T1 L6, The Adrenal cortex Flashcards
Which part of the adrenal gland is essential for life?
The functioning adrenal cortex
Which is the outer layer of the adrenal cortex?
The zona Glomerulosa
Which is the middle layer of the adrenal cortex?
The zona Fasciculata
Which is the innermost layer of the adrenal cortex?
The zona Reticularis
In which adrenal cortex layers is the enzyme 17a-hydroxylase present?
The zona Fasciculata and zona Reticularis
In which adrenal cortex layer is cortisol synthesised?
In the zona Fasciculata
In which adrenal cortex layer are androgens synthesised?
In the zona Reticularis
How is glucocorticoid secretion controlled?
By a feedback loop and cortisol acting as that messenger
The hypothalamus releases CRH which stimulates the anterior pituitary gland to release ACTH which stimulates the adrenal cortex to release cortisol. The Cortisol will then signal to the hypothalamus
Describe the secretion of ACTH throughout the day
The peak is in the early morning and lowest in the middle of the night
There is increased secretion during prolonged stress
Describe the secretion of ACTHB throughout the day
The secretion pattern is similar to ACTH but the lowest and highest is about 2 hours later after the those of ACTH
What % of cortisol is free in the blood and active?
10%
How does the amount of free blood cortisol change during pregnancy?
It stays the same. There is an increase in circulating plasma but cortisol concentrations stay the same
Where are adrenal steriods metabolised?
Mainly in the liver where they are glucuronidated to form water soluble forms which can be excreted in urine
How do glucocorticoids produce their effects?
They act on intracellular receptors and alter gene expressions
At normal physiological concentrations, what is the most important action of cortisol?
It’s role in carbohydrate metabolism
What are the roles of Cortisol?
The opposite effects to insulin:
- Antagonises the effects of insulin on cellular uptake of glucose
- Stimulates glycogenolysis
- Stimulates hepatic gluconeogenesis
- Stimulates lipolysis
- potentiates the effects of growth hormone and catecholamines
- Direct effects on the brain
- Indirect effects on pain
What effects does cortisol have when it’s in excessive concentrations?
Fat synthesis and deposition in new sites Eg, face, trunk, intrascapular region
What does cortisol do in the liver?
Stimulates amino acid uptake leading to enhanced gluconeogenesis
What does cortisol do in the periphery?
It inhibits amino acid uptake and protein synthesis, resulting in a net loss of skeletal protein
Is it true that Glucocorticosteroids can also stimulate aldosterone receptors?
Yes
What does the enzyme 11beta-hydrosteroid dehydrogenase do?
It converts cortisol into inactive cortisone
At what conditions are the mineralocorticoid actions of glucocorticoids only apparent?
In high concentrations
Which hormone if in excess, can enhance vasoconstrictor responses to catecholamines which increases blood pressure?
Cortisol
Is it true that glucocorticosteroids can produce psychological effects with possible feelings of elation or sedation?
Yes
