Kerala PSC - Biology - Human Body (Nervous System)

• The fundamental unit of the nervous system - Nerve cell or Neuron
• Nervous system is formed by brain, spinal cord and sensory receptor nerves.
• Nerves are the pathways through which messages travel.
• The functional junction between neurons is called synapse.
• Neuron has the following parts
• Cell body
• Axon
• Dendron
• The long fiber that arises from the cell body of a neuron - Axon
• Axons are enveloped by a covering made of lipid known as Myelin sheath
• Myelin sheath is white in colour.
• The neurons that carry impulses from receptors to central nervous system are called sensory neurons.
• The neurons that carry impulses from the central nervous system to effectors are called motor neurons.
• Based on the property of nerve fibres, the nerves are classified into
• Sensory nerves Eg. Optic nerve
• Motor nerves Eg. Hypoglossal nerve
• Mixed nerves Eg. Vagus, Facial, Spinal nerves etc
• Cell bodies of neurons form a group enveloped by a membrane called Ganglion.
• The region where the axonite of one neuron are connected to the dendrites of another neuron - Synapse
• Three types of Nervous system are
• Central nervous system
• Peripheral nervous system
• Autonomic nervous system
• Central nervous system is composed of Brain and Spinal Cord.