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4) Metabolic Endocrinology > 10) Adrenal Medulla > Flashcards

10) Adrenal Medulla Flashcards

1
Q

The adrenal medulla constitutes __% of the weight of the total adrenal gland.

A

15

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2
Q

The adrenal medulla and pre-ganglia are part of which nervous system?

A
  • Autonomic

- Sympathetic

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3
Q

The adrenal medulla is under (conscious/unconscious) control.

A

unconscious control

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4
Q

What is the overall function of the adrenal medulla? What are characteristic effects?

A
  • Coordinates the “fight-or-flight” response

- Increases blood pressure and cardiac output, dilates pupils

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5
Q

What is the function of pre-ganglionic neurons from the spinal cord in terms of the adrenal medulla?

A

Stimulates medullary modified nervous cells to release hormones

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6
Q

What are the hormones that are synthesized and released from the adrenal medulla?

A

Catecholamines (norepinephrine and epinephrine)

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7
Q

Which metabolite is the precursor to the catecholamine hormones?

A

Tyrosine

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8
Q

What is the rate-limiting enzyme in the synthesis of catecholamines?

A

Tyrosine hydroxylase

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9
Q

(Norephrine/epinephrine) is synthesized from (norepinephrine/epinephrine).

A

Epinephrine

norepinephrine

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10
Q

What are the four intermediate steps in the biosynthesis of epinephrine?

A

1) Tyrosine
2) Dopamine
3) Norepinephrine
4) Epinephrine

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11
Q

Which enzyme catalyzes the conversion of norepinephrine to epinephrine?

A

PNMT

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12
Q

_____ is required to enhance the actions of PNMT.

A

Cortisol

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13
Q

Stress increases _____, which increases ______.

A

cortisol

PNMT

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14
Q

Which tissues contain PNMT?

A
  • Lung
  • Kidney
  • Pancreas
  • Adrenal medulla
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15
Q

What is the effect of a decreased quantity of PNMT on the biosynthesis of catecholamines?

A
  • Less cortisol
  • Less PNMT
  • Less epinephrine
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16
Q

__% of released catecholamines are epinephrine, and __% are norepinephrine.

A

80

20

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17
Q

The conversion of norepinephrine to epinephrine requires which metabolite? What structure provides the metabolite?

A
  • Glucocorticoids

- Cortical capillaries relay the cortisol produced in the zona fasciculata to the adrenal medulla

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18
Q

What are the two different pathways for degradation of the catecholamines?

A
  • MAO (monoamine oxidase)

- COMT (catechol-O-methyltransferase)

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19
Q

The inactivation of norepinephrine or epinephrine by MAO produces which metabolite? What does further degradation by COMT produce?

A
  • DOMA

- VMA

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20
Q

The inactivation of norepinephrine by COMT produces which metabolite?

A

Metanoradrenaline

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21
Q

The inactivation of epinephrine by COMT produces which metabolite?

A

Metepinephrine

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22
Q

The inactivation of metanoradrenaline and metepinephrine produce which metabolite?

A

VMA

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23
Q

Are catecholamines stored or released following synthesis?

A

They are stored in granules in the cytoplasm, and released upon stimulation

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24
Q

Which metabolites are contained within granules of the catecholamines? What are they related to?

A
  • Met-enkephalin
  • Leu-enkephalin
  • Related to endorphins
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25
Q

What are functions of enkephalins? (2)

A

1) Block neurotransmitters (similar to morphine)

2) Act as an endogenous analgesic

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26
Q

What is an example of enkephalins acting as an endogenous analgesic?

A

Runners overcoming pain and being euphoric

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27
Q

In response to a stressor, what are the two responses of the hypothalamus? (2)

A

1) Activation of the sympathetic nervous system

2) Activates the adrenal-cortical system by releasing CRH

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28
Q

What is the immediate effect of the activation of the sympathetic nervous system?

A

Impulses activate glands and smooth muscles

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29
Q

What is the slower effect of the activation of the sympathetic nervous system?

A
  • Activates the adrenal medulla

- Releases norepinephrine and epinephrine from granules into the bloodstream

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30
Q

What is the slowest effect caused by the fight-or-flight response?

A
  • Hypothalamus releases CRH
  • Anterior pituitary synthesizes ACTH
  • ACTH stimulates the biosynthesis of hormones from the adrenal cortex de novo
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31
Q

What are the four immediate short-term responses to crises? (4)

A

1) Mobilization of glucose reserves
2) Changes in circulation
3) Increases in heart and respiratory rates
4) Increased energy use by all cells

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32
Q

What are the four immediate long-term metabolic adjustements to crises? (4)

A

1) Mobilization of remaining energy reserves (lipids, amino acids)
2) Conservation of glucose (breakdown of lipids to obtain energy)
3) Elevation of blood glucose concentrations (glucagon)
4) Conservation of salts and water, loss of K+ and H+

33
Q

As a long-term metabolic adjustment, how are the remaining energy reserves mobilized?

A
  • Lipids are released from adipose tissue

- Amino acids are released by skeletal muscle

34
Q

As a long-term metabolic adjustment, how is glucose conserved? Where?

A
  • Peripheral tissue (except neural tissue)

- Breakdown of lipids to obtain energy

35
Q

As a long-term metabolic adjustment, how are blood glucose concentrations kept elevated?

A
  • Liver synthesizes glucose from other carbohydrates, amino acids, and lipids
  • Under the influence of glucagon
36
Q

As a long-term metabolic adjustment, how is salt and water conserved?

A
  • ADH, aldosterone, and angiotensin

- Results in the loss of potassium and H+

37
Q

What are causes of the exhaustion phase due to the stress response?

