Explanation: The SA node initiates the electrical impulse that triggers each heartbeat, setting the pace of cardiac rhythm.
5. Which part of the brain regulates balance and coordination?
A. Cerebrum
B. Cerebellum
C. Medulla oblongata
D. Hypothalamus
✅ Answer: B. Cerebellum
💡 Explanation: The cerebellum coordinates voluntary movements, balance, and posture, ensuring smooth and precise body functions.
6. Which hormone stimulates milk production after childbirth?
A. Oxytocin
B. Prolactin
C. Estrogen
D. Progesterone
✅ Answer: B. Prolactin
💡 Explanation: Prolactin, secreted by the anterior pituitary gland, stimulates mammary glands to produce milk. Oxytocin, on the other hand, helps with milk ejection.
7. Gas exchange between blood and tissues occurs at which level?
A. Arteries
B. Veins
C. Capillaries
D. Venules
✅ Answer: C. Capillaries
💡 Explanation: Capillaries have thin walls that allow oxygen, nutrients, and waste products to move between blood and body tissues.
8. Which part of the digestive system is the primary site of nutrient absorption?
A. Stomach
B. Small intestine
C. Large intestine
D. Esophagus
✅ Answer: B. Small intestine
💡 Explanation: The small intestine, especially the jejunum and ileum, absorbs most nutrients like carbohydrates, proteins, fats, vitamins, and minerals.
9. Which ion is most important in generating an action potential in nerve cells?
A. Calcium
B. Sodium
C. Potassium
D. Chloride
✅ Answer: B. Sodium
💡 Explanation: The rapid influx of sodium ions into the neuron causes depolarization, leading to the generation of an action potential.
10. Which blood vessel carries oxygenated blood from the lungs to the heart?
A. Pulmonary artery
B. Aorta
C. Pulmonary vein
D. Vena cava
✅ Answer: C. Pulmonary vein
💡 Explanation: Unlike most veins, the pulmonary vein carries oxygen-rich blood from the lungs to the left atrium of the heart.
11. Which structure prevents food from entering the trachea during swallowing?
A. Uvula
B. Epiglottis
C. Pharynx
D. Larynx
✅ Answer: B. Epiglottis
💡 Explanation: The epiglottis acts like a flap, closing over the trachea when swallowing, ensuring that food enters the esophagus instead of the airway.
12. What is the normal resting heart rate in a healthy adult?
A. 40–60 beats per minute
B. 60–100 beats per minute
C. 100–120 beats per minute
D. 120–140 beats per minute
✅ Answer: B. 60–100 beats per minute
💡 Explanation: The normal range is 60–100 bpm. Rates lower may indicate bradycardia, and higher may suggest tachycardia.
13. Which part of the nephron is mainly responsible for urine concentration?
A. Bowman’s capsule
B. Loop of Henle
C. Distal convoluted tubule
D. Proximal convoluted tubule
✅ Answer: B. Loop of Henle
💡 Explanation: The descending loop reabsorbs water, while the ascending loop reabsorbs ions. Together, they concentrate urine efficiently.
14. Which vitamin is essential for normal blood clotting?
A. Vitamin A
B. Vitamin D
C. Vitamin E
D. Vitamin K
✅ Answer: D. Vitamin K
💡 Explanation: Vitamin K is vital for synthesizing clotting factors (prothrombin and others) in the liver, preventing excessive bleeding.
15. The “lub-dub” sound of the heart is caused by:
A. Blood flowing through coronary arteries
B. Contraction of atria and ventricles
C. Closure of heart valves
D. Electrical conduction
✅ Answer: C. Closure of heart valves
💡 Explanation: “Lub” = closure of atrioventricular valves (tricuspid & mitral). “Dub” = closure of semilunar valves (aortic & pulmonary).
16. Which lobe of the brain processes visual information?
A. Frontal lobe
B. Parietal lobe
C. Temporal lobe
D. Occipital lobe
✅ Answer: D. Occipital lobe
💡 Explanation: The occipital lobe contains the primary visual cortex, responsible for interpreting signals from the eyes.
17. What is the primary function of platelets in the blood?
A. Oxygen transport
B. Fighting infection
C. Blood clotting
D. Hormone transport
✅ Answer: C. Blood clotting
💡 Explanation: Platelets form clots by aggregating at injury sites and activating clotting factors, preventing excessive blood loss.
18. The hormone aldosterone primarily regulates:
A. Blood sugar levels
B. Sodium and potassium balance
C. Calcium metabolism
D. Protein synthesis
✅ Answer: B. Sodium and potassium balance
💡 Explanation: Aldosterone, secreted by the adrenal cortex, increases sodium reabsorption and potassium excretion, helping regulate blood pressure.
