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PHSL231 > Lecture 27- Stress and the Adrenal Glands > Flashcards

Lecture 27- Stress and the Adrenal Glands Flashcards

1
Q

What is the basic hormone path for the adrenal glands?

A

CRH produced by the hypothalamus
ACTH produced by the anterior pituitary
ACTH acts on the adrenal gland

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2
Q

Where is the adrenal gland?

How many do we

A

Sits on top of the kidney.

We have 2 to match the number of kidneys we have

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3
Q

What are the two layers of the adrenal gland?

What percentage do they respectively make up?

A
  • Cortex= 80%

- Medulla= 20%

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4
Q

What is the main function of the zones in the adrenal gland?

A

They are what secrets hormones

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5
Q

What are the 5 zones of the adrenal gland and what hormone does each of them produce?

A
  • Capsule
  • Glomerulosa (aldosterone)
  • Fasciculata (cortisol)
  • Reticularis (androgens)
  • Medulla (epinephrine, norepinephrine)
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6
Q

What is the precursor to stress hormones?

A

Cholesterol

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7
Q

What is the rate determining step in the conversion of cholesterol to stress hormones?

A

Cholesterol to pregnenolone via P450 side-chain cleavage

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8
Q

What 3 hormones can come from pregnenolone? and what area of the adrenal gland does each correspond to?

A
  • Glucocorticoids: Cortisol, Corticosterone (zona fasciculata)
  • Mineralocorticoid: Aldosterone (Zona glomerulosa)
  • Sex steroid precursors: Androstenedione (Zona reticularis)
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9
Q

What are the functions of aldosterone and it’s site of action?

A
  • Aldosterone acts to maintain fluid volume
  • Main site of action: kidneys
  • Increases the reabsorption of sodium and water
  • Increases secretion of potassium
  • Aldosterone increases water retention and increases BP
  • Aldosterone binds mineralocorticoid receptors (MR)
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10
Q

How does cell signaling of aldosterone work?

A
  • Aldosterone comes in to the cell and attaches to a mineralocorticoid receptor
  • The hormone-receptor complex then diffuses into the nucleus where the hormone response element causes transcription to form response genes.
  • Response genes then cause mRNA to be converted to protein and protein has 2 effects.
  • It acts on ENaC on the apical side to increase the amount of sodium coming into the cell. It also acts on Na/K- ATPase on the basolateral side (sodium leave, potassium come in). And the amount of potassium leaving the cell via channels on the apical side is increased. Basically movement of sodium is from the apical side/ tubule across the cell into the interstitium and water follows via the collecting duct. Potassium moves in the opposite direction.
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11
Q

What is the name of the system that controls aldosterone release and involves multiple different organs?

A

Renin-angiotensin system

Refer to diagram in slides to see the interactions that occur

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12
Q

How is the release of cortisol controlled?

A
  • Cells in the Paraventricular nucleus of the hypothalamus project to the medial eminence and onto to the portal capillary vasculature
  • Hypothalamic CRH stimulates the release of ACTH from the pituitary which in turn acts on the adrenal cortex.
  • Adrenal cortex produces cortisol
  • Glucocorticoids feedback negatively to both the anterior pituitary (cortisol) and hypothalamus (ACTH directly and cortisol)
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13
Q

What is the relationship between POMC and glucocorticoids (corticosterone and cortisol)?

A

-POMC is a long precursor protein which can be cleaved into smaller parts creating the hormones we know of e.g. ACTH

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14
Q

What receptors do ACTH act on to increase P450scc enzyme activity (produce more (Glucocorticoids: Cortisol, Corticosterone)?

A

melanocortin (MC2) receptors

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15
Q

What hormone can augment ACTH secretion?

A

ADH

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16
Q

When is cortisol important to survival?

A

During stressful situations

17
Q

What actions does cortisol have in the body?

A

Cortisol stimulates glucose production in the liver, stimulates break down of triglycerides into fatty acids, break down protein to amino acids then this can be used to make glucose.

Basically it generates glucose and uses other substrates to do it

-Has a whole bunch of other effects (can refer to slide)

18
Q

What hormone does cortisol inhibit and why?

A

Inhibits insulin as this is the hormone that ‘gets rid of’ glucose

19
Q

How is glucose stored in the liver?

A

As glycogen

20
Q

What hormones are produced by the cortex of the adrenal gland as opposed to the medulla?

A
  • Cortex= Cortisol, aldosterone, sex steroid hormone precursors
  • Medulla= catecholamines (epinephrine, norepinephrine)
21
Q

What control is the adrenaline medulla under? What does this mean?

A
  • Sympathetic

- Means can get immediate action

22
Q

What are the cardiovascular effects of adrenaline and the cell types responsible for each action?

A
  • Increase cardiac contractility (β1)
  • Increase heart rate (β1)
  • Dilate smooth muscle around arterioles (β2)
  • Constrict other arterioles so blood only goes to ‘right’ organs that need it (α1)

Main effect: shunt blood to exercising muscles and the brain, and away from other tissues

23
Q

What is the metabolic effect of adrenaline?

A
  • Stimulates glucose production in the liver
  • Glycogen breakdown from muscle into lactic acid
  • Convert triglycerides into free fatty acids and converted in liver to keto acids
  • Glucagon release is increased and insulin release is inhibited from the pancreatic islets
24
Q

How is stress defined biologically?

A

The sum of the biological reactions to any adverse stimulus, physical, mental or emotional, internal or external, that disturbs homeostasis

Physiologists use ‘stress’ to mean any event that increases cortisol secretion

25
Q

What two hormones are invovled in the acute stress response/ what effect do they cause?

A
  • Often called fight of flight response
  • Animals react to threats with a discharge of the sympathetic nervous system causing the adrenal medulla to release adrenaline (epinephrine).This response results in vascular changes.
  • The second ‘component’ is the release of cortisol from the adrenal cortex which results in energy mobilization.
26
Q

What are the effects of cortisol during stress?

A

Energy mobilization:

  • stimulating gluconeogenesis in the liver
  • inhibiting glucose uptake by muscle and adipose cells
  • promoting protein breakdown in skeletal muscle, fatty acids in adipose tissue to supply fuel for glucose synthesis
27
Q

What are the consequences of chronic stress i.e. the consequences of high levels of cortisol?

A
  • decreases immune function
  • increases risk of infection and cancer
  • worsens diabetes due to antiinsulin effects
  • possibly increases neuronal death rate
  • might enhance artherosclerosis and hypertension (increased blood lipid, increases cardiac work)
  • decreases bone density
  • induces infertility

PHSL231 (28 decks)

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