Adrenal Glands Flashcards
What is the role of the adrenal medulla
Homeostasis
What does the adrenal medulla secrete
Adrenaline
Noradrenaline
(both hormones)
What are the two major structure of the adrenal glands
Outer adrenal cortex
Inner adrenal medulla
What are the main secreting cells of the adrenal medulla
Chromaffin cells
When is adrenaline released
Response to activation of the sympathetic nervous system
Fibres of which are carried to the adrenal medulla by the thoracic splanchnic nerves
What are adrenaline and noradrenaline produced from
Tyrosine
Where is synthesised adrenaline stored
Vesicles before being released into the blood stream
Part of flight or fight response
Describe the Zona Fasciculata
Middle zone of adrenal cortex
Made up of parenchymal cells
Function to secrete glucocorticoids - cortisol and corticosterone
What is the role of cortisol
Hormone
Regulates carbohydrate metabolism - especially in flight or fight (time of stress)
Approximately how much cortisol is secreted in an adult over a 24 hour time period
10mg
Describe the production of cortisol
Cholesterol precursor
- initiated by ACTH and angiotensin II - activate adenylyl cyclase and phospholipases C (respectively =)
- cholesterol converted to pregnenolone by cytochrome P450
- All mineralocorticoids, glucocorticoids and androgens can be synthesised from pregnenolone in a multi-step enzyme assisted pathway
- In zona fasciculate enzyme 11b-hydroxylase catalyses final step of reaction that forms cortisol
Describe the Zona Glomerulosa
Outermost of the adrenal cortex
Responsible for secreting mineralocorticoid hormones e.g. aldosterone
Describe the Zona Reticularis
Innermost layer of the adrenal cortex
Responsible for the production and secretion of androgens
What do most things produced by the adrenal cortex originate from
Cholesterol
What is the role of the adrenal glands
Secrete steroid and catecholamine directly into the blood
What does the cortex secrete
Two cholesterol derived hormones
- corticosteroids
- androgens
What are the three functional groups of the cortex
Zona glomerulosa
Zona fasciculata
Zona reticularis
What is the role of the zona glomerulosa
Produces and secretes mineralocorticoids e.g. aldosterone
What is the role of zona fasciculata
Produces and secretes corticosteroids e.g. cortisol
Secretes a small amount of androgens
What is the role of the zona reticularis
Produces and secretes androgens e.g. DHES
Secretes small amount of corticosteroids
What is the role of medulla
Contains chromaffin cells
Secrete catecholamines e.g. adrenaline into the blood in response to stress
What is the arterial supply to the adrenal glands
Superior, middle and inferior adrenal artery
What is the innervation to the adrenal glands
Coeliac plexus
Greater splanchnic nerves
Sympathetic innervation to adrenal medulla via myelinated pre-synaptic fibres - T10-L1
