L36. Physiology - Adrenal Gland

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is a key mechanism by which cortisol exerts its anti-inflammatory effects?

Direct inhibition of T-cell activation, preventing the formation of antibody-producing cells.

Activation of phospholipase-A2, leading to increased prostaglandin synthesis.

Stimulation of the release of anti-inflammatory cytokines, such as IL-10.

Suppression of prostaglandin production through inhibition of phospholipase-A2. (correct)

Which of the following conditions is most closely associated with chronic hypercortisolemia and often presents with diabetes due to insulin resistance?

Cushing's disease (correct)

Hypothyroidism

Hyperparathyroidism

Addison's disease

Which of the following best describes the primary action of aldosterone?

Maintenance of electrolyte balance through sodium and water retention and potassium excretion. (correct)

Regulation of blood glucose levels by promoting insulin sensitivity.

Promotion of bone formation by increasing calcium absorption.

Enhancement of immune function by stimulating T-cell proliferation.

What is the physiological role of the renin-angiotensin system in aldosterone regulation?

Activation of the pathway leading to aldosterone production in the adrenal cortex. (C) Signup and view all the answers

What is a potential consequence of long-term glucocorticoid therapy?

Suppressed immune system and an increased susceptibility to infections. (A) Signup and view all the answers

What is the primary target of cortisol's action in relation to insulin signaling?

Liver and muscle cells, inhibiting insulin action. (B) Signup and view all the answers

What is the physiological consequence of cortisol's influence on insulin signaling?

Insulin resistance and a predisposition to diabetes. (A) Signup and view all the answers

Which hormone is primarily responsible for stimulating cortisol production?

Adrenocorticotropic hormone (ACTH) (B) Signup and view all the answers

What is the primary role of cortisol in regulating the immune system?

Suppressing immune responses to prevent autoimmune reactions. (B) Signup and view all the answers

Which of these is NOT a direct clinical application of glucocorticoids?

Treatment of thyroid disorders. (A) Signup and view all the answers

Which of the following peptides is NOT produced in the adrenal medulla?

β-Endorphin (A), γ-MSH (C), α-MSH (D) Signup and view all the answers

In the adult, what is the primary product of POMC processing in the anterior pituitary?

ACTH (C) Signup and view all the answers

What is the role of the J-Peptide in the processing of POMC?

J-Peptide is a byproduct of the processing of POMC, not a precursor to any other peptide (B) Signup and view all the answers

Which peptide is responsible for hyperpigmentation of the skin when produced in excess?

α-MSH (A) Signup and view all the answers

Which of the following statements regarding POMC processing is correct?

POMC processing produces different sets of peptides in adults and fetuses, with unique products in each stage of life. (D) Signup and view all the answers

Why does the content mention the production of different sets of peptides during fetal life and pregnancy?

To highlight the role of POMC processing in the development of key endocrine functions during fetal life. (B) Signup and view all the answers

What is the significance of the difference in POMC processing between adults and fetuses?

It illustrates the importance of hormonal regulation across various stages of life. (B) Signup and view all the answers

What is the main takeaway from the provided content regarding POMC processing?

POMC is a versatile precursor that can be processed into various peptides with diverse physiological functions, depending on the stage of life. (B) Signup and view all the answers

What does aldosterone primarily regulate in the kidney nephron?

Sodium and potassium exchange (C) Signup and view all the answers

Which enzyme is responsible for converting angiotensinogen to angiotensin I?

Renin (B) Signup and view all the answers

What is the net effect of aldosterone action on plasma K+ ions?

Net loss of plasma K+ into the urine (A) Signup and view all the answers

In which cells of the kidney nephron does the mineralocorticoid receptor primarily function?

Principal cells (B) Signup and view all the answers

What happens to water when sodium ions are reabsorbed due to aldosterone?

Water follows sodium into the blood (C) Signup and view all the answers

Which of the following accurately describes the embryological origin of the adrenal cortex and medulla?

The cortex is derived from mesoderm, and the medulla is derived from neural crest cells. (A) Signup and view all the answers

Given the information on the adrenal cortex's hormone production, which of the following would likely be a direct target for a steroid hormone produced by the adrenal cortex?

