neurons and synaptic transmission

Question 1

where are 80% of neurons in the body located?

Answer 1

in the brain

Question 2

how do neurons provide the nervous system with its primary means of communication?

Answer 2

by transmitting signals electrically and chemically

Question 3

what are the three types of neurons?

Answer 3

sensory neuron
relay neurons
motor neurons

Question 4

How do neurons vary in size?

Answer 4

From less than a millimetre up to a metre long.

Question 5

what does the cell body of a neuron include?

Answer 5

a nucleus which contains the genetic material of the cell

Question 6

what are the branchlike structures of a neuron called and what do they do?

Answer 6

dendrites which carry nerve impulses from neighbouring neurons towards the cell body

Question 7

what does the axon do?

Answer 7

carry impulses away from the cell body down the legnth of the neuron

Question 8

what is the axon covered in?

Answer 8

a fatty layer of myelin sheath that protects the axon and speeds up electrical transmission of the impulse

Question 9

what would happen if the myelin sheath was continuous?

Answer 9

this would slow down electrical impulses

Question 10

what is the myelin sheath segmented by?

Answer 10

nodes of ranvier

Question 11

what do nodes of Ranvier do?

Answer 11

speed up the transmission of the impulse by forcing it to ‘jump’ across the gaps along the axon

Question 12

what is at the end of the axon?

Answer 12

terminal buttons that communicate with the next neuron in the chain across a synapse

Question 13

Where might cell bodies of motor neurons be?

Answer 13

In the CNS but also might have long axons which form part of the PNS.

Question 14

where are sensory neurons located?

Answer 14

In the PNS in clusters (ganglia)

Question 15

what % of neurons do relay neurons make up?

Answer 15

97% and most are found in the brain and visual system

Question 16

when a neuron is in a resting state inside the cell how is it charged?

Answer 16

negatively compared to the outside of the cell.

Question 17

what causes an action potential to occur?

Answer 17

when a neuron is activated by a stimulus, the inside of the cell becomes positively charged for a split second.

Question 18

what does an action potential create?

Answer 18

an electrical impulse that travels down the axon towards the end of the neuron

Question 19

how do neurons communicate?

Answer 19

within neural networks

Question 20

how are signals within neurons transmitted?

Answer 20

electrically

Question 21

how are signals between neurons transmitted?

Answer 21

chemically across the synapse

Question 22

what happens when the electrical impulse reaches the end of the neuron (presynaptic terminal)?

Answer 22

it triggers the release of neurotransmitter from synaptic vesicles

Question 23

what are neurotransmitters?

Answer 23

chemicals that diffuse across the synapse to the next neuron in the chain

Question 24

what happens once a neurotransmitter crosses the gap?

Answer 24

it is taken up by the postsynaptic receptor site of the next neuron

Question 25

why can the direction of travel only be one way?

Answer 25

because neurotransmitters are released from the presynaptic neuron terminal and received by the postsynaptic neuron

Question 26

what do neurotransmitters have either of?

Answer 26

excitatory or inhibitory effect on the neighbouring neuron

Question 27

what does te process of summation decide?

Answer 27

wether a postsynaptic neuron fires

Question 28

what is likely to happen if the net effect on the postsynaptic neuron is inhibitory

Answer 28

the postsynaptic neuron is less likely to fire

Question 29

what is likely to happen if the net effect is excitatory?

Answer 29

it is more likely to fire

Question 30

when is the action potential of the postsynaptic neuron triggered?

Answer 30

if the sum of the excitatory and inhibitory signals at any one time reaches the threshold