Adrenal gland

Question 1

stress definition

Answer 1

A change that disturbs or threatens to disturb homeostasis- for example physical trauma, infection, intense heat or cold, starvation, surgery, severe blood loss, pain and dehydration, anxiety and depression

Question 2

How does optimal performance vary with stress?

Answer 2

low stress, an individual is often inactive and laidback

medium stress- peak, best optimal performance

between medium and high appears the stress zone- an individual is anxious

high stress- panic, anger and violence- overload

Question 3

Adrenal gland definition

Answer 3

Suprarenal endocrine gland that produce a variety of hormones, including adrenaline and steroids aldosterone and cortisol

Question 4

Location of adrenal glands

Answer 4

Two, each found above the kidneys

Question 5

vasculature of adrenal glands

Answer 5

adrenal arteries branch from the renal and inferior phrenic arteries

left adrenal vein drains to renal vein

right adrenal vein drains into inferior vena cava

small arterioles from an arterial plexus beneath the capsule surrounding the adrenal gland and then enter a sinusoidal system that penetrates the cortex and the medulla, draining into a single central adrenal vein in each gland

Question 6

Two components of the adrenal glands + brief function

Answer 6

inner medulla- secretes catecholamines noradrenaline and adrenaline

outer cortex- secretes steroid hormones

Question 7

Explain the embryology of the adrenal glands

Answer 7

adrenal cortex and adrenal medulla develop from different origins

cortex- develops from mesoderm close to the mesonephros

medulla- develops from neural crest tissue

adrenal gland is identifiable as a separate organ at 2 months gestation and is composed of a fetal zone and definitive zone

‘fetal zone’ is prominent in the fetus but regresses after birth

The fetal zone produces androgens which the placenta aromatises to oestrogens

the definitive zone is similar to the adult adrenal cortex

Question 8

structure of adrenal gland

Answer 8

inner adrenal medulla formed of groups of chromaffin cells packed with catecholamine granules which store large quantities of adrenaline and noradrenaline

adrenal cortex is formed of sheets of cells surrounded by capillaries and arranged in three zones

zona glomerulosa: outer that produces aldosterone

zona fasciculata: middle that makes cortistol

zona reticularis- inner that makes small amounts of androgens

Question 9

innervation of kidney

Answer 9

principally to the medulla- innervated by thoracic preganglionic sympathetic nerves which release ACh that act upon nicotinic receptors

Question 10

Length of time of adrenaline release during stress

Answer 10

seconds

Question 11

Length of time of adrenaline half life during stress

Answer 11

10 seconds

Question 12

Length of time of adrenaline action during stress

Answer 12

seconds

Question 13

How much adrenaline is depleted?

Answer 13

only a small fraction

Question 14

synthesis of adrenaline

Answer 14

In the cytoplasm of chromaffiin cells tyrosine is converted into L DOPA by tyrosine hydroxylase

DOPA to dopamine by DOPA carboxylase

dopamine is then pumped into granules and is converted into noradrenaline by dopamine beta hydroxylase

noradrenaline is then stored or pumped out of the granule for conversion into adrenaline by phenyl-N-methyl transferase in the cytoplasm

adrenaline is then pumped into granules for storage and release

Question 15

In a broad way, increased adrenaline secretion causes what changes

Answer 15

increase the circulation

increase the availability of energy substrates

decreases non essential activities

Question 16

disorders of adrenal medulla function

Answer 16

phaeochromocytoma- tumour arising from chromaffin cells which leads to the uncontrolled secretion of adrenaline and noadrenaline

symptoms- hypertension and tachycardia

Question 17

How much adrenaline is secreted relative to noradrenaline?

Answer 17

adrenaline 80%

noradrenaline 20%

Question 18

3 main hormones the cortex produces and

Answer 18

cortisol- glucocorticoid

aldosterone- mineralcorticoid

androgens from cholesterol

Question 19

synthesis of adrenal steroid hormone

Answer 19

1. cholesterol is stored in lipid droplets as cholesterol ester in adrenal cortex cells and is mobilised by adrenocorticotropic hormone
2. the rate limiting step is the cleavage of the side chain of cholesterol by cytochrome P450 side chain cleave enzyme to yield pregnenolone
3. enzymes which convert pregnenolone to glucocorticoids and mineralcorticoids via intermediates are found in the mitochondria and smooth endoplasmic reticulum, therefore these organelles are prominent in the cortex cells

Question 20

plasma transport of cortisol

Answer 20

binds to cortisol-binding globulin in plasma with high affinity and to albumin with low affinity

Question 21

plasma transport of aldosterone

Answer 21

no high affinity binding protein is present in plasma, so weakling binds to albumin and has a shorter half life than cortisol as a result

Question 22

corticosteroid definition

Answer 22

class of steroid hormones that are produced in the adrenal cortex of vertebrates

Question 23

glucocorticoid definition

Answer 23

class of corticosteroids that are involved in the regulation of glucose metabolism, hence the name

