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VMP824 Physiology/Microanatomy 2 > Lecture 20 3/7/24 > Flashcards

Lecture 20 3/7/24 Flashcards

1
Q

What is the starting material for all hormones?

A

cholesterol

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2
Q

Which enzyme is shared by all zones of the adrenal cortex?

A

cholesterol desmolase

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3
Q

What is the role of cholesterol desmolase?

A

required to activate cholesterol for further chemical modification

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4
Q

Which hormone must be present for cholesterol desmolase to be expressed?

A

ACTH

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5
Q

Which enzyme is present in the zona glomerulosa?

A

aldosterone synthase

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6
Q

What is the role of aldosterone synthase?

A

responsible for the synthesis of aldosterone from corticosterone

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7
Q

Which system is responsible for stimulation of aldosterone synthase?

A

renin angiotensin system

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8
Q

Why is it important that most chemical reactions are one way?

A

enzyme deficiency causes steroids to accumulate behind the blockades

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9
Q

When is enzyme deficiency more serious/potentially lethal?

A

when enzyme failure occurs close to cholesterol, causing adrenal cortex deficiency

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10
Q

What are the characteristics of CRH?

A

-secreted in median eminence of hypothalamus
-transported in portal pituitary vessels to adenohypophysis
-stimulates secretion of ACTH/family

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11
Q

What are the characteristics of ACTH?

A

-concentrations of ACTH and cortisol in blood are increased by CRH
-half-life of about 10 minutes

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12
Q

What blocks CRH and ACTH secretions?

A

endogenous and exogenous glucocorticoids

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13
Q

What steps occur when ACTH binds its receptor?

A

-a G protein activates adenylcyclase ->
-formation of cAMP ->
-activation of protein kinase A ->
-phosphorylation of cholesterol ester lipase

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14
Q

What is the first hormone-dependent rate limiting step in the ACTH stim. of zona fasciculata cells?

A

transportation of cholesterol through the mitochondrial membrane

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15
Q

What is StAR?

A

a small but fundamental transport protein that is induced by ACTH

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16
Q

What is the role of cholesterol desmolase in the mitochondria?

A

conversion of cholesterol to pregnenolone

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17
Q

Why must pregnenolone be transferred from the mitochondria to the smooth ER?

A

pregnenolone cannot be converted to cortisol directly

18
Q

How is the smooth ER involved in cortisol production?

A

it converts pregnenolone into 11-deoxycortisol, which can go back to the mitochondria for conversion into cortisol

19
Q

Which plasma proteins are involved in cortisol transport?

A

-CBG/transcortin
-albumin

20
Q

What are the characteristics of CBG in cortisol binding?

A

-relatively low conc. in plasma
-only one cortisol receptor site per molecule
-low capacity for binding cortisol despite the molecule binding strongly
-binds majority of cortisol in blood (75%)

21
Q

What are the characteristics of albumin in cortisol binding?

A

-much greater capacity for binding cortisol
-weaker binding to cortisol
-binds about 15% of cortisol in blood

22
Q

What are the main functions of carrier proteins?

A

-protect cortisol from kidney excretion and liver inactivation
-provide water solubility to cortisol
-provide dynamic storage for hormone and regulate hormone availability to effector tissues

23
Q

Which conditions lead to increased total cortisol and increased CBG?

A

-pregnancy
-estrogen therapy

24
Q

Which conditions lead to decreased total cortisol and decreased CBG?

A

-chronic liver disease
-starvation
-nephrotic syndrome

25
Q

How does cortisol lead to immunosuppression?

A

-increased neutrophil demargination/decreased neutrophil emigration
-decreased macrophage function
-decreased lymphocytes in circulation
-decreased eosinophils in circulation

26
Q

How does cortisol lead to anti-inflammatory responses?

A

-decreased release of pro-inflammatory enzymes
-blockage of arachidonic acid metabolism
-decreased release of macrophage and lymphocyte-derived cytokines and interleukins

27
Q

What effect does cortisol have at normal concentrations?

A

stops inflammatory processes

28
Q

How does cortisol impact carbohydrate metabolism?

A

-hyperglycemic effect
-gluconeogenesis
-increased insulin resistance
-glycogenosynthesis

29
Q

How does cortisol impact protein metabolism?

A

-catabolic effect
-decreased muscle mass
-decreased collagen/bone formation
-increased free AAs in serum
-increased excretion of nitrogen in urine

30
Q

How does cortisol impact lipid metabolism?

A

-lipolysis
-lipogenesis
-redistribution of body fat

31
Q

How does cortisol impact mineral metabolism?

A

-decreased serum Ca++
-decreased intestinal reabsorption
-increased renal excretion

32
Q

How does cortisol impact water metabolism?

A

increased water diuresis

33
Q

Where does the majority of aldosterone metabolism occur?

A

liver and kidney

34
Q

What is the action of aldosterone?

A

-Na+ reabsorption
-K+ and H+ excretion

35
Q

How does the pituitary impact aldosterone regulation?

A

aldosterone regulation is pituitary independent

36
Q

What are the characteristics of the adrenal medulla?

A

-catecholamine-secreting cells are chromaffin cells
-majority of cells secrete epinephrine over norepinephrine

37
Q

What stimulates the adrenal medulla?

A

-sympathetic neurons
-cortisol

38
Q

What are the characteristics of catecholamines in the plasma?

A

-50% loosely bound to albumin
-50% free
-half-life of about 2 minutes

39
Q

What are the metabolic effects of catecholamines?

A

-glycogenolysis in skeletal muscle and liver -> hyperglycemia
-lipolysis and fat mobilization
-stimulation of basal metabolic rate and calorigenesis

40
Q

What are the cardiovascular effects of catecholamines?

A

-tachycardia and increased BP
-vasoconstriction in the skin and GI tract
-vasodilation in skeletal muscle and liver
-smooth muscle/bronchiole dilation

VMP824 Physiology/Microanatomy 2 (50 decks)

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