neurons

• how many neurons in our nervous system and what do they do

  100billion- 80% in brain, transmits signals electrically and chemically provides the nervous system with its primary means of communication
• what are the types of neurons?

  -sensory: carry messages from the peripheral nervous system (PNS) to the central nervous system(CNS), long dendrites, shortaxons,

  -motor: connect the CNS to effectors such as muscles and glands, short dendrites, long axons

  -relay: connect, sensory neurons to motor, short dendrites, short axons
• The structure of a neuron

  -cell body: includes nucleus, dendrites

  -axon: carries impulses away from cell body down the neuron, covered in Myelin sheath to protect it (segmented by gaps, called nodes of Ranvier to speed up transmission)

  -terminal buttons: communicate with the next neuron in the chain across a gap known as the synapse
• Location of Neurons

  -sensory neurons: outside CNS, in the PNS in clusters known as ganglia

  - relay neurons: make up 97% of all neurons, found within brain and visual system