🧬 NCLEX Physiology MCQs (101–150) with Answers and Explanations
Welcome to NCLEX Physiology MCQs Part 3 (101–150). 🎓 In this section, you’ll find 50 new multiple-choice questions with answers and explanations, carefully designed for NCLEX and nursing exam preparation. These MCQs cover key physiological systems—cardiovascular, respiratory, renal, and endocrine—helping students build exam confidence and improve understanding.
Whether you’re preparing for NCLEX (USA), NMC (UK), or any nursing board exam worldwide, these questions will strengthen your knowledge and boost your preparation.
101. The normal pacemaker of the heart is:
A) AV node
B) SA node ✅
C) Purkinje fibers
D) Bundle of His
Explanation: The sinoatrial (SA) node is the heart’s natural pacemaker. It generates the electrical impulses that set the rhythm of the heartbeat, normally 60–100 beats per minute.
102. Which part of the nephron is primarily responsible for filtration?
A) Loop of Henle
B) Distal tubule
C) Bowman’s capsule ✅
D) Collecting duct
Explanation: Bowman’s capsule surrounds the glomerulus and is the site where blood is filtered. About 180 liters of filtrate are formed daily.
103. Tidal volume in a healthy adult is approximately:
A) 100 ml
B) 500 ml ✅
C) 1000 ml
D) 1500 ml
Explanation: Tidal volume is the amount of air inhaled or exhaled in a normal breath, about 500 ml in adults.
104. Which hormone increases blood calcium levels?
A) Calcitonin
B) Parathyroid hormone (PTH) ✅
C) Insulin
D) Thyroxine
Explanation: Parathyroid hormone increases blood calcium by stimulating bone resorption, enhancing calcium absorption in intestines, and reducing excretion from kidneys.
105. What is the normal resting cardiac output in an adult?
A) 2 L/min
B) 3 L/min
C) 5 L/min ✅
D) 8 L/min
Explanation: Cardiac output is the volume of blood pumped by the heart per minute. At rest, it averages 5 liters per minute.
106. Which neurotransmitter is released at the neuromuscular junction?
A) Dopamine
B) Acetylcholine ✅
C) Serotonin
D) Noradrenaline
Explanation: At the neuromuscular junction, acetylcholine (ACh) is released, binding to receptors on muscle fibers and causing contraction.
107. The hormone aldosterone acts mainly on the:
A) Proximal tubule
B) Loop of Henle
C) Distal tubule & collecting duct ✅
D) Glomerulus
Explanation: Aldosterone promotes sodium and water reabsorption, and potassium excretion, in the distal tubule and collecting ducts of the nephron.
108. Which part of the brain regulates body temperature?
A) Cerebrum
B) Hypothalamus ✅
C) Cerebellum
D) Medulla
Explanation: The hypothalamus regulates temperature, hunger, thirst, and homeostasis. It acts like the body’s “thermostat.”
109. Which blood vessel carries oxygenated blood from the lungs to the heart?
A) Pulmonary artery
B) Pulmonary vein ✅
C) Aorta
D) Superior vena cava
Explanation: The pulmonary veins carry oxygenated blood from the lungs to the left atrium. This is an exception, as veins usually carry deoxygenated blood.
110. The normal pH of human blood is:
A) 6.8–7.0
B) 7.35–7.45 ✅
C) 7.5–7.8
D) 8.0–8.2
Explanation: Normal blood pH is 7.35–7.45, slightly alkaline. Maintaining this range is critical for enzymatic and cellular functions.
111. The exchange of gases between alveoli and blood is called:
A) Internal respiration
B) External respiration ✅
C) Cellular respiration
D) Diffusion respiration
Explanation: External respiration refers to the exchange of oxygen and carbon dioxide between alveoli and pulmonary capillaries.
112. The functional unit of the nervous system is the:
A) Brain
B) Neuron ✅
C) Spinal cord
D) Synapse
Explanation: The neuron is the structural and functional unit of the nervous system, responsible for transmitting electrical impulses.
113. Which part of the brain controls balance and coordination?
A) Medulla oblongata
B) Hypothalamus
C) Cerebellum ✅
D) Thalamus
Explanation: The cerebellum coordinates voluntary movements, posture, and balance.
114. The normal volume of cerebrospinal fluid (CSF) in adults is:
A) 10–50 ml
B) 150 ml ✅
C) 500 ml
D) 1000 ml
Explanation: Adults normally have about 150 ml of CSF, which cushions and protects the brain and spinal cord.
