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Physiology Y2S1-CVS > Adrenal functions > Flashcards

Adrenal functions Flashcards

1
Q

What percentage of the adrenal gland is formed by the zona fasciculata, and what does it secrete?

A
  • 75%
  • Glucocorticoids (cortisol) and some (adrenal androgens and estrogen)
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1
Q

What percentage of the adrenal gland is formed by the zona glomerulosa, and what does it secrete?

A
  • 15%
  • It secretes mineralocorticoids (aldosterone)
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2
Q

What percentage of the adrenal gland is formed by the zona reticularis, and what does it secrete?

A
  • 10%

1) Adrenal androgens (DHEA, Androstenedione)

2) Small amounts of estrogens and glucocorticoids)

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3
Q

What stimulates the release of aldosterone from the zona glomerulosa?

A

1) Angiotensin-II

2) Potassium

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4
Q

What stimulates the zona fasciculata of the adrenal cortex?

A

ACTH

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5
Q

What stimulates the zona reticularis of the adrenal cortex?

A

ACTH

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6
Q

What is aldosterone?

A
  • Steroid mineralocorticoid hormone
  • Essential for survival, released by the zona glomerulosa
  • It has a short half-life
  • it has 90% of the mineralocorticoid activity (as some mineralocorticoids share some of the glucocorticoid functions)
  • 40% of it is free
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7
Q

How is aldosterone regulated?

A

1) Renin-angiotensin-aldosterone mechanism

2) Increased Na+ will stimulate the release of aldosterone

3) ACTH will to some extent

4) Increased potassium level will stimulate its release to

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8
Q

Through which type of receptor does Ang-II promote the secretion of aldosterone?

A
  • G-protein signaling, which induces the hydrolysis of PIP2 to IP3 and Diacylglycerol, which will lead to an intracellular increase in calcium and thus exocytosis
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9
Q

What are the different functions of aldosterone?

A
  • It acts on the principal cells of the late distal tubule and collecting ducts

1) It stimulates the absorption of sodium

2) It increases the secretion of potassium

3) It increases the secretion of hydrogen ion

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10
Q

What is the mechanism of action of aldosterone?

A

It synthesizes N+ transporters (like Na+/K+ pumps) and channel proteins

  • Excess aldosterone will cause hypokalemia, alkalosis (due to hydrogen loss), and muscle weakness, while hyperkalemia will cause cardiac toxicity
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11
Q

What is meant by the aldosterone escape (natriuresis/diuresis) phenomenon?

A

The amount of sodium not excreted due to the effects of aldosterone won’t affect the osmolarity very much as water is reabsorbed via osmotic absorption, thirst is also triggered due to high sodium levels, + the release of ADH which will reduce the water loss and osmolarity further

  • This will all balance the Na and prevent hypernatremia
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12
Q

What are the effects of androgens?

A
  • Dehydroepiandrosterone (DHEA)

1) They are converted to testosterone and estrogen in the peripheral tissues (mainly in the peripheral tissues)

2) The amount synthesized in the adrenal gland is small compared to the gonads

3) ACTH regulates the secretion of adrenal androgens

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13
Q

What are glucocorticoids?

A
  • Steroid hormone (cortisol/hydrocortisone) which has 95% of G.C function
  • 4% of the glucocorticoid is corticosterone but it has significant activity
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14
Q

To what protein is the cortisol hormone bound?

A

1) Cortisol-binding hormone (transcortin)

2) Albumin

  • 90/95% of cortisol is bound to transcortin
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15
Q

What are the functions of glucocorticoids?

A

1) Suppresses the immune system

2) Promotes gluconeogenesis in the liver (Insulin-antagonist)

3) Extra-hepatic protein catabolism

4) Lipolysis by the adipose tissue

5) Inhibits uptake of glucose in tissue leaving it for the brain and heart mainly

16
Q

Describe the cycle that controls the levels of glucocorticoids

A

1) CRH (Controlled by stress and circadian rhythm “it is more in the morning)

2) CRH will release ACTH

3) ACTH will release Cortisol

  • Cortisol will negatively inhibit ACTH & CRH
17
Q

What are the effects of short-term stress?

A

1) Increases the HR

2) Increases the BP

3) The liver will convert glycogen to glucose and release it to the blood

4) Dilation of the bronchioles

5) Changes in blood flow, leading to a decreased systemic activity and reduced urine output

6) Increases the metabolic rate

18
Q

What are the long term effects of stress?

A

1) Sodium and water retention by the kidneys

2) Increased blood volume and pressure

3) Protein and fats are converted to glucose/broken down for energy

4) Increased blood glucose

5) Suppression of the immune system

19
Q

What is the effect of cortisol on inflammation?

