The Adrenal Gland and Hormones Quiz

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Questions and Answers

What is the primary function of aldosterone?

  • To regulate blood sugar levels
  • To control sodium and water levels (correct)
  • To promote the synthesis of catecholamines
  • To stimulate the production of adrenal androgens

Catecholamines are primarily produced by the adrenal cortex.

False (B)

Which enzyme is responsible for converting norepinephrine to epinephrine in chromaffin cells?

phenylethanolamine-N-methyl transferase (PNMT)

The adrenal cortex develops from __________ cells.

<p>mesodermal</p> Signup and view all the answers

Match the following terms with their descriptions:

<p>Aldosterone = Regulates sodium and water levels Cortisol = Inhibits neuronal differentiation in chromaffin cells Catecholamines = Primary hormonal products of the adrenal medulla SGK = Serine/threonine-protein kinase involved in regulation</p> Signup and view all the answers

What triggers the opening of voltage-gated calcium channels in glomerulosa cells?

<p>Depolarization from high extracellular potassium (B)</p> Signup and view all the answers

Angiotensin II binds to receptors influencing aldosterone synthesis.

<p>True (A)</p> Signup and view all the answers

What is the role of the adrenal medulla in the stress response?

<p>It secretes catecholamines such as epinephrine and norepinephrine.</p> Signup and view all the answers

What is the primary function of catecholamines released from the adrenal medulla?

<p>Act as hormones in the bloodstream (C)</p> Signup and view all the answers

Epinephrine is released primarily from postganglionic sympathetic nerve terminals.

<p>False (B)</p> Signup and view all the answers

What are the two main catecholamines synthesized in the adrenal medulla?

<p>Epinephrine and norepinephrine</p> Signup and view all the answers

The adrenal medulla is regulated primarily by __________ signals in response to stress.

<p>descending sympathetic</p> Signup and view all the answers

Match the processes with their corresponding hormones or actions:

<p>ACTH = Stimulates the secretion of cortisol Cortisol = Promotes the synthesis of catecholamines Epinephrine = Primarily responsible for fight or flight response Norepinephrine = Primarily released from sympathetic nerve terminals</p> Signup and view all the answers

Which part of the nervous system is primarily involved in the regulation of catecholamine secretion?

<p>Sympathetic nervous system (A)</p> Signup and view all the answers

Where are catecholamines stored in the adrenal medulla?

<p>Chromaffin granules</p> Signup and view all the answers

Cortisol has no effect on catecholamine synthesis.

<p>False (B)</p> Signup and view all the answers

Approximately _____% of the adrenal medulla cells secrete epinephrine.

<p>70-80</p> Signup and view all the answers

What role does the hypothalamus play in catecholamine regulation?

<p>It initiates sympathetic responses. (B)</p> Signup and view all the answers

What is the primary site for aldosterone synthesis?

<p>Zona glomerulosa (D)</p> Signup and view all the answers

Aldosterone secretion is primarily regulated by the renin-angiotensin system.

<p>True (A)</p> Signup and view all the answers

Name the two primary hormones produced in the adrenal medulla.

<p>Epinephrine and norepinephrine</p> Signup and view all the answers

Aldosterone stimulates the absorption of __________ in the kidneys.

<p>sodium</p> Signup and view all the answers

Match the following hormones with their primary effects:

<p>Aldosterone = Na+ retention and K+ secretion Epinephrine = Increased heart rate and blood flow Norepinephrine = Vasoconstriction and blood pressure increase Cortisol = Regulation of metabolism and immune response</p> Signup and view all the answers

Which of the following actions is NOT a result of norepinephrine and epinephrine during exercise?

<p>Increased motility in the GI tract (D)</p> Signup and view all the answers

Epinephrine and norepinephrine can lead to vasodilation and vasoconstriction.

<p>True (A)</p> Signup and view all the answers

What is the role of epinephrine in increasing glucose availability during exercise?

<p>Epinephrine promotes glycogenolysis and gluconeogenesis to increase blood glucose levels.</p> Signup and view all the answers

The adrenal medulla responds rapidly because it is directly innervated by the __________.

<p>autonomic nervous system</p> Signup and view all the answers

Match the following catecholamines with their effects during exercise:

<p>Epinephrine = Increases glucose availability Norepinephrine = Increases heart rate Both = Vasodilation and vasoconstriction Neither = Increases GI tract motility</p> Signup and view all the answers

Which of the following best describes phenochromocytoma?

