Term
| what is the action potential directly related to? |
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Definition
| the opening and closing of Na/K pumps |
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Term
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Definition
| a brief electrical event in which the membrane potential of a cell changed rapidly in a predictable manner |
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Term
|
Definition
| how the receptor identifies a molecule |
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Term
| describe a multiunit sodium channel. |
|
Definition
has several gates
has a selectivity filter |
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Term
| T/F there is only one gate in sodium channel. |
|
Definition
false
2-activation and inactivation gate |
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Term
| explain the steps of the Na+ channel when an AP occurs. |
|
Definition
1-before depolarization the activation gate is closed, Na cannot pass
2-a change in polarity causes the activation gate to open and allow for Na to flow into the cell (spike in AP)
3-miliseconds later the inactivation gate swings closed to allow the cell to (back to RMP) |
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Term
| what is the absolute refractory period? |
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Definition
| period after the threshold is met where it is impossible to induce another action potential |
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Term
| what is the relative refractory period? |
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Definition
| period where a stronger-than-usual stimulus is required to cause another AP |
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Term
| what causes the absolute and relative refractory periods? |
|
Definition
| conformational and sequential changes in the sodium and potassium channel molecules |
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Term
| outline the absolute refractory period. |
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Definition
| the point when the inactivation gate closes the Na channel |
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Term
| what is the absolute refractory period responsible for? |
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Definition
| unidirectional propagation of APs along axons |
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Term
| outline the relative refractory period. |
|
Definition
| the point at which most of the sodium channels are back to resting potential while some potassium channels remain open, which require a greater than normal stimulus |
|
|
Term
|
Definition
stimulus applied
Na+ influx channels open
the inside of the cell becomes much more positively charged as we top out |
|
|
Term
|
Definition
at rest
Na+ and K+ channels are closed with K+ leak channels active |
|
|
Term
|
Definition
Na+ channels close
K+ concentration greater than Na+
K+ efflux |
|
|
Term
|
Definition
| rest restored as K+ and Na+ channels close and K+ leak channels become active |
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Term
|
Definition
| membrane potential at which enough voltage gated sodium channels open |
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Term
| what happens during the rising phase? |
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Definition
| sodium rushes into the cell causing rapid depolarization |
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Term
|
Definition
| membrane permeable to Na+ resulting in equilibrium potential for Na+ |
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Term
| what happens during the falling phase? |
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Definition
| action of both the sodium and potassium channels where sodium channel becomes inactive and K+ channels open which cause K+ to rush out of the cell to re-establish a more negative membrane potential |
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Term
|
Definition
|
|
Term
| what is happening during the absolute refractory period? |
|
Definition
| Na+ channels inactivate when strongly depolarized AND they cannot be activated until membrane potential goes more negative |
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|
Term
| what is happening during the relative refractory period? |
|
Definition
| membrane potential stays hyper polarized until potassium channels close. this means that more depolarization current is required to bring the membrane potential to threshold |
|
|
Term
| what is the rate of AP generation dependent upon? |
|
Definition
| magnitude of the depolarizing current |
|
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Term
| T/F there is no limit to the rate at which neurons can generate an AP. |
|
Definition
false
limited to about 1000 per second |
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|
Term
| T/F the AP is always the same amount of mV. |
|
Definition
|
|
Term
| what two major factors determine conduction velocity? |
|
Definition
time constant
length constant |
|
|
Term
| what is the time constant for conduction velocity? |
|
Definition
| how quickly a cell membrane depolarizes or how quickly it hyper polarizes |
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|
Term
| what is good about high membrane resistance? |
|
Definition
| the current does not flow across the cell membrane without the use of pores which makes it difficult to change membrane potential |
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|
Term
| what is membrane capacitance? |
|
Definition
| the ability of the cell membrane to store charge |
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|
Term
| membrane resistance and membrane capacitance must be low/high for time constant to be greatest. |
|
Definition
|
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Term
|
Definition
| how far a depolarizing current will spread along a nerve |
|
|
Term
| what is internal resistance? |
|
Definition
| the ease of current flow in the cytoplasm of the nerve fiber |
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|
Term
| for length constant to be greatest membrane resistance would need to be high/low and internal resistance would need to be high/low. |
|
Definition
|
|
Term
| if the axon is small with many pores, which direction will the AP likely travel? |
|
Definition
|
|
Term
| if the axon is large with few pores, which direction will the AP likely travel? |
|
Definition
|
|
Term
| T/F the larger the diameter of the axon, the greater the conduction velocity. |
|
Definition
|
|
Term
| T/F neural pathways important for survival have evolved unusually small axons. |
|
Definition
false
unusually larger axons |
|
|
Term
| T/F smaller axons require greater stimulation and are typically more sensitive to anesthetics |
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Definition
|
|
Term
| T/F you want the AP to spread across the membrane, |
|
Definition
|
|
Term
| what is the myelin sheath? |
|
Definition
| insulation of the axon thereby keeping the electrical impulse within the axon |
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|
Term
| T/F the myelin sheath does not increase conduction velocity. |
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Definition
|
|
Term
| what are breaks in the myelin sheath called? |
|
Definition
|
|
Term
| what is saltatory conduction? |
|
Definition
| the AP jumping from segment to segment to increase the conduction |
|
|
Term
| where are the sodium channels most concentrated on the axon? |
|
Definition
| near the membrane of the nodes |
|
|
Term
| what is Multiple Sclerosis? |
|
Definition
| a disease of the nervous system that attacks the myelin sheaths of bundles of axons in the brain, spinal cord, and optic nerves |
|
|
Term
| what does Multiple Sclerosis lead to? |
|
Definition
weakness
lack of coordination
impaired vision
impaired speech |
|
|
Term
|
Definition
MRI to see bright spots in areas of the brain
EEG to measure the speed of electrical activity in the brain |
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