The nucleus of a target cell. (C) Signup and view all the answers

Which of the following best describes the primary function of the adrenal medulla in the 'fight-or-flight' response?

The medulla releases epinephrine, a catecholamine that mediates physiological responses to stress. (A) Signup and view all the answers

Which of the following accurately reflects the relationship between the adrenal cortex and medulla in terms of hormone production?

The cortex produces steroid hormones, and the medulla produces amine hormones. (D) Signup and view all the answers

Based on the text, what would be the expected outcome of a prolonged, chronic stress response on the adrenal gland?

Increased production of aldosterone by the zona glomerulosa. (C) Signup and view all the answers

If a patient exhibited an inability to regulate blood glucose levels effectively, which of the following adrenal gland zones would MOST likely be dysfunctional?

Zona fasciculata. (B) Signup and view all the answers

Which of the following statements best reflects the primary function of the adrenal gland?

The adrenal gland is primarily involved in the production of hormones that regulate metabolism, stress response, and electrolyte balance. (B) Signup and view all the answers

What are the peptide hormones produced from POMC in the anterior pituitary?

ACTH, β-LPH, J peptide (B) Signup and view all the answers

Which of the following is NOT a product of POMC processing in the intermediate pituitary?

ACTH (B) Signup and view all the answers

Which enzyme is primarily responsible for the rate-limiting step in cortico-steroid synthesis stimulated by ACTH?

SSC (CYP11A1) (C) Signup and view all the answers

Which physiological condition primarily stimulates aldosterone production?

Increased blood potassium levels (A) Signup and view all the answers

What effect does chronically elevated ACTH levels have on the adrenal cortex?

Hyperplasia of adrenal cortex (B) Signup and view all the answers

What is the primary receptor for cortisol in target cells?

Gluco-corticoid receptor (D) Signup and view all the answers

Which of the following is NOT a mechanism of action for ACTH in the adrenal cortex?

Stimulating alpha-MSH production (B) Signup and view all the answers

During which period is the metabolism by the intermediate lobe of POMC particularly important?

Pregnancy (C) Signup and view all the answers

What is the role of cholesterol ester hydrolysis in steroid biosynthesis?

To generate free cholesterol for steroid synthesis (D) Signup and view all the answers

Which peptide is produced from POMC processing in both the anterior and intermediate pituitary?

J peptide (B) Signup and view all the answers

Study Notes

Adrenal Gland Overview

The adrenal glands produce steroid hormones (mineralocorticoids, glucocorticoids, and adrenal androgens) and catecholamine hormones (epinephrine and norepinephrine).
Cortisol, a glucocorticoid, regulates carbohydrate and protein metabolism, and affects many bodily systems.
Aldosterone, a mineralocorticoid, maintains salt and water balance.
DHEA and androstenedione, adrenal androgens, affect secondary sex characteristics.
Epinephrine (adrenaline) mediates 'flight-or-fight' responses to stress.

Session Learning Objectives

Describe the adrenal gland anatomy and hormonal output of the cortex and medulla.
Outline the biosynthesis pathways for cortical and medullary hormones.
Explain ACTH's regulation of cortisol production, including cellular mechanisms and feedback loops.
Detail the cellular actions and physiological effects of cortisol and aldosterone.
Describe the receptors and signaling pathways used by cortical and medullary hormones.
Explain the functional relationship between the adrenal medulla and the sympathetic nervous system, and hormone regulation.
Describe the effects of epinephrine on the liver.
Describe Cushing's syndrome and Addison's disease.

Session Outline

Overview of the adrenal gland
Biosynthesis of adrenal cortical hormones
Corticoid steroid action
Biosynthesis and regulation of catecholamines from the adrenal medulla
Epinephrine action

Biosynthesis of Adrenal Cortical Hormones

Biosynthesis begins with the enzymatic removal of the cholesterol side chain.
Pregnenolone is converted into cortisol, aldosterone, or androgens via enzymatic steps.
Mutations in enzymes reduce cortisol and aldosterone production, and increase androgen production.
Reduced activity of 21-hydroxylase diminishes cortisol and aldosterone, and increases sex steroid production.

