Keiser University
Course Number: BSC2085C
Course Title: Human Anatomy & Physiology I
Credit Hours:4.0
Exam: Midterm
Date:2026
Which ion is primarily responsible for depolarization during an action potential in skeletal muscle
fibers?
A. Calcium
B. Sodium
C. Potassium
D. Chloride
Answer: B. Sodium
Rationale: Sodium influx through voltage‑gated channels initiates depolarization, while potassium
efflux restores repolarization.
---
The primary pacemaker of the heart is located in the:
A. AV node
B. SA node
C. Bundle of His
1
,D. Purkinje fibers
Answer: B. SA node
Rationale: The sinoatrial node generates spontaneous action potentials, setting the rhythm for
cardiac contraction.
---
Which connective tissue layer surrounds individual muscle fibers?
A. Epimysium
B. Perimysium
C. Endomysium
D. Sarcolemma
Answer: C. Endomysium
Rationale: Endomysium is the delicate connective tissue surrounding each muscle fiber, while
epimysium surrounds the entire muscle.
---
Which organelle in hepatocytes is most responsible for detoxification of lipid‑soluble drugs?
A. Mitochondria
B. Rough ER
C. Smooth ER
D. Lysosomes
Answer: C. Smooth ER
Rationale: Smooth ER contains enzymes for lipid metabolism and detoxification.
2
, ---
Which hormone increases blood calcium by stimulating osteoclast activity?
A. Calcitonin
B. Parathyroid hormone
C. Aldosterone
D. Cortisol
Answer: B. Parathyroid hormone
Rationale: PTH raises serum calcium by stimulating bone resorption, renal reabsorption, and
vitamin D activation.
---
Which structure prevents backflow of blood into the right atrium during ventricular contraction?
A. Pulmonary valve
B. Tricuspid valve
C. Mitral valve
D. Aortic valve
Answer: B. Tricuspid valve
Rationale: The tricuspid valve ensures unidirectional flow from right atrium to right ventricle.
---
Which neurotransmitter is released at the neuromuscular junction?
A. Dopamine
B. Acetylcholine
3
Course Number: BSC2085C
Course Title: Human Anatomy & Physiology I
Credit Hours:4.0
Exam: Midterm
Date:2026
Which ion is primarily responsible for depolarization during an action potential in skeletal muscle
fibers?
A. Calcium
B. Sodium
C. Potassium
D. Chloride
Answer: B. Sodium
Rationale: Sodium influx through voltage‑gated channels initiates depolarization, while potassium
efflux restores repolarization.
---
The primary pacemaker of the heart is located in the:
A. AV node
B. SA node
C. Bundle of His
1
,D. Purkinje fibers
Answer: B. SA node
Rationale: The sinoatrial node generates spontaneous action potentials, setting the rhythm for
cardiac contraction.
---
Which connective tissue layer surrounds individual muscle fibers?
A. Epimysium
B. Perimysium
C. Endomysium
D. Sarcolemma
Answer: C. Endomysium
Rationale: Endomysium is the delicate connective tissue surrounding each muscle fiber, while
epimysium surrounds the entire muscle.
---
Which organelle in hepatocytes is most responsible for detoxification of lipid‑soluble drugs?
A. Mitochondria
B. Rough ER
C. Smooth ER
D. Lysosomes
Answer: C. Smooth ER
Rationale: Smooth ER contains enzymes for lipid metabolism and detoxification.
2
, ---
Which hormone increases blood calcium by stimulating osteoclast activity?
A. Calcitonin
B. Parathyroid hormone
C. Aldosterone
D. Cortisol
Answer: B. Parathyroid hormone
Rationale: PTH raises serum calcium by stimulating bone resorption, renal reabsorption, and
vitamin D activation.
---
Which structure prevents backflow of blood into the right atrium during ventricular contraction?
A. Pulmonary valve
B. Tricuspid valve
C. Mitral valve
D. Aortic valve
Answer: B. Tricuspid valve
Rationale: The tricuspid valve ensures unidirectional flow from right atrium to right ventricle.
---
Which neurotransmitter is released at the neuromuscular junction?
A. Dopamine
B. Acetylcholine
3
