Endocrine 3: adrenal gland and stress

Question 1

3. Describe the role of the hypothalamic-pituitary-adrenal axis in the body’s response to stress

Answer 1

Response is characterised by the corticotrophin releasing hormone, from the hypothalamus. When CRH binds to corticothropin receptors in the anterior pituitary, ACTH is released.
ACTH binds to the adrenal receptors, stimulates adrenal release of cortisol.

Hypothalamus releases CRH which acts on the anterior pituitary and stimulates release of glucocorticoids, and mineralocorticoids; aldosterone.

Question 2

Chronic ACTH.
high ACTH = hypertrophy
Low ACTH= hyperplasia

Answer 2

leads to hypoplasia and hypertrophy of the adrenal cortex.

• all tissues have cortisol receptors.
• In skeletal muscle: turns off protein synthesis an turns on protein degradation. Releases AA’s. Decreases glucose uptake,
• Adipose tissue: causes glycolysis.
  provides energy for fight or flight response.

Question 3

What stimulus causes the release of adrenaline? Write or draw pathway’s possible.

Answer 3

The sympatho-adrenal axis.

In response to stress. The sympathetic nerve endings of pre-ganglionic fibres, secrete ACH onto chromatin cells containing adrenaline and noradrenaline. This is then secreted into the systemic circulation.

sympathetic nerve activation.

Question 4

4. Describe the role of the sympatho-adrenal axis in the body’s response to stress

Answer 4

Adrenaline plays a role in this process.
- part of fight of flight response.
Stress is detected by higher brain centres.
1. sympathetic nerves are activated, and act via spinal cord pathways to inveterate the medulla of adrenal gland.
2. the nerve endings of the pre-ganglionic fibres secrete ACH, onto the chromatin cells in the adrenal medulla. These cells have noradrenaline and adrenaline.
3. The medulla secretes 80% adrenaline and 20% noradrenaline into the systemic circulation. Can increase HR.

Question 5

Cushing’s syndrome

Answer 5

Cortisol disorder.
Adrenal hyperfunction.
- excessive secretion of cortisol (pituitary tumour)
- cause can be primary: failure of adrenal gland itself. In this case, high levels or cortisol, but low levels of ATCH. (ACTH INDEPENDENT)
- cause can be secondary due to over secretion by the hypothalamus or pituitary gland. in this case there will be high levels of ACTH or CRH ( ACTH dependent).

Question 6

Effects of increased cortisol secretion:

Answer 6

Weight gain
Fat deposition on trunk and face
Insulin resistance

Question 7

Addison’s disease (opposite of Cushing’s)

Answer 7

Adrenal hypofunction

• diminished cortisol secretion
• cause can be primary (failure of the adrenal gland itself). Low levels of cortisol and high levels of ACTH.
• Can be secondary: low levels of cortisol and low levels of ACTH or CRH. Hypothalamus/ pituitary problem (Acth dependent)

Question 8

Addison’s/ decreased cortisol effects and treatments:

Answer 8

weakness, fatigue, anorexia

Give glucocorticoids (even for asthma)

Question 9

Response to glucocorticoids:

Answer 9

• ACTH levels will go down
• If ACTH levels go down, the adrenal cortex will atrophy (breakdown of tissues). Person will not be able to make cortisol themselves.

important not to suddenly stop taking glucocorticoids, because it will take time to start making cortisol again. Give pituitary time to increase ACTH and gives adrenal gland time to hypertrophy and make enzymes to make its own glucocorticoids.