HESI A2
HESI A2 Anatomy and Physiology 2023
1. Which gland is responsible for regulating metabolism and calcium levels?
- A. Pituitary gland
- B. Adrenal gland
- C. Thyroid gland
- D. Pineal gland
Correct answer: C
Rationale: The correct answer is the thyroid gland (Choice C). The thyroid gland plays a crucial role in regulating metabolism by producing hormones like thyroxine, which control the body's metabolic rate. It also helps in controlling calcium levels in the blood through the release of calcitonin. The pituitary gland (Choice A) is known as the 'master gland' as it controls other glands but is not primarily responsible for regulating metabolism and calcium levels. The adrenal gland (Choice B) produces hormones like cortisol and adrenaline, which are involved in the stress response and metabolism, but they do not specifically regulate calcium levels. The pineal gland (Choice D) mainly produces melatonin, a hormone that helps in regulating sleep-wake cycles and has no direct role in metabolism or calcium level regulation.
2. Which of the following describes the process of osmosis?
- A. Diffusion of solutes across a membrane
- B. Movement of water across a selectively permeable membrane
- C. Movement of gases across a membrane
- D. Active transport of ions across a membrane
Correct answer: B
Rationale: Osmosis is the process where water molecules move across a selectively permeable membrane from an area of lower solute concentration to an area of higher solute concentration. This movement of water helps to equalize the concentration of solutes on both sides of the membrane. The correct description of osmosis is the movement of water across a selectively permeable membrane, making choice B the right answer. Choices A, C, and D are incorrect because osmosis specifically refers to the movement of water molecules, not solutes, gases, or ions across a membrane.
3. Which hormone regulates the sleep-wake cycle?
- A. Melatonin
- B. Insulin
- C. Cortisol
- D. Thyroxine
Correct answer: A
Rationale: Melatonin, produced by the pineal gland, is the hormone that regulates the sleep-wake cycle. Its secretion is influenced by light exposure, with levels typically rising in the evening to promote sleep and falling in the morning to encourage wakefulness. Insulin is involved in regulating blood sugar levels, not the sleep-wake cycle. Cortisol plays a role in the body's stress response and circadian rhythm but is not the primary hormone regulating sleep-wake cycles. Thyroxine is a hormone produced by the thyroid gland that regulates metabolism, not the sleep-wake cycle.
4. When the pulmonary valve and aortic valves are open, where can blood flow?
- A. Between the two ventricles of the heart
- B. From atrium to ventricle within the heart
- C. Between the heart and the rest of the body
- D. Between the atria in the heart
Correct answer: C
Rationale: When the pulmonary valve and aortic valves are open, blood can flow between the heart and the rest of the body. The pulmonary valve allows blood to flow from the right ventricle to the lungs for oxygenation, while the aortic valve permits blood to flow from the left ventricle to the rest of the body for distribution of oxygen and nutrients. This circulation pathway ensures that oxygen-rich blood is pumped to the body tissues. Choices A, B, and D are incorrect because when the pulmonary valve and aortic valves are open, blood is not flowing between the ventricles, from atrium to ventricle, or between the atria; instead, it is being pumped out of the heart to the lungs and the rest of the body.
5. Which hormone is produced by the pineal gland?
- A. Corticosteroid
- B. Oxytocin
- C. Prolactin
- D. Melatonin
Correct answer: D
Rationale: Melatonin is the hormone produced by the pineal gland. It plays a crucial role in regulating the sleep-wake cycle and is instrumental in maintaining the body's circadian rhythm. Melatonin production is triggered by darkness and inhibited by light, aiding in signaling the body when it is time to sleep. Corticosteroid, oxytocin, and prolactin are hormones produced by other glands in the body and are not associated with the pineal gland. Therefore, they are incorrect choices for this question.
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