19. Which type of muscle is found in the walls of internal organs like the stomach and intestines?
A. Skeletal muscle
B. Smooth muscle
C. Cardiac muscle
D. Voluntary muscle
✅ Answer: B. Smooth muscle
💡 Explanation: Smooth muscle is involuntary and non-striated, controlling slow, sustained contractions in organs like the stomach, intestines, and bladder.
20. Which ion is essential for muscle contraction by binding to troponin?
A. Sodium
B. Potassium
C. Calcium
D. Magnesium
✅ Answer: C. Calcium
💡 Explanation: Calcium ions bind to troponin, allowing actin and myosin filaments to interact, which initiates muscle contraction.
21. Which part of the nervous system controls involuntary activities like heartbeat and digestion?
A. Somatic nervous system
B. Autonomic nervous system
C. Central nervous system
D. Peripheral nervous system
✅ Answer: B. Autonomic nervous system
💡 Explanation: The autonomic nervous system (sympathetic & parasympathetic) regulates involuntary functions such as heart rate, digestion, and gland activity.
22. Which chamber of the heart pumps oxygenated blood to the entire body?
A. Right atrium
B. Right ventricle
C. Left atrium
D. Left ventricle
✅ Answer: D. Left ventricle
💡 Explanation: The left ventricle has thick muscular walls that pump oxygenated blood into the aorta for distribution throughout the body.
23. What is the functional unit of the nervous system?
A. Nephron
B. Neuron
C. Axon
D. Synapse
✅ Answer: B. Neuron
💡 Explanation: Neurons transmit electrical and chemical signals, making them the fundamental units of the nervous system.
24. Which organ produces bile?
A. Pancreas
B. Liver
C. Stomach
D. Gallbladder
✅ Answer: B. Liver
💡 Explanation: The liver produces bile, which is stored in the gallbladder and released into the small intestine to help digest fats.
25. Which part of the respiratory system is the site of gas exchange?
A. Trachea
B. Bronchi
C. Alveoli
D. Pleura
✅ Answer: C. Alveoli
💡 Explanation: Alveoli are tiny air sacs in the lungs where oxygen diffuses into the blood and carbon dioxide diffuses out.
26. Which blood group is considered the universal donor?
A. A+
B. B–
C. AB+
D. O–
✅ Answer: D. O–
💡 Explanation: O negative blood has no antigens on red cells and can be safely transfused to almost all patients.
27. Which organ regulates blood glucose by secreting insulin and glucagon?
A. Pancreas
B. Kidney
C. Liver
D. Thyroid
✅ Answer: A. Pancreas
💡 Explanation: The pancreas secretes insulin (lowers glucose) and glucagon (raises glucose) to maintain blood sugar balance.
28. Which structure connects muscles to bones?
A. Ligaments
B. Tendons
C. Cartilage
D. Fascia
✅ Answer: B. Tendons
💡 Explanation: Tendons are strong fibrous tissues that attach muscles to bones, enabling movement.
29. Which blood vessel carries oxygenated blood from the lungs to the heart?
A. Pulmonary artery
B. Pulmonary vein
C. Aorta
D. Vena cava
✅ Answer: B. Pulmonary vein
💡 Explanation: Unlike most veins, pulmonary veins carry oxygen-rich blood from the lungs to the left atrium.
30. Which hormone regulates metabolism by controlling the rate of energy use in cells?
A. Cortisol
B. Insulin
C. Thyroxine (T4)
D. Aldosterone
✅ Answer: C. Thyroxine (T4)
💡 Explanation: Thyroxine, produced by the thyroid gland, regulates basal metabolic rate and energy usage.
31. Which organ is primarily responsible for detoxifying harmful substances?
A. Kidney
B. Liver
C. Spleen
D. Lungs
✅ Answer: B. Liver
💡 Explanation: The liver detoxifies drugs, alcohol, and harmful substances while producing vital proteins.
32. The sinoatrial (SA) node is also known as:
A. Pacemaker of the heart
B. AV node
C. Bundle of His
D. Purkinje fibers
✅ Answer: A. Pacemaker of the heart
💡 Explanation: The SA node generates electrical impulses that set the rhythm of the heartbeat.
33. Which type of blood cell is primarily responsible for immune defense?
A. Red blood cells
B. Platelets
C. White blood cells
D. Plasma cells
✅ Answer: C. White blood cells
💡 Explanation: WBCs (lymphocytes, neutrophils, etc.) fight infection and provide immunity.
34. Which part of the brain regulates balance and coordination?
A. Cerebrum
B. Cerebellum
C. Brainstem
D. Hypothalamus
✅ Answer: B. Cerebellum
💡 Explanation: The cerebellum integrates sensory input to coordinate voluntary movements and maintain balance.
