8. Adrenal gland and its hormones Flashcards
What are the 2 sections of the adrenal glands?
- Inner - medulla
- Outer - cortex
What type of hormones does the medulla secrete?
Secretes catecholamines e.g. adrenaline, noradrenaline
What type of hormones does the cortex secrete?
Secretes adrenocortical steroid hormones
Describe the structure of the cortex of the adrenal glands.
- Zona glomerulosa
- Zona fasciculata
- Zona reticularis
State the hormones made by the different sections of the cortex.
- Zona glomerulosa -> Mineralcorticoids e.g. Aldosterone
- Zona fasciulata -> Glucocorticoids e.g. Cortisol, Cortisone
- Zona reticularis -> Androgens (sex hormone precursors)
GFR – Makes Good Sex
Mnemonic to remember the order of adrenal cortex sections and their respective released hormones.
GFR – Makes Good Sex
Glomerulosa, Fasciculata, Reticularis -> Mineralcorticoids, Glucocorticoids, Sex hormone precursors (androgens)
What are adrenalcortical hormones synthesised from?
Cholesterol
Describe the initial conversion of cholesterol.
Cholesterol converted to Pregnenolone via enzyme, Cholesterol desmolase:
Cholesterol
↓ Enzyme, cholesterol desmolase
Pregnenolone
Cholesterol desmolase - stimulated by ACTH
What stimulates cholesterol desmolase secretion?
Cholesterol desmolase - stimulated by ACTH
Describe aldosterone synthesis in the zona glomerulosa.
What stimulates aldosterone synthase?
Angiotensin II
State 3 functions of aldosterone.
- Regulates extracellular fluid volume
- Potassium homeostasis
- Increase renal water + sodium reabsorption via RAAS
Describe cortisol synthesis in the zona fasciculata.
State 5 functions of cortisol.
- Stress response
- Metabolic effects
- Immunosuppressive effects
- Anti-inflammatory effects
- Vascular effects
Describe the metabolic effects of cortisol.
- ↑ blood glucose by ↑ hepatic glycogenolysis
(‘diabetogenic hormone’) - ↑ lipolysis
- ↑ protein catabolism
- ↓ cellular insulin sensitivity
Describe the immune effects of cortisol.
↓↓ intensity of immune + inflammatory responses:
- ↓ production of Arachidonic Acid metabolites e.g. prostaglandin, thromboxane, leukotrienes
- ↓ production of interleukins,, interferons + TNF
- ↓ T-cell proliferation
- ↓ neutrophil phagocytosis
Describe the vascular effects of cortisol.
Involved in normal vascular blood pressure maintenance.
Supports vascular smooth muscle responsiveness to catecholamine vasoconstrictive effects.
Give 3 functions of cortisol in response to stress.
- Mobilises energy sources -> lipolysis, gluconeogenesis and protein break down.
- Vasoconstriction.
- Suppresses inflammatory and immune repsonses.
- Inhibits non-essential functions e.g. growth and reproduction.
What is important about the androgens in the adrenal cortex for females?
Only source of androgens in biologically-female individuals
Describe the mechanism of ACTH.
Hypothalamus -> CRH -> AP -> ACTH -> adrenal cortex (zona fasciculata) -> glucocorticoid synthesis e.g. cortisol.
Cortisol has a negative feedback effect on the hypothalamus and the anterior pituitary.
What is the affect of cortisol on insulin and glucagon?
Cortisol inhibits insulin and activates glucagon.
Describe the pattern of cortisol release.
Normal pulsatile secretion.
Approx. 10 surges in diurnal (daily) pattern.
Highest concentration in the morning; lowest in the evening.
What regulates the secretion of ACTH and cortisol?
The suprachiasmatic nucleus (SCN) in the hypothalamus
State 2 ways cortisol secretion is stimulated.
- Stress
e.g. infection, trauma, F/F response, psychological stressors - Negative feedback loop
