The Nervous System

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What are the three types of neurones that make up the nervous system?
Sensory Neuron, Motor Neuron, Relay Neuron
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What does a sensory neurone do?
Transmits nerve impulses from receptors to the CNS and converts stimulus energy into electrical energy making it a transducer.
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Why does the sensory neurone cell body have dendrites?
To carry nerve impulses towards cell body
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Why does the sensory neurone have an axon?
To carry nerve impulses from cell body to axon terminal
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What does a motor neurone do?
Transmits nerve impulses from the CNS to the effectors
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Why does the motor neurone's cell body have dendrites?
To carry nerve impulses from the CNS to the cell body
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Why does the motor neurone have an axon?
To carry nerve impulses from axon to effector cells
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What are three structural differences between a sensory and motor neurone?
Motor Neurone has short dendrites, long axon and cell body at the end of the neurone. A sensory neurone has long dendrites, a short axon and the cell body is in the middle of the neurone
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What does a relay neurone do?
Transmits nerve impulses between sensory and motor neurones.
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What is resting state level?
-70mv
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How is resting potential created and maintained?
By sodium-potassium pumps, sodium ion channels, potassium ion channels.
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How does depolarisation occur?
Neurone cell membrane becomes depolarised when stimulated. When the stimulus reaches threshold potential it causes voltage gated sodium ion channels to open. Sodium diffuses into sodium ion channels and into the membrane.
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What happens in depolarisation?
Inside of the neurone becomes less negative (more positive)
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What is repolarisation?
At around +40mc sodium ion channels close and voltage gated potassium ion channels open. Membrane is more permeable to potassium and so ions diffuse out of the neurone and down potassium ion concentration gradient, through potassium ion channels.
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What is hyper polarisation?
Voltage gated potassium ion channels are too slow to close, therefore it overshoots and neurone becomes more negative than the resting potential.
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What is the refractory period?
When the sodium potassium pump returns to resting potential by moving 3 potassium into the membrane and 2 sodium ions out of the membrane.
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How does an action potential move along a neurone?
Sodium ions diffuse along neurone sideways causing sodium ion channels in the next region to open. The sodium ions then diffuse into that part of the neurone causing a wave of depolarisation to travel along the neurone.
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What happens in areas of the neurone in the refractory period?
Sodium ions move away from these areas because they can't fire an action potential there.
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Where does depolarisation occur?
Only at the nodes
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How does saltatory conduction work?
The neurones cytoplasm conducts an electrical charge to polarise the next node, so nerve impulse jumps from node to node.
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What is the name of tiny gaps in the bare membrane of a neurone called?
Nodes of Ranvier
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Where are sodium ion channels concentrated?
At the nodes
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What is a myelin sheath made from?
Shwaan cells
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What do Schwaan cells do?
They are electrical insulators
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Card 2

Front

What does a sensory neurone do?

Back

Transmits nerve impulses from receptors to the CNS and converts stimulus energy into electrical energy making it a transducer.

Card 3

Front

Why does the sensory neurone cell body have dendrites?

Back

Preview of the front of card 3

Card 4

Front

Why does the sensory neurone have an axon?

Back

Preview of the front of card 4

Card 5

Front

What does a motor neurone do?

Back

Preview of the front of card 5
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