CSCS: Structure & Function of Body System Flashcards

Which hormone is primarily responsible for stimulating the reabsorption of sodium in the kidney's distal tubule?

Answer: Aldosterone

Aldosterone, secreted by the adrenal cortex, promotes sodium reabsorption in the distal convoluted tubule and collecting duct to regulate fluid balance.

The sliding filament theory of muscle contraction states that muscle shortening occurs because:

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.

Which joint type allows the greatest range of motion in multiple planes?

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.

The aorta exits from which chamber of the heart?

Answer: Left ventricle

The aorta, the largest artery in the body, arises from the left ventricle and carries oxygenated blood to the systemic circulation.

Which term describes the movement of decreasing the angle at a joint?

Answer: Flexion

Flexion decreases the angle between body segments at a joint, such as bending the elbow or knee.

What is the primary energy substrate for the phosphagen (ATP-PCr) energy system?

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.

The brachial plexus innervates which region of the body?

Answer: Upper extremity

The brachial plexus is a network of nerves originating from C5–T1 that innervates the shoulder, arm, forearm, and hand.