What constitutes the adrenal glands?
Adrenal cortex and medulla - 2 endocrine glands of different embryological origin that fused during development.
What is the adrenal medulla?
A modified sympathetic ganglion the secretes catecholamines - neurohormones.
What is the adrenal cortex?
A true endocrine gland; secretes steroids - classical hormones.
What are the 3 different layers to the adrenal cortex?
Zona glomerulosa, fasciculata and reticularis.
What do each of the different zones of the adrenal cortex secrete?
- Glomerulosa: aldosterone
- Fasciculata: glucocorticoids
- Reticularis: sex hormones
Where are sex hormones secreted from?
Zona reticularis and fasciculata
Which sex hormones are secreted from the adrenal cortex?
Androgens, estrogens, dehydroepiandosterone (DHEA)
Where are glucocorticoids secreted from?
Zona fasciculata and reticularis
Which glucocorticoids are secreted from the adrenal cortex?
Cortisol, stimulated by: HPAA, ACTH tropic to ZF&ZR
Where are the mineralocorticoids secreted from the adrenal cortex?
Which mineralocorticoids are secreted from the adrenal cortex?
What is aldosterone secreted stimulated by?
RAAS & plasma K+
Why do cells produce different steroids?
Because they have different enzymes
What is the precursor to corticosteroid?
What is the precursor to oestradiol?
Testosterone and estrone
Why can steroids have crossover effects?
Because different steroids are chemically related
What is the HPA pathway for the control of cortisol secretion?
CRH from hypothalamus stimulates anterior pituitary to release ACTH which stimulates adrenal cortex to release cortisol.
What stimulates the hypothalamus to release CRH?
Circadian rhythm and stress
Where does cortisol act? What does it do at these sites?
- Immune system (suppression)
- Liver (gluconeogenesis)
- Muscle (protein catabolism)
- Adipose tissue (lipolysis).
How is cortisol release inhibited?
By cortisol negatively feeding back to anterior pituitary and hypothalamus.
What is CRH?
Corticotropin releasing hormone
What is ACTH?
What does CRH mediate other than release of ACTH?
- Effects on inflammation and immune responses
- Inhibition of appetite
- Signals the onset of labour
- Appears linked to several mood disorders
- Urocortin: brain neuropeptide ↓ appetite
What is POMC?
Pro‐opiomelanocortin: a large protein that yields several bioactive peptides by proteolysis
What are some of the peptides produced by proteolysis of POMC?
- ACTH and beta‐endorphin in the anterior pituitary
- Alpha-MSH outside the pituitary
What is beta-endorphin?
Pain perception blocker
What is alpha-MSH?
Melanocyte‐stimulating hormone: ↓ food intake & ↑ skin melanin
What are the melanocortins?
- Family name for the MSH hormones and ACTH
- The effects of the peptides depend on which melanocortin receptor subtypes are stimulated
What does cortisol help the body cope with?
How does cortisol protect against hypoglycaemia?
By stimulating catabolism of energy stores