A
  • Exhaustion of lipid reserves
  • Inability to produce glucocorticoids
  • Failure of electrolyte balance
  • Cumulative structural or functional damage to vital organs
38
Q

An acute, integrate adjustment occurs during the fight-or-flight response in which vital organs?

A
  • Organs vital to the response

- Brain, muscles, cardiopulmonary system, liver

39
Q

The fight-or-flight response occurs at the expense of which organs?

A
  • Organs less immediately involved

- Skin, GI

40
Q

What is the effect of epinephrine on lipid metabolism?

A

Mobilizes fatty acids as the primary fuel for muscle action

41
Q

What is the effect of epinephrine on skeletal muscle?

A

Increases muscle glycogenolysis

42
Q

How does epinephrine increase the quantity of glucose available to the brain?

A

Increase in hepatic glycogenolysis and gluconeogenesis

43
Q

How does epinephrine preserve glucose for the CNS?

A
  • Decrease in insulin release

- Leading to reduced glucose uptake by muscle and adipose tissue

44
Q

How does epinephrine affect the cardiovascular system?

A

Increases cardiac output

45
Q

How does norepinephrine affect the cardiovascular system? (2)

A
  • Increases blood flow

- Decreases insulin secretion

46
Q

How is blood flow redirected to vital organs by the fight-or-flight response?

A

Selective vasoconstriction

47
Q

Which catecholamine affects the respiratory system? What is the effect?

A
  • Epinephrine

- Dilation of the respiratory pathways

48
Q

How does the fight-or-flight response affect lactic acid, glucose, and fatty acid concentrations?

A
  • Lactic acid: increase
  • Glucose: increase
  • Fatty acids: increase
49
Q

How does the fight-or-flight response affect muscle to mobilize energy?

A
  • Increase in glycogenolysis

- Excretion of lactic acid

50
Q

How does the fight-or-flight response affect the liver to mobilize energy?

A
  • Increase in gluconeogenesis

- Increase in glycogenolysis

51
Q

How does the fight-or-flight response affect adipocytes to mobilize energy?

A

Increase in lipolysis

52
Q

How does the fight-or-flight response affect insulin and glucagon release to mobilize energy?

A
  • Decrease in insulin

- Increase in glucagon

53
Q

How does epinephrine affect the CNS?

A
  • Increases arousal and alertness within the CNS

- Many stimulants act by altering catecholamine levels in the brain

54
Q

How does epinephrine affect sweat glands? Why?

A
  • Increased sweating

- To dissipate extra heat generated by the muscles

55
Q

How does epinephrine affect the eyes? How?

A
  • Dilation of pupils
  • Flattening of lenses
  • By action on smooth muscle fibers
56
Q

Which adrenergic receptors bind both epinephrine and norepinephrine?

A

a and B1 receptors

57
Q

Which catecholamine does the B2 receptor bind primarily?

A

Epinephrine

58
Q

How are different tissue responses to the catecholamines modulated?

A

Different receptor distributions in different target tissues

59
Q

Which receptor does Salbutamol affect? What are the effects? How does it affect B1 receptors in the heart?

A
  • B2 receptors
  • Dilates bronchioles
  • Does NOT affect B1 receptors in the heart
60
Q

What is the potency of the a1 receptor acting by Gq?

A

Norepinephrine > epinephrine

61
Q

What is the potency of the a1 receptor acting by Gi?

A

Epinephrine > norepinephrine

62
Q

What is the potency of the B1 receptor?

A

Norepinephrine > epinephrine

63
Q

What is the potency of the B2 receptor?

A

Epinephrine > norepinephrine

64
Q

How does the B1 receptor exert its signal transduction pathway?

65
Q

How does the B2 receptor exert its signal transduction pathway?

66
Q

What are the target tissues of the a1 receptor acting by Gq?

A

Smooth muscle (skin, GI)

67
Q

What are the target tissues of the a1 receptor acting by Gi?

A

Nerve terminals for synaptic transmission

68
Q

What are the target tissues of the B1 receptor?

A
  • Heart

- Cerebral cortex

69
Q

What are the target tissues of the B2 receptor?

A
  • Lung
  • Smooth muscle
  • Cerebellum
70
Q

Which catecholamine leads to a greater cardiac stimulation to increase cardiac output? Which receptor is implicated?

A
  • Epinephrine&raquo_space; norepinephrine

- B receptor

71
Q

Which catecholamine has a greater effect on vasoconstriction of blood vessels?

A

Norepinephrine&raquo_space; epinephrine

72
Q

Which catecholamine has a greater effect on the increase in metabolism?

A

Epinephrine&raquo_space; norepinephrine

73
Q

What are causes of an adrenomedullary deficiency?

A
  • Surgery, trauma
  • Suppression of cortisol levels, resulting in an epinephrine deficiency
  • Hypotension
  • Hypoglycemia
74
Q

How may an adrenomedullary deficiency lead to death?

A
  • They don’t

- Adrenal catecholamines are not essential for life

75
Q

_______________ is a tumour that overproduces catecholamines.

A

Pheochromocytoma

76
Q

When are pheochromocytoma often diagnosed?

A
  • Relatively rare
  • Usually, not diagnosed until autopsy
  • 1/3 cause death prior to diagnosis
77
Q

What are the usual symptoms of a pheochromocytoma?

A
  • Headache
  • Hypertension
  • Sweating
  • These are common symptoms, which make a proper diagnosis difficult
78
Q

What is the treatment for a pheochromocytoma?

A
  • Surgery to remove the tumour (or the adrenal gland, if necessary)
  • An individual may easily survive with a single adrenal gland

4) Metabolic Endocrinology (15 decks)

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