Reflex actions

Voluntary actions involve conscious thought (thinking time).

Reflex actions do not involve conscious thought (thinking time) and happen very quickly to avoid unnecessary damage to the body.

One example of this is rapidly removing your hand from a hot plate before it gets burned.

Reflex arc

A reflex action happens quickly because the reflex pathway is kept short and involves the smallest number of neurones and synapses possible.

Reflex arc

Synapse

A synapse is a small gap exists between two neurones, which an electrical impulse cannot pass across.

There are 2 synapses in the above reflex arc:

  • Between the sensory and association neurones.
  • Between the association and motor neurones.

There are 3 neurones and 2 synapses involved in a reflex arc.

  • The sensory neurone - carries information from the receptor to the spinal cord (coordinator).
  • The association neurone - joins the sensory neurone and motor neurone.
  • The motor neurone - carries information from the spinal cord to an effector that can cause a response.

The association and motor neurones both begin with the cell body.

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