Describe how a reflex occurs?

A reflex is an innate (in built) action designed to keep an organism safe from harm.  A good example of a reflex is to imagine you touch a hot pan, you immendiately withdraw your hand from the painful stimulus in order to prevent your finger from burning.

The main componants of the reflex arc are:

1.The sensory receptors (the receptors in your finger which feel the heat).

2.The sensory neurone which conveys this information to the spinal cord via a relay neurone.

3.The motor neurone which acts to contract the effector muscle and relax the antagonistic muscle to move your hand away.

Each of these neurones communicates with another via a synapse. These work by one nerve ending receiving the electrical impulse and releasing chemicals called neurotransmitters between the gap. These then bind to receptors on the other nerve ending which stimulates the electrical impulse to then transmit along that axon. 

Reflexes occur without having to think about it and are therefore autonomic responses. They are extremely important in minimising damage done to ourselves.