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Co-ordination In Animals

It is brought about in higher animals by nervous Co-ordination and chemical Co-ordination.

Nervous Co-ordination

This type of Co-ordination involves specialised cells or neurons linked togather directly or via the central nervous system, to form network that connects the cell or organs which receives stimuli (receptors) and those which carry out actions or responses (effectors). The neuron has the capacity to generate and conduct impulses which travel across the synapse and pass from the receptors to the effectors, brings about nervous Co-ordination. The elements of nervous system which help in Co-ordination are:

  1. Receptors
  2. Neurons
  3. Effectors

1. Receptors

The neuron fibers and cell bodies can be excited by small electric shocks, mechanical, chemical light and temperature stimuli. Receptors detect changes in the external and internal environment of the animal. The neuron fibers and cell bodies can be excited by small electric shocks, mechanical, chemical light and temperature stimuli. Receptors detect changes in the external and internal environment of the animal. The receptor May be a cell, or neuron ending or a receptor organ. Receptor classified as follows :

a) Chemoreceptors

These aare for smell, taste and for blood CO2 oxygen, glucose, amino acids and fatty acids. (e.g. receptors in the hypothalamus)

b) Mechanoreceptors

These detect stimuli of touch, pressure, hearing and equilibrium. (e.g. Free nerve endings + expanded tip endings + stray endings)

c) Photoreceptors

(Electromagnetic receptors), these respond to stimuli of light for example in eyes, rods and cones.

d) Thermoreceptors

These are free nerve endings. These show response to cold and warmth.

e) Nociceptors

(UUndifferentiated endings) which produce the sensation of pain.

Each type of the principle type of sensation that we can experience pain, touch, sight, sound and so forth are called modalities of sensation. Yet despite the fact that we experience these different modalities of sensation; nerve fibers transmit only impulses. Hoe is it that different nerve fibers transmit different modalities of sensation? The answer to this question is:

  1. Each nerve tract terminates at a specific point in the CNS; and the type of sensation is determined by the point in the nervous system to which the fiber leads. So touch stimulus is carried by nerve impulse in the ‘touch’ area of the brain. Similarly fibers from the eyes (retina) terminate in the visual cortex of the brain.
  2. Moreover, each receptor organ is specialized to receive a particular type of stimulus and this is carried to the particular area of the brain. Moreover, each receptor organ is specialized to receive a particular type of stimulus and this is carried to the particular area of the brain.

2. Neurons

The chief structural and functional units of the nervous system are neurons, but there are other cells, in higher animals, and in humans called neuroglia, which make up as much as half of the nervous system. Neuroglia play a vital role in the nutrition of neurons and their protection by myelin sheath. There are three functional types of neurons the sensory, associative (intermediate/relay) and motor neurons, in mammals.

3. Effectors

These are the structures which respond when they are stimulated by impulse coming via motor neurons. The principal effectors are glands, which respond by secreting; and muscles which respond by contracting. These are the structures which respond when they are stimulated by impulse coming via motor neurons. The principal effectors are glands, which respond by secreting; and muscles which respond by contracting.

Flow of information through the nervous system is explained with the help of a reflex arc.

Reflex Arc

Flow of impulse through the nervous system involving receptors, neurons and effectors will be clear if we study an example of a reflex arc. Reflex arc is the path way of passage of impulse during a reflex action. Reflex action is a type of involuntary action. The direction of stimulus is from receptors to sensory neurons to associative neuron and then through motor neurons to the effectors. Flow of impulse through the nervous system involving receptors, neurons and effectors will be clear if we study an example of a reflex arc. Reflex arc is the path way of passage of impulse during a reflex action. Reflex action is a type of involuntary action. The direction of stimulus is from receptors to sensory neurons to associative neuron and then through motor neurons to the effectors.

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