- Reflexes have to be quick and they are so because they are automatic. The message of a reflex does not go up the brain which is why they are involuntary.
- Many reflexes occur naturally such as accommodation and sneezing but some can be learned e.g. conditional reflex.
- These prevent us from being injured, or at least reduce the potential injury.
- The passage of information in a reflex is called a reflex arc.
- The neurones in the reflex arc go through the spinal cord or through an unconscious part of the brain (you don’t have to think).
- When a stimulus (e.g. pin) is detected by the receptors, impulses are sent along a sensory neurone to the CNS.
- In the CNS the sensory neurone passes on the message to a relay neurone.
- Relay neurones relay the impulses to a motor neurone.
- The impulses then travel along the motor neurone to the effector (e.g. muscle)
- The muscle then contracts and moves the hand away from the pin.
- As you don’t have to think about this response, it’s quicker than a normal response.
What occurs at a synapse
- Electrical impulse travels along the first neurone (pre-synaptic)
- If the impulse is strong enough it causes neurotransmitters to be released across the synapse (gap between two neurones).
- The neurotransmitter is detected by receptors on the next neurone (post-synaptic)
Once enough neurotransmitter is detected the post-synaptic neurone transmits the electrical signal again.