115. The hormone secreted by the pineal gland is:
A) Melatonin ✅
B) Serotonin
C) Dopamine
D) Cortisol
Explanation: Melatonin regulates sleep–wake cycles and circadian rhythm.
116. What is the primary function of hemoglobin?
A) Buffering blood pH
B) Transporting oxygen ✅
C) Digesting proteins
D) Producing antibodies
Explanation: Hemoglobin in red blood cells binds oxygen in the lungs and delivers it to tissues.
117. Which structure prevents food from entering the trachea during swallowing?
A) Uvula
B) Tonsils
C) Epiglottis ✅
D) Larynx
Explanation: The epiglottis acts as a flap that closes over the trachea to prevent aspiration during swallowing.
118. Normal adult respiratory rate is:
A) 8–10 breaths/min
B) 12–20 breaths/min ✅
C) 25–30 breaths/min
D) 30–40 breaths/min
Explanation: Normal resting respiration for adults is 12–20 breaths per minute.
119. Which ion is most important for muscle contraction?
A) Sodium
B) Calcium ✅
C) Potassium
D) Chloride
Explanation: Calcium ions bind to troponin, allowing actin–myosin interaction and muscle contraction.
120. Which chamber of the heart pumps blood into the systemic circulation?
A) Left atrium
B) Right atrium
C) Right ventricle
D) Left ventricle ✅
Explanation: The left ventricle pumps oxygenated blood into the aorta, supplying the entire body.
121. The enzyme that digests proteins in the stomach is:
A) Amylase
B) Pepsin ✅
C) Lipase
D) Maltase
Explanation: Pepsin, activated by stomach acid, breaks proteins into smaller peptides.
122. The hormone responsible for uterine contractions during childbirth is:
A) Progesterone
B) Estrogen
C) Oxytocin ✅
D) Prolactin
Explanation: Oxytocin stimulates uterine contractions during labor and milk ejection during breastfeeding.
123. Which organ is the main site of detoxification in the body?
A) Kidney
B) Liver ✅
C) Pancreas
D) Lungs
Explanation: The liver metabolizes toxins, drugs, and produces bile for fat digestion.
124. The largest part of the human brain is:
A) Cerebrum ✅
B) Cerebellum
C) Brainstem
D) Hypothalamus
Explanation: The cerebrum controls voluntary activities, intelligence, memory, and emotions.
125. Which vitamin is essential for normal blood clotting?
A) Vitamin A
B) Vitamin D
C) Vitamin E
D) Vitamin K ✅
Explanation: Vitamin K helps in the synthesis of clotting factors in the liver.
126. The main function of white blood cells is:
A) Transport oxygen
B) Defense against infections ✅
C) Carry nutrients
D) Store energy
Explanation: Leukocytes (WBCs) protect the body from infections and foreign substances.
127. The smallest functional unit of the kidney is:
A) Nephron ✅
B) Glomerulus
C) Loop of Henle
D) Collecting duct
Explanation: The nephron performs filtration, reabsorption, and excretion. Each kidney has about 1 million nephrons.
128. Which organ produces insulin?
A) Liver
B) Pancreas ✅
C) Stomach
D) Gallbladder
Explanation: The beta cells of the pancreas secrete insulin, regulating blood glucose levels.
129. Which muscle is responsible for breathing?
A) Diaphragm ✅
B) Intercostal muscles
C) Abdominal muscles
D) Pectoral muscles
Explanation: The diaphragm contracts during inhalation, increasing lung volume.
130. The main function of platelets is:
A) Oxygen transport
B) Blood clotting ✅
C) Immunity
D) Energy storage
Explanation: Platelets (thrombocytes) are essential for coagulation and stopping bleeding.
131. Which type of joint is the shoulder joint?
A) Hinge
B) Pivot
C) Ball-and-socket ✅
D) Saddle
Explanation: The shoulder joint allows wide range of movements due to its ball-and-socket structure.
132. The fluid-filled sac around the heart is called:
A) Pleura
B) Pericardium ✅
C) Endocardium
D) Myocardium
Explanation: The pericardium surrounds and protects the heart, reducing friction during contractions.
133. Which type of blood vessel carries blood away from the heart?
A) Veins
B) Arteries ✅
C) Capillaries
D) Venules
Explanation: Arteries always carry blood away from the heart. Most carry oxygenated blood, except the pulmonary artery.