<p>A tumor caused by hyperplasia of adrenal medulla (D)</p> Signup and view all the answers

The sympathoadrenal response includes an increase in energy demand by visceral smooth muscle.

<p>False (B)</p> Signup and view all the answers

What are the two primary catecholamines involved in the sympathoadrenal response during exercise?

<p>Norepinephrine and epinephrine</p> Signup and view all the answers

Epinephrine acts on which type of receptor to induce vasoconstriction?

<p>α (alpha)</p> Signup and view all the answers

Match the physiological actions to the corresponding catecholamine:

<p>Epinephrine = Promotes glycogenolysis Norepinephrine = Acts on the heart to increase stroke volume Both = Increase cardiac output Neither = Stimulates GI motility</p> Signup and view all the answers

What is the primary chemical signal that stimulates catecholamine secretion from the adrenal medulla?

<p>Acetylcholine (A)</p> Signup and view all the answers

Cortisol has no influence on the production of catecholamines in the adrenal medulla.

<p>False (B)</p> Signup and view all the answers

What are the two primary enzymes involved in the degradation of catecholamines?

<p>monoamine oxidase (MAO) and catechol-O-methyltransferase (COMT)</p> Signup and view all the answers

The primary receptor type that increases IP3 and DAG in vascular smooth muscle is the ______.

<p>α1 receptor</p> Signup and view all the answers

Match the adrenergic receptor type to its mechanism of action and tissue distribution:

<p>α1 = ↑IP3, DAG; Vascular smooth muscle β1 = ↑cAMP; Heart β2 = ↑cAMP; Liver α2 = ↓cAMP; Pancreatic β cells</p> Signup and view all the answers

Which catecholamine has greater potency at the β2 receptor?

<p>Epinephrine (D)</p> Signup and view all the answers

The half-life of catecholamines in circulation is approximately 10 minutes.

<p>False (B)</p> Signup and view all the answers

What role does cortisol play in the synthesis of catecholamines?

<p>Cortisol maintains adequate levels for the production of epinephrine.</p> Signup and view all the answers

The predominant enzyme for catecholamine degradation in neuronal mitochondria is ______.

<p>monamine oxidase (MAO)</p> Signup and view all the answers

Which of the following statements about catecholamine synthesis is accurate?

<p>The synthesis of catecholamines is tied directly to their secretion. (A)</p> Signup and view all the answers

Flashcards

Aldosterone Regulation

Aldosterone production is regulated by sodium and water levels, angiotensin II (ang II), and potassium levels in the blood.

Angiotensin II (Ang II)

A hormone that stimulates aldosterone production.

ROMK Channel

Renal Outer Medullary Potassium channel, plays a role in potassium secretion in the kidneys.

ENaC Channel

Epithelial Sodium Channel, helps regulate sodium reabsorption in the kidneys.

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Adrenal Medulla

Inner part of the adrenal gland, produces catecholamines.

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Cortisol's Influence

Cortisol inhibits neuronal differentiation in chromaffin cells and promotes epinephrine production from norepinephrine.

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Adrenal Cortex Development

Develops from mesodermal cells and produces steroid hormones.

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Chromaffin Cells

Cells in the adrenal medulla that produce catecholamines.

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Aldosterone's function

Aldosterone regulates extracellular volume (ECV) by increasing sodium retention/absorption in the kidneys. This means it helps maintain the balance of fluids and electrolytes in the body.

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How does aldosterone work?

Aldosterone acts on the kidneys to increase sodium and water reabsorption while promoting potassium secretion. It has similar effects in the colon, salivary glands, and sweat glands.

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What stimulates aldosterone synthesis?

Angiotensin II (Ang II), extracellular potassium levels ([K+]), and ACTH stimulate aldosterone production. These factors increase the activity of enzymes involved in aldosterone synthesis.

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Aldosterone's synthesis site

Aldosterone is synthesized exclusively in the zona glomerulosa of the adrenal cortex. Only these cells contain aldosterone synthase, the enzyme needed for its production.

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How is aldosterone regulated?

The renin-angiotensin system (RAS) and aldosterone work together to regulate blood pressure and fluid balance. Angiotensin II, a key player in the RAS, stimulates aldosterone production.

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Adrenal medulla function

The adrenal medulla bridges the endocrine and sympathetic nervous systems, secreting catecholamines (like epinephrine and norepinephrine) into the blood.

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Catecholamine storage

Catecholamines are stored in chromaffin granules along with ATP, calcium, and chromogranins.

