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If the local potential brings the cell to threshold, the result in a(n):
action potential
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Define threshold.
the minimum change in potential needed to initiate an action potential
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What is the threshold potential for a neuron?
-60 mV
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True or False: Everytime a cell reaches threshold, an action potential results.
True
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The concept that states that if a cell does not reach threshold, there can be no action potential is the:
all or none principle
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What type of ion movement causes the depolarization of cells?
influx of positively charged sodium ions
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How does membrane potential change during depolarization?
- it becomes more "positive" in charge
- -70 mV to +20 mV
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How does membrane potential change during repolarization?
- it becomes more negative
- +20 mV to -70 mV
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What type of ion movement will occur during repolarization?
outflux of positively charged potassium ions
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What type of ion movement occurs during hyperpolarization?
outflux of positively charged potassium ions
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How does membrane potential change when the cell hyperpolarizes?
- it becomes more negative
- -70 mV to -90 mV
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How will hyperpolarization affect the ability of the cell to reach threshold.
it will make it harder to reach threshold
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On an action potential graph, what two things occur when the ligand-gated channels open?
- small amount of sodium comes in
- cell moves towards threshold
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On an action potential graph, what two things occur when the voltage-gated channels open?
- large amounts of sodium comes in
- cell depolarizes
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At +20 mV, the apex of the action potential graph, what two things occur?
- sodium channels close
- potassium channels open
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On an action potential graph, what two things occur as the cell repolarizes?
- potassium leaves the cell in large amounts
- as potential approaches threshold, K gates close
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The period of time in which an excitable cell can't generate a second action potential in response to a normal stimulus is known as the:
refractory period
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What two things are occuring during the refractory period?
- reestablishment of ion gradients
- potential returns to resting value
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True or False: A relative refractory period can generate a second response if the stimulus is strong enough.
True
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Define Excitatory Postsynaptic Potential (EPSP).
small depolarization of the membrane which brings cell closer to threshold
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Define Inhibitory Postsynaptic Potential (IPSP).
a small hyperpolarization of the membrane which brings the cell further away from threshold
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Will an EPSP inhibit or stimulate the postsynaptic cell.
stimulate the postsynaptic cell
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Will an IPSP inhibit or stimulate the postsynaptic cell?
inhibit the postsynaptic cell
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Multiple stimuli applied at the same location, but at different times, will result in which type of summation?
temporal summation
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Two or more stimuli applied at the same time at different locations will result in which type of stimulation?
spatial summation
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Which type of summation is quicker, temporal or spatial?
spatial summation
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Which will result in summation, EPSP or IPSP?
EPSP
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If a neuron has a threshold value of -60 mV, will a local potential of -65 mV result in an action potential?
no, it will not
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If a neuron has a threshold value of -60 mV, will a local potential of -59 mV result in an action potential?
yes, it will
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What cellular function returns the ion gradients after the depolarization and repolarization of a cell membrane?
the sodium/potassium pump
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