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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
What are functions of enkephalins? (2)
1) Block neurotransmitters (similar to morphine) | 2) Act as an endogenous analgesic
26
What is an example of enkephalins acting as an endogenous analgesic?
Runners overcoming pain and being euphoric
27
In response to a stressor, what are the two responses of the hypothalamus? (2)
1) Activation of the sympathetic nervous system | 2) Activates the adrenal-cortical system by releasing CRH
28
What is the immediate effect of the activation of the sympathetic nervous system?
Impulses activate glands and smooth muscles
29
What is the slower effect of the activation of the sympathetic nervous system?
- Activates the adrenal medulla | - Releases norepinephrine and epinephrine from granules into the bloodstream
30
What is the slowest effect caused by the fight-or-flight response?
- Hypothalamus releases CRH - Anterior pituitary synthesizes ACTH - ACTH stimulates the biosynthesis of hormones from the adrenal cortex de novo
31
What are the four immediate short-term responses to crises? (4)
1) Mobilization of glucose reserves 2) Changes in circulation 3) Increases in heart and respiratory rates 4) Increased energy use by all cells
32
What are the four immediate long-term metabolic adjustements to crises? (4)
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
As a long-term metabolic adjustment, how are the remaining energy reserves mobilized?
- Lipids are released from adipose tissue | - Amino acids are released by skeletal muscle
34
As a long-term metabolic adjustment, how is glucose conserved? Where?
- Peripheral tissue (except neural tissue) | - Breakdown of lipids to obtain energy
35
As a long-term metabolic adjustment, how are blood glucose concentrations kept elevated?
- Liver synthesizes glucose from other carbohydrates, amino acids, and lipids - Under the influence of glucagon
36
As a long-term metabolic adjustment, how is salt and water conserved?
- ADH, aldosterone, and angiotensin | - Results in the loss of potassium and H+
37
What are causes of the exhaustion phase due to the stress response?
- Exhaustion of lipid reserves - Inability to produce glucocorticoids - Failure of electrolyte balance - Cumulative structural or functional damage to vital organs
38
An acute, integrate adjustment occurs during the fight-or-flight response in which vital organs?
- Organs vital to the response | - Brain, muscles, cardiopulmonary system, liver
39
The fight-or-flight response occurs at the expense of which organs?
- Organs less immediately involved | - Skin, GI
40
What is the effect of epinephrine on lipid metabolism?
Mobilizes fatty acids as the primary fuel for muscle action
41
What is the effect of epinephrine on skeletal muscle?
Increases muscle glycogenolysis
42
How does epinephrine increase the quantity of glucose available to the brain?
Increase in hepatic glycogenolysis and gluconeogenesis
43
How does epinephrine preserve glucose for the CNS?
- Decrease in insulin release | - Leading to reduced glucose uptake by muscle and adipose tissue
44
How does epinephrine affect the cardiovascular system?
Increases cardiac output
45
How does norepinephrine affect the cardiovascular system? (2)
- Increases blood flow | - Decreases insulin secretion
46
How is blood flow redirected to vital organs by the fight-or-flight response?
Selective vasoconstriction
47
Which catecholamine affects the respiratory system? What is the effect?
- Epinephrine | - Dilation of the respiratory pathways
48
How does the fight-or-flight response affect lactic acid, glucose, and fatty acid concentrations?
- Lactic acid: increase - Glucose: increase - Fatty acids: increase
49
How does the fight-or-flight response affect muscle to mobilize energy?
- Increase in glycogenolysis | - Excretion of lactic acid
50
How does the fight-or-flight response affect the liver to mobilize energy?
- Increase in gluconeogenesis | - Increase in glycogenolysis
51
How does the fight-or-flight response affect adipocytes to mobilize energy?
Increase in lipolysis
52
How does the fight-or-flight response affect insulin and glucagon release to mobilize energy?
- Decrease in insulin | - Increase in glucagon
53
How does epinephrine affect the CNS?
- Increases arousal and alertness within the CNS | - Many stimulants act by altering catecholamine levels in the brain
54
How does epinephrine affect sweat glands? Why?
- Increased sweating | - To dissipate extra heat generated by the muscles
55
How does epinephrine affect the eyes? How?
- Dilation of pupils - Flattening of lenses - By action on smooth muscle fibers
56
Which adrenergic receptors bind both epinephrine and norepinephrine?
a and B1 receptors
57
Which catecholamine does the B2 receptor bind primarily?
Epinephrine
58
How are different tissue responses to the catecholamines modulated?
Different receptor distributions in different target tissues
59
Which receptor does Salbutamol affect? What are the effects? How does it affect B1 receptors in the heart?
- B2 receptors - Dilates bronchioles - Does NOT affect B1 receptors in the heart
60
What is the potency of the a1 receptor acting by Gq?
Norepinephrine > epinephrine
61
What is the potency of the a1 receptor acting by Gi?
Epinephrine > norepinephrine
62
What is the potency of the B1 receptor?
Norepinephrine > epinephrine
63
What is the potency of the B2 receptor?
Epinephrine > norepinephrine
64
How does the B1 receptor exert its signal transduction pathway?
Gs
65
How does the B2 receptor exert its signal transduction pathway?
Gs
66
What are the target tissues of the a1 receptor acting by Gq?
Smooth muscle (skin, GI)
67
What are the target tissues of the a1 receptor acting by Gi?
Nerve terminals for synaptic transmission
68
What are the target tissues of the B1 receptor?
- Heart | - Cerebral cortex
69
What are the target tissues of the B2 receptor?
- Lung - Smooth muscle - Cerebellum
70
Which catecholamine leads to a greater cardiac stimulation to increase cardiac output? Which receptor is implicated?
- Epinephrine >> norepinephrine | - B receptor
71
Which catecholamine has a greater effect on vasoconstriction of blood vessels?
Norepinephrine >> epinephrine
72
Which catecholamine has a greater effect on the increase in metabolism?
Epinephrine >> norepinephrine
73
What are causes of an adrenomedullary deficiency?
- Surgery, trauma - Suppression of cortisol levels, resulting in an epinephrine deficiency - Hypotension - Hypoglycemia
74
How may an adrenomedullary deficiency lead to death?
- They don't | - Adrenal catecholamines are not essential for life
75
_______________ is a tumour that overproduces catecholamines.
Pheochromocytoma
76
When are pheochromocytoma often diagnosed?
- Relatively rare - Usually, not diagnosed until autopsy - 1/3 cause death prior to diagnosis
77
What are the usual symptoms of a pheochromocytoma?
- Headache - Hypertension - Sweating - These are common symptoms, which make a proper diagnosis difficult
78
What is the treatment for a pheochromocytoma?
- 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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