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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


- 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


- 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


-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