Neurons

• There are three types of neurons: sensory, relay and motor.
• The cell body includes a nucleus, which contains the genetic material of the cell
• Branchlike structures called dendrites protrude from the cell body. These carry nerve impulses from neighbouring neurons towards the cell body.
• The axon carries the impulses away from the cell body. The axon is covered in a fatty layer of myelin sheath that protects the axon and speeds up transmission.
• The myelin sheath is segmented by gaps called nodes of Ranvier. These speed up the transmission of the impulse by forcing it to 'jump' across the gaps along the axon.
• At the end of the axon are terminal buttons that communicate with the next neuron in the chain across a synapse.
• The cell bodies of motor neurons may be in the CNS but they have long axons which form part of the PNS.
• Sensory neuons are located outside of the CNS, in the PNS in clusters known as ganglia.
• Relay neurons are found within the brain and visual system.
• When a neuron is in a resting state the inside of the cell is negatively charged compared to the outside. When a neuron is activated by a stimulus, the inside of the cell becomes positively charged for a split second causing an action potential to occur. This creates an electrical impulse that travels down the axon towards the end of the neuron.