Table of contents

1. Introduction to Anatomy & Physiology5h 43m
2. Cell Chemistry & Cell Components12h 36m
3. Energy & Cell Processes10h 6m
4. Tissues & Histology10h 3m
5. Integumentary System2h 20m
6. Bones & Skeletal Tissue2h 16m
7. The Skeletal System2h 35m
8. Joints2h 17m
9. Muscle Tissue2h 33m
10. Muscles1h 11m
11. Nervous Tissue and Nervous System1h 35m
12. The Central Nervous System1h 6m
- Introduction to the Central Nervous System
  18m
- The Cerebrum
  48m
13. The Peripheral Nervous System1h 26m
14. The Autonomic Nervous System1h 38m
15. The Special Senses2h 41m
16. The Endocrine System2h 48m
17. The Blood3h 22m
18. The Heart3h 42m
19. The Blood Vessels3h 35m
20. The Lymphatic System3h 16m
21. The Immune System14h 37m
22. The Respiratory System3h 20m
23. The Digestive System2h 5m
24. Metabolism and Nutrition4h 0m
25. The Urinary System2h 39m
26. Fluid and Electrolyte Balance, Acid Base Balance37m
27. The Reproductive System2h 5m
28. Human Development1h 21m
29. Heredity3h 32m

16. The Endocrine System

The Hypothalamus and Pituitary Gland

Anatomy & Physiology

16. The Endocrine System

The Hypothalamus and Pituitary Gland

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Problem 15

Textbook Question

Describe the components of the hypothalamic-pituitary-adrenocortical axis, and explain how it regulates secretion from the adrenal gland.

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The hypothalamic-pituitary-adrenocortical (HPA) axis is a major neuroendocrine system that regulates stress responses, energy metabolism, and immune function. It involves three primary components: the hypothalamus, the pituitary gland, and the adrenal glands.

The hypothalamus, located in the brain, releases corticotropin-releasing hormone (CRH) in response to stress or other stimuli. CRH travels through the hypophyseal portal system to the anterior pituitary gland.

The anterior pituitary gland responds to CRH by secreting adrenocorticotropic hormone (ACTH) into the bloodstream. ACTH acts as a signaling molecule that targets the adrenal glands, located on top of the kidneys.

The adrenal glands consist of two main regions: the adrenal cortex and the adrenal medulla. ACTH specifically stimulates the adrenal cortex to produce and release glucocorticoids, such as cortisol, which play a key role in stress response, metabolism, and immune regulation.

Cortisol exerts negative feedback on both the hypothalamus and the anterior pituitary gland, reducing the secretion of CRH and ACTH to maintain homeostasis and prevent excessive hormone production. This feedback loop ensures the HPA axis remains balanced.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Hypothalamic-Pituitary-Adrenocortical Axis (HPA Axis)

The HPA axis is a complex set of interactions among the hypothalamus, pituitary gland, and adrenal glands that regulates stress response and various bodily functions. It begins with the hypothalamus releasing corticotropin-releasing hormone (CRH), which stimulates the pituitary gland to secrete adrenocorticotropic hormone (ACTH). This hormone then prompts the adrenal glands to produce cortisol, a key stress hormone.

Corticotropin-Releasing Hormone (CRH)

CRH is a peptide hormone produced by the hypothalamus that plays a crucial role in the stress response. It is released into the bloodstream and acts on the anterior pituitary gland to stimulate the secretion of ACTH. Elevated levels of CRH are typically associated with stress, leading to a cascade of hormonal changes that prepare the body to respond to stressors.

Adrenal Gland Function

The adrenal glands, located on top of each kidney, are responsible for producing various hormones, including cortisol, adrenaline, and aldosterone. In the context of the HPA axis, cortisol is particularly important as it helps regulate metabolism, immune response, and blood pressure, while also playing a role in the body's response to stress. The secretion of these hormones is tightly regulated by feedback mechanisms involving the hypothalamus and pituitary gland.

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Related Practice

Textbook Question

The thyroid gland consists of:

a. Follicle cells that secrete calcitonin

b. Spherical thyroid follicles that contain iodine-containing colloid

c. Parafollicular cells that produce thyroid hormones

d. Spherical thyroid follicles that surround parathyroid hormone–secreting cells

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Textbook Question

Which of the following is not an effect of thyroid hormones?

a. Regulation of the metabolic rate

b. Promotion of growth and development

c. Thermoregulation

d. Synergism with the parasympathetic nervous system

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Textbook Question

Mark the following statements as true or false. If a statement is false, correct it to make a true statement.

Thyroid hormones are produced by follicle cells.

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Textbook Question

The outer part of the adrenal gland is the______, which secretes______. The inner part of the adrenal gland is the_____, which secretes ______.

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Textbook Question

Which of the following statements about the adrenal medulla is false?

a. Secretion from the adrenal medulla is triggered by ACTH and the sympathetic nervous system.

b. The adrenal medulla consists of glandular epithelial cells.

c. The adrenal medulla is a modified postsynaptic sympathetic ganglion.

d. The products of the adrenal medulla prolong the effects of the sympathetic response.

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Textbook Question

A patient has a brain tumor that necessitates removal of his pituitary gland. Will its removal affect production of ADH and oxytocin? Explain.

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Textbook Question

Ms. Reczkiewicz has her thyroid gland removed to treat hyperthyroidism. Her condition is stable after surgery, but one day later she develops symptoms of severe hypocalcemia. What has happened? How would you correct this problem?

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Textbook Question

Kyle, a 5-year-old boy, has been growing by leaps and bounds; his height is 100% above normal for his age. He has been complaining of headaches and vision problems. A CT scan reveals a large pituitary tumor.

(a) Which hormone is being secreted in excess?

(b) What condition will Kyle exhibit if corrective measures are not taken?

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