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Physiology- Endocrine > Adrenal Medulla > Flashcards

Adrenal Medulla Flashcards

1
Q

What are the adrenomedullary hormones?

A

Norepinephrine and Epinephrine

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2
Q

What is the percentages of andrenomedullary hormones?

A

90% Epi, 10% NE

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3
Q

The adrenal medulla is part of what nervous system?

A

Sympathetic Nervous System

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4
Q

What is the functional unit of the adrenal medulla? What do they function as?

A

Chromaffin Cells; Post-ganglionic nerves that secrete Epi and NE into the blood

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5
Q

How are the chromaffin cells stimulated?

A

Chromaffin cells are directly stimulated by ACTH released from sympathetic preganglionic fibers (splanchnic nerve); Chromaffin cells synthesize/secrete Epi/NE directly into the blood and is carried to various organs in the body

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6
Q

What are chromaffin granules?

A

storage and secretory granules for Epi and NE and play a major role in their synthesis

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7
Q

What is the rate-limiting step in Epi synthesis?

A

Tyrosine –> DOPA (by Tyrosine hydroxylase)

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8
Q

What enzyme converts Epi into NE? What stimulates this enzyme?

A

PNMT; Cortisol

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9
Q

What is one chromaffin granule that converts dopamine to NE?

A

Dopamine B-hydroxylase

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10
Q

What are the physiologic factors for synthesis and secretion of Epi/NE? (6)

A

(1) Anxiety
(2) Pain
(3) Trauma
(4) Hypovolemia
(5) Hypoglycemia
(6) Hypothemia

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11
Q

What does Chromogranin do?

A

It is a secretory peptide

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12
Q

What is VMAT? What does it do?

A

Vesicular Monoamine Transporter; moves Epi into the secretory vesicles that are released into the synapse

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13
Q

What is the negative feedback process by Epi and NE?

A

They negatively feedback Tyrosine Hydroxylase to stop the synthesis of more catecholamines

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14
Q

Acute regulation increases ACTIVITY/SYNTHESIS of TH?

A

ACTIVITY

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15
Q

Chronic regulation increases ACTIVITY/SYNTHESIS of TH?

A

BOTH

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16
Q

In chronic regulation, what else is secreted into the Chromaffin cell? What does it do?

A

Cortisol; it increases activity of PNMT to convert NE to EPI

17
Q

What are circulating blood levels of EPI, NE at basal and stimulated?

A

EPI (adrenal medulla)- Basal 20-50 pg/ml, Stimulated >250 pg/ml; NE (sympathetic nerves)- Basal 100-200 pg/ml; Stimulated >1000 pg/ml

18
Q

What is the half life of Epi/NE?

A

1-3 minutes

19
Q

T/F Epi/NE is carried in the plasma in free form

A

TRUE; there is no binding protein

20
Q

What are the major sites of Epi and NE metabolism?

A

Liver, Kidney, and Sympathetic nerve endings

21
Q

Epi and NE are acted up by what enzymes?

A

Catechol-O-Methyl Tranferase and Monoamine Oxidase

22
Q

What are inactive metabolites that form by the actions of the enzymes? Where are they excreted?

A

VMA, Metanephrine (EPI), Normetanephrine (NE); secreted in the urine

23
Q

What are the catecholamine receptors?

A

Adrenergic receptors; Alpha and Beta

24
Q

Which has the greatest effect on Epi than NE?

A

B-2

25
Q

Epi and NE have similar potency effects at what?

A

A-1, A-2, B-1, B-3

26
Q

Why are there different adrenergic receptor subtypes?

A

SPECIFICITY; different adrenergic receptor subtypes mediate specific actions of Epi/NE at different tissues

27
Q

What are the physiological actions of catecholamines?

A

Fight or Flight; effects on metabolism, hormone secretion, cardiovascular system

28
Q

What are the metabolic effects of catecholamines in the liver? (2)

A

(1) increase liver glycogenolysis

(2) increase gluconeogenesis

29
Q

What are the metabolic effects of catecholamines in the adipose tissue? (2)

A

(1) inhibits glucose uptake into adipose

(2) increases lipolysis

30
Q

What are the metabolic effects of catecholamines in the skeletal muscle?

A

(1) increase in glycogenolysis

(2) decrease in glucose uptake

31
Q

What are the metabolic effects of catecholamines in the pancreas?

A

(1) decrease insulin secretion

(2) increase glucagon secretion

32
Q

What is the net effect of catecholamines?

A

Increase blood glucose, increase blood keto-acids

33
Q

Cardiovascular Effects?

A
  • Increase blood supply to working muscles such as cardiac and skeletal muscle
  • increase blood supply to areas that produce nutrients (liver) and to those that utilize nutrients and oxygen (brain, heart, and skeletal muscle)
34
Q

What is Pheochromocytoma?

A

An adrenal chromaffin cell tumor that produces and secretes large amounts of NE and Epi

  • Secretion occurs in bursts
  • Severe HBP, headache, anxiety, sweating, feeling hot but hands are cold
  • Associated with large increase in VMA in urine

Physiology- Endocrine (7 decks)

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