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Endocrine physiology > The adrenal gland > Flashcards

The adrenal gland Flashcards

1
Q

Describe the basic anatomy of the adrenal glands

A
  • Located superior to the kidneys
  • Around the level of the 12 thoracic vertebrae
  • Is reteroperitoneal
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2
Q

Describe the drainage of the left adrenal gland compared to the right

A
  • The left adrenal gland drains straight into the renal vein

- While the right adrenal gland drains straight into the IVC

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3
Q

What are the two different parts of the adrenal gland

A
  • The adrenal medulla (25%), which is a modified sympathetic ganglion derived from neural crest tissue
  • The adrenal cortex (75%), is a true endocrine gland derived from the mesoderm, outer layer
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4
Q

What does the adrenal medulla secrete

A

Catacholamines (Amine hormone dervied from tyrosine)

  • Epinephrine
  • Nonepinephrine
  • Dopamine
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5
Q

What does the adrenal cortex secrete

A

Steroid hormones
Zona glomerulosa - Mineralocorticoids, Aldersterone involved in regulation of Na and K
Zona fasiculata - Involved in secretion of glucocorticoids
Zona reticularis - Involved in Androgen secretion

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6
Q

What is the enzyme used to create Aldersterone and cortisol

A

21 - hydroxylase

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7
Q

What is DHEA

A

Dehydropiandrosterone, It is the pre-hormone of testosterone and oestrogen, it has a marked decline with age

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8
Q

What happens when there is a defect in 21-hydroxylase

A
  • Common cause of congenital adrenal hyperplasia- Resulitng in the deficiency of alderstone and cortisol
  • Androgen synthesis isnt effected however and overproduction of androgens can be made
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9
Q

Describe the pathophysiology of congenital hyperplasia

A
  • Lack of 21-hydroxylase inhibits the synthesis of cortisol
  • This removes the negative feedback on the anterior pituitary and hypothalamus
  • CRH and ACTH synthesis is increased
  • This results in hyperplasia of the adrenal glands
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10
Q

Describe the binding and transport of cortisol

A
  • 95% of cortisol is bound to a carrier protein Cortisol binding globulin
  • All nucleated receptors have cytoplasmic glucocorticoid receptors
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11
Q

Describe the MOA of the cortisol-receptor complex

A
  • The hormone complex migrates to the nucleus
  • ## Binds to DNA via hormone response element and alters gene expression, transcription and translation
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12
Q

Describe characteristics of cortisol release

A
  • Cortisol release has a marked circadian rhythm
  • Cortisol release is largest in the morning between 6-9am
  • Its at its lowest level at midnight
  • Similar pattern of ACTH release but cortisol lasts longer due to its longer half life
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13
Q

What hormone does cortisol have permissive action on

A
  • Cortisol has permissive action on glucagon and nonepinephrine
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14
Q

Describe the main diabetogenic actions of cortisol

A
  1. Gluconeogensis - Cortisol stimulates the formation of gluconeogenic enzymes in the liver resulting in increased gluconeogensis and glucose production
  2. Proteolysis - Cortisol stimulates the breakdown of muscle protein to provide gluconeogenic substrates for the liver
  3. Lipolysis - Break down of FFA creating alternative food supply
  4. Decrease insulin sensitivity of muscle and adipose tissue
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15
Q

Additional actions of cortisol

A
  1. Neagtive effect of Ca balance, Decreases absorption from the gut, increases excretion in the kidneys
  2. Impairment of mood and cognition, depression and impaired cognitive function associated with excess cortisol
  3. Permissve of nonepinephrine, cushings disease is strongly assoicated with hypertension
  4. Suppression of the immune system, cortisol reduces the circulating lymphocyte count, reduces antibody formation
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16
Q

What are the side effects of cortisol

A
  • Frequent infections
  • Muscle wasting
  • Loss of percutaneous fat stores, skin thinning
17
Q

Describe the basic characteristics of aldosterone

A
  • Secreted from the zona glomerulosa of the adrenal cortex
  • Steroid hormone which acts on the distal tubule of the nephron
  • Increases Na absorption and K excretion, BP increases
  • Controlled mainly by the RAAS
18
Q

Describe stimuli that effect cortisol release

A
  • Stress increases release
  • Alcohol - Increases release
  • Caffeine - Increases release
  • Lack of sleep - Increases release
19
Q

Describe the tissue of the adrenal medulla

A
  • Not true endocrine tissue, similar to posterior pituitary in having neuroendocrine role
  • Preganglionic fibres temerminate on sympathetic postganglionic fibres in adrenal medulla
  • Postganglionic fibres dont have axons and release straight into the blood
20
Q

What recepotors are activated in order to ellict vasoconstriction

A
  • B1 receptors
21
Q

Why is caution needed when withdrawing exogenous cortisol treatment

A
  • Supplementary cortisol enhances negative feedback on hypothalamus and pituitary release of CRH and ACTH
  • Loss of trophic action of ACTH can cause atrophy of the gland
  • Risk of adrenal insufficiency if withdrawal too fast

Endocrine physiology (11 decks)

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