134. What is the normal lifespan of a red blood cell?
A) 30 days
B) 60 days
C) 90 days
D) 120 days ✅
Explanation: RBCs live for about 120 days, after which they are broken down in the spleen and liver.
135. Which structure connects the throat to the middle ear?
A) Nasal cavity
B) Cochlea
C) Eustachian tube ✅
D) Auditory canal
Explanation: The Eustachian tube equalizes air pressure between the middle ear and throat.
136. Which muscle type is involuntary and non-striated?
A) Skeletal
B) Smooth ✅
C) Cardiac
D) None
Explanation: Smooth muscle is found in walls of hollow organs (stomach, intestines, vessels) and works involuntarily.
137. Which electrolyte imbalance can cause cardiac arrhythmias?
A) Sodium excess
B) Calcium deficiency
C) Potassium imbalance ✅
D) Chloride excess
Explanation: Potassium imbalance (hyperkalemia or hypokalemia) directly affects cardiac rhythm.
138. The reflex arc involves:
A) Brain, spinal cord, and muscles
B) Receptor, sensory neuron, interneuron, motor neuron, effector ✅
C) Heart and lungs
D) Spinal fluid only
Explanation: A reflex arc is the neural pathway that controls reflex actions without conscious brain involvement.
139. Which cranial nerve is responsible for vision?
A) Olfactory
B) Optic ✅
C) Vagus
D) Trigeminal
Explanation: The optic nerve (cranial nerve II) carries visual information from the retina to the brain.
140. The largest artery in the human body is:
A) Pulmonary artery
B) Aorta ✅
C) Carotid artery
D) Femoral artery
Explanation: The aorta carries oxygenated blood from the left ventricle to the systemic circulation.
141. The fluid that surrounds and cushions the fetus during pregnancy is:
A) Amniotic fluid ✅
B) Synovial fluid
C) Pleural fluid
D) Pericardial fluid
Explanation: Amniotic fluid protects and nourishes the fetus, maintaining stable temperature and cushioning.
142. The normal respiratory center is located in the:
A) Cerebrum
B) Medulla oblongata ✅
C) Cerebellum
D) Pons
Explanation: The medulla oblongata regulates automatic breathing rhythm.
143. Which part of the small intestine is mainly responsible for absorption of nutrients?
A) Duodenum
B) Jejunum ✅
C) Ileum
D) Stomach
Explanation: The jejunum is the primary site for absorption of carbohydrates, proteins, and fats.
144. The hormone responsible for milk production is:
A) Estrogen
B) Prolactin ✅
C) Oxytocin
D) Progesterone
Explanation: Prolactin, secreted by the anterior pituitary, stimulates milk synthesis after childbirth.
145. The fluid mosaic model describes:
A) Bone growth
B) Cell membrane structure ✅
C) Blood circulation
D) Kidney filtration
Explanation: The fluid mosaic model represents the cell membrane as a dynamic structure with proteins floating in a lipid bilayer.
146. The primary site of gas exchange in the lungs is:
A) Trachea
B) Bronchi
C) Alveoli ✅
D) Pleura
Explanation: Alveoli are tiny sacs where oxygen enters blood and carbon dioxide is expelled.
147. Which cranial nerve is called the “wandering nerve”?
A) Trigeminal
B) Vagus ✅
C) Glossopharyngeal
D) Accessory
Explanation: The vagus nerve (cranial nerve X) extends from the brainstem to many organs, including heart, lungs, and gut.
148. The pigment responsible for skin color is:
A) Hemoglobin
B) Carotene
C) Melanin ✅
D) Keratin
Explanation: Melanin produced by melanocytes gives skin its color and protects against UV rays.
149. Which valve prevents backflow of blood into the left atrium?
A) Aortic valve
B) Tricuspid valve
C) Mitral (bicuspid) valve ✅
D) Pulmonary valve
Explanation: The mitral valve prevents blood from flowing back into the left atrium during ventricular contraction.
150. The longest nerve in the human body is:
A) Sciatic nerve ✅
B) Vagus nerve
C) Phrenic nerve
D) Median nerve
Explanation: The sciatic nerve runs from the lower back to the feet, making it the longest and thickest nerve in the body.
That’s the end of NCLEX Physiology MCQs Part 3 (101–150) ✅. You’ve now completed a total of 150 high-quality physiology questions with answers and explanations. Keep practicing consistently and explore our Pharmacology, Anatomy, and Microbiology MCQs to cover all NCLEX subjects. 🌍