Regulation of Corticosteroid Production

Cortisol secretion is primarily controlled by ACTH (adrenocorticotropic hormone).
ACTH production is controlled by the hypothalamus.
Cortisol exerts negative feedback on ACTH and CRF (corticotropin-releasing factor) release.

ACTH

Cortisol is secreted in an episodic pattern following a 24-hour circadian cycle.
ACTH is released in a highly pulsatile manner throughout the day, but with higher overall rate in the morning hours.
ACTH is generated from proteolytic digestion of the POMC (proopiomelanocortin) precursor peptide.
In adults, POMC yields ACTH and other peptides. In fetuses, different peptides (MSHs) are produced.

ACTH action in the adrenal cortex

ACTH acts via a specific GPCR (the ACTH receptor) to stimulate hormone production via multiple mechanisms.
It influences the rate-limiting step in cortisol synthesis, stimulates other enzymes needed, promotes cholesterol uptake, and other mechanisms.
Chronic elevated ACTH levels can lead to adrenal cortex hyperplasia.
Other factors besides ACTH, such as potassium/sodium levels and angiotensin II, affect aldosterone production.

Corticosteroid Action

Cortisol acts through intracellular receptors (GRs) within target cells.
The receptors translocate to the nucleus, bind to hormone response elements (HREs), and stimulate (or suppress) transcription of target genes.
Different genes are activated in different tissues in response to cortisol.
Cortisol receptor 'cross-talk' may occur due to structural similarity between cortisol and aldosterone.

Physiological Effects of Cortisol

Carbohydrate metabolism- Increase blood glucose levels via stimulating gluconeogenesis and inhibiting peripheral glucose utilization.
Protein metabolism - Cortisol inhibits protein synthesis and increases protein breakdown, especially in muscle and liver.
Lipid metabolism - Increases lipolysis, raises circulating fatty acid levels.

Physiological effects of cortisol continued

Cortisol affects inflammation and the immune response, and is used clinically to suppress these in certain situations.
The immune suppression, and other effects of cortisol, come with an elevated risk for infections and Cushing's syndrome.

Biosynthesis and Regulation of Catecholamine production

Adrenal medulla produces catecholamines (norepinephrine, epinephrine, dopamine).
Norepinephrine is both a neurotransmitter and a hormone.
Epinephrine's function is primarily as a hormone.
Catecholamine release is controlled by the sympathetic nervous system and often associated with stress responses.
Tyrosine hydroxylase, the rate-limiting enzyme in the pathway, is stimulated by sympathetic nerve action.
Norepinephrine synthesis is converted to epinephrine via PNMT.

Catecholamine Action

Norepinephrine and epinephrine act via α and β adrenergic receptors, resulting in various effects.
These effects include; increased heart rate and contractility, constriction or dilation of blood vessels, elevation of blood glucose, and other responses.

Factors that stimulate catecholamine release

Fight-or-flight stimuli
Anxiety
Pain
Increased sympathetic nervous system tone
Trauma
Hypoglycemia
Anoxia
Exercise
Extreme temperatures

Rapid degradation of catecholamines

Catecholamines are rapidly degraded by enzymes, primarily COMT and MAO.
Metabolites are converted into products such as vanillylmandelic acid (VMA).

Adrenal Gland Pathologies

Glucocorticoid excess is associated with conditions like Cushing's syndrome.
Symptoms including truncal obesity, hypertension, loss of subcutaneous fat, muscle weakness, and hyperglycemia.
It can be caused by excess cortisol production due to primary adrenal tumors or secondary to pituitary adenomas (Cushing's disease).

Glucocorticoid & Mineralocorticoid Deficiency

Deficiency of both cortisol and aldosterone is known as Addison's disease.
Symptoms are hypotension, hyperkalaemia, hypoglycemia, and hyperpigmentation.
Common causes are autoimmune reactions and infectious diseases.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This quiz assesses your understanding of cortisol and its role in the endocrine system. You'll explore its anti-inflammatory effects, its regulation of insulin signaling, and its consequences in chronic conditions. Test your knowledge on related hormones and processes.