MCAT Biology : Endocrine System

Study concepts, example questions & explanations for MCAT Biology

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Example Questions

Example Question #34 : Hormones

Which hormone is responsible for increasing episodes of mitosis, increasing cell size, and increasing the rate of protein synthesis?

Possible Answers:

Thyroid-stimulating hormone

Growth hormone

Adrenocorticotropic hormone

Prolactin

Correct answer:

Growth hormone

Explanation:

Growth hormone is secreted by the anterior pituitary and is responsible for increased metabolism and cell growth. Growth hormone increases glucose and free fatty acid levels in the blood, increasing substrates for metabolism for other cells in the body.

Example Question #711 : Mcat Biological Sciences

Which anterior pituitary hormone plays a role in stimulating spermatogenesis in males?

Possible Answers:

Estradiol

Testosterone

Follicle-stimulating hormone

Adrenocorticotropic hormone

Correct answer:

Follicle-stimulating hormone

Explanation:

Under normal conditions, spermatogenesis is somewhat inhibited. Follicle-stimulating hormone, luteinizing hormone, and testosterone can act to overcome this inhibition and promote sperm development. Testosterone, however, is produced in the testes, not the anterior pituitary.

Example Question #11 : Hormone Mechanisms And Effects

Which hormone is required for milk secretion in women?

Possible Answers:

Estrogen

Oxytocin

Luteinizing hormone

Prolactin

Correct answer:

Oxytocin

Explanation:

Oxytocin is responsible for milk secretion in women. Notice that prolactin is responsible for milk production, but oxytocin is responsible for milk secretion. Oxytocin is released from the posterior pituitary and is responsible for contractions during pregnancy and milk secretion.

Example Question #35 : Hormones

Mineralocorticoids, including aldosterone, are able to maintain blood pressure during times of stress. Which of the following is not an effect of aldosterone?

Possible Answers:

Decreased blood potassium levels

Increased blood pressure

Decreased blood sodium levels

Decreased urine sodium content

Correct answer:

Decreased blood sodium levels

Explanation:

The mineralocorticoid aldosterone is stimulated by the renin-angiotensin system of the kidney when blood volume falls. Aldosterone acts at the distal convoluted tubule of the kidney to increase sodium reabsorption, thus raising sodium levels in the blood and lowering sodium levels in the urine. Aldosterone also increases potassium excretion, thus causing low levels of potassium in the blood. The overall retention of sodium draws water from the filtrate into the blood, causing increased blood pressure by increasing blood volume.

Example Question #712 : Mcat Biological Sciences

Cortisol, a glucocorticoid, is able to help maintain the body's metabolic state during times of stress. Which of the following is not a function of cortisol?

Possible Answers:

Increase blood free fatty acids

Increase sex hormone levels

Increase protein metabolism

Increase blood glucose

Correct answer:

Increase sex hormone levels

Explanation:

Cortisol secretion, stimulated from the adrenal cortex by adrenocorticotropic hormone from the anterior pituitary, is responsible for protecting against hypoglycemia and hypotension. Cortisol increases blood glucose, increases blood free fatty acids by stimulating lipolysis, and increases breakdown of muscle proteins. The net result is more substrate to undergo glycolysis and the citric acid cycle during periods of poor nutrition and starvation.

Cortisol does not elevate sex hormone levels. Evolutionarily, it is disadvantageous to produce offspring during times of stress or poor nutrition.

Example Question #713 : Mcat Biological Sciences

What hormone is directly responsible for increasing the amount of water reabsorbed in the kidney collecting ducts?

Possible Answers:

Renin

Vasopressin

Aldosterone

Adrenocorticotropic hormone

Correct answer:

Vasopressin

Explanation:

Vasopressin (antidiuretic hormone) is responsible for placing aquaporin channels on the collecting ducts of the kidney to allow for increased water reabsorption. This increased water reabsorption allows for blood pressure to be maintained. Interestingly, coffee and alcohol are vasopressin blockers, causing a large increase in urine volume when ingested.

Aldosterone, in contrast, causes a retention of sodium ions, which indirectly draws water out of the filtrate to concentrate the urine. Aldosterone does not affect permeability of the collecting duct to water. Renin indirectly leads to increases in both vasopressin and aldosterone, but has no direct effect on the collecting duct by itself.

Example Question #13 : Hormone Mechanisms And Effects

Which hormone is responsible for stimulating milk production in women?

Possible Answers:

Prolactin

Luteinizing hormone

Oxytocin

Estrogen

Correct answer:

Prolactin

Explanation:

Prolactin is responsible for stimulating milk production in women. While other hormones need a stimulus to trigger secretion, prolactin is tonically secreted, but its action is stopped by the neurotransmitter dopamine. During the period of nursing, the stimulus of the baby suckling inhibits dopamine, allowing for the release of prolactin and the production of milk.

Example Question #16 : Hormone Mechanisms And Effects

Which hormone is responsible for stimulating the production of T4 and T3 from the thyroid gland?

Possible Answers:

Thyrotropin-releasing hormone

Parathyroid hormone

Growth hormone

Thyroid-stimulating hormone

Correct answer:

Thyroid-stimulating hormone

Explanation:

Thyroid-stimulating hormone is produced by the anterior pituitary, and is responsible for stimulating T4 (tetraiodothyronine) and T3 (triiodothyronine) release from follicular cells in the thyroid gland. Too much thyroid-stimulating hormone can cause large lumps in the neck due to thyroid gland inflammation, called goiters. Goiters commonly result from an iodine deficiency, as the structures of both T4 and T3 require a central iodine atom.

Thyrotropin-releasing hormone is responsible for stimulating release of thyroid-stimulating hormone. Parathyroid hormone is important for regulating blood calcium, while growth hormone is involved in mitotic stimulation and nutrient balances.

Example Question #71 : Endocrine System

Which hormone is responsible for stimulating estrogen synthesis in the female ovaries?

Possible Answers:

Oxytocin

Prolactin

Progesterone

Follicle-stimulating hormone

Correct answer:

Follicle-stimulating hormone

Explanation:

Follicle-stimulating hormone is responsible for stimulating estrogen synthesis in the female ovaries.

Luteinizing hormone acts on Theca cells to stimulate androstenedione production (the precursor to estrogen), then follicle-stimulating hormone acts on granulosa cells to stimulate estrogen production. Both luteinizing hormone and follicle-stimulating hormone are required for estrogen production, but follicle-stimulating hormone is ultimately required for estrogen synthesis and secretion.

Example Question #714 : Mcat Biological Sciences

A camper becomes lost and does not drink water for 48 hours. At the end of this time, which significant changes in hormone production would be expected in the camper?

Possible Answers:

Increased insulin

Decreased glucocorticoids

Decreased aldosterone

Increased antidiuretic hormone (ADH)

Correct answer:

Increased antidiuretic hormone (ADH)

Explanation:

The function of antidiuretic hormone, or vasopressin, is to reabsorb water in the kidney tubules, thereby retaining water in the body. After dehydration, the camper's antidiuretic hormone levels would be high in order to preserve the water in his or her body.

Glucocorticoids, such as cortisol, have various functions; they reduce inflammation and prepare the body for long-term stress. Dehydration signals the body to prepare for long-term stress, increasing glucocorticoid levels.

Aldosterone increases sodium retention, drawing water out of filtrate and acting to counter dehydration. We would expect aldosterone to be elevated.

Insulin lowers blood glucose, but the camper would need to use glucose as energy causing this hormone to be decreased.

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