introduction to human nervous system, neuron, types & related term detail explanation | class 10th |

Human Nervous System We have understood the basic model of the working of nervous system. The nervous system in man and in other higher animals is composed of two major components i.e. central nervous system and peripheral nervous system.
Central nervous system comprises of coordinators i.e. brain and spinal cord while peripheral nervous system consists of nerves that arise from central nervous system and spread in different parts of body. All these components are made of neurons. Now we will first examine the structure and types of neuron and then we will go to the divisions of nervous system.
Nerve cell or Neuron Nerve cell or neuron is the unit of the nervous system. The human nervous system consists of billions of neurons plus supporting (neuroglial) cells. Neurons are specialized cells that are able to conduct nerve impulses from receptors to coordinators and from coordinators to effectors. In this way they communicate with each other and with other types of body cells. The nucleus and most of the cytoplasm of a neuron is located in its cell body. Different processes extend out from cell body. These are called dendrites and axons. Dendrites conduct impulses toward cell body and axons conduct impulses away from cell body.
Schwann cells are special neuroglial cells located at regular intervals along axons. In some neurons, Schwann cells secrete a fatty layer called myelin sheath, over axons. Between the areas of myelin on an axon, there are nonmyelinated points, called the nodes of Ranvier. Myelin sheath is an insulator so the membrane coated with this sheath does not conduct nerve impulse. In such impulses are called saltatory (‘jumping’) impulses. This increases the speed of nerve impulse.
On the basis of their functions, neurons are of three types; 1. Sensory neurons conduct sensory information (nerve impulse) from receptors towards the CNS. Sensory neurons have one dendrite and one axon. 2. Interneurons form brain and spinal cord. They receive information, interpret them and stimulate motor neurons. They have many dendrites and axons. 3. Motor neurons carry information from interneurons to muscle or glands (effectors). They have many dendrites but only one axon.
Nerve A nerve means the union of several axons that are enveloped by a covering made of lipid. Based on the property of axons, the nerves are classified into three types. 1. Sensory nerves contain the axons of sensory neurons only. 2. Motor nerves contain the axons of motor neurons only. 3. Mixed nerves contain the axons of both i.e sensory and motor neurons.
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