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Year 2 - Endocrine System > The Adrenal Gland > Flashcards

The Adrenal Gland Flashcards

1
Q

Around how many grams does each adrenal gland roughly weigh?

A
  • 4g
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2
Q

State the names of the 2 seperate endocrine glands that make up the adrenal gland

A
  • Adrenal medulla
  • Adrenal cortex
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3
Q

What is the adrenal medulla derived from?

A
  • Neural crest tissue (ectoderm)
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4
Q

What does the adrenal medulla secrete?

A
  • Catecholamines

(adrenaline, noradrenaline and dopamine)

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5
Q

What is the adrenal cortex derived from?

A
  • Mesoderm
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6
Q

The adrenal cortex is a true endocrine gland that secretes which 3 classes of steroid hormones?

A
  • Mineralocorticoids (e.g. aldosterone: involved in the regulation of Na+and K+) - ESSENTIAL FOR SURVIVAL
  • Glucocorticoids (e.g. cortisol: involved in maintaining plasma glucose) - ESSENTIAL FOR SURVIVAL
  • Sex steroids (e.g. testosterone)
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7
Q

In the adrenal cortex, the

(a) Zona glomerulosa secretes
(b) Zona fasciculata secretes
(c) Zona reticularis secretes

A

(a) Aldosterone
(b) Glucocorticoids
(c) Sex hormones

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8
Q

In the adrenal cortex, how are different products produced in the different adrenal zones?

A
  • All steroid hormones are derived from cholesterol, but different enzymes are found in different adrenal zones, resulting in different end products (hormones)
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9
Q

What is the prehormone of testosterone and oestrogen that is secreted by the adrenal cortex?

A
  • DHEA

(dehydroepiandosterone)

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10
Q

Defects in 21-hydroxylase is a common cause of what?

A
  • Congenital adrenal hyperplasia

(resulting in deficiency of aldosterone and cortisol and associated disruption of salt and glucose)

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11
Q

Descibe the control pathway for cortisol secretion

A
  • It is known as the Hypothalamic-Pituitary-Adrenal Pathway
  • The hypothalamus secretes the hormone CRH into the hypothalamic-hypophyseal system and transported to the anterior pituitary
  • CRH then stimulates the release of ACTH from the anterior pituitary
  • There is a short-loop feedback by ACTH on CRH
  • ACTH in turn acts on the adrenal cortex to promote synthesis and release of cortisol
  • Cortisol then acts as a negative feedback signal, inhibiting ACTH and CRH secretion
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12
Q

Why does a deficit in 21-hydroxylase results in adrenal hyperplasia?

A
  • Lack of 21-hydroxylase inhibits synthesis of cortisol
  • This removes the negative feedback on ACTH and CRH release
  • Increased ACTH secretion is responsible for enlargement of adrenal glands.
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13
Q

Cortisol is a _________ hormone. What does this mean?

A
  • Glucocorticoid
  • Influences glucose metabolism
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14
Q

After diffusing out of adrenal glands into the plasma, how is most cortisol transported in the blood?

A

~ 95% of plasma cortisol is bound to a carrier protein, cortisol binding globulin (CBG)

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15
Q

What does cortisol do when it is released out of the blood and goes into taget cells?

A
  • Cortisol is a steroid hormone therefore its receptor is in either the cytoplasm or nucleus
  • Cortisol enters the cell and binds to a cytoplasmic/nuclear receptor
  • This hormone receptor complex then migrates to the nucleus (if not already in the nucleus) and binds to DNA
  • This alters gene expression, translation and transcription
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16
Q

Comparing ACTH to cortisol, which has “bursts” that last longer and why?

A
  • Cortisol
  • The half-life of cortisol is much longer
17
Q

Describe the circadian rhythm of cortisol

A
  • Peak is 6am - 9am
  • Lowest level ~ midnight

(Notes: Other fluctutations during the day are due to effects of other stimuli which are related to stress. Diagram shows cortisol bursts > ACTH bursts)

18
Q

If the adrenal glands are removed from an animal, what are the consequences?

A
  • DEATH (within a few weeks)
  • Loss of cortisol means animals cannot deal with stress, particularly in terms of maintaining blood glucose levels.

(the animal dies when exposed to any environmental stress - silverthorn)

19
Q

Why is cortisol important for the brian?

A
  • Cortisol helps to maintain blood glucose levels and so is crucial in helping to protect the brain from hypoglycaemia
20
Q

What is more vital for the brain?

Cortisol or glucagon?

Why?

A
  • Cortisol
  • Glucagon alone is inadequete in responding to a hypoglycaemic challenge (in the absence of cortisol)

(Cortisol is required for full glucagon activity)

21
Q

What are the 4 actions of cortisol on glucose metabolism? (glucocorticoid actions)

A
  • Gluconeogenesis
  • Decreases insulin sensitivity of muscle and adipose tissue
  • Proteolysis (breakdown of skeletal muscle proteins is a substrate for gluconeogenesis)
  • Lipolysis (gylcerol is a substrate for gluconeogenesis, free fatty acids is an alternative fuel supply that allows BG to be protected)
22
Q

Excess cortisol?

A
  • Diabetogenic

(becuase too much glucose will be release into the blood)

23
Q

State the additonal actions of of cortisol (non- glucocorticoid)

(LATER)

A

LATER

24
Q

What are the side effects of glucocorticoid therapy (cortisol)?

A
  • Increased severity and frequency of infection (funciton of the immune system is suppressed)
  • Muscle wastage (muscle is broken down - protein catabolism)
  • Loss of percutaneous fat stores gives the appearance of thinning skin making it more fragile (lipolysis of adipose tissue)
25
Q

Aldosterone increase the reabsorption of ___ ions and promotes the excretion of ___ ions

A

Aldosterone increase the reabsorption of Na+ ions and promotes the excretion of K+ ions

26
Q

Increased aldosterone causes increased/decreased blood pressure.

A
  • INCREASED

(Aldosterone release causes sodium and water retention, which causes increased blood volume, and a subsequent increase in blood pressure)

27
Q

Hypersecretion of cortisol causes _________ while hyposecretion of cortisol causes __________

A

Hypersecretion = Cushing’s Syndrome

Hyposecretion = Addison’s Disease

28
Q

Pheochromocytoma notes:

A

Pheochromocytoma is a rare neuroendocrine tumour, found in adrenal medulla which results in excess catecholamines (i.e noradenaline). This leads to:

↑HR → ↑­CO → ­­↑BP

Diabetogenic due to adrenergic effect on glucose metabolism.

Responds well to surgery.

29
Q

Withdrawing chronic glucocorticoid treatment (LATER)

A
  • LATER

Year 2 - Endocrine System (29 decks)

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