What are dendrites?
Dendrites carries nervous impulses towards a cell body
What are axons?
Carries nervous impulses away from the cell body
What is the cell body?
Where the nucleus is normally located
What are Schwann cells?
Schwann cells are wrapped around the axon of the neurone to form the myelin sheath.
What are the nodes of Ranvier?
Gaps between adjacent Schwann cells
At a neurones resting state what is the charge inside?
At resting state there is a difference in charge across the neurone membrane: the inside is more negatively charged than outside
More positive ions outside than inside
-70mv
What is a difference in charge?
A potential difference
How do Schwann cells act as insulators for neurons?
Schwann cells wrap around the axon of neurones to create a myelin sheath
The myelin sheath acts as an electrical insulator because it it impermeable to ions (Na+/K+)
Depolarisation and action potentials cannot occur at myelinated parts, only in the gaps between (Nodes of Ranvier)
What effect does temperature have on nerve impulses?
An increase in temperature increases kinetic energy
Ions move across the membrane more rapidly when they have more kinetic energy
Describe the synaptic knob
Is the end of the axon of the presynaptic neurone
Is a swelling which contains synaptic vesicles
Is the location where the nerve impulse is transmitted across the synaptic cleft
There are lots of mitochondria present as lots of energy is needed to synthesise neurotransmitters
What happens when excitatory neurotransmitters bind to the receptors on the postsynaptic membrane?
The membrane is depolarised
What happens when inhibitory neurotransmitters bind to the receptors on the postsynaptic membrane?
The membrane is hyperpolarised
What is a neuromuscular junction?
A neuromuscular junction is a synapse between a motor neurone and a muscle cell. An action potential is transmitted across the synapse using the neurotransmitter acetylcholine.
What ion channel is found at the postsynaptic membrane?
Na+
What ion channel is found at the presynaptic membrane?
Ca+
What is a neurones threshold potential?
-55mv
What is a neurones resting potential?
-70mv
What is the period during hyperpolarisation called?
Refractory period
Describe how sodium potassium pumps help maintain a resting potential.
3 Na+ ions are actively transported out of the neurone by the pumps for every two k+ ions that are transported in
This leads to a build-up of positive ions out of the cell
Describe the steps of depolarisation.
Na+ ion channels in the cell membrane open when a neurone is stimulated
Na + ions flood into the neurone
If the PD across increases above the threshold (-55mv) then more Na+ channels open and there is a sharp increase in PD to about 30mv (where the Na+ ions shut)
What is meant by depolarisation being n all or nothing response?
If the PD reaches the threshold (-55mv), depolarisation will always take place and change in PD will always be the same
If the stimulus is stronger, action potentials will be produced more frequently but their size will not increase
What PD does a neurone reach at depolarisation?
+40mv
What occurs at repolarisation?
Sodium ion channels shut and potassium ion channels open
K+ ions are transported back out the neurone and the PD becomes more negative
What is the name of the period of hyperpolarisation?
Refractory period
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Topic 1 key terms51
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topic 2 key terms56
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topic 3 key terms41
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topic 4 key terms45
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topic 5 key terms43
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Topic 6 key terms44
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topic 7 key terms59
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Topic 8 key terms44
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topic 350
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Topic 612
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muscles and movement1
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Protein synthesis7
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DNA replication4
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Topic 219
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Hardy-Weinberg principle5
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Topic 48
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Topic 511
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Paper 1 questions28
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Topic 730
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Topic 843
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random23
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Mock11
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Topic 143
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Random paper 16
