(a) What is a hormone? (b) Outline the role played by adrenaline in an emergency situation. (c) In a tabular form, list five differences between hormonal co...
Question 1 Report
(a) What is a hormone?
(b) Outline the role played by adrenaline in an emergency situation.
(c) In a tabular form, list five differences between hormonal co-ordination and nervous co-ordination.
(d) Name three animal hormones and two plant hormones.
Answer Details
(a) What is a hormone?
A hormone is a chemical substance (chemical messenger) secreted in small quantities directly into the blood by an endocrine (ductless) gland, and carried by the blood to a target organ where it regulates or coordinates a particular body activity.
(b) Role of adrenaline in an emergency situation
Adrenaline is secreted by the adrenal (suprarenal) glands during fright, anger or excitement to prepare the body for 'fight or flight'. It:
- Increases the heart rate and force of heartbeat, and raises blood pressure, so more blood reaches the muscles.
- Raises the blood glucose level by converting stored glycogen in the liver to glucose, supplying energy.
- Increases the rate and depth of breathing, supplying more oxygen.
- Dilates the pupils and diverts blood from the gut and skin to the skeletal muscles, making the body alert and ready for vigorous action.
(c) Five differences between hormonal and nervous coordination
| Hormonal (endocrine) coordination | Nervous coordination |
|---|---|
| Message is carried as chemicals (hormones) | Message is carried as electrical impulses |
| Transmitted through the blood stream | Transmitted through nerves (neurones) |
| Response is usually slow | Response is very fast |
| Effect is usually long-lasting | Effect is usually short-lived |
| Response is usually widespread (affects many organs) | Response is usually localised to a specific part |
(d) Three animal hormones and two plant hormones
- Animal hormones: adrenaline, insulin, thyroxine (also acceptable: oestrogen, testosterone).
- Plant hormones: auxin, gibberellin (also acceptable: cytokinin, abscisic acid, ethylene).
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