03 Hormones of the medulla (amino-acid derivatives; controlled by nerves)
Adrenaline and noradrenaline
- — the "emergency hormones" ("fight, flight or fright").
- They prepare the body for emergencies such as fear, anger, excitement and muscular exercise:
- raise blood glucose by breaking down liver glycogen to glucose;
- increase the speed and force of the heartbeat and raise blood pressure;
- increase breathing rate and oxygen consumption, dilate the vessels of muscles and constrict those of the skin and gut;
- as a result the muscles obtain the energy and oxygen they need for contraction.
✍️ Worked examples
Worked example 8.
- A student jumps at a sudden loud noise: his heart pounds, mouth goes dry, and he is pale.
- Which hormone and why?
- Adrenaline from the adrenal medulla: more blood and glucose go to the muscles, while skin vessels constrict (pallor).
1Position
Adrenal cortex
- Outer
Adrenal medulla
- Inner
2Hormones
Adrenal cortex
- Glucocorticoids, mineralocorticoids, sex hormones
Adrenal medulla
- Adrenaline, noradrenaline
3Chemical nature
Adrenal cortex
- Steroids
Adrenal medulla
- Amino-acid derivatives
4Control
Adrenal cortex
- ACTH from pituitary
Adrenal medulla
- Nervous (sympathetic) stimulation
5Importance
Adrenal cortex
- Long-term balance of sugar and minerals
Adrenal medulla
- Immediate response to emergencies