MCAT Biology : Endocrine System

Study concepts, example questions & explanations for MCAT Biology

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Example Questions

Example Question #2 : Other Endocrine Glands

The adrenal medulla is responsible for secreting which hormone?

Possible Answers:

Aldosterone

Corticotropin-releasing hormone

Epinephrine

Cortisol

Correct answer:

Epinephrine

Explanation:

The adrenal medulla, derived from neural crest cells, is responsible for making and releasing epinephrine and norepinephrine. Epinephrine and norepinephrine are responsible for increasing heart rate and activating the sympathetic nervous system when released.  

In contrast, the adrenal cortex is derived from mesoderm and releases steroid hormones like aldosterone and cortisol. Corticotropin-releasing hormone is made by the parvocellular neurons of the hypothalamus.

Example Question #31 : Glands

The adrenal medulla is responsible for secreting which of the following hormones?

Possible Answers:

Epinephrine

Growth hormone

Thyroid-stimulating hormone

Adrenocorticotropic hormone

Correct answer:

Epinephrine

Explanation:

Epinephrine and norepinephrine are released by the neuroendocrine cells of the adrenal medulla. In times of stress and sympathetic nervous system activation, the adrenal medulla will release epinephrine to cause blood vessel constriction. These hormones allow for the "fight-or-flight" response.

In contrast, the adrenal cortex will secrete cortisol and other mineralcorticoids in response to long-term stress. These hormones are not involved in the fight-or-flight response, and rather serve to prepare the body to endure prolonged harsh conditions, such as dehydration, starvation, and extreme temperatures. Adrenocorticotropic hormone is released from the anterior pituitary to stimulate the adrenal cortex.

Growth hormone and thyroid-stimulating hormone do not interact with the adrenal gland.

Example Question #31 : Endocrine System

The hormone cortisol is synthesized in the __________ and the hormone aldosterone is synthesized in the __________.

Possible Answers:

adrenal cortex . . . adrenal cortex

adrenal medulla . . . adrenal cortex

adrenal cortex . . . adrenal medulla

adrenal medulla . . . adrenal medulla

Correct answer:

adrenal cortex . . . adrenal cortex

Explanation:

Hormones cortisol and aldosterone are synthesized in the adrenal glands. Adrenal glands are made up of the adrenal cortex and the adrenal medulla. Adrenal medulla is involved in the synthesize of catecholamines (epinephrine and norepinephrine) whereas adrenal cortex synthesizes mineralocorticoids (aldosterone), glucocorticoids (cortisol), and androgens (testosterone, DHT, and DHEA). 

Aldosterone is released upon stimulation from the renin-angiotensin system and serves to increase reabsorption of sodium in the collecting ducts of the kidney. Cortisol is released due to stress and serves to increase the metabolic rate. 

Example Question #33 : Glands

Which of the following hormones is produced by the pituitary gland?

Possible Answers:

Antidiuretic hormone

Aldosterone

Luteinizing hormone

Thyroxine

Epinephrine

Correct answer:

Luteinizing hormone

Explanation:

Luteinizing hormone is produced and secreted by the anterior pituitary gland.

Antidiuretic hormone is produced by the hypothalamus, but secreted by the posterior pituitary gland. Epinephrine is produced by the adrenal medulla; aldosterone is produced by the adrenal cortex. Thyroxine (T4) is produced by the thyroid.

Example Question #671 : Mcat Biological Sciences

A person who has over-functioning pancreatic alpha cells may display what clinical feature?

Possible Answers:

Constipation

Elevated glucose levels

Decreased glucose levels

Increased digestion

Correct answer:

Elevated glucose levels

Explanation:

The pancreatic alpha cells produce the hormone glucagon, which is responsible for stimulating gluconeogenesis and glycogenolysis. Gluconeogenesis is de novo formation of glucose, while glycogenolysis is the breakdown of glycogen into glucose. An increase in glucagon production through hyperactive alpha cells will result in increased blood glucose levels, at least temporarily. In a healthy individual, this will be combatted by an increase in insulin production from the pancreatic beta cell.

Example Question #2 : Hormone Origins And Targets

The activity of which of the following increases when parathyroid hormone is released into the blood stream?

