CSCS CSCS: Structure & Function of Body System 3 — Questions and Answers
Question 1: Which hormone is primarily responsible for stimulating the reabsorption of sodium in the kidney's distal tubule?
- Cortisol
- Aldosterone (Correct answer)
- Antidiuretic hormone (ADH)
- Glucagon
Correct answer: Aldosterone
Aldosterone, secreted by the adrenal cortex, promotes sodium reabsorption in the distal convoluted tubule and collecting duct to regulate fluid balance.
Question 2: The sliding filament theory of muscle contraction states that muscle shortening occurs because:
- Actin and myosin filaments shorten in length
- Myosin filaments slide over titin proteins
- Actin filaments slide over myosin filaments, reducing sarcomere length (Correct answer)
- Z-discs dissolve during contraction
Correct answer: Actin filaments slide over myosin filaments, reducing sarcomere length
During contraction, myosin cross-bridges pull actin filaments toward the center of the sarcomere, reducing sarcomere length without changing filament lengths.
Question 3: Which joint type allows the greatest range of motion in multiple planes?
- Hinge joint
- Pivot joint
- Ball-and-socket joint (Correct answer)
- Condyloid joint
Correct answer: Ball-and-socket joint
Ball-and-socket joints (e.g., hip and shoulder) allow movement in all three planes, providing the greatest overall range of motion.
Question 4: The aorta exits from which chamber of the heart?
- Right ventricle
- Left atrium
- Right atrium
- Left ventricle (Correct answer)
Correct answer: Left ventricle
The aorta, the largest artery in the body, arises from the left ventricle and carries oxygenated blood to the systemic circulation.
Question 5: Which term describes the movement of decreasing the angle at a joint?
- Extension
- Hyperextension
- Flexion (Correct answer)
- Abduction
Correct answer: Flexion
Flexion decreases the angle between body segments at a joint, such as bending the elbow or knee.
Question 6: What is the primary energy substrate for the phosphagen (ATP-PCr) energy system?
- Glucose
- Free fatty acids
- Phosphocreatine (Correct answer)
- Glycogen
Correct answer: Phosphocreatine
The phosphagen system relies on stored phosphocreatine (PCr) to rapidly resynthesize ATP, providing energy for high-intensity efforts lasting up to ~10 seconds.
Question 7: The brachial plexus innervates which region of the body?
- Lower extremity
- Upper extremity (Correct answer)
- Thoracic wall
- Abdominal organs
Correct answer: Upper extremity
The brachial plexus is a network of nerves originating from C5–T1 that innervates the shoulder, arm, forearm, and hand.
CSCS CSCS: Structure & Function of Body System 3
Which hormone is primarily responsible for stimulating the reabsorption of sodium in the kidney's distal tubule?