Reflex Actions

A reflex action is a response to a change in environment that does notinvolve any processing in the brain to coordinate the movement

The nervous pathway is as short as possible so that the reflex is rapid.

Most reflex pathway consist of three neurones:

1. Sensory neurones

2. Relay neurones (in the brain)

3. Motor neurones

The brain may be informed that a reflex has happened but it will not be involved

A reflex occurs in order to ensure survival and protection of the body

Blinking reflex

This involves temporary closure of the eyelids to protect the eyes from damage. The nervous pathway for the blinking reflex passes through part of the brain.

This is a cranial reflex

As the pathway is a direct path it does not involve any thought process

Blinking may be stimulated by sudden changes in the environment:

Corneal reflex

1. This is mediated by a sensory neurone from the cornea which enters the pons

2. A synapse connects the sensory neurone to a relay neurone which passes the action potential to the motor neurone.

3. The motor neurone passes back out of the brain to the facial muscles, causing the eyelid to blink.

This is a very short and direct pathway so the corneal reflex is very rapid

It takes about 0.1 seconds

The corneal reflex causes both eyes to blink even if only 1 eye is affected.

1. The sensory neurone involved in the corneal reflex passes the action potential to myelinated neurones in the pons.

2. These myelinated neurones carry the action potential to the sensory region in the cerebral…