adrenal gland Flashcards
composition of adrenal glands
2 endocrine glands
adrenal medulla
adrenal cortex
what controls adrenal cortex
hormones from anterior pituitary gland
describe blood flow to adrenal glands
rich blood supply
adrenal arteries arise directly from aorta
blood flows through cortex and drains into medulla
histologically describe adrenal gland
3 layers of cortex
1 layer of medulla
properties of adrenal medulla
part of sympathetic nervous system
not under hormonal control (not a true endocrine gland)
enlarged & specialised sympathetic ganglion
secretes catelcholamine hormones :
- adrenaline
- noradrenaline
- Instead of noradrenaline being released into the synaptic cleft as a nuerotransmitter, it is released into the circulation as a hormone.
neutrotransmitter = acetylcholine
composition of adrenal medulla
mostly chromaffin cells
Specialised postganglionic neurons
Preganglionic = Splanchnic nerve fibres
Neurotransmitter is acetylcholine
80% of the medulla secretions is ADRENALINE (epinephrine)
20% is NORADRENALINE (norepinephrine)
what are chromaffin cells & what roles
specialised cells in the medulla
depolarisation releases noradrenaline and adrenaline
also secrete dopamine
roles of adrenaline and noradrenaline
part of general sympathetic stimulation
short lived and rapid effects
- rapidly inactivated after
fight or flight response
prepares body for acute stress
cardiovascular effects of adrenaline
- Increases Heart rate and stroke volume
- Increase in blood pressure (systolic)
- Vasodilation of coronary and skeletal muscle blood vessels
- increase blood flow to heart and skeletal muscles
- Vasoconstriction of blood vessels to ‘non-essential’ tissues (GIT, skin, kidneys)
- Bronchodilation
- to get oxygen
metabolic effects of adrenaline
- Increases the amount of energy for immediate use
- Liver converts glycogen to glucose
- Metabolic rate increases
- Blood flow changes, reducing digestive system activity and urine output
roles of beta blockers
- for individuals with high blood pressure
- adrenaline usually binds to beta receptors
- beta blockers suppress action of adrenaline
draw summary of differences between adrenal medulla and adrenal cortex
structure of adrenal cortex
3 morphological distinct zones:
- Zona Glomerulosa Mineralocorticoids
- (Aldosterone)
- salt
- Zona Fasciculata Glucocorticoids
- (Cortisol)
- controlling blood glucose levels
- sugar
- (Cortisol)
- Zona Reticularis Gondocorticoids
- (Androgens)
- sex
GFR
What type of hormones are produced in adrenal cortex? where are their receptors
steroid hormones
receptors are inside the cells - inside the nucleus
hormones differ due to different enzyme
draw flowchart of biosynthesis of the adrenal cortex hormones
cholesterol is starting point for all steroid biosynthesis
hydroxylation reactions to achieve hormones
how does synthesis of adrenal cortex hormones differ from one another?
depends on enzymes. different enzymes in each layer
e.g.
zona glomerulosa lacks 17a-hydroxylase
zona fasciculata & zona reticularis lack 18 hydroxylase
role of andrenal androgens
- produce testosterone precursors:
- Dehyroepiandrosterone (DHEA)
- dehydroepiandrosterone sulfate (DHEA-S),
- androstenedione.
