neurones

what are the 3 types of neurones

sensory relay motor

describe the sensory neurone

transmits signal back from the skin/ muscle back to the CNS

describe the relay

This connects the sensory and motor neurones. They are found in the CNS. They have short dendrites and axons.

describe the motor

These are connected to the relay neurone and at the other end the effector.

what is an effector

muscle and glands

reflex arch

stimulus, sensory neurone, relay(CNS), motor neurone, effector responds. At each synapse the electrical signal is converted into a chemical signal.

label the synapse diagram

describe how messages get across a synapse

1. An electrical impulse travels down the axon into the presynaptic neurone this is know as an action potential

2. The electrical impulse stimulates the vesicles to merge with the membrane of the presynaptic neurone and release the neurone transmitters into the synaptic cleft.

3. The neurone transmitters diffuse across the gap reaching the postsynaptic neurone and binding to receptors on its surface.

4. To make an action potential fire the electrical charge has to reach a threshold.

5. when the neurone transmitters bind to the receptors they can either give and excitory or inhibitory response depending on the neurontransmitter.

6. excitory effect the electrical charge is more positive this is called depolarization. This happens when the receptors allow positively charged sodium ions enter the cell.

7. An inhibitory effect is when the cell become hyperpolarised (more negative) this happens when positive potassium ions released out of the cell making it negative.

8. The sum of all the exitory and inhibitory neurone transmitters and added up. If the sum meets threshold the action potential will fire