A mutation in the genes encoding dystrophin protein leads to:
AType 1 diabetes
BDuchenne muscular dystrophy
CMyasthenia gravis
DTetanus
Correct Answer:
B. Duchenne muscular dystrophy
EXPLANATION
Dystrophin is a structural protein that stabilizes muscle cell membranes; its absence causes Duchenne muscular dystrophy with progressive muscle weakness.
During inspiration, which of the following occurs?
ADiaphragm relaxes and thoracic cavity volume decreases
BExternal intercostal muscles contract and thoracic cavity volume increases
CIntrapleural pressure increases
DAir moves out of the lungs
Correct Answer:
B. External intercostal muscles contract and thoracic cavity volume increases
EXPLANATION
During inspiration, external intercostal muscles contract, increasing thoracic volume, decreasing intrapleural pressure, and allowing air to flow into lungs.
The countercurrent multiplier mechanism in the Loop of Henle is essential for:
AFiltration of blood
BProduction of hyperosmotic urine
CSecretion of excess ions
DReabsorption of glucose
Correct Answer:
B. Production of hyperosmotic urine
EXPLANATION
The countercurrent multiplier creates an osmotic gradient allowing the production of concentrated urine by establishing osmolarity differences in the medulla.
A student experiences increased heart rate and dilated pupils during an exam. Which division of the autonomic nervous system is responsible?
AParasympathetic division
BSympathetic division
CEnteric nervous system
DSomatic nervous system
Correct Answer:
B. Sympathetic division
EXPLANATION
The sympathetic nervous system triggers 'fight or flight' responses including increased heart rate and pupil dilation via norepinephrine and epinephrine.
Which of the following is the primary site of digestion of carbohydrates?
AMouth and small intestine
BStomach only
CLarge intestine
DEsophagus
Correct Answer:
A. Mouth and small intestine
EXPLANATION
Carbohydrate digestion begins in the mouth with salivary amylase and continues in the small intestine with pancreatic amylase and brush border enzymes.
During the refractory period following an action potential, why is it difficult to generate another action potential?
AAll sodium channels are permanently closed
BVoltage-gated sodium channels are inactivated while potassium channels are still open
CThe membrane potential has become more negative than resting potential
DNeurotransmitters have been depleted
Correct Answer:
B. Voltage-gated sodium channels are inactivated while potassium channels are still open
EXPLANATION
During the refractory period, sodium channels enter an inactivated state (unable to reopen immediately) while potassium channels remain open, hyperpolarizing the membrane.
A patient with severe dehydration experiences increased blood osmolarity. Which hormone is primarily released to counteract this condition?
AAldosterone
BAntidiuretic hormone (ADH)
CAtrial natriuretic peptide
DParathyroid hormone
Correct Answer:
B. Antidiuretic hormone (ADH)
EXPLANATION
ADH (vasopressin) is released in response to increased blood osmolarity, increases aquaporin-2 channels in collecting ducts, and promotes water reabsorption.
Which of the following represents the correct sequence of blood flow through the heart?
ARA → RV → Lungs → LA → LV → Aorta
BLA → LV → Lungs → RA → RV → Aorta
CRA → LA → RV → LV → Lungs → Aorta
DRV → RA → LA → LV → Lungs → Aorta
Correct Answer:
A. RA → RV → Lungs → LA → LV → Aorta
EXPLANATION
Deoxygenated blood returns to right atrium, passes to right ventricle, pumped to lungs, oxygenated blood returns to left atrium, then left ventricle, and exits via aorta.
