the structure and function of nerurons

Question 1

type of neurons

Answer 1

sensory neurons

relay neurons

motor neurons

Question 2

the structure of a neuron

Answer 2

vary in size from less than a millimetre to up to a metre long

all share the same basic structure

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

axon- carries the impulses away from the cell body down the length of the neuron
covered in a fatty layer of myelin sheath that protects the axon and speeds up electrical transmission of the impulse

myelin sheath - if it was continuous this would have the reverse effect and slow down the electrical impulse
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

terminal buttons- ommunicate with the next neuron in the chain across a gap known as the synapse

Question 3

location of neurons

Answer 3

cell bodies of motor neurons may be in the central nervous system

but they have long axons which form part of the peripheral nervous system

sensory neurons are located outside the CNS in the PNS in clusters known as ganglia

Relay neurons make up 97% of all neurons and most are found in the brain and the visual system

Question 4

electrical transmission - the firing of a neuron

Answer 4

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 a neuron