MCAT Biology : Endocrine System

Study concepts, example questions & explanations for MCAT Biology

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Example Questions

Example Question #651 : Mcat Biological Sciences

Which of the following hormones is not produced by the anterior pituitary gland?

Possible Answers:

Follicle-stimulating hormone

Growth hormone

Oxytocin

Prolactin

Correct answer:

Oxytocin

Explanation:

Oxytocin is produced by the hypothalamus and stored in the posterior pituitary gland. Upon stimulation, oxytocin is released from the posterior pituitary to cause lactation and uterine contractions during pregnancy, though it has also been linked to some social phenomena.

Growth hormone, follicle-stimulating hormone, and prolactin are produced and secreted from the anterior pituitary gland. Growth hormone promotes bone elongation and cell division. Follicle-stimulating hormone works to regulate the menstrual cycle. Prolactin stimulates milk production, while oxytocin stimulates the actual act of lactation.

Example Question #652 : Mcat Biological Sciences

A researcher is analyzing an individual with dwarfism who has a height of 4’6”. Which of the following is likely true regarding this individual?

Possible Answers:

The hGH is not synthesized properly in the hypothalamus

The LH is not synthesized properly in the hypothalamus

The LH is not synthesized properly in the anterior pituitary gland

The hGH is not synthesized properly in the anterior pituitary gland

Correct answer:

The hGH is not synthesized properly in the anterior pituitary gland

Explanation:

A major player in a growing person is the human growth hormone (hGH). hGH is a peptide hormone released from the anterior pituitary gland. Recall that the hormones secreted from the anterior pituitary gland are synthesized in the gland itself. It receives signaling hormones from the hypothalamus which tells the anterior pituitary gland to start synthesizing a particular hormone. In the case of hGH, hypothalamus releases GHRH (growth hormone releasing hormone) which signals the anterior pituitary to signal and release hGH. Since this person has a short stature, the person likely has a problem with synthesis or release of hGH from anterior pituitary gland.

Example Question #613 : Systems Biology And Tissue Types

Which of the following is false regarding the posterior and the anterior pituitary gland?

I. Posterior pituitary gland receives hormones that are synthesized in the hypothalamus

II. Both glands release peptide and steroid hormones

III. Both glands synthesize hormones that are released after they receive a signal from the hypothalamus

Possible Answers:

II and III

II only

I only

I and II

Correct answer:

II and III

Explanation:

Posterior pituitary gland has a direct connection to the hypothalamus whereas the anterior pituitary gland does not. The hormones secreted from posterior pituitary gland (oxytocin and ADH) are synthesized in the hypothalamus. Since there is a direct connection between the hypothalamus and the posterior pituitary, the synthesized hormones are transported directly into the posterior pituitary where they are stored and secreted. 

Both glands are involved in releasing several important hormones; however, all the hormones released by both pituitary glands are peptide hormones. Steroid hormones are typically synthesized in the gonads and in the adrenal medulla. 

Posterior pituitary does not synthesize its own hormones. As mentioned earlier, it receives hormones synthesized in the hypothalamus. Posterior pituitary serves to store and secrete the hormones. Anterior pituitary, on the other hand, can synthesize hormones. It often receives a signaling hormone from hypothalamus that initiates synthesis and release of hormones. For example, growth hormone releasing hormone (GHRH) released from the hypothalamus signals the anterior pituitary to synthesize growth hormone.

Example Question #653 : Mcat Biological Sciences

The luteal surge in females results when there is an increase in the concentration of __________ which, subsequently, __________ the concentration of estrogen.

Possible Answers:

follicle-stimulating hormone . . . decreases

luteinizing hormone . . . increases

follicle-stimulating hormone . . . increases

luteinizing hormone . . . decreases

Correct answer:

luteinizing hormone . . . increases

Explanation:

In a female, the luteal surge occurs during the menstrual cycle. Its main function is to increase the concentration of luteinizing hormone, or LH. LH is released in both males and females and its main function is to increase the concentration of testosterone in males and estrogen in females; therefore, the luteal surge in females increases the concentration of LH, which causes an increase in estrogen.

Example Question #654 : Mcat Biological Sciences

What hormone functions to prepare the uterus for fertilization and produces menstrual bleeding if fertilization does not occur?

Possible Answers:

Luteinizing hormone

Follicle-stimulating hormone

Progesterone

Gonadotropin-releasing hormone

Estrogen

Correct answer:

Progesterone

Explanation:

Progesterone functions to prepare the lining of the uterus for implantation of the egg, and also produces menstrual bleeding if pregnancy does not occur.

