Home » Biology Theory (a) What is a hormone? (b) Outline the role played by adrenaline in an emergency…

Biology Theory (a) What is a hormone? (b) Outline the role played by adrenaline in an emergency…

(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.