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The Nervous System

Control and coordination

  • Working together of various integrated body systems in response to changes in the surrounding for the maintenance of bodily functions is known as control and coordination
  • Nervous system and endocrine system provide control and coordination in animals.

Nervous system

  • Neurons -functional units of the nervous system, conduct messages in the form of electrical and chemical impulses
    • Neuron composed of cell body and dendrite, axon and nerve endings.


  • Types of neuron:-
    • Sensory neuron
    • Motor neuron
    • Relaying or intermediate neuron
  • Nerve: A nerve is a collection of nerve fibres (or axons) enclosed in a tubular medullary sheath. This sheath acts as an insulation and prevents mixing of impulses in the adjacent fibres.​
  • Transmission of nerve impulse:
    Under normal conditions, the outer side of the nerve fibre consists of positive charge as more Na+ ions are present outside axon membrane. The neuron is then said to be in polarised state. On stimulation, the membrane becomes more permeable and Na+ ions move inside causing depolarisation.  Such a region is known as excited region. The point of depolarisation behaves as stimulus for the neighbouring area and this goes on. In the mean time, the pre…

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