Q: Which of the following is a correct sequence of events in the cyclic AMP (cAMP) second-messenger mechanism for water-soluble hormones?

$$\text{Hormone binds receptor} \rightarrow \text{Receptor activates G protein} \rightarrow \text{G protein activates adenylate cyclase} \rightarrow \text{Adenylate cyclase converts ATP to cAMP} \rightarrow \text{cAMP activates protein kinases}$$

Question 1

Which of the following best describes the main difference between endocrine and exocrine glands?

Accepted Answer

Endocrine glands are ductless and secrete hormones directly into the extracellular fluid, while exocrine glands have ducts and secrete nonhormonal substances onto membrane surfaces.

Question 2

Amino acid–based hormones (except thyroxine) are generally unable to cross the plasma membrane. How do they exert their effects on target cells?

Accepted Answer

By binding to membrane receptors and activating second-messenger systems such as cAMP.

Question 3

Which of the following is a correct sequence of events in the cyclic AMP (cAMP) second-messenger mechanism for water-soluble hormones?

Accepted Answer

$$	ext{Hormone binds receptor} ightarrow 	ext{Receptor activates G protein} ightarrow 	ext{G protein activates adenylate cyclase} ightarrow 	ext{Adenylate cyclase converts ATP to cAMP} ightarrow 	ext{cAMP activates protein kinases}$$

Question 4

Which hormone is released in response to declining blood calcium levels, and what is its primary effect?

Accepted Answer

Parathyroid hormone (PTH); stimulates osteoclasts to release calcium from bone

Question 5

A patient is experiencing symptoms of hyperglycemia. Which hormone is most likely deficient or not functioning properly, and what is its normal effect?

Accepted Answer

Insulin; lowers blood glucose by enhancing cellular uptake of glucose

Question 6

Which of the following best explains why steroid hormones typically have a longer onset of action compared to peptide hormones?

Accepted Answer

Steroid hormones activate gene transcription and protein synthesis, which takes more time.

Question 7

Which of the following is a major effect of thyroid hormone (T3 and T4) in the body?

Accepted Answer

Increases the rate of cellular metabolism

Question 8

A patient with a tumor in the adrenal cortex is found to have high blood pressure and low blood potassium. Which hormone is likely being overproduced?

Accepted Answer

Aldosterone

Question 9

Which of the following best describes the role of melatonin secreted by the pineal gland?

Accepted Answer

Promotes sleep and regulates circadian rhythms

Question 10

Which of the following is an example of a hormonal stimulus for hormone release?

Accepted Answer

Hypothalamic hormones stimulate the anterior pituitary to release its hormones.

Question 11

Which of the following statements about hormone receptors is correct?

Accepted Answer

Target cells can up-regulate or down-regulate their receptors in response to hormone levels.

Question 12

Which hormone is secreted by the heart in response to high blood volume and pressure, and what is its effect?

Accepted Answer

Atrial natriuretic peptide (ANP); increases sodium excretion and decreases blood pressure

Question 13

Which of the following best describes the effect of glucocorticoids (such as cortisol) during long-term stress?

Accepted Answer

They increase blood glucose by promoting gluconeogenesis and mobilizing fats.

Question 14

A patient is found to have low blood sodium and high blood potassium. Which hormone is most likely deficient?

Accepted Answer

Aldosterone

Question 15

Which hormone is produced by the kidneys in response to low blood oxygen, and what is its effect?

Accepted Answer

Erythropoietin; stimulates red blood cell production

Question 16

Which of the following is a correct example of a humoral stimulus for hormone release?

Accepted Answer

Low blood calcium stimulates the parathyroid glands to release PTH.

Question 17

Which hormone is secreted by adipose tissue and acts to suppress appetite?

Accepted Answer

Leptin

Question 18

Which of the following best describes the effect of up-regulation of hormone receptors?

Accepted Answer

Target cells increase the number of receptors in response to low hormone levels, making them more sensitive.

Question 19

Which hormone is primarily responsible for stimulating the development of T lymphocytes in the thymus?

Accepted Answer

Thymosins

Question 20

Which of the following is a direct effect of parathyroid hormone (PTH) on the kidneys?

Accepted Answer

Increases calcium reabsorption and stimulates activation of vitamin D

Chapter 16: The Endocrine System – Structured Study Notes

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