Adrenal structure and function Flashcards
Where are the adrenal glands located?
Above the kidneys
What are the layers of the adrenal gland (5)?
Medulla Zone reticularis (cortex) Zone fasciculata (cortex) Zona glomerulosa (cortex) Capsule
What adrenohormones are produced in the cortex?
Zona gomerulosa=mineralocorticoids (aldosterone)
Zona fasciculata=glucocorticoids (cortisol)
Zona reticularis= androgens
What adrencortical hormones are produced in the medulla?
Catecholamines (adrenaline and noradrenaline)
What is the function and control of the zona glomerulosa?
Outer layer
Minerolocorticoid (aldosterone)
Function: salt
Control: renin
What is the function and control of the zona fasciculata?
Middle layer
Glucocorticoid (cortisol)
Function=sweet
Control=ACTH
What is the function and control of the zona reticulata?
Inner layer
Sex steroids (DHEA, DHEAS)
Function=sex
Control ACTH
What is the function and control of the medulla?
Adrenaline/ noradrenaline
Function=fight or flight
Control=sympathetic nervous system
What is adrenocorticotropic hormone (ACTH)?
Hormone produced in the anterior, or front pituitary Gland in the brain. Regulates levels of cortisol
Describe the structure of steroid hormones
All derived from cycopetanoperhydrophenanthrene (all have 3 cyclohexane rings and a single cyclopentane ring)
What is the purpose of the HPA axis?
Regulation of glucocorticoid secretion
Describe the HPA axis
CRH (from hypothalamus) -> ACTH release (anterior pituitary) -> cortisol release (from adrenal cortex) -> cortisol -ve feedback on CRH and ACTH.
- How does stress affect HPA axis?
2. What effect does cortisol have on the immune system
- People who are stressed have overactive HPA axis
2. Decreases immune response
What are the systemic effects of cortisol release?
Gluconeogenesis
Protein mobilisation
Fat mobilisation
Decreased inflammation
- How does cortisol levels affect sleep
2. How may this be affected
- Cortisol levels are low at night to promote sleep
- Cushing’s disease (excess cortisol), cortisone treatment, chronic stress, diurnal variation lost in Cushing syndrome (test for high midnight cortisol), night shifts, jet lag, exogenous steroids
How is aldosterone regulated?
RAAS
Aldosterone can be increased due to: increased ang II, increased potassium, increased ACTH, decreased sodiu
Describe the process of aldosterone regulation
Dehydration/Na+ deficiency/haemorrhage -> decreased blood vol. and pressure -> juxtagomerular cells increase renin -> angiotensinogen converted to ang I -> ACE (lungs) converts Ang I to Ang II -> adrenal cortex increases aldosterone (also vasoconstriction of arterioles) -> kidneys increase Na+ and H2O reabsorption and increased H+ and K+ secretion -> blood vol and pressure return to normal
What are the functions of aldosterone?
Increased Na+ and H2O reabsorption to increase blood vol.
Increase K+ and H+ secretion
What are the effects of aldosterone?
Increase renal tubular re-absorption of sodium and secretion of potassium
Increases ECF volume
Increases arterial pressure
What is the significance of the structures of glucocorticoids and mineralocorticoids?
They look similar due to ring structure
Cortisol can act as a mineralocorticoid and bind to these receptors and cause similar effects to aldosterone