Question 24

mineralocorticoid definition

Answer 24

class of corticosteroid that are involved in the retention of sodium, a mineral, hence the name

Question 25

cortisol receptors

Answer 25

glucocorticoid receptors that are present in almost all cells located in the cytoplasm of cells and migrate to the nucleus to regulate gene transcription when cortisol binds

Question 26

metabolism of cortisol explained

Answer 26

cortisol is converted in the liver to the relatively inactive metabolite, cortisone by 11B-hydroxysteroid dehydrogenase

Question 27

control of cortisol output explained

Answer 27

1. hypothalamus releases corticotrophin releasing factor in response to stress 2. CRF acts on the anterior pituitary corticotrophis to stimulate adrenocorticotrophic hormone production and release 3. ACTH is cleaved from the prohormone POMC and stimulates the zona fasciculata cells via cyclic AMP to stimulate cortisol production

Question 28

actions of cortisol

Answer 28

provides protection of the body in prolonged stress- primarily to preserve glucose for the brain exerts widespread actions on many tissues cortisol stimulates the metabolism of: - carbohydrates- stimulates glucose production- opposite effect to insulin - lipids- stimulates lipolysis and ketogenesis- results in redistribution of fat to trunk if fatty acids are in excess - proteins- stimulates gluconeogenesis cardiovascular effects - maintains the circulation via increased myocardial contraction, increases vascular tone - maintains plasma volume by preventing increased vascular permeability ion control - promotes sodium retension and potassium excretion haemopoiesis stimulation immune system - immunosuppressive actions - inhibits leukocyte translocation from blood to sites of tissue damage or infection - stimulates lymphocyte destruction - glucocorticoid selective drugs used therapeutically to treat inflammatory diseases such as asthma and eczema

Question 29

Addison's disease explained

Answer 29

cortisol insufficiency where the adrenal glands do not produce enough steroid hormones darkening of the skin may occur due to high levels of circulating melanocyte stimulating hormone most often autoimmune secondary adrenal insufficiency is caused by not enough ACTH produced by the anterior pituitary

Question 30

Cushing's disease explained

Answer 30

coritsol excess characterised by the increased secretion of ACTH from the anterior pituitary often due to a functioning pituitary adenoma glaucoma often happens- tumour presses on optic nerve weight gain, hypotension, poor memory loss, irritability, moon face and red stretch marks

Question 31

aldosterone receptors explained

Answer 31

mineralcorticoid receptors are present in the nuclei of only a few cell types: kidney collecting tubule epithelia, salivary and sweat glands cortisol also binds to the mineralcorticoid receptors therefore in aldosterone targets, cortisol is deactivated to prevent unwanted cortisol activation

Question 32

actions of aldosterone

Answer 32

in kidney regulates ion transport in the collecting tubules in order to stimulate reabsorption of sodium in exchange for secretion of potassium, hydrogen and ammonium ions in salivary and sweat glands, aldosterone regulates ion transport to retain sodium

Question 33

why is there a 2h lag in response to aldosterone?

Answer 33

MR effects are via stimulating transcription of the Na/K ATPase protein

Question 34

control of aldosterone output

Answer 34

stimulated by the renin-angiotensin system, which in turn is stimulated by low plasma sodium or low renal blood pressure low plasma sodium and low blood pressure stimulates renin release which acts in the lungs to stimulate the conversion of angiotensin I to angiotensin II by activating angiotensin converting enzyme ACE. AII stimulates output of aldosterone from the zona glomerulosa of the adrenal cortex

Question 35

angiotensin II function

Answer 35

causes arteriolar constriction and drinking in response to thirst

Question 36

examples of abnormal plasma concentrations of aldosterone

Answer 36

hypoaldosteronism- in adrenal failure, leads to sodium loss, low blood volume and low blood pressure hyperaldosteronism- Conn's syndrome, results in excess sodium retention, water retention and an increase in blood pressure

Question 37

treatment for hyperaldosteronism

Answer 37

spironolactone - an aldosterone antagonist used as an antihypertensive

Question 38

example of a weak androgen

Answer 38

DHEA- dehydroepiandrosterone

Question 39

DHEA action

Answer 39

stimulates axillary/pubic hair development at puberty and libido

Question 40

What is DHEA release stimulated by?

Answer 40

Adrenocorticotropic hormone

Question 41

How much DHEA is released?

Answer 41

very little

Question 42

disease associated with androgens

Answer 42

congenital adrenal hyperplasia inability to produce adrenal steroids an inherited disorder arising from mutations in enzymes or steroid synthesis, such as 21-hydroxylase leads to masculination of females and precocious puberty

Question 43

What is Nelson's syndrome?

Answer 43

Addison's disease, due to the surgical removal of the adrenals

Question 44

what clears the corticosteroids?

Answer 44

kidney filters free steroid hormones but reabsorbs 90% liver converts steroid hormones to hydrophilic metabolites by hydroxylation and conjugation reactions- can cause liver damage such as cirrhosis in alcoholics causing cortisol build up.