A

1) It has an anti-inflammatory & immuno-suppressive effect

2) It blocks the early stages of the inflammatory process

  • Reduces inflammation and increases the speed of healing rapidly
20
Q

What is the mechanism by which cortisol exhibits its anti-inflammatory effects

A

1) Stabilizes the lysosomes (proteolytic enzymes won’t escape)

2) Decreases the permeability of the capillaries

3) Decreases the migration of WBCs and phagocytosis of inflamed cells

4) Decreases the production of T-lymphocytes and antibodies

5) Reduces fever by decreasing the release of IL-1

21
Q

What are the anti-allergic effects of cortisol?

A

1) Blocks the inflammatory response

2) While the basic allergic reaction wont be affected it can be life-saving

3) Decreases the number of Eosinophils, basophils, and lymphocytes

4) It increases the number of RBC

5) Large doses of cortisol will lead to the atrophy of the lymphoid tissues and decrease the production of T-cells and antibodies, decreasing the immunity

22
Q

How is the release of cortisol controlled?

A

1) Long-loop inhibition: Where cortisol will inhibit its own release through the hypothalamus (Inhibiting the release of CRF)

2) CRF controls ACTH (the main regulator) and CRF is controlled by negative feedback

23
Q

At what time during the day is CRF highest?

A

1) It is the highest in the very early morning

2) Lowest near midnight

24
Q

What is the effect of epinephrine and norepinephrine on Cortisol?

A

It will stimulate the release of CRF and ACTH

25
Q

What is the effect of stress on cortisol?

A

During stress, very high quantities of CRF and ACTH are released

26
Q

What are the different diseases of increased production by the adrenal cortex?

A

1) Primary aldosteronism

2) Congenital adrenal hyperplasia (in case of increased adrenal androgens)

3) Cushing’s syndrome (in case of increased cortisol and to a lesser extent androgens)

27
Q

What will happen if there is a decreased production of the adrenal cortex?

A

Addison’s disease (due to decreased cortisol and aldosterone)

28
Q

What is meant by the hypertensive syndrome?

A

Increased catecholamine secretion by the adrenal medulla due to a pheochromocytoma

29
Q

What are the clinical manifestations of addisons diseases?

A
  • Decreased production of mineralocorticoids and glucocorticoids

1) It will ultimately lead to the atrophy of the adrenal gland due to:

  • Tuberculosis
  • Autoimmune disorders (in 80% of the patients)
  • Cancer
  • It will also cause pigmentation due to increased ACTH and MSH
30
Q

How does our body deal with aldosterone deficiency?

A
  • It will lead to death within 3 days to 2 weeks unless:

1) Extensive salt therapy

2) Mineralocorticoid injection

31
Q

What will happen if aldosterone deficiency was not treated?

A

1) Increased potassium and decreased Sodium

2) Decreased chlorine

3) ECF and BV will drop preciptously

4) CO will decrease which might precipitate as a circulatory shock

5) Hyperkalemia might lead to cardiac toxicity (weak contrations, arrhythmias, HF)

32
Q

What are the manifestations of cortisol deficiency?

A

1) Inability to handle stress

2) Hypoglycemia

3) Fatigue and weakness

4) Hypotension

5) Decreased appetite and weight loss

6) Anemia

7) Hyperpigmentation due to the excess ACTH secretion and thus MSH

8) GI discomfort, nausea and vomiting

33
Q

What is cushings syndrome?

A
  • Increased cortisol and to a lesser extent the androgens
  • Usually caused by:

1) an adenoma of the anterior pituitary increases the secretion of ACTH, leading to adrenal hyperplasia, and thus increased cortisol secretion

2) Increased secretion of CRH from the hypothalamus (increasing ACTH)

3) Ectopic secretion of ACTH from tumors elsewhere in the body

4) Adenoma of the adrenal cortex

34
Q

What are the clinical presentation of cushing syndrome?

A

1) Buffalo like torso

2) Moon Face

3) Acne and hirsutism (due to an increase in the androgenic effect)

4) Muscle weakness and wasting

5) Slender extremities

6) Hypertension

7) Menstrual irregularities

8) Purple striae in the abdomen

9) Osteoporosis

10) Glucose intolerance

11) Poor wound healing

12) Easy bruising

35
Q

What is Conn’s syndrome?

A
  • Hypokalemia (muscles will become sluggish and weak -> muscle paralysis due to slow action potential transmission), hypernatremia

1) A tumor of the zona glomerulosa, secreting large amounts of aldosterone

2) It will slightly increase the ECF volume and BV

3) Modest increase in plasma sodium concentration

4) Hypertension

5) Decreased plasma renin concentration

  • You must surgically excise the tumor

Physiology Y2S1-CVS (17 decks)

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