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11 Cards in this Set
- Front
- Back
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Excitable Tissue |
Tissue cells that are capable of responding to and/or generating changes in membrane potential are excitable tissues |
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Membrane Potential |
- membrane potential less negative = depolarization - membrane potential MORE negative = hyperpolarization |
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Graded Potential |
- triggers depolarization - increase in amplitude when you increase stimulus --> generates larger graded potentials - spatially and temporally summate in space and time -decreases in amplitude over distance -two diff stimulus sets cause summation - not regenerable - NO threshold -NO refractory period -initiated by environmental factors -mechanism depends on ligand |
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Depolarization |
- depends on sodium permeability - will go from -70mV to +60mV - |
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Saltatory Conduction |
- jumping of AP from node of ranvier to node of ranvier |
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Myelinated Fiber |
-will always conduct more rapidly |
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FACTS |
- Action Potentials ALWAYS make Graded Potential but Graded Potential don't always make AP -The Myelinated Fiber will ALWAYS conduct more rapidly - |
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Action Potential |
-triggered by Graded Depolarization - a threshold of depolarization MUST be reached to trigger an AP - At the peak of an AP, the membrane potential reverses sign and becomes more positive inside -During AP, there is a time interval called ABSOLUTE REFRACTORY PERIOD, during which it is impossible to fire another AP -amplitude is INDEPENDENT of the size - has a refractory period - |
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What does it mean when a membrane is REFRACTORY? |
- incapable of generating another AP - This occurs for a certain period of time, called ABSOLUTE REFRACTORY PERIOD (period on the descending limb when you have increase in K+ which is IRRELEVANT, cannot generate another AP, because voltage gated Na+ channel is NOT in CLOSED configuration - |
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Relative Refractory Period |
-MAYBE can generate another AP only if it is depolarized to a value more positive than normal threshold - membrane must be depolarized well above the threshold (superthreshold) - opens some Na+ and keeps enough of them in the closed state |
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Excitability |
-probability of opening voltage gated Na+ channel -during ARP, probability is 0 - at the end, you get an increase in excitability --> increase in probability of firing another AP--> increase in numbers of voltage gated Na+ channels in CLOSED state |
