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11 Cards in this Set

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Excitable Tissue

Tissue cells that are capable of responding to and/or generating changes in membrane potential are excitable tissues

Membrane Potential

- membrane potential less negative = depolarization


- membrane potential MORE negative = hyperpolarization

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

Depolarization

- depends on sodium permeability


- will go from -70mV to +60mV


-

Saltatory Conduction

- jumping of AP from node of ranvier to node of ranvier

Myelinated Fiber

-will always conduct more rapidly

FACTS

- Action Potentials ALWAYS make Graded Potential but Graded Potential don't always make AP


-The Myelinated Fiber will ALWAYS conduct more rapidly


-

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


-

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


-

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

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