Possible Answers:

T-cell maturation

Osteocytes

Osteoclasts

Osteoblasts

The parathyroid gland

Correct answer:

Osteoclasts

Explanation:

Parathyroid hormone causes calcium to be released from the bone into the blood stream, raising blood calcium levels. Osteoclasts reside in bone and are responsible for resorbing the hydroxyapatite matrix, releasing sequestered calcium into the blood.

Osteoblasts counter osteoclasts, building the hydroxyapatite matrix and sequestering calcium stores. Osteocytes are mostly involved in signaling. The parathyroid gland releases parathyroid hormone, but is not affected by the hormone itself. T-cell mature in the thyroid, and are not affected by parathyroid activity.

Example Question #2 : Hormones

Which hormone is responsible for stimulating glucocorticoid release from the adrenal cortex?

Possible Answers:

Prolactin

Adrenocorticotropic hormone

Thyroid-stimulating hormone

Growth hormone

Correct answer:

Adrenocorticotropic hormone

Explanation:

Adrenocorticotropic hormone (ACTH) is released from the anterior pituitary, and is responsible for stimulating secretion of glucocorticoids from the adrenal cortex. While cortisol is the most common and physiologically relevant glucocorticoid, others may also be synthesized. Adrenocorticotropic hormone release is stimulated by stress.

Example Question #4 : Hormone Origins And Targets

The hypothalamus uses two specialized types of neuron to stimulate the pituitary. Magnocellular neurons carry hormones directly to the posterior pituitary. Parvocellular neurons secrete hormones into the hypophyseal portal system, where they are delivered to the anterior pituitary.

The magnocellular neurons of the hypothalamus are responsible for secreting which hormone?

Possible Answers:

Thyroid-stimulating hormone (TSH)

Oxytocin

Dopamine

Thyrotropin-releasing hormone (TRH)

Correct answer:

Oxytocin

Explanation:

The hypothalamus is divided up into two parts: the magnocellular neurons and the parvocellular neurons. The magnocellular neurons synthesize antidiuretic hormone (ADH) and oxytocin, which are then transported to the posterior pituitary for secretion. The parvocellular neurons secrete hormones such as corticotropin-releasing hormone (CRH) and thyrotropin-releasing hormone (TRH), which are released into portal circulation to be transported to the anterior pituitary.

Example Question #5 : Hormone Origins And Targets

Which of the following statements concerning hormonal transport is true?

Possible Answers:

The thyroid hormones are able to move freely in the bloodstream

Pancreatic hormones are able to move freely through the bloodstream

Steroid hormones are able to move freely through the bloodstream

All hormones require chylomicrons in order to move through the bloodstream

Correct answer:

Pancreatic hormones are able to move freely through the bloodstream

Explanation:

The type of transport that a hormone will have through the bloodstream depends on the type of hormone. Peptide hormones are polar and can move freely through the bloodstream, while lipid soluble hormones require a carrier protein in order to move through the blood. The pancreatic hormones, glucagon and insulin, are peptide hormones. This means they can move through the bloodstream without a carrier protein.

In contrast, steroid hormones are derived from cholesterol and thyroid hormones are derived from tyrosine. Both of these hormone classes are lipid soluble, and require transport proteins to travel through the blood. The hormone-protein unit is known as a chylomicron.

Example Question #1 : Hormones

When calcitonin is released into the blood stream, the activity of which cell type is increased the most?

Possible Answers:

Osteoblasts

Osteoclasts

Hydroxyapatite cells

Osteocytes

Erythropoietic stem cells

Correct answer:

Osteoblasts

Explanation:

Calcitonin is a hormone secreted by the thyroid in response to increased blood calcium levels. It counteracts high blood calcium by stimulating the deposit of calcium into bone. Osteoblasts are the most active cells in building the hydroxyapatite matrix of bone, and would be most stimulated by the release of calcitonin.

Osteocytes are matured osteoblasts in the bond interior, and are more active in signaling and regulation than bond formation. Osteoclasts counteract osteoblasts and break down bone, usually in response to parathyroid hormone. Hydroxyapatite is the crystalline matrix encasing the bone cells, but is not a type of cell itself. Erythropoietic stem cells reside in the bone marrow and produce blood cells, but are not involved in calcium regulation.

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