Structure and functiom of neurons

Question 1

Describe neurons

Answer 1

Fundamental units of the brain and the nervous system, responsible for receiving sensory input and sending electrical impulse between the brain and body to transfer messages

Question 2

What is the role of neurons

Answer 2

Pass messages via electrical impulses
- receive and transmit between brain cells in response to info received from the rest of the body

Question 3

Describe dendrites

Answer 3

Collects chemical signal from another neuron
Receives message to send to soma
Branched and short extension

Question 4

Describe the soma (cell body)

Answer 4

Life support
Receives chemical signal from dendrite and changes it to electrical signals
Contains nucleus, DNA, ribosomes and mitochondria

Question 5

Describe the axon

Answer 5

Long cable like extension
Sends a nerve impulse ( action potential ) through the neuron to transmit a message to the next neuron

Question 6

Describe the myelin sheath

Answer 6

Protect the axon
Speed up transmission of the message by providing insulation

Question 7

Describe the axon terminal (terminal button)

Answer 7

End of the neuron
Contains vesicles that store neurotransmitter
Sends the information through the neuron to the next neuron through the release of neurotransmitters
Pass nerve impulse from cell body to part of the body they control or activate

Question 8

When do neurones transmit signals.

Answer 8

When stimulated by the sensory input or triggered by neighbouring neurones

Question 9

What are the contact points between neurons

Answer 9

Synapses

Question 10

What is sent across the synaptic cleft

Answer 10

Neurotransmitters- Chemical messages

Question 11

What happens if the neurotransmitter isn’t accepted into the next neurone

Answer 11

It is reabsorbed by the pre synaptic neurone

Question 12

Describe the sensory neuron

Answer 12

Send info from the sense (PNS) towards the brain (CNS)
Receptors found in eyes,ears, tongue, skin
Long dendrites and short axon

Question 13

Describe the relay neuron

Answer 13

Connect sensory neuron to motor neuron or other relay neurons
Involved in analysing the sensations from these neurons and deciding how to respond
Short dendrites and short axon

Question 14

Describe the motor neuron

Answer 14

Send info via long axons from the brain ( CNS) through to the effector eg muscle or glands
Long axon and short dendrites

Question 15

Explain neurotransmitter and there functions

Answer 15

Chemical messages within the brain
Stored in vesicles
Only located in the presynaptic neuron
Transmit info from one neurone to another so a person performers an action

Question 16

What is the synaptic cleft

Answer 16

The gap between each neuron

Question 17

Where are receptors site found

Answer 17

Only on postsynaptic neuron

Question 18

Describe excitatory neurotransmitter

Answer 18

Makes it more likely that the post synaptic neuron will fire so a impulse will travel down the axon
Increase the brain activity in the CNS
example-noradrenaline
Involved in maintaining alertness and arousal
Low levels casue- low energy, poor concentration
High levels cause - nervousness, high blood pressure

Question 19

Describe inhibitory neurotransmitter

Answer 19

Prevents or reduces the likelihood that the next neuron will fire
Decrease the brains actively in the CNS
example - serotonin
Helps maintain a stable mood and plays a role in sleep,appetite and the pain response
Low levels cause - low mood, depression, aggression, sleep problems
High levels cause - happiness , risk taking behaviour

Question 20

What is summation

Answer 20

When the excitatory and inhibitory influence are added together
If overall effect is mainly inhibitory- decrease likelihood of next neurone firing
If overall effect is mainly excitatory - increase likelihood of next neuron firing

Question 21

Explain the role of serotonin

Answer 21

Helps maintain a stable mood and plays a role in sleep,appetite and the pain response
Low levels cause - low mood, depression, aggression, sleep problems
High levels cause - happiness , risk taking behaviour

Question 22

Explain the role of noradrenaline

Answer 22

Involved in maintaining alertness and arousal
Low levels casue- low energy, poor concentration
High levels cause - nervousness, high blood pressure

Question 23

Jeremy is digging in the garden. He feels the spade hit a rock and stops digging immediately.
Explain how sensory, relay and motor neurons would function in this situation.(6 marks)

Answer 23

The sensory neuron sends the information from the sense to the brain(CNS). The receptors in Jeremy’s hand would sense the jolt of the spade hitting the rock and send that information via the peripheral nervous system to his brain/CNS.Relay neurons connect with other neurons, mostly found in the brain/CNS - here they would be involved in analysis of the sensation, what it means, deciding about how to respond to it, thus acting between the sensory and motor neurons.Motor neurons send messages via long axons from the brain to the muscles or effectors – here the message from the brain instructs Jeremy’s arm muscles to stop working and stop the digging action.

Question 24

Briefly outline how excitation and inhibition are involved in synaptic transmission.(4 marks)

Answer 24

Excitation and inhibition is the effect the neurotransmitter has on the likelihood of the next neuron being ready to fire. If the neurotransmitter is excitatory it increases the likelihood of the postsynaptic neuron firing an impulse which increases brain activity in the central nervous system for example noradrenaline. Whereas,if the neurotransmitter is inhibitory it decreases the likelihood of postsynaptic neuron firing an impulse which decreases brain activity in the central nervous system for example serotonin. The excitatory and inhibitory influences are summed, if the net effect on the postsynaptic neuron is inhibitory, the neuron will be less likely to ‘fire’ and if the net effect is excitatory, the neuron will be more likely to fire