Neural Control and Coordination
In all the multicellular animals above the level of sponges,the system meant to perceive stimuli detected by the receptors,to transmit these to various body parts,and to effect respones through effectors,is called nervous system.In vertebrates,it is highly specialized and plays at least three vital roles.
- Sensory function:
- Integrative functions:
- Motor function:
It senses certain changes(stimuli) both within body(internal environment) and out side body(external environment).
It analyses the sensory information,store some aspects,and make decisions regarding appropriate behaviour.
It may respond to stimuli by initiating muscular contractions or glandular secretions.
Nervous systems in various animals:
True nerve cell or ganglion cells occur for the first time in coelenterates.They are derived from interstitial cells of epidermis,forming nerve net or nerve plexus below whole epidermis, A polar neurons are found in coelenterata.
Nervous system of planarians marks the beginning of a centralized nervous system
encountered in higher animals.That is made up of brain or cerebral ganglia,two
lateral logitudinal nerve chords,numerous peripheral nerves and transverse commissures
or connectives.This is sometimes called the ladder type of nervous system.
In Nematoda (e.g.ascaris)these system made up of central nervous system,peripheral nervous system and rectal nervous system.Rectal nervous system more developed in male.Ascaris with dorsal,ventral and lateral nerve cords.
Nervous system well developed and concentrated.It consists of three parts: Central nervous system,peripheral nervous system and sympathetic nervous system,central N.S made up of Nerve ring and ventral nerve cord.Nerves are of mixed type,consisting of both afferent(sensory) and efferent(motor)fibres.