Session 12 ILOs - The Adrenal glands, RAAS and Adrenal disorders Flashcards
Describe the anatomical division of the adrenal gland in terms of the different layers of the cortex and the relationship between the cortex and medulla
To ask:
Is the androgens the main hormone produced by the zona reticularis?
What are androgens - what is the relationship between androgens, oestrogen and testosterone?
- Capsule protects the adrenal glands
- Cortex is the layer above the medulla but beneath the capsule
- Cortex - contains 3 layers, each producing different hormones (GFR (Glomerular filtration rate), Salt, sugar, sex)
Zona Glomerulosa - produces mineralocorticoids e.g. aldosterone
Zona Fasiculata - produces glucocorticoids e.g. cortisol
Zona Reticularis - produces glucocorticoids + small amounts of androgens (sex hormones which can be converted to oestrogen and testosterone in peripheral tissues) androgens - e.g testerone and oestrogen
Medulla - contains chromaffin cells
Produces Adrenaline (80%) and Noradrenaline (20%)
Describe the difference in origin tissues of different parts of the adrenal gland
Different areas of the adrenal glands arise from different tissues:
Cortex = mesoderm origin
Medulla = neural crest cell origin which subsequently migrate into the developing cortex
Name the hormones produced by the different layers of the adrenal cortex
Cortex:
Zona Glomerulosa - mineralocorticoids e.g. aldosterone
Zona Fasciculata - glucocorticoid e.g. cortisol
Zona Reticularis - produces glucocorticoids + small amounts of androgens (sex hormones which can be converted to oestrogen and testosterone in peripheral tissues)
Medulla (not part of the adrenal cortex)
Adrenaline (80%) - fight or flight response
Noradrenaline (20%) - fight or flight response
What are the functions of mineralocorticoids like aldosterone?
Zona Glomerulosa - mineralocorticoids e.g. aldosterone
- Central role in regulation of plasma Na+, K+ and arterial blood pressure
- Promotes expression of Na+/K+ pump increasing reabsorption of sodium and water back into the blood
- This influences water retention, blood volume & therefore blood pressure
- Central component of renin-angiotensin-aldosterone system (RAAS)
What are the functions of glucocorticoids like cortisol?
Zona Fasciculata - glucocorticoid e.g. cortisol
- Exerts it’s actions by Regulating gene transcription
- Has negative feedback to the hypothalamus to inhibit CRH and ACTH release
- Many actions but main =
- Increased proteolysis in muscle
- Increased lipolysis in fat
- Increased gluconeogenesis in liver
- Anti-inflammatory effects
- Depression of immune response
- Resistance to stress
What are the functions of androgens?
Zona Reticularis - androgens
- Promote axillary and pubic hair growth in both sexes
- In males, DHEA converted to testosterone in testes (after puberty this is insignificant since testes release far more testosterone themselves)
- In females, promote libido and are converted to oestrogens by
other tissues. After menopause this is only source of oestrogens.
Give 2 examples of androgens
- (DHEA) and androstenedione are types of androgens
What are the functions of adrenaline, produced from the medulla?
Medulla
Adrenaline (80%) - fight or flight response
Noradrenaline (20%) - fight or flight response
F or F: (6)
- Increased HR
- Increased contractility
- Increased bronchodilation
- Increased vasodilation (mucles)
- Increased vasoconstriction (skin and GI tract, so it can go to muscles)
- Increased glycolysis in muscles
Describe in general terms the structure and functions of the steroid hormones
And give 5 examples of steroid hormones
- All made from cholesterol in adrenal glands or gonads
- All lipid soluble
Bind to receptors of the nuclear receptor family to modulate gene transcription
• Glucocorticoids
• Mineralocorticoids
• Androgens
• Oestrogens
• Progestins
What are corticosteroids?
Name the 2 kinds
- Corticosteroids are a class of steroid hormones
- Produced in the adrenal cortex or made synthetically. There are two kinds: glucocorticoids and mineralocorticoids
Explain how the steroid hormones affect their target tissues (check discussion board)
Explain how corticosteroids act
- Corticosteroids diffuse across plasma membrane
- Bind to glucocorticoid receptors which causes dissociation of chaperone proteins
- Receptor/ligand complex then translocates to the nucleus
- Dimerisation with other receptors can occur
- Receptors bind to glucocorticoid response elements or other transcription factors
Explain how cortisol secretion is controlled by ACTH and CRH
- Cortisol is controlled by negative feedback of the hypothalamic pituitary adrenal axis
- Low ATCH or CRH would decrease cortisol production whereas increased ATCH or CRH would increase cortisol production
- However, high cortisol would inhibit ATCH or CRH production therefore lowering cortisol levels again
Explain how ACTH can lead to increased pigmentation in certain areas of the body
- Lower levels of ACTH will decrease the level of cortisol
- Decreased cortisol means that there is decreased negative feedback on the anterior pituitary
- So we need to synthesise more acth
- ACTH is made from POMC, so more is POMC required to synthesise ACTH
- However POMC also makes MSH (melanin stimulating hormone) which increases melanin production and therefore hyperpigmentation
Describe the main actions of cortisol
- Exerts it’s actions by Regulating gene transcription
- Negative feedback to the hypothalamus to inhibit CRH and ATCH release
- Increases protein breakdown
- Increased lipolysis in fat
- Gluconeogensis in liver
- Anti-inflammatory effect
- Immune response depression
- Resistance to stress
Describe in general terms the structure and functions of adrenaline
Adrenaline is formed from Tyrosine
Tyrosine -> Levodopa -> Dopamine -> Noradrenaline -> Adrenaline
N-methyltransferase is required to convert Noradrenaline to Adrenaline
Adrenaline binds to adrenergic receptors involved in the sympathetic or fight or flight response to cause:
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