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Epinephrine vs. Norepinephrine

70-80% of adrenal medulla cells secrete epinephrine, the remaining 20-30% secrete norepinephrine, although circulating norepinephrine also comes from sympathetic nerves.

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Epinephrine source

Circulating epinephrine is entirely derived from the adrenal medulla.

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Norepinephrine source

Only about 30% of circulating norepinephrine comes from the adrenal medulla, the rest comes from postganglionic sympathetic nerves.

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Catecholamine secretion regulation

Catecholamine secretion is mainly controlled by descending sympathetic signals, activated by types of stress (like exercise, low blood sugar, and surgery).

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Autonomic Centers

Hypothalamus and brainstem control sympathetic responses, receive inputs from different areas of the brain such as cerebral cortex, limbic system.

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Chromaffin Granule Recycling

VMATs transport catecholamines back into the chromaffin granules.

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CRH/ACTH/Cortisol Synergy

There's a synergy between the stress response (CRH/ACTH/cortisol) and sympathetic epinephrine axis.

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Stress & Catecholamine

Stress is a key regulator of epinephrine and norepinephrine release.

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Catecholamine's Diverse Effects

A single catecholamine can trigger multiple different responses in the body, depending on its concentration and the receptors it binds to. For example, epinephrine can cause both vasodilation and vasoconstriction.

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Catecholamine secretion signal

Acetylcholine (ACh) is the chemical signal that triggers catecholamine release from the adrenal medulla.

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Sympathoadrenal Response

The body's rapid and coordinated response to stress involving the sympathetic nervous system and adrenal medulla. It activates the release of catecholamines, such as norepinephrine and epinephrine, to prepare the body for action. It involves various organs and systems.

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Chromaffin cell receptors

Chromaffin cells in the adrenal medulla have nicotinic receptors that bind acetylcholine.

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Adrenomedullary Response Speed

The adrenal medulla, directly controlled by the autonomic nervous system, responds very quickly to stress.

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Anticipatory Response

Sympathoadrenal responses can be triggered even before the actual stressor occurs. The nervous system anticipates the need for action.

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Catecholamine synthesis regulation

Cortisol regulates epinephrine production by ensuring sufficient levels of norepinephrine.

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Sympathoadrenal Response to Exercise

Similar to the 'fight-or-flight' response, exercise triggers the release of catecholamines, particularly norepinephrine and epinephrine, to meet the increased energy demands of the body.

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Catecholamine degradation

Catecholamines are degraded by monoamine oxidase (MAO) and catechol-O-methyltransferase (COMT).

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Catecholamine Effects on Heart

Norepinephrine and epinephrine act on the heart to increase heart rate, strength of contractions, and constrict veins and lymphatics, all to increase blood flow to the muscles.

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Catecholamine action mechanism

Catecholamines act through adrenergic G protein-coupled receptors (GPCRs).

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α1 receptor action

α1 adrenergic receptors increase IP3 and DAG levels, leading to various effects like vasoconstriction.

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Catecholamine's Role in Glucose Availability

Epinephrine promotes glycogenolysis in muscles to provide energy. It also increases blood glucose by promoting glycogenolysis and gluconeogenesis in the liver.

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Catecholamine's Effect on Smooth Muscle

The sympathoadrenal response generally decreases the activity of smooth muscles in the digestive and urinary systems, conserving energy for essential functions.

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α2 receptor action

α2 adrenergic receptors decrease cAMP levels, leading to effects like decreased insulin secretion.

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β1 receptor action

β1 adrenergic receptors increase cAMP levels, leading to effects like increased heart rate.

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Pheochromocytoma

A rare tumor caused by excessive growth of chromaffin cells in the adrenal medulla or other locations. These tumors release large amounts of catecholamines, leading to a variety of symptoms.

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β2 receptor action

β2 adrenergic receptors increase cAMP levels, leading to effects like bronchodilation.

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β3 receptor action

β3 adrenergic receptors increase cAMP levels, primarily in adipose tissue.

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Study Notes

The Adrenal Gland and Adrenal Hormones

  • Aldosterone, epinephrine, and norepinephrine are hormones
  • Aldosterone's class: steroid hormone
  • Epinephrine's class: amine hormone
  • Norepinephrine's class: amine hormone
  • Location of aldosterone synthesis: zona glomerulosa of adrenal cortex
  • Location of epinephrine synthesis: adrenal medulla
  • Location of norepinephrine synthesis: adrenal medulla
  • Aldosterone regulation: primarily by renin-angiotensin system
  • Renin-angiotensin system: a cascade of hormones that affects blood pressure and volume
  • Mechanism of aldosterone action: modulating gene transcription after binding to MRs; regulates Na+ reabsorption and K+ secretion primarily in the distal tubule and collecting duct
  • Aldosterone synthesis involves: steroidogenic cells; the rate-limiting step in aldosterone synthesis is controlled by a rate-limiting enzyme; ACTH and potassium levels in the blood influence aldosterone production in the zona glomerulosa cell.