Estrogen induces the development of female sex characteristics. Follicle-stimulating hormone stimulates the synthesis and secretion of estrogen. Luteinizing hormone stimulates progesterone production. Gonadotropin-releasing hormone controls the release of follicle-stimulating hormone. 

Example Question #1 : Pancreas, Liver, And Kidney

What is the site of synthesis of glucagon?

Possible Answers:

All of these are sites of glucagon synthesis

Islets of Langerhans

Anywhere glucagon synthase is present

Alpha cells

Pancreas

Correct answer:

All of these are sites of glucagon synthesis

Explanation:

Glucagon acts in a negative feedback loop with insulin to regulate blood sugar concentration. Both hormones are secreted from the Islets of Langerhans in the pancreas. Alpha cells in the pancreas have high levels of glucagon synthase, allowing them to synthesize the hormone.

Essentially, glucagon synthase is located in alpha cells, which are found in Islets of Langerhans within the pancreas; thus, all of these answers describe the site of glucagon synthesis.

Example Question #655 : Mcat Biological Sciences

Which of the following structures acts as both an exocrine and an endocrine gland?

Possible Answers:

The pancreas

The thyroid

The gall bladder

The adrenal cortex

Correct answer:

The pancreas

Explanation:

There is a key difference between exocrine and endocrine glands. Exocrine glands release their product to the external environment, while endocrine glands release their product directly into bodily fluids. The answer is the structure that accomplishes both of these actions. The pancreas does both: it releases digestive enzymes into the small intestine (external environment), and releases hormones into the bloodstream (body fluid). Remember that the entire digestive tract is considered part of the outside environment and is lined by epithelium, rather than endothelium.

The adrenal cortex and thyroid perform only endocrine functions, while the gall bladder is only exocrine.

Example Question #632 : Biology

Insulin is secreted from what endocrine structure?

Possible Answers:

Alpha cells of the pancreas

Acinar cells of the pancreas

Adrenal medulla

Beta cells of the pancreas

Adrenal cortex

Correct answer:

Beta cells of the pancreas

Explanation:

Insulin is secreted from the beta cells of the pancreas. The alpha cells secrete glucagon, which acts in a negative feedback loop with insulin to regulate blood glucose levels.

The acinar cells of the pancreas secrete digestive enzymes, and serve the exocrine (rather than the endocrine) function of the pancreas. The adrenal medulla secretes epinephrine and norepinephrine, while the adrenal cortex releases aldosterone.

Example Question #656 : Mcat Biological Sciences

Which hormone, released from delta cells in the pancreas, is responsible for inhibiting both insulin and glucagon release?

Possible Answers:

Thyroxine

Amylin

Ghrelin

Somatostatin

Correct answer:

Somatostatin

Explanation:

Somatostatin is synthesized in the delta cells in the islets of Langerhans in the pancreas, and serves to inhibit insulin and glucagon secretion from beta and alpha cells, respectively. Somatostatin serves a number of other purposes, including inhibition of growth hormone and inhibition of the release of pancreatic digestive enzyme release.

Amylin, along with insulin, is released from the beta cells of the pancreas and acts as a synergist to insulin. Ghrelin is released from epsilon cells of the pancreas and has an array of different functions, including inducing appetite. Thyroxine refers to the thyroid hormone T4, or tetraiiodothyronine, which plays a role in metabolism.

Example Question #5 : Pancreas, Liver, And Kidney

Which of the following does NOT perform endocrine function?

Possible Answers:

Thyroid

Liver

Testes

Pancreas

All of these are endocrine organs

Correct answer:

All of these are endocrine organs

Explanation:

Endocrine organs are capable of secreting hormones into the bloodstream. Each of the given answer options performs some sort of endocrine function.

The testes secrete testosterone, and are responsible for the development of most secondary sex characteristics in males.

The thyroid gland secretes calcitonin and thyroid hormones, responsible for elevating calcium levels and increasing metabolism, respectively.

The pancreas and liver are both endocrine AND exocrine organs. As an endocrine organ, the pancreas secretes the hormones insulin and glucagon. As an exocrine organ, it secretes several enzymes that are essential for digestion in the small intestine. The liver secretes insulin-like growth factors in response to stimulation by growth hormone. As an exocrine organ, it is also responsible for producing bile to aid in digestion.

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