Human Nervous System (Edexcel IGCSE Biology)

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The Human Nervous System: Structure

  • The human nervous system consists of:
    • Central nervous system (CNS) – the brain and spinal cord
    • Peripheral nervous system (PNS) – all of the nerves in the body
  • Information is sent through the nervous system as electrical impulses – these are electrical signals that pass along nerve cells known as neurones
    • A bundle of neurones is known as a nerve
  • The nerves spread out from the central nervous system to all other regions of the body and importantly, to all of the sense organs
    • The CNS, therefore, acts as a central coordinating centre for the impulses that come in from (or are sent out to) any part of the body

The human nervous system, a nerve and a neurone

The human nervous system is comprised of the CNS and the PNS

The Human Nervous System: Function

  • The pathway through the nervous system can be summarised as follows:

stimulus → sensory neurone → relay neurone → motor neurone → effector → response

  1. A stimulus is received by a sensory (receptor) neurone
    • Most receptors are specialised to detect particular stimuli
    • When a receptor is stimulated, it produces electrical impulses
  2. These impulses then travel along a sensory neurone to the central nervous system (the coordinator is either the brain or the spinal cord)
  3. In the CNS, the impulses are passed on to a relay neurone
  4. The relay neurone links to a motor neurone, along which the impulses travel until they reach the effector
  5. The effector is what carries out the response (the effector may be a muscle or gland)

Nerve pathway stimulus to response

From stimulus to response: an example of a nerve pathway showing how an electrical impulse travels through sensory, relay and motor neurones

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Lára

Author: Lára

Expertise: Biology Lead

Lára graduated from Oxford University in Biological Sciences and has now been a science tutor working in the UK for several years. Lára has a particular interest in the area of infectious disease and epidemiology, and enjoys creating original educational materials that develop confidence and facilitate learning.