Synthesis of Aldosterone

  • Aldosterone synthesized from cholesterol
  • Zona glomerulosa cells are the only cells that have aldosterone synthase
  • Aldosterone secretion is limited by the rate of synthesis in the glomerulosa cells
  • ACTH and extracellular K+ and Angiotensin II levels stimulate aldosterone production in the zona glomerulosa cells.
  • Enzymes like the SCC enzyme and aldosterone synthase are involved.
  • 37% of circulating aldosterone is in free form in plasma
  • The rest (21% and 42%) bind weakly to CBG and albumin

Mechanism of Action of Aldosterone

  • Major action: stimulate kidney to reabsorb Na+, and enhance potassium secretion in kidneys
  • Also effects colon, salivary glands, and sweat glands
  • Physiologic role in myocardium, liver, brain, and other tissues is unclear
  • Acts by modulating gene transcription after binding to the mineralocorticoid receptor (MR)

Mechanism of Action of Aldosterone (in Renal Tubules)

  • Increases activity of several key proteins involved in Na+ transport
  • Increases transcription of Na-K pump, to augment distal Na+ reabsorption
  • Increases apical Na+ channels and Na/K/Cl cotransporters
  • ROMK = renal outer medullary potassium channel
  • ENaC = epithelial sodium channel
  • SGK = Serine/threonine-protein kinase

Regulation of Aldosterone Synthesis

  • Feedback regulation via blood levels of Na+ and K+
  • RAS (renin-angiotensin-aldosterone system) is a major regulator
  • ACTH (adrenocorticotropic hormone) stimulates aldosterone synthesis
  • High extracellular K+ depolarizes glomerulosa cells, increasing Ca2+
  • Ca2+ stimulates production of aldosterone

The Adrenal Medulla: Catecholamines

Development of the Adrenal Gland (AG)

  • Adrenal cortex develops from mesodermal cells; produces steroid hormones
  • Chromaffin cells migrate into the cortex from neural crest cells; produce catecholamines
  • Cortisol inhibits neuronal differentiation of chromaffin cells; promotes PNMT expression for epinephrine production

The Adrenal Medulla

  • Bridges endocrine and sympathetic nervous systems
  • Secreted catecholamines into blood; act as hormones
  • Has chromaffin cells to secrete catecholamines

Synthesis of Catecholamines

  • Tyrosine is the precursor for catecholamines
  • Storage in chromaffin granules, complexed with proteins, ATP, and Ca2+
  • Norepinephrine converted to epinephrine by PNMT
  • VMATS move neurotransmitters into vesicles
  • CRH/ACTH/cortisol and sympathetic epinephrine axis cause release to adrenal medulla
  • 70% epinephrine and 30% norepinephrine are circulating hormones

Regulation of Catecholamines

  • Primarily regulated by descending sympathetic signals from centers in CNS
  • Feedback mechanisms regulate blood levels of catecholamines
  • Autonomic centers in brain stem and hypothalamus initiate sympathetic responses
  • Acetylcholine (ACh) stimulates catecholamine secretion
  • ACh enhances the activity of tyrosine hydroxylase, dopamine β-hydroxylase
  • Cortisol maintains adequate epinephrine production

Degradation of Catecholamines

  • Catecholamines have a short half-life
  • Degradation primarily by monoamine oxidase (MAO) and catechol-O-methyltransferase (COMT).

Mechanism of Action of Catecholamines

  • Act through adrenergic GPCRs
  • Differential potency at adrenergic receptors; epinephrine is more potent for certain receptors
  • Multiple responses possible with single catecholamine

Physiologic Actions of Catecholamines

  • Rapid adrenomedullary responses
  • Increase blood flow to muscles, blood glucose, energy use
  • Key role in the body's responses to exercise, stress, etc

Pheochromocytoma

  • Rare adrenal medulla tumor, causes excessive catecholamine production
  • Symptoms: hypertension, headaches, sweating, anxiety.
  • Diagnosis: detects urinary catecholamines and metabolites. Possible treatment: adrenalectomy and subsequent hormone replacement therapy.

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