which hormone is responsible for regulating the sleep wake cycle
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HESI A2

HESI A2 Practice Test Anatomy and Physiology

1. Which hormone is responsible for regulating the sleep-wake cycle?

Correct answer: A

Rationale: Melatonin, produced by the pineal gland, regulates the sleep-wake cycle by responding to light and darkness in the environment. It plays a crucial role in signaling the body when it's time to sleep and wake up, helping to establish and maintain a healthy circadian rhythm. Thyroxine, Insulin, and Cortisol do not directly regulate the sleep-wake cycle, making them incorrect choices for this question.

2. What condition might result from a lack of vitamin C?

Correct answer: D

Rationale: Scurvy is the correct answer. Scurvy is a condition caused by a deficiency of vitamin C in the diet. Vitamin C is essential for collagen synthesis, and its deficiency leads to symptoms such as weakness, swollen and bleeding gums, joint pain, fatigue, and easy bruising. If left untreated, scurvy can lead to more severe complications. Choices A, B, and C are incorrect. Kwashiorkor is a severe form of malnutrition due to insufficient protein intake, pellagra is caused by a deficiency of niacin (vitamin B3), and rickets results from a deficiency of vitamin D, calcium, or phosphate.

3. Which hormone is released by the adrenal glands during stress?

Correct answer: B

Rationale: Adrenaline, also known as epinephrine, is released by the adrenal glands during stress to prepare the body for rapid action. It helps in triggering the body's fight-or-flight response, increasing heart rate, and providing a burst of energy when faced with stressful situations. Insulin (Choice A) is produced by the pancreas to regulate blood sugar levels, not by the adrenal glands. Melatonin (Choice C) is a hormone that regulates sleep-wake cycles and is produced by the pineal gland, not the adrenal glands. Cortisol (Choice D) is another hormone produced by the adrenal glands, but it is not the primary hormone released during immediate stress responses; it is more involved in long-term stress regulation.

4. What is the primary function of the small intestine in the digestive system?

Correct answer: B

Rationale: The correct answer is B: To absorb nutrients. The small intestine's main role in the digestive system is to absorb nutrients from digested food. It has specialized structures, such as villi and microvilli, that increase its surface area for efficient absorption of nutrients into the bloodstream. Choice A is incorrect because the small intestine does not primarily secrete digestive enzymes; that role is mainly carried out by the pancreas and other digestive organs. Choice C is incorrect because the small intestine primarily absorbs nutrients rather than breaking down food. Choice D is incorrect because the absorption of water primarily occurs in the large intestine, not the small intestine.

5. Which structure in the kidney is responsible for filtering blood?

Correct answer: A

Rationale: The glomerulus is the correct answer. It is a vital structure in the kidney responsible for filtering blood. The glomerulus is a network of capillaries that filters waste products and excess substances from the blood to form urine. While the Bowman's capsule, Loop of Henle, and Collecting duct are also essential components of the nephron, the primary site of blood filtration occurs at the glomerulus. The Bowman's capsule surrounds the glomerulus and collects the filtered fluid, the Loop of Henle reabsorbs water and important ions, and the Collecting duct further concentrates the urine, but none of these structures are primarily responsible for filtering blood as the glomerulus is.

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