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endocrine > Physiology 6 - Adrenal > Flashcards

Physiology 6 - Adrenal Flashcards

1
Q

Where are the adrenal glands found?

A

On the superior pole of the kidneys at roughly T12.

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2
Q

How are the adrenal glands peritonised?

A

Retroperitoneal just like the kidneys

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3
Q

Describe the arterial blood supply of the adrenal gland?

A

Aorta:

  • > Inf Phrenic Art -> Sup suprarenal Art
  • > Middle Suprarenal Art
  • > Renal Artery -> Inf Suprarenal Art
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4
Q

DEscribe the venous drainage of the adrenal gland?

A

Different on each side

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

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5
Q

Describe the structure of the adrenal gland?

A

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

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6
Q

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

A

Adrenal cortex is a true endocrine gland derived from mesoderm

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

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7
Q

What is secreted the zona glomerulosa?

A

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

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8
Q

What is secreted by the zona fasciculata?

A

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

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9
Q

What does the Zona reticularis do?

A

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

(most sex steroids are produced in the gonads)

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10
Q

What is produced in the adrenal medulla?

A

Catecholamines (tyrosine derived, water soluble amines)

E.g. Epinephrine, Norepinephrine and dopamine

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11
Q

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

A

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

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12
Q

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

A

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.

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13
Q

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

A

Hypothalamus = Corticotrophin Releasing Hormone (CRH)

Ant Pituitary = Adrenocorticotrophic Hormone (ACTH)

Zona Fasciculata = Cortisol

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14
Q

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

A

95% of cortisol is bound to Cortisol Binding Globulin

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15
Q

Describe the -ve feedback control of Cortisol

A

Cortisol has a -ve feedback on CRH & ACTH

ACTH has a -ve feedback on CRH

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16
Q

How does cortisol work?

A

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
17
Q

Does cortisol secretion follow any pattern or rhythm?

A

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

18
Q

What are cortisols affects on glucose?

A
  • Permissive to GLucagon
  • Increased Gluconeogenesis (stimulates gluconeogenic enzyme formation)
  • Increased Proteolysis
  • Increased Lipolysis
  • Decreases Insulin sensitivity
19
Q

What are cortisols affect on calcium?

A
  • Decreases gut absorption
  • Increases Kidney excretion
  • Increases bone resorption
20
Q

What are cortisols affects on the brain?

A

Excess cortisol linked to depression and impaired cognitive function

21
Q

What are cortisols affect on norepinephrine?

A

Permissive to norepinephrine

Specifically in regards to vasoconstriction

22
Q

What are cortisols effects on immunity?

A

Depresses immunity by:

  • Reducing lymphocyte count
  • Reducing Antibody formation
  • Reducing inflammatory response
23
Q

Summary of cortisols affects?

A
  • Increases plasma glucose
  • Decreases plasma Calcium
  • Increases bone resorption
  • Permissive to vasoconstrictive action of norepinephrine
  • Supresses Immunity
24
Q

In what way is cortisol particularly essential for life?

A

Its permissive effect on glucagon is most important.

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

25
Q

How is cortisol related to diabetes?

A

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

Therefore excess cortisol is considered diabetogenic

26
Q

What does it mean to be a mineralocorticoid?

A

A hormones that effects resorption/excretion of minerals

27
Q

What are the effects of aldosterone?

A

Increases Na+ resorption

Incerases K+ Excretion

28
Q

What triggers secretion of aldosterone?

A

The Renin-angiotensin-Aldosterone system (RAAS)

Part of the long term control of blood pressure

29
Q

What would happen with excess or insufficient aldosterone?

A

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

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

30
Q

Pathology in the hypothalamus effect on HPA

A
  • Increased CRH
  • Increased ACTH
  • Increased Cortisol
31
Q

Pathology in adrenal cortex effect on HPA

A
  • Decreased CRH
  • Decreased ACTH
  • Increased Cortisol
32
Q

Pathology on anterior pituitary effect on HPA

A
  • Decreased CRH
  • Increased ACTH
  • Increased Cortisol
33
Q

Why do you need to be careful when removing therapeutic treatment of Glucocorticorticoid

A

Need to be careful as it will lead to an XS response from the negative feedback loop:

  • When therapeutic cortisol provided this reduces activity of CRH and ACTH
  • Reduced activity of ACTH can lead to atrophy of the gland
  • So risk of adrenal insufficiency if the therapeutic hormone is released too quickly
34
Q

Pheocromocytoma

A
  • Rare tumour which leads to the release of XS catecholamines from the adrenal medulla (e.g. epinephrine, norepinephrine, Ach).
  • Bind to smooth muscle and cardiac muscle, some adipose tissue and some glands
  • Leads to increased HR, CO and therefore BP
  • Has a DIABETOGENIC EFFECT as it has an adrenergic effect upon glucose metabolism
35
Q

Main causes for hyper secretion of cortisol

A

Main causes:

  • Tumour in the adrenal cortex: primary
  • Tumour in the pituitary: secondary

Presentation

  • Depletion of proteins/fats in the extremities due to catabolic actions of cortisol
  • For some unknown reason redistributed to the trunk

IATROGENIC
-Too much cortisol administered therapeutically

36
Q

Main causes for hyposecretion of cortisol

A

ADDISON’S DISEASE

  • Hyposecretion of all the steroid hormones of the adrenal gland
  • Due to autoimmune destruction of the adrenal cortex
37
Q

Effects of caffeine/ alcohol/stress on CRH and ACTH release

A
  • These substances disinhibit the HPA axis
  • This increases the release of cortisol
  • Increases suppression of the immune system which can be cause for increased risk of infection

(Alcohol in particular depresses the negative feedback system)

38
Q

How can cortisol release lead to muscle wastage

A
  • Too much lipolysis
  • Too much protein catabolism
  • Makes skin appear thin and fragile
39
Q

How can cortisol release lead to infection

A

Suppression of the immune system

-stronger and more frequent infections

endocrine (25 decks)

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