Physiology 6 - Adrenal Flashcards Preview

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Flashcards in Physiology 6 - Adrenal Deck (29):

Where are the adrenal glands found?

On the superior pole of the kidneys at roughly T12.


How are the adrenal glands peritonised?

Retroperitoneal just like the kidneys


Describe the arterial blood supply of the adrenal gland?

-> Inf Phrenic Art -> Sup suprarenal Art
-> Middle Suprarenal Art
-> Renal Artery -> Inf Suprarenal Art


DEscribe the venous drainage of the adrenal gland?

Different on each side

Left adrenal veins --> Left renal vein
Right Adrenal veins --> IVC


Describe the structure of the adrenal gland?

Adrenal Cortex: (Steroid hormones)
Zona Glomerulosa
Zona Fasciculata
Zona Reticularis

Then the adrenal medulla in the middle

The whole thing is surrounded by a fibrous capsule


What kind of tissue makes up the adrenal cortex vs medulla?

Adrenal cortex is a true endocrine gland derived from mesoderm

Adrenal Medulla is a modified symp. ganglion made of neural crest tissue


What is secreted the zona glomerulosa?

Outer section of Adrenal cortex secreates Mineralocorticoids e.g. Aldosterone


What is secreted by the zona fasciculata?

Middle section of adrenal cortex secretes glucocorticoids e.g. Cortisol


What does the Zona reticularis do?

Inner layer of adrenal cortex secretes sex steroids e.g. testosterone

(most sex steroids are produced in the gonads)


What is produced in the adrenal medulla?

Catecholamines (tyrosine derived, water soluble amines)
E.g. Epinephrine, Norepinephrine and dopamine


The adrenal medulla has an unusual autonomic nerve supply, how so?

Pre-ganglionic fibres synapse to cells in the adrenal medulla.

Instead of having post-synaptic fibres, the medulla secretes its neurohormones directly into the blood


Briefly describe the pathway of steroid synthesis in the adrenal cortex?

All start with cholesterol.
Different enzymes are found in each layer, sending them down different branches and so producing the different hormones.

The most important is 21-hydroxylase, found in the pathway for producing aldosterone and cortisol.


remind yourself of the HPA axis (Specifically for glucocorticoids) and the hormones involved?

Hypothalamus = Corticotrophin Releasing Hormone (CRH)

Ant Pituitary = Adrenocorticotrophic Hormone (ACTH)

Zona Fasciculata = Cortisol


As a steroid hormone, describe how Cortisol travels the blood?

95% of cortisol is bound to Cortisol Binding Globulin


Describe the -ve feedback control of Cortisol

Cortisol has a -ve feedback on CRH & ACTH

ACTH has a -ve feedback on CRH


How does cortisol work?

It bind to cytoplasmic glucorticoid receptors (found in all nucleated cells)
-> Hormone-receptor complex migrates to nucleus
-> Binds to DNA
-> Alters gene expression, transcription & translation


Does cortisol secretion follow any pattern or rhythm?

Yes a Marked Circadian rhythm!

Cortisol peaks at 6-9am and has its nadir at 12pm

Preceded by a similar ACTH rhythm

Smaller fluctuations occur throughout the day due to stress stimuli


What are cortisols affects on glucose?

- Permissive to GLucagon
- Increased Gluconeogenesis (stimulates gluconeogenic enzyme formation)
- Increased Proteolysis
- Increased Lipolysis
- Decreases Insulin sensitivity


What are cortisols affect on calcium?

- Decreases gut absorption
- Increases Kidney excretion
- Increases bone resorption


What are cortisols affects on the brain?

Excess cortisol linked to depression and impaired cognitive function


What are cortisols affect on norepinephrine?

Permissive to norepinephrine

Specifically in regards to vasoconstriction


What are cortisols effects on immunity?

Depresses immunity by:
- Reducing lymphocyte count
- Reducing Antibody formation
- Reducing inflammatory response


Summary of cortisols affects?

- Increases plasma glucose
- Decreases plasma Calcium
- Increases bone resorption
- Permissive to vasoconstrictive action of norepinephrine
- Supresses Immunity


In what way is cortisol particularly essential for life?

Its permissive effect on glucagon is most important.
Without cortisol glucagon can't sufficiently respond to hypoglycaemia and your brain would die.


How is cortisol related to diabetes?

Cortisol is glucose counter-regulatory, meaning it raises blood glucose.

Therefore excess cortisol is considered diabetogenic


What does it mean to be a mineralocorticoid?

A hormones that effects resorption/excretion of minerals


What are the effects of aldosterone?

Increases Na+ resorption
Incerases K+ Excretion


What triggers secretion of aldosterone?

The Renin-angiotensin-Aldosterone system (RAAS)
Part of the long term control of blood pressure


What would happen with excess or insufficient aldosterone?

Excess aldosterone --> Excess Na+ --> Increased blood volume & hypertension

Insufficient aldosterone --> Insufficient Na+ --> DIminished blood volume and hypotension