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SFIV Test 2 > Adrenal Gland 1 > Flashcards

Adrenal Gland 1 Flashcards

1
Q

What part of the adrenal gland secretes catecholamines?

A

Adrenal medulla located in the cetner of the adrenal gland

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2
Q

What are the three zones of the adrenal cortex and what do they synthesize?

A

Zona glomerulosa - outer

Zona fasciculata - middle

Zona reticularis- inner

All three zones produce both pregnenolone and progersterone

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3
Q

Where does the conversion of cholesterol to 11-deoxycorticosterone (DOC) occur?

A

Zona glomerulosa and Zona fasciculata

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4
Q

What zone synthesizes aldosterone?

A

Zona glomerulosa

Only zone that expresses aldosterone synthase that converts DOC to aldosterone

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5
Q

What is the functions of 11B-hydroxylase?

A

Converts DOC to corticosterone (cortisol) in the zona fasciculata

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6
Q

What is enzyme P450c17?

A

Enzyme required for the synthesis of cortisol and androgen synthesis

Has 17a-hydroxylase and 17,20-lyase activities

Expressed in both the zona fasciculata and zona reticularis

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7
Q

Where are glucocorticoids mainly synthesized?

A

Zona fasciculata with small amounts in the zona reticularis

Zona glomerulosa lacks 17a-hydroxylase activity so it is unable to synthesize cortisol and androgens

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8
Q

Where are androgens mainly synthesized?

A

Zona reticularis

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9
Q

How is transcription of StAR induced in the zona fasciculata and reticularis?

A

ACTH via a cAMP-dependent mechanism

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10
Q

How is transcription of StAR induced in the zona glomerulosa?

A

Angiotensin II via Ca-calmodulin-dependent mechanism

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11
Q

What is the effect off K on aldosterone synthesis?

A

K induces aldosterone synthesis in the zona glomerulosa via activation of VG-Ca channels

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12
Q

What is the primary action of mineralcorticoids?

A

Maintain ECF volume by regulating Na reabsorption

Also promote K and H excretion

Principal mineralcorticoid is aldosterone

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13
Q

What adrenal steroids have mineralcorticoid activity?

A

DOC and Cortisol

Aldosterone is quantitatively more important than DOC because of its large free fraction (40-50% compared to 5%)

Cortisol contributes very little to mineralcorticoid activity

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14
Q

Why doesn’t cortisol contribute to mineralcorticoid activity?

A

It is converted to cortisone by 11B-HSD2

This enzyme is expressed in tissues with glucocorticoid receptors

Cortisol can cause hypertension if this enzyme is inhibited

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15
Q

What is the principal adrenal androgen released by the zona reticularis?

A

Dehydroepiandrosterone (DHEA)

Secreted as DHEA sulfate (DHEAS)

High affinity for albumin

Small amounts of androstenedione are also released

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16
Q

Why do DHEA and androstenedione have little androgen activity?

A

Low affinity for the androgen receptor

They are converted to more potent androgens peripherally

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17
Q

Describe androgen production during pregnancy?

A

Fetal adrenal gland produces large amounts of DHEA sulfate, which is converted to estrogen by the placenta

18
Q

What layers is the fetal adrenal cortex composed of?

A

Neocortex

Fetal zone - source of DHEAS

19
Q

What is adrenarche?

A

Increase in circulating levels of adrenal androgens starting at 6-7 in girls and 7-8 in boys and continue to increase progressively through adolesence

Not invovled in the initiation of puberty

20
Q

What is the relationship between ACTH and adrenal androgens?

A

ACTH plays a role in regulating adrenal androgen secretion, but it is not the only factor

Adrenal androgens do not exert a negative feedback on ACTH secretion

21
Q

What is the state of circulating cortisol?

A

5-10% of circulating cortisol is free

75% bound to Corticosteroid binding globulin (CBG)

15% bound to albumin

22
Q

What is the most accurate measurement of daily cortisol output?

A

24-hour urinary excretion of unmetabolized cortisol

23
Q

Why do synthetic glucocorticoids have enhanced activity?

A

Increased receptor affinity

Delayed plasma clearance

24
Q

What is the principal physiological regulator of cortisol release?

A

ACTH

Released in secretory pulses throughout the day

25
Q

What are the acute actions of ACTH?

A

Increase hydrolysis of cholesterol esters

Synthesis of StAR

Increased blood flow to the adrenal cortex

26
Q

What are the chronic effects of ACTH?

A

Increase in growth and cell proliferation in the Zona reticularis and fasciculata

Increased synthesis of steroidogenic enzymes, LDL receptors

27
Q

What results from long-term suppression of ACTH?

A

Adrenal gland atrophy

Conversely, excessive ACTH production will cause adrenal gland hypertrophy

28
Q

How is ACTH release controlled?

A

CRH is the principal regulator of ACTH secretion

29
Q

What is the circadian pattern of cortisol release?

A

Diurnal rhythm

Cortisol levels are highest in the morning upon awakening

30
Q

How does stress affect cortisol?

A

Stress increases cortisol release via the CNS

CNS increases the activity of CRH-secreting hypothalamic neurons

Also causes the release of vasopressin that potentiates CRH-mediated ACTH secretion

Strong, overrides negative feedback control

31
Q

What is the negative feedback loop for cortisol?

A

Cortisol exerts a negative feedback effect on the hypothalamus and pituitary

32
Q

What is the permissive effect of cortisol?

A

Doesn’t initiate processes specifically, but rather ensures the cell has the capacity to fully respond to stimuli by regulating the expression of certain genes for a particular process

E.g. maintains glycogen synthase, therefore has a permissive effect on glucagon- and epinephrine-induced glycogenolysis

33
Q

How does cortisol protect against hypoglycemia?

A

Promotes gluconeogenesis via pathway enzyme production

Mobilizes amino acids for use in gluconeogenesis

Permissive effect on glycogenolysis

34
Q

What is the effect of cortisol on fat metabolism?

A

When present, promotes fat deposition in the trunk and face

Permissive effect on enzymes necessary to support fat mobilization

35
Q

What are the metabolic effects experienced by hypo- and hyperadrenal patients?

A

Hypoadrenal - fasting hypoglycemia

Glucocorticoid excess- hyperglycemic and hyperinsulinemic

36
Q

What are the cardiovascular effects of cortisol?

A

Required for normal responsiveness of blood vessels to vasoconstrictors

Stimulates erythropoietin

37
Q

What are the nervous system effects of cortisol?

A

Mood, behavior, wakefulness and the perception of sensory signal intensity

38
Q

What are the developmental effects of glucocorticoids?

A

Alveolar maturation and surfactant production

39
Q

What are the effects of cortisol on calcium homeostasis?

A

Excess levels of glucocorticoids increases risk for osteoporosis

Antagonize the effects of Vitamin D

Inhibit renal Ca reabsorption

Inhibits bone formation

40
Q

What are the anti-inflammatory actions of glucocorticoids?

A

Suppress the inflammatory response by blocking the expression of genes that code for pro-inflammatory cytokines

Inhibit enzymes like phospholipase A2 and NO synthase

Induces synthesis of Lipocortin (inhiibts PPLA2)

SFIV Test 2 (13 decks)

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