NRCMA Anatomy and Physiology 2 — Questions and Answers
Question 1: The sinoatrial (SA) node is known as the heart's pacemaker because it:
- Regulates blood pressure
- Initiates the electrical impulse that triggers each heartbeat (Correct answer)
- Controls heart valve opening
- Supplies blood to the myocardium
Correct answer: Initiates the electrical impulse that triggers each heartbeat
The SA node, located in the right atrium, spontaneously generates electrical impulses at 60–100 times per minute, setting the normal heart rate.
Cardiac conduction: SA node (60–100 bpm) → AV node (40–60 bpm backup) → Bundle of His → bundle branches → Purkinje fibers → ventricular contraction. The AV node delays impulse conduction to allow atrial emptying before ventricular contraction. Dysfunction of the SA node causes sick sinus syndrome. The EKG P wave represents SA node and atrial depolarization.
Question 2: The nephron is the functional unit of which organ?
- Liver
- Spleen
- Kidney (Correct answer)
- Pancreas
Correct answer: Kidney
Each kidney contains approximately one million nephrons, which filter blood, reabsorb nutrients, and produce urine.
Nephron structure: glomerulus (filtration) → Bowman's capsule → proximal convoluted tubule (reabsorbs ~65% Na+, water, glucose) → loop of Henle → distal convoluted tubule → collecting duct → renal pelvis → ureter → bladder. Aldosterone increases Na+ reabsorption; ADH increases water reabsorption. GFR measures overall kidney function.
Question 3: Which vitamin is synthesized by the skin upon exposure to ultraviolet B (UVB) radiation?
- Vitamin A
- Vitamin B12
- Vitamin C
- Vitamin D (Correct answer)
Correct answer: Vitamin D
Ultraviolet B radiation converts 7-dehydrocholesterol in the skin to previtamin D3, which is then converted to active vitamin D (calcitriol) in the liver and kidneys.
Vitamin D (cholecalciferol/D3 from sun or diet) undergoes two-step activation: liver converts to 25-hydroxyvitamin D (calcidiol), then kidneys convert to active 1,25-dihydroxyvitamin D (calcitriol). Calcitriol increases intestinal calcium absorption and regulates bone mineralization. Deficiency causes rickets in children and osteomalacia in adults.
Question 4: The function of the cerebellum is primarily to:
- Control conscious thought and decision-making
- Regulate voluntary movement, coordination, and balance (Correct answer)
- Control the autonomic nervous system
- Regulate hormone production
Correct answer: Regulate voluntary movement, coordination, and balance
The cerebellum coordinates voluntary movements, maintains balance and posture, and refines motor skills through feedback from muscles, joints, and the vestibular system.
Brain regions: Cerebrum (frontal, parietal, temporal, occipital lobes) — conscious thought, sensation, voluntary movement. Cerebellum — movement coordination, balance. Brainstem (midbrain, pons, medulla) — vital functions such as heart rate and respiration. Hypothalamus — autonomic/endocrine regulation. Cerebellar damage causes ataxia and intention tremor.
Question 5: Which hormone is released by the posterior pituitary and promotes water reabsorption by the kidneys?
- Oxytocin
- Growth hormone (GH)
- Antidiuretic hormone (ADH/vasopressin) (Correct answer)
- Thyroid-stimulating hormone (TSH)
Correct answer: Antidiuretic hormone (ADH/vasopressin)
ADH (antidiuretic hormone, also called vasopressin) is released from the posterior pituitary in response to high blood osmolality, stimulating renal water reabsorption to concentrate urine.
ADH is produced in hypothalamic neurons and released from the posterior pituitary. Triggers include dehydration and high plasma osmolality. ADH acts on collecting ducts to insert aquaporin channels, increasing water reabsorption. Deficiency causes diabetes insipidus (excessive dilute urine). Excess (SIADH) causes dilutional hyponatremia.
Question 6: The largest artery in the human body is the:
- Pulmonary artery
- Femoral artery
- Carotid artery
- Aorta (Correct answer)
Correct answer: Aorta
The aorta is the largest artery, arising from the left ventricle and distributing oxygenated blood to the entire systemic circulation.
The aorta is divided into: ascending aorta (coronary arteries), aortic arch (subclavian, carotid arteries), descending thoracic aorta, and abdominal aorta (divides into iliac arteries). An aortic aneurysm is a life-threatening dilation. The pulmonary artery is the only artery carrying deoxygenated blood — from the right ventricle to the lungs.
NRCMA Anatomy and Physiology 2
The sinoatrial (SA) node is known as the heart's pacemaker because it: