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49 Cards in this Set
- Front
- Back
action potential |
Abrupt depolarization of the membrane for a very brief period of time that allows the neuron to communicate over long distances |
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membrane potential |
the electrical charge across a cell membrane or the difference in the electrical potential inside and outside of the cell
Measured w/ respect to the outside of the cell |
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resting potential |
the membrane potential of a neuron at rest or when it is not being excited or inhibited by other inputs
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Microelectode |
a very fine electrode that can be used to electrically stimulate or record from a neuron |
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oscilloscope |
measures and shows voltage over time |
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Depolarization |
reduction of the membrane potential from its normal resting potential
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Hyperpolarization |
increase in the membrane potential relative to the normal resting potential
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Threshold of excitation |
voltage level that triggers an action potential |
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Diffusion- |
movement of molecules from regions of high concentrations to regions of low concentrations |
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Molecules tend to |
distribute themselves evenly throughout the medium over time |
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Electrolytes |
materials that are charged in water |
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Ion- |
charged particle
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Cation- |
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Anion- |
negative charge |
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Electrostatic pressure |
force of attraction or repulsion between ions |
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Ion channels |
channels in the cell membrane that allow for the passage of particular ions either in or out of the cell |
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Voltage dependent ion channels |
ion channels that open in response to changes in membrane potential |
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V-D Na+ channels require_________ to open |
depolarization |
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V-D K+ channels are __________ and require ____________ to open |
less sensitive
more polarization |
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What if the membrane suddenly became permeable to Na+? |
? |
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Once threshold is reached Na+ channels...... |
..... open and Na+ rushes into the cell
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The K+ channels open ..... |
slightly later |
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At height of AP Na+ channels become .... |
Refactory |
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No more Na+ entering and K+ is still leaving the cell |
Inside of cell is now depolarized so K+ leaves the cell |
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The outflow of cations returns the membrane back to resting potential |
overshoot |
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The sodium - potassium pump |
Also called Na+/K+ transporter |
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Rate Law |
variations in the intensity of a stimulus or other information transmitted in an axon are represented by variations in the firing rate |
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All or none law |
an action potential once triggered is transmitted without decreasing in size to the end of the neuron |
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Advantages of s |
Economy |
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What about myelin and the nodes of Ranvier? |
Node of Ranvier is in contact with the extracellular fluid |
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Salatary conduction |
conduction of AP’s in myelinated axons. The AP “jumps” from one node of Ranvier to the next |
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AP is always the same _____ |
size |
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AP travels one way because it starts at the_____ and also the____maintains this |
soma
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Advantages of salutary conduction |
Economy |
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SO basically.... |
Allows for faster reaction times, faster thinking
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What would happen in the AP if you flooded the extracellular space with K+? |
Excess extracellular K+ depolarizes the neuron so if it stays high then no more AP’s. A ten-fold rise in K+ eliminates the resting potential. Brain is partially protected from this by the BBB and by glia cells, particularly astrocytes, which help regulate extracellular K+ levels. |
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if you added enough Na+ to reach threshold you would elicit an AP. |
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What would happen to the membrane potential if you added Cl- to the cell? |
The cell would become hyperpolarized and it would be harder to reach threshold and therefore harder to fire and AP. |
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What would happen if you made the Na+/K+ pump inactive? |
The pump maintains the resting potential and if you made it inactive it could not keep the resting potential and the neuron would eventually be unable to fire and AP. |
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Membrane potential is produced |
a balance between the forces of diffusion and electrostatic pressure
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Organic anions (A-) |
Only intracellular |
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Chloride ions (Cl-) |
Mostly extracellular |
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Sodium ions (Na+) |
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Potassium (K+) |
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2 forces acting on the K+ ion, do what:
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Diffusion pushes it out of the cell |
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2 forces acting on the Cl- ion (do what) |
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2 forces acting on the Na+ ion ( do what) |
Diffusion = in |
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Absolute refactory period
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when the sodium channels are refractory and cannot open regardless of the voltage.
In this time no AP can be elicited. |
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Relative refactory period |
the time immediately after the AP has fired when the resting potential has been overshot and the membrane is hyperpolarized. In the relative refractory period the V-D Na+ channels can open but the voltage is below resting (so below –70mV) and a stronger than normal stimulus is required to fire an AP. |