Chapter: Biology: Structural Organization and Acquaintance of Animals
Toad: Nervous system
Nervous system: This nervous system of Toad requires a central coordinationarrangement
to conduct different organs efficiently. The nervous system an endocrine or
hormone system conducts controls and coordinates all the activities of the body
of toad. The system through which the animal response to stimuli, maintains the
connections of various organs, coordinates various activities and maintains
relations with the environment is called the nervous system.
The nervous system of toad, can be divided into three main divisions
based on the origin, structure, distribution and functions.
1.
Central nervous system
2.
Peripheral nervous system
3.
Autonomic nervous system
l. Central nervous system: The central nervous system consists of the brain and the spinal cord.
2. Peripheral nervous system: The periphery or lateral nerve originates fromthe lateral sides of the
brain and spinal cord formed of ten pairs of cranial nerves and ten pairs of
spinal nerves.
3. Autonomic nervous system: In the body of animals there is a kind of nervewhich is not directly-
controlled by the central nervous system but control independently the
activities of various organs. The autonomic Nervous system is formed with these
nerves. This system is formed with a pair of sympathetic nerve cord with their
branches.
Description of central nervous
system: The central nervous system of
toadformed of the brain and the spinal cord. The part of the central nervous
system which is enclosed within the skull, is called the brain.
The brain of toad is elongated. The middle part is thick and two ends a
n-arrow and bi-laterally syrumetrical. The brain is covered by two membrane The
outer thick, hard, translucent and blood vessels enriched membrane called dura
matter and the inner thin membrane is called pia matter. These two membranes
together are called meninges. Meninges cover the brain and spinal cord protects
them.
The brain is formed of neurons or nerve cells. One neuron is joined with
the other neuron by the synapse and form the nervous tissue. The outer part of
the brain is formed of grey matter i.e. nerve cell bodies. The white part towards
its inner side is called the white matter. This part is formed of nerve fibres.
The brain and spinal cord of vertebrate animals are not solid. In its
inner Part there are hollow cavities or brain ventricles. The brain cavities
remain filled up with a kind of fluid.
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