Physiology 6 - Adrenal

Question 1

Where are the adrenal glands found?

Answer 1

On the superior pole of the kidneys at roughly T12.

Question 2

How are the adrenal glands peritonised?

Answer 2

Retroperitoneal just like the kidneys

Question 3

Describe the arterial blood supply of the adrenal gland?

Answer 3

Aorta:

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

Question 4

DEscribe the venous drainage of the adrenal gland?

Answer 4

Different on each side

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

Question 5

Describe the structure of the adrenal gland?

Answer 5

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

Question 6

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

Answer 6

Adrenal cortex is a true endocrine gland derived from mesoderm

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

Question 7

What is secreted the zona glomerulosa?

Answer 7

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

Question 8

What is secreted by the zona fasciculata?

Answer 8

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

Question 9

What does the Zona reticularis do?

Answer 9

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

(most sex steroids are produced in the gonads)

Question 10

What is produced in the adrenal medulla?

Answer 10

Catecholamines (tyrosine derived, water soluble amines)

E.g. Epinephrine, Norepinephrine and dopamine

Question 11

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

Answer 11

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

Question 12

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

Answer 12

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.

Question 13

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

Answer 13

Hypothalamus = Corticotrophin Releasing Hormone (CRH)

Ant Pituitary = Adrenocorticotrophic Hormone (ACTH)

Zona Fasciculata = Cortisol

Question 14

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

Answer 14

95% of cortisol is bound to Cortisol Binding Globulin

Question 15

Describe the -ve feedback control of Cortisol

Answer 15

Cortisol has a -ve feedback on CRH & ACTH

ACTH has a -ve feedback on CRH

Question 16

How does cortisol work?

Answer 16

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

Question 17

Does cortisol secretion follow any pattern or rhythm?

Answer 17

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

Question 18

What are cortisols affects on glucose?

Answer 18

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

Question 19

What are cortisols affect on calcium?

Answer 19

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

Question 20

What are cortisols affects on the brain?

Answer 20

Excess cortisol linked to depression and impaired cognitive function

Question 21

What are cortisols affect on norepinephrine?

Answer 21

Permissive to norepinephrine

Specifically in regards to vasoconstriction

Question 22

What are cortisols effects on immunity?

Answer 22

Depresses immunity by:

• Reducing lymphocyte count
• Reducing Antibody formation
• Reducing inflammatory response

Question 23

Summary of cortisols affects?

Answer 23

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

Question 24

In what way is cortisol particularly essential for life?

Answer 24

Its permissive effect on glucagon is most important.

Without cortisol glucagon can’t sufficiently respond to hypoglycaemia and your brain would die.

Question 25

How is cortisol related to diabetes?

Answer 25

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

Therefore excess cortisol is considered diabetogenic

Question 26

What does it mean to be a mineralocorticoid?

Answer 26

A hormones that effects resorption/excretion of minerals

Question 27

What are the effects of aldosterone?

Answer 27

Increases Na+ resorption

Incerases K+ Excretion

Question 28

What triggers secretion of aldosterone?

Answer 28

The Renin-angiotensin-Aldosterone system (RAAS)

Part of the long term control of blood pressure

Question 29

What would happen with excess or insufficient aldosterone?

Answer 29

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

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