HESI A2 Anatomy and Physiology Quizlet

Correct Answer: C

Rationale: The correct answer is C: Pineal gland. The pineal gland secretes melatonin, a hormone responsible for regulating sleep-wake cycles. It receives signals from the retina about light levels, which helps to synchronize the body's internal clock. The hypothalamus (A) regulates various bodily functions but is not specifically responsible for sleep-wake cycles. The thalamus (B) is involved in relaying sensory information but not directly related to sleep regulation. The cerebellum (D) is primarily involved in motor control and coordination, not sleep regulation. Therefore, the pineal gland is the structure in the brain that directly regulates sleep and wakefulness.

Correct Answer: C

Rationale: The correct answer is C: Pineal gland. The pineal gland secretes melatonin, a hormone responsible for regulating sleep-wake cycles. It receives signals from the retina about light levels, which helps to synchronize the body's internal clock. The hypothalamus (A) regulates various bodily functions but is not specifically responsible for sleep-wake cycles. The thalamus (B) is involved in relaying sensory information but not directly related to sleep regulation. The cerebellum (D) is primarily involved in motor control and coordination, not sleep regulation. Therefore, the pineal gland is the structure in the brain that directly regulates sleep and wakefulness.

Correct Answer: C

Rationale: The main component of the cell membrane is lipids, specifically phospholipids. They form a lipid bilayer that provides structure and acts as a barrier to regulate what enters and exits the cell. Proteins are also important in the cell membrane for various functions, but they are not the main component. Carbohydrates are found on the surface of the cell membrane for cell recognition and communication, not as the main component. Nucleic acids are not found in the cell membrane, as they are responsible for genetic information storage and protein synthesis inside the cell.

Correct Answer: B

Rationale: The correct answer is B: Vitamin K. Vitamin K is essential for blood clotting as it helps in the production of proteins necessary for the clotting process. Deficiency in Vitamin K can lead to excessive bleeding. A: Vitamin A is important for vision and immune function, not blood clotting. C: Vitamin C is important for collagen synthesis and immune function, not blood clotting. D: Vitamin D is important for calcium absorption and bone health, not blood clotting.

Correct Answer: B

Rationale: The correct answer is B: Pivot joint. Pivot joints allow for rotational movement around a single axis. This type of joint is found in the neck, allowing the head to rotate side to side. Hinge joints (choice A) allow movement in one plane like the elbow. Ball and socket joints (choice C) allow for a wide range of movement in multiple directions like the hip and shoulder. Saddle joints (choice D) allow for movement in two axes like the thumb. Therefore, the correct answer is pivot joint as it specifically allows for rotational movement around a single axis.