35. Which hormone triggers ovulation in females?
A. FSH
B. LH
C. Estrogen
D. Progesterone
✅ Answer: B. LH (Luteinizing Hormone)
💡 Explanation: LH surge triggers the release of an egg from the ovary during ovulation.
36. Which organ is known as the “filter” of the blood?
A. Kidney
B. Liver
C. Spleen
D. Pancreas
✅ Answer: A. Kidney
💡 Explanation: The kidneys filter waste products, excess salts, and water from the blood to form urine.
37. Which vitamin deficiency causes rickets?
A. Vitamin A
B. Vitamin B12
C. Vitamin C
D. Vitamin D
✅ Answer: D. Vitamin D
💡 Explanation: Lack of Vitamin D leads to poor calcium absorption, causing soft and weak bones (rickets).
38. Which artery supplies blood to the heart muscle itself?
A. Pulmonary artery
B. Coronary arteries
C. Aorta
D. Carotid arteries
✅ Answer: B. Coronary arteries
💡 Explanation: Coronary arteries supply oxygen-rich blood directly to the heart muscle.
39. Which part of the digestive system absorbs most nutrients?
A. Stomach
B. Small intestine
C. Large intestine
D. Esophagus
✅ Answer: B. Small intestine
💡 Explanation: The small intestine has villi and microvilli that increase surface area for nutrient absorption.
40. Which structure carries urine from the kidneys to the bladder?
A. Urethra
B. Ureter
C. Nephron
D. Renal vein
✅ Answer: B. Ureter
💡 Explanation: The ureters are muscular tubes that transport urine from kidneys to bladder.
41. What is the primary gas that stimulates breathing?
A. Oxygen
B. Carbon dioxide
C. Nitrogen
D. Carbon monoxide
✅ Answer: B. Carbon dioxide
💡 Explanation: Rising CO₂ levels in blood stimulate the medulla to increase breathing rate.
42. Which gland regulates sleep-wake cycles by producing melatonin?
A. Pituitary gland
B. Pineal gland
C. Adrenal gland
D. Thyroid gland
✅ Answer: B. Pineal gland
💡 Explanation: The pineal gland produces melatonin, regulating circadian rhythms and sleep.
43. Which structure connects the fetus to the placenta?
A. Amniotic sac
B. Umbilical cord
C. Yolk sac
D. Cervix
✅ Answer: B. Umbilical cord
💡 Explanation: The umbilical cord supplies oxygen and nutrients from the placenta to the fetus.
44. Which muscle is primarily responsible for breathing?
A. Intercostal muscles
B. Pectoralis major
C. Diaphragm
D. Latissimus dorsi
✅ Answer: C. Diaphragm
💡 Explanation: The diaphragm contracts and flattens to expand the lungs during inhalation.
45. Which hormone is released during stress as the “fight or flight” response?
A. Insulin
B. Cortisol
C. Adrenaline (epinephrine)
D. Thyroxine
✅ Answer: C. Adrenaline (epinephrine)
💡 Explanation: Epinephrine increases heart rate, blood pressure, and energy supply during emergencies.
46. Which part of the eye controls the amount of light entering?
A. Retina
B. Cornea
C. Iris
D. Lens
✅ Answer: C. Iris
💡 Explanation: The iris adjusts pupil size, controlling how much light enters the eye.
47. Which blood vessel returns deoxygenated blood from the body to the right atrium?
A. Pulmonary artery
B. Pulmonary vein
C. Aorta
D. Vena cava
✅ Answer: D. Vena cava
💡 Explanation: The superior and inferior vena cava return deoxygenated blood from the body to the right atrium.
48. What is the basic structural and functional unit of the kidney?
A. Nephron
B. Glomerulus
C. Loop of Henle
D. Ureter
✅ Answer: A. Nephron
💡 Explanation: Each kidney contains about a million nephrons that filter blood and produce urine.
49. Which electrolyte imbalance can cause irregular heart rhythms?
A. Sodium
B. Potassium
C. Chloride
D. Calcium
✅ Answer: B. Potassium
💡 Explanation: Both hyperkalemia and hypokalemia can disrupt cardiac electrical activity.
50. Which part of the brain regulates hunger, thirst, and body temperature?
A. Cerebellum
B. Hypothalamus
C. Brainstem
D. Cerebrum
✅ Answer: B. Hypothalamus
💡 Explanation: The hypothalamus maintains homeostasis by regulating vital drives and body temperature.
Also Visit: NCLEX Pharmacology
Regular practice of Physiology MCQs can make complex concepts easier and boost exam confidence. This Part 1 (1–50) is the beginning of a complete Physiology MCQs series for NCLEX preparation. Here is the Part 2 (51–100) and further sets covering more challenging and clinically relevant questions. Keep practicing and enhance your success rate in NCLEX and other nursing exams.