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.

Correct Answer: A

Rationale: The spleen plays a crucial role in the immune system by filtering blood, specifically removing old or damaged red blood cells. It also stores lymphocytes, which are white blood cells that help fight infections. While the spleen does not produce white blood cells or antibodies, its main functions lie in blood filtration and storage of immune cells. Therefore, the correct answer is A. Choice B is incorrect because the spleen does not produce white blood cells. Choice C is incorrect as the spleen stores lymphocytes but does not primarily function to do so. Choice D is incorrect because the spleen does not produce antibodies.

Correct Answer: B

Rationale: The correct answer is B: Melatonin. Melatonin, produced by the pineal gland, is the hormone involved in regulating the sleep-wake cycle. It plays a crucial role in signaling the body that it is time to sleep and is influenced by light exposure. Melatonin levels typically rise in the evening, promoting sleep, and decrease in the morning, helping in waking up. Choice A, Insulin, is involved in regulating blood sugar levels, not the sleep-wake cycle. Choice C, Cortisol, is a stress hormone that helps regulate metabolism and immune response but is not primarily involved in the sleep-wake cycle. Choice D, Thyroxine, is a hormone produced by the thyroid gland that regulates metabolism, growth, and development, but it is not directly involved in regulating the sleep-wake cycle.

Correct Answer: B

Rationale: Vitamin A is the correct answer. It is essential for maintaining healthy skin and vision, especially in low-light conditions. Vitamin A helps in the production of retinal pigments necessary for vision in dim light and supports skin health by promoting cell turnover and repair. Choice A, Vitamin C, is important for the immune system and collagen production but is not specifically known for maintaining skin and vision health. Choice C, Vitamin D, is crucial for bone health and immune function but is not directly related to skin and vision health. Choice D, Vitamin K, is necessary for blood clotting and bone health but does not play a significant role in maintaining healthy skin and vision.

Correct Answer: B

Rationale: The correct answer is B: 'To break down food.' The stomach's primary function in digestion is to break down food mechanically and chemically. It accomplishes this by mixing food with gastric acid and digestive enzymes, resulting in the formation of chyme, a semi-liquid mixture that moves on to further digestion in the small intestine. Choice A is incorrect because the absorption of nutrients occurs mainly in the small intestine, not in the stomach. Choice C is incorrect because while the stomach does secrete digestive enzymes like pepsin, its primary role is not just limited to enzyme secretion. Choice D is incorrect because the storage of glucose primarily occurs in the liver and muscles, not in the stomach.