- out into circulation - peripheral conversion into testosterone
- DHEA/DHEAS not involved in feedback
- adrenal gland controlled by anterior pituitary gland
- by ACTH
effect of adrenal androgens in males
- no function in men
- testosterone produced by testes in high level
- male secondary characteristics
- aggressive young boys
- over-secretion or under-secretion has very little consequences in men
effect of adrenal androgen in female
- ovaries make testosterone - most is convered into oestrogen immediately
- adrenal glands produce abundance
- production of pubic hair & sex drive
- kick starts puberty
effect of excessive production of adrenal androgen in women
- over production of ACTH or tumour in adrenal cortex or Cushing’s syndrome
- masculinisation of women
- facial hair, acne, irregular periods
- play a role in PCOS
treatment
- medication that blocks androgens
- reduces symptoms
Adrenal aldosterone
- Mineralocorticoid – Zona glomerulosa
- Essential to life
- absence leads to circulatory failure & death within a few days if removed
- Aldosterone secretion is regulated by the plasma levels of sodium and potassium via the renin-angiotensin system (covered in Kidney lectures)
renin-angiotensin-aldosterone system (RAAS)
angiotensin converting enzyme - produced in the lungs
cascade of events leading to production of aldosterone
roles of aldosterone
- Control ECF volume
- Conserve body sodium
- Stimulates reabsorption of sodium in renal distal convoluted tubules in exchange for potassium
- Control of release
- Response to renin-angiotensin system (RAAS)
- Decreased ECF volume (hypovolaemia or hypotension) and decreased renal blood flow
- Response to high plasma potassium
adrenal cortisol importance
- Glucocorticoid: Zona Fasiculata
- Wide range of actions; essential to life
- Stress is a powerful stimulator of cortisol production
- Stress = physical trauma, intense heat or cold, infection, mental or emotional trauma
roles and effects of adrenal cortisol
- Mediates the body’s response to stress in response to endocrine signals
- Metabolic effects
- Cortisol increases plasma glucose and FFA concentration
- Provide energy substrates to body tissues for their response to the stressful event that stimulated cortisol production
- Increased catabolism:
- Cortisol increases skeletal muscle protein catabolism. Amino acids are then converted to glucose (gluconeogenesis)
- breaks down muscle mass
- energy source
- Increased lipolysis:
- Liberate free fatty acids & triglycerides from adipose tissue.
- Used as an energy source
- Increased intake: Stimulates appetite.
- If the stressful event doesn’t involve physical activity = weight gain
orther actions of adrenal cortisol
- cortisol causes fat stores and excess fat to be relocated in the abdomen and face
- lipolysis enhances obesity
- blood sugar levels rise as gluconeogenesis - insulin increases
- stimulates lipogenesis =
- May contribute to emotional instability
- Anti-inflammatory
- blocks the processes which lead to inflammation (in high doses)
- Immunosuppressive
- fall in antibody production and number of circulating lymphocytes
- Used clinically: to treat patients following transplant
control of cortisol release
- CRH – Corticotrophin Releasing Hormone
- ACTH – Adrenocorticothrophic Hormone
- Secretion of both the glucocorticoids and adrenal androgens are controlled by ACTH secretion
- negative feedback
examples of adrenal cortex hyperfunction
CUSHINGS SYNDROME
- Overproduction of cortisol
- Excess cortisol binds to aldosterone receptor
- As a result of an adrenal tumour or pituitary tumour
- Redistribution of body fat
- Muscle wastage
- Thin skin, bruising abnormal pigmentation
- Changes in CHO and protein metabolism
- Hyperglyceamia
- Hypertension
- Cortisol has weak mineralocorticoid activity
- moonface, abdominal striae, acne, baldness
- Treatment
- Surgery, radiation, medication
Conns disease
- Mineralocorticoid excess
- Rare
- Overproduction of Aldosterone
- Retention of sodium, loss of potassium and alkalosis
- high blood pressure
- Hypertension through expansion of plasma volume
Excessive production of adrenal androgens
- Overproduction of ACTH
- Acne, frontal baldness and hirsutism
examples of adrenal function hypofunction
Addison’s disease
- Rare
- Damage to adrenal glands, autoimmune disease or pituitary damage
- Deficits in glucocorticoids and mineralocorticoids
- Progressive weakness, lassitude and weight loss
-
Pigmentation of the skin and mucosal membranes
- low cortisol, low aldosterone, low androgens
- excess ACTH - acts like MSH
- patients with addisons have high ACTH because low cortisol is detected
if there was autoimmune destruction of adrenal cortex, what would happen to the plasma hormone levels of :
- cortisol
- ACTH
- CRH
- aldosterone
- DHEA (androgen)
- Adrenaline
- cortisol
- decreased
- ACTH
- increased
- CRH
- increased
- aldosterone
- decreased
- DHEA (androgen)
- decreased
- Adrenaline
- normal
