Lecture 28

Question 1

What are the components of the adrenal glands and their purpose?

Answer 1

• capsule = outer connective tissue
• cortex = outer functional part, secretes glucocorticoids, mineralcorticoids, sex hormones
• medulla = innermost layer, adrenaline and noradrenaline

Question 2

What is the Zona glomerulosa?

Answer 2

• outer layer of adrenal gland
• produces aldosterone
• Increases sodium reabsorption in kidney and potassium excretion
• Aldosterone secretion stimulated by angiotensin
  II and high potassium

Question 3

What is the Zona fasciculata?

Answer 3

• middle zone
• Secretes glucocorticoids (e.g. cortisol)

Question 4

What is the Zona reticularis?

Answer 4

• Inner zone of adrenal cortex
• Secretes adrenal androgens
• Role in fetal and pre-pubertal development + mild effects in females after puberty

Question 5

What is the Adrenal Medulla?

Answer 5

• Functionally related to the SNS
• makes adrenaline and noradrenaline
• Neurons in hypothalamus analogous to preganglionic sympathetic neurons
• Chromaffin cells in medulla are analogous to postganglionic sympathetic neurons (but without axons)

Question 6

How is glucocorticoid secretion controlled?

Answer 6

• Hypothalamus secretes corticotrophin releasing
  hormone (CRH)
• CRH acts on anterior pituitary causing it to secrete ACTH in
  diurnal pattern

Question 7

What is Adrenocorticotropic hormone (ACTH) and what does it do?

Answer 7

• ACTH is a peptide hormone
  produced by corticotropes cells of the anterior pituitary
• ACTH acts on the inner 2 layers of the adrenal cortex
• ACTH binds with G-protein coupled receptors in adrenal cortex
• ACTH Increases cortisol and
  adrenal androgen synthesis by
  increasing expression/activity of
  steroidogenic enzymes.

Question 8

What do Glucocorticoids do to help resist physiological stress?

Answer 8

• Increase responsiveness to catecholamines (so help maintain BP)
• Increase gluconeogenesis in the liver
• Mobilizes amino acids from extrahepatic tissues especially
  muscle
• Promotes mobilization of lipids from fat
• Reducing/limiting inflammatory and/or immune reactions.

Question 9

What does aldosterone do and in response to what?

Answer 9

• Secreted by cells of Zona glomerulosa in
  response to:
• Activation of the renin-angiotensin system ( i.e
  angiotensin II)
• High ECF potassium
• Low ECF sodium
• Aldosterone acts on nephrons in kidney to increase reabsorption of sodium
• Increases renal excretion of potassium in urine

Question 10

What are some responses from alarm phase of stress? For how long?

Answer 10

• seconds to hours
• • Increased alertness and ability to focus
• Dilated pupils
• Increased heart rate, cardiac output and BP
• More blood flow to heart, skeletal muscles
• Increased respiratory rate and O2 consumption
• Smooth muscle in airways relaxes
• Reduced bloodflow to kidneys and gut
• Increased breakdown of glycogen in muscle
• Mobilization of liver glycogen&raquo_space; ↑ BGL
• Increased sweating

Question 11

What are some responses from resistance phase of stress? For how long?

Answer 11

• hours, weeks, months
• gluconeogenesis
• • Switch in metabolism of many tissues
    to using lipids as energy source ‘spares’
    available glucose for the brain
• Increased BGLs
• Conservation of sodium and water but
  loss of potassium

Question 12

What are some responses from exhaustion phase of stress? For how long?

Answer 12

• exhaustion of protein and lipid reserves
• Inability of maintain acceptable blood glucose concentration
• Failure to maintain adequate fluid and electrolyte balance
• Cardiovascular damage due to prolonged elevation in blood volume, BP, BGL etc

Question 13

What is cushing’s disease? What are the possible causes?

Answer 13

• due to excess of glucocorticoids
• from medication, tumours

Question 14

What is addison’s disease? What are the possible causes?

Answer 14

• loss of glucocorticoids and mineralcorticoids
• may be due to autoimmune adrenalitis, infection, metastatic cancer