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Regulatory Physiology > The Pituatary Adrenal Axis (week 2) > Flashcards

The Pituatary Adrenal Axis (week 2) Flashcards

1
Q

what class of hormones does cortisol belong

A

Glucocorticoid

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2
Q

Where is cortisol synthesised

A

The adrenal cortex

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3
Q

What is the adrenal gland

A

It is a hybrid gland consisting of a cortex and a medulla. The hormones of the adrenal gland are important regulators of metabolism and serve an important role in adaptation of stress

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4
Q

What can a deficiency in cortisol result in

A

Hypoglycaemia (level of glucose in the blood drops below what is normal)

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5
Q

Why are synthetic analogs widely used in the treatment of disorders ranging from skin rashes to arthritis

A

Because of the anti-inflammatory and immunosuppressive actions of adrenal corticosteroids

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6
Q

What is aldosterone and what does it do

A

It is a mineralcorticoid and it promotes salt and water retention by the kidney, it is critical for salt/water balance

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7
Q

Where is the adrenal gland located

A

On top of both kidneys

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8
Q

What else does the adrenal cortex synthesise and secrete

A

Androgenic steroids which may be converted by peripheral tissue to testosterone

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9
Q

Where are chromaffin cells located and what do they secrete

A

They are located in the medulla and secrete epinephrine which are catechlomines

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10
Q

What are the 3 parts of the adrenal cortex and what do they secrete

A

Zona glomerulosa -aldosterone
Zona fasciculata- cortisol
Zona reticularis- weak androgens

These are all steroid hormones

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11
Q

How is the adrenal medulla signalled

A

Nerve impulses

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12
Q

How is the adrenal cortex signalled

A

Hormonal signals

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13
Q

What are the effects of epinephrine and norepinephrine

A

Glycogen gets broken down to glucose; increased blood glucose
Increased blood pressure
Increased breathing rate
Increased metabolic rate
Change in blood flow patterns, leading to increased alertness

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14
Q

What are the effects of mineralcorticoids

A

Retention of sodium ions and water by kidneys

Increased volume and blood pressure

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15
Q

What are the effects of glucocorticoids

A

Proteins and fats broken down and converted to glucose

Partial suppression of the immune system

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16
Q

Where do all steroid hormones derive from

A

Cholesterol and differ only in the ring structure and side chains attached to it

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17
Q

All steroid hormones are lipid soluble, what does this mean

A

They are freely permeable to membranes so are not stored in cells; they leave cells shortly after synthesis

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18
Q

Steroid hormones are carried in the blood to specific binding globulins, give an example

A

Corticosteroid binding globulin transports cortisol

19
Q

Where are enzymes that produce steroid hormones from cholesterol located

A

In the mitochondria and SmER

20
Q

How is cholesterol converted into all other steroid hormones

A

A series of enzymatic steps in the mitochondria and Er of steroidogenic tissues

21
Q

What is the rate limiting step in steroid hormone synthesis and hou is it carried out

A

The transport of free cholesterol from the cytoplasm into mitochondria, carried out by the steroidogenic acute regulatory protein (star) moving cholesterol from the over membrane to the inner membrane

22
Q

What is cholesterol converted into before it becomes a steroid hormone

A

Pregnenolone

23
Q

What de the three steroid hormones that can be made from prognenolone

A

Mineralcorticoids (aldosterone)
Glucocorticoids (cortisol)
Androstenedione

24
Q

What determines which pathway is taken

A

Each step of the pathway is regulated by a specific enzyme.
Different zones of the adrenal cortex have different relative activities of enzymes, resulting in different chemical reactions

25
Q

What is cortisol bound to when transported in the blood

A

Corticosteroid-binding globulin (CBG) also called transcortin, binds 90%

26
Q

What is the circulating half life of cortisol

A

70 minutes

27
Q

Explain the mechanism of action

A

1) hydrophobic steroids bound to plasma protein carriers
2) steroid hormone receptors are in the cytoplasm or nucleus
3) receptor-hormone complex binds to DNA and activates or represses one more gene
4) activated genes create new mRNA that moves back to cytoplasm
5) translation produces new proteins for cell processes
6) some SH bind to membrane receptors that use second messenger systems to create rapid cellular response

28
Q

What happens if the adrenal cortex is not functioning or is removed

A

Exogenous glucocorticoids must be administered or death will ensue

29
Q

Why are glucocorticoids so important

A

Their actions are essential for glucogenesis, for vascular responsiveness to catechloamines, for suppression of inflammatory and immune responses, and for modulation of CNS function

30
Q

Name some metabolic effects of cortisol

A

Stimulates protein and triglyceride catabolism
Stimulated “glucogenesis” in liver
Inhibits bone formation
Inhibition of non-essential functions (reproduction, growth)

31
Q

What are some side effects to the distruption of physiologic homeostasis
(Cortisol takes immune response)

A

Alterations in water balance
Weight gain
Hypertension
Muscle weakness
Diabetes
Osteoporosis

32
Q

What is the enzyme that converts cortisol to its inactive form

A

11b-hydroxysteroid dehydrogenase type 2 (11b-HSD2)

33
Q

What is the enzyme that converts cortisol to its active form

A

11b-hydroxysteroid dehydrogenase type 2 (11b-HSD2)
This enzyme is only present in tissues that express the GR including the liver, adipose skin, and CNS.

34
Q

What does natural black licorice contain and what does it do

A

It contains glycyrrhiziz acid (GZA)
It inhibits 11b-HSD2, increasing mineralcorticoid activity of cortisol leading to sodium retention,
Spikes in blood pressure
Muscle spasms
Disturbance of the acid-base balance

35
Q

What does ACTH stand for

A

Adrenocorticotropic hormone

36
Q

What is the HPA axis

A

Hypothalamic-pituitary- adrenal axis

37
Q

What tells pituitary gland to ACTH

A

Corticotropin releasing hormone (crh)

38
Q

What is hypocortisolism

A

(Primary adrenal insufficiency, addisons disease) There is hypoglycemia

39
Q

What is hypercortisolism

A

Cushing’s syndrome, there is hyperglycaemia

40
Q

How is Cushing’s syndrome cause

A

Non cancerous tumor of the pituitary gland, tumour makes too much ACTH and so there is too much cortisol

41
Q

What can salt and water retention with renal loss of K+ cause

A

Moon face

42
Q

What does catabolism cause (all part of Cushing syndrome)

A

Muscle wasting
Fat accumulation
Osteoporosis with kyphosis
Buffalo hump
Fractures

43
Q

What is Addison’s disease

A

A disease in which the adrenal gland does not produce enough cortisol

44
Q

What are some symptoms of Addison’s disease

A

Overproduction of ACTH due to decreased negative feedback by cortisol
Skin hyperpigmentation

Regulatory Physiology (13 decks)

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