neurons

Question 1

what are neurons?

Answer 1

nerve cells that process and transmit messages through electrical and chemical signals

over 100 billion in human nervous system (80% in brain)

Question 2

types of neurons

Answer 2

sensory neurons, relay neurons and motor neurons

Question 3

what are sensory neurons?

Answer 3

carry messages from PNS to CNS

long dendrites and short axons

Question 4

what are relay neurons?

Answer 4

connect sensory neurons to motor or other relay neurons

short dendrites and short axons

Question 5

what are motor neurons?

Answer 5

connect CNS to effectors such as muscles and glands

short dendrites and long axons

Question 6

structure of neurons

Answer 6

cell body- includes nucleus containing genetic material of cell
dendrites protrude from cell body- carry nerve impulses from neighbouring neurons towards cell body

axon- carries impulses away from cell body down length of neuron
covered in layer of myelin sheath- protects axon and speeds up electrical transmission of impulse
segmented by gaps/ nodes of Ranvier- speed up impulse transmission by forcing it to ‘jump’ across gaps along axon

terminal buttons at end of axon- communicate with next neuron in chain across a gap known as the synapse

Question 7

location of neurons

Answer 7

motor neurons- cell bodies may be in CNS but long axons form part of PNS

sensory neurons- located outside CNS, in PNS in clusters (ganglia)

relay neurons- 97% of all neurons, most within brain and visual system

Question 8

electrical transmission

Answer 8

neuron in resting state- inside of cell neg charged compared to outside

activated by stimulus- inside becomes pos charged for split second- action potential occurs

creates electrical impulse- travels down axon towards end of neuron