Neurones

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what is the resting potential
is the potential difference across the membrane while the neurone is at rest
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why does it have negative resting potential
as outside has more positive ions outside than inside
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what is the resting potential measured in
mv (milivolts)
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how is the resting potential maintained
by keeping more positive ions outside the cell than the inside
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what action maintains the resting potential
the sodium-potassium pump
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how does it change the concentration of ions inside and outside the cell
high potassium inside high sodium outside
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what is the membrane permeale to
it is permeable to potassium but not sodium
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what are the two types of gradients acting on the potassium ions
an electrical gradient and a concentration gradient
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what does the electrical gradient do
it pulls potassium ion into the cell and concentration pulls them out
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which gradient has a stronger effect
the concentration gradient
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benefit of the concentration gradient
more positive char has left the cell, the resting potential of the neurone decreases further
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what does polarised mean
when it maintains a negative resting potential
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why is negative resting potential required
so when the neuron needs to transmit an impulse sodium ions can enter
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what is the threshold potential
the depolarisation has to reach a certain point for an action potential to occur to send a signal onwards
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what is depolarisation
when the sodium ions move back into the cell
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what happens when the depolarisation is enough
it will activate the voltage-gated sodium channels in the first section of the axon
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what is the voltage gated sodium channels
opens at membrane channels above -50 mv
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what is positive feedback
mechanism where a change moves the system further away from the optimum
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what is repolarisation
taking the membrane back to a polar state. Sodium channels close and potassium channels opens and potassium leaves the cell
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what is hyperpolarisation
high is sodium ions low in potassium ions on the inside when the membrane potential is lower than the resting potential
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what is refractory period
it is impossible to initiate another action potential
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what is the importance of the refractory period
to ensure the action potential only travels in one direction
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what is the all or nothing principle
signal must be at the threshold or above if not then no action potential happens and if above then an action potential occurs
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what is the myelin sheath
having layers of fat covering axon
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what are the gaps between myelin sheath
nodes of Ranvier
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what is the myelin sheath made of
Schwann cells
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other functions of Schwan cells
engulfing debris and neuronal regeneration
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non-myelinated neurones
wrap loosely
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what do sodium ions do when they have enter the membrane
small number leak out of membrane, some of them are attracted to negative charge nearby and get stuck at membrane
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what is the local circuit
process of movement of charge inside and outside the membrane
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importance of myelination to the local circuit
sodium ion cant leak out of membrane fatty insulation from Schwann cells stops them getting attracted to the negative charge - increases length of local circuit
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what is saltatory conduction
is there the action potential jumps form one node of Ranvier to the next
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differences in myelination
myelination - when sodium has to diffuse over a long distance non-myelination - over a short distance
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what is a synapse
link two or more neurones together
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parts of the synapse
pre-synaptic, synaptic cleft and post synaptic
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what are vesicles filled with
neurotransmitters
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cholinergic synapse
uses acetylcholine as heir neurotransmitter
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what does the synapse contain
synapse contains enzyme acetylcholine esterase
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what is an EPSP
it is an excitatory post synaptic potential
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what is an IPSP
it is an inhibits post synaptic potential
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how is an IPSP brought about
it hyperpolarises the postsynaptic neurone instead of depolarising
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action potential is only one way because...
neurotransmitter are stored in the presynaptic cell
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what is spatial summation
when multiple EPSPs from the multiple presynaptic neurone are added together in post synaptic neurone
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what is temporal summation
when a neurone receives a very strong stimulation from a single
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what is strong stimulus graphically
multiple actin potential over a small space of time
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what is habituation
reduction in neuronal signalling due to repeated stimulation
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Card 2

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why does it have negative resting potential

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as outside has more positive ions outside than inside

Card 3

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what is the resting potential measured in

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Card 4

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how is the resting potential maintained

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Card 5

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what action maintains the resting potential

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