NEURAL CONTROL AND COORDINATION
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In human body the neural system and the endocrine system jointly coordinate and integrate all the
activities of the organs so that they function in a synchronised fashion. Co-ordination is the process through
which two or more organs interact & complement the functions of one another. The neural system provides an
organised network of point-to-point connections for a quick coordination. The endocrine system provides
chemical integration through hormones.
* Nervous system and endocrine system are called Integrative system of the body.
* Nervous system carries informations in the form of impulses to the different parts of body. High speed services
are offered by this system.
NEURAL SYSTEM
* The neural system of all animals is composed of highly specialised cells called neurons which can detect,
receive and transmit different kinds of stimuli.
* The neural organisation is very simple in lower invertebrates. For example, in Hydra it is composed of a
network of neurons.
* The neural system is better organised in insects, where a brain is present along with a number of ganglia and
neural tissues.
* The vertebrates have a more developed neural system.
HUMAN NEURAL SYSTEM
The human neural system is divided into two parts :
(i) Central neural system (CNS)
(ii) Peripheral neural system (PNS)
The CNS includes the brain and the spinal cord and is the site of information processing and control. The PNS
comprises of all the nerves of the body associated with the CNS (brain and spinal cord). The nerve fibres of the
PNS are of two types :
(a) Afferent fibres
(b) Efferent fibres
* The afferent nerve fibres transmit impulses from tissues/organs to the CNS and the efferent fibres transmit
regulatory impulses from the CNS to the concerned peripheral tissues/organs.
* The PNS is divided into two divisions :-
(A) Somatic neural system (SNS)
(B) Autonomic neural system (ANS)
* The somatic neural system relays impulses from the CNS to skeletal muscles while the autonomic neural
system transmits impulses from the CNS to the involuntary organs and smooth muscles of the body.
* The autonomic neural system is further classified into sympathetic neural system and parasympathetic neural system.
NEURON (NERVE CELL)
It is the functional and structural unit of nervous system. It generates and transmits nerve impulses. It is the
longest cell of the body
( C A) Cell body or Cyton or soma or perikaryon:-
* It contains uninucleated cytoplasm.
* Except centriole, all cell organelles are found in cytoplasm.
* Centriole is absent in the nerve cell thus cell division is absent.
* Some other cell organelles like Nissl's granule and neurofibril are also found in nerve cell.
(i) Nissl's granules :
* Endoplasmic reticulum & ribosome form granules like structure called as Nissl's granules or Tigroid
body.
* These are the centre of protein synthesis.
* Site . Cyton & dendron
(ii) Many small fibrils are found in the cytoplasm called neurofibrils, these help in internal conduction in the cyton
(B) Cell processes :
(i) Dendron :.
* It is small cell process. It's fine branches are called dendrites. Some receptor's are found on the dendrites,
so dendron receive the stimuli & produce centripetal (towards the cell body) conduction.
(ii) Axon (Long process = Axon = Nerve fibre) .
* It is longest cell process of cyton, its diameter is uniform.
* Axon is covered by Axolemma. Part of cyton where axon arises called Axon hillock.
* Cytoplasm which contains in axon is axoplasm.
* Nissl's granules are absent in the axoplasm.
* Axoplasm of axon contains only neurofibrils and mitochondria.
* The axon hillock is the neuron's trigger zone, because it is the site where action potential are triggered.
* The terminal end of axon is Telodendria and button shape structure are called as Synaptic knob, which
possess synaptic vesicles containing chemicals called neurotransmitters. The axons transmit nerve
impulses away from the cell body to a synapse or to a neuro-muscular junction.
* More mitochondria are found in the telodendria which synthesize neurotransmitters like Acetylcholine
(Ach) with the help of Acetyl-choline transferase enzyme.
* Axon is the functional part of nerve cell, therefore term nerve fibre usually refer to Axon
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