When the brain receives impulses from receptor cells it creates a response. Response impulses are sent to the effectors which carry out an action.
Neurones that receive impulses from receptor cells are Sensory Neurones. They have a long dendron and an axon.
Neurones that take impulses to effectors are Motor Neurones. They have no dendron. Their dendrites are on the cell body.
Relay neurones are short neurones which are found in the spinal cord. This is where they link Motor and Sensory neurones. They also make up the brain.
It's important to remember the following order:
Stimulus
Receptors
Sensory Neurone
Relay Neurone
Motor Neurone
Effectors
Response
Sensory Neurone:
Myelinated Sheath is a fatty layer that surrounds the axon. It insulates neurones from surrounding tissue and allows impulses to be carries faster.
A Synapse is the point at which two neurones meet. There is a tiny gap between neurones at a synapse , which can not transmit an electrical impulse. Impulses are transmitted across the gap by a chemical substance called Neurotransmitters.
When you pick up a hot object you drop it suddenly to stop it burning you, and you don't have to think about it first. This is a reflex. Reflex actions are automatic responses that are very quick and protect the body. They use reflex arcs which are neurone pathways where a sensory neurone directly controls a motor neurone.
Key Words:
Response
Effectors
Sensory Neurones
Motor Neurones
Relay Neurones
Myelinated Sheath
Synapse
Neurotransmitter
Reflexes
Reflex Arcs
Questions:
1. Where are the receptor cells that receive the stimulus?
2. What is the order in which neurones follow?
3. What is a reflex?
4. Why is it useful to have reflexes without having to think?
5. What is a synapse?
What you should've learnt:
The structure and function of Sensory, relay and motor neurones and synapses including:
a. The role of the myelinated sheath
b. The role of neurotransmitters
c. The reflex arc
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