Components of Nervous System
All messages are received and transferred to different body parts through specialised cells (neurons) that constitute Nervous system. Nervous system consists of central nervous system, peripheral nervous system and autonomic nervous system. The central nervous system is mainly made up of brain and spinal cord. There are three protective layers of brain and spinal cord namely dura mater, arachnoid and pia mater which together constitute the meninges. Brain is manly divided into three parts which are forebrain, midbrain and hindbrain. Fore brain is the lasgets part of the brain which is differentiated into olfactory lobes, cerebrum and diencephalon. Midbrain connects the hind brain with the forebrain and conveys impluses. Hindbrain comprises of cerebellum, medulla oblongata and pons varoli. An instrument electroencephalogram (EEG) records the waves of the brain. The cerebrospinal fluid serves as the shock absorbing medium in brain and spinal cord. The peripheral nervous system comprises cranial nerves (12 pairs of nerves arising from brain) and spinal nerves (31 pairs of nerves arising from spinal cord). All spinal nerves are mixed nerves. The autonomic nervous system controls all the involuntary activities of the body. It is further classified into sympathetic and parasympathetic nervous system. Reflex action is a speedy spontaneous action in response to any external or internal stimulus. Reflex arc is the shortest pathway that can be taken by an impulse from receptor to an effector. There are two types of reflex actions namely conditioned and unconditioned reflex actions.
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