Adrenal Medulla
Adrenal medulla is completely surrounded by adrenal cortex.
It is stimulated by its extensive sympathetic nerve supply to produce hormone adrenaline (epinephrine), noradrenaline (norepinephrine).
Adrenal medulla secretes hormones called catecholamines, that help body respond to stress.
Epinephrine and norepinephrine produce fight or flight response similar to effect from sympathetic nervous system, response by -
1. Increasing heart rate
2. Increasing blood pressure
3. They stimulate glycogenolysis (glycogen to glucose) and Gluconeogenesis (synthesis of glucose from fats and proteins).
4. Ensure adequate supply of glucose to brain, epinephrine inhibits insulin secretion and use of glucose by muscles or organ.
5. Increasing metabolic rate
6. Dilating pupils
Adrenaline has greater effect on heart and metabolic processes where as noradrenaline has more influence on blood vessels.
Response to Stress
When body under stress homeostasis is disturbed. To restore it and, to maintain life there are immediate response. Stressors include;
Excercise, fasting, fright, temperature, changes, infection, disease, emotional situation.
To immediate response is sometime described as preparing for fight or flight, maintain by sympathetic part of autonomic nervous system.
In longer term, ACTH (adrenocorticotropic hormone) from anterior pituitary stimulates release of Glucocorticoids and mineralocorticoides from adrenal cortex and more prolonged responses to stress occur.
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