(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.
Explanation
(a) A hormone can be defined as a chemical substance produced in small quantities by endocrine/ductless glands and carried to all other parts of the body/target organs by blood stream/vascular system, where it produces/exerts a response.
(b) Role of adrenaline in an emergency: -
- Any emergency experienced by an animal usually causes a sudden rage/fear/fright
- This leads to the release of adrenalin into the blood; which stimulates the sympathetic nervous system and consequently many different organs
- The rate of heart beat is increased and there is heavy breathing
- Similarly, there is increase in the body blood sugar/conversion of liver glycogen into glucose.
- The muscular tone/power is increased/ there is resistance to fatigue, the pupils of the eyes dilate and the visceral muscles are affected, the animal reacts quickly and energetically.
(c) Differences between hormonal co-ordination and nervous co-ordination
| Hormonal co-ordination | Nervous co-ordination |
| Involves transmission of chemicals | Involves transmission of electrical impulses and chemical substances by the nervous system |
| Response to stimulus is slower | Response to stimulus is faster |
| Hormones are secreted into the blood and carried to any part of the body | Nerve impulses are transmitted to a particular location/target organ by a particular set of neurons |
| The target is usually far away from the site of production | Target organ maybe near or far |
| Response may last for a long time | Response are short lived |
| secretion of hormones and their actions are involuntary | nervous actions and their responses are voluntary and involuntarily |
| Hormonal co-ordination occurs in both plants and animals | Nervous co-ordination occurs only in animals |
(d)(1) Animal Hormones: -
- Somatotropic hormone
- Prolactin
- Gonatotropic
- Thyroxine
- Thyrotropic hormone
- Oxytocine
- Anti-diuretic hormone/A.D.H.
- Parafhormone
- Adrenalin
- Insulin
- Oestrogen
- Progesterone
- Testosterone And
- rosterone
(ii) Plant Hormones: -
- 1 AA/indole-3- Acetic acid/Auxin
- 2-4D/2-4 Dichlorophenoxy
- acetic acid
- Gibberellins
- Cydtokinins/kinins
- Abscisie/Absisic acid
- Benzoic acid
- NAA/Naphthalene acetic acid
- IBA/Indolebutryric acid
- Ethelene
- Vernalin.