Action Potential Flashcards

1
Q

What is the value at which there is no net move of ions in the cell

A

-70mV

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2
Q

What is the value for K

A

At -94 millivolts no net K+ diffusion outside

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3
Q

What is the value for Na?

A

At +61 millivolt no net diffusion of Na+.

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4
Q

What is an action potential?

A

change in permeability of the membrane due to activation of voltage-gated channels which are inactive at rest state

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5
Q

-EMF- electromotive force?

A

The net driving forces for ion diffusion (electrical and chemical) inside and outside.

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6
Q

Cations- (Vdf>0) ___________
(Vdf<0) __________

A

outward, inward

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6
Q

Every cell has different ____________ value.

A

resting potentiala

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6
Q

Anions- (Vdf>0) ________
(Vdf<0) ______

A

inward, outward

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6
Q

____________________ for each ion tends to cause net movement of the ion across the membrane. This driving force is equal to the difference between the membrane potential (Vm) and the equilibrium potential of the ion (Veq)- Vdf = Vm – Veq

A

electrochemical driving force (Vdf)

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7
Q

-Equilibrium potential?

A

is the point at which there is no net movement of an ion into or out of a cell. It occurs when the concentration gradient of the ion is in balance with the electrical gradient of the ion

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8
Q

-At resting potential charge of cells is __________ inside and __________ outside

A

negative, positive

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8
Q

action potential has 3 stages:

A

1) resting stage - 70mV

2) Depolarization - electrical gradient raises until its positive (+35mV) aka hyperpolarization state. This is due to influx of sodium.

3) Repolarization - electrical gradient is lowered again until it reaches rest state (going through a -94mV, hyperpolarization state). The Na+ channels begin to close as the K+ channels open. Diffusion of K+ to the exterior re-establishes the normal negative resting membrane potential

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9
Q

-Voltage gated Na+ channel- has __ gates and __ stages. They can be at ___________________

A

2, 3 , rest, activated or inactivated.
At rest inactivated gate is opened and activated is close. Increase of voltage opens activation gate and closes inactivation gate. Activation gate recloses when the cell is back to rest state potential (-70mV). The activation gate opens quickly and it takes time for inactivation gate to close while sodium influx (depolarization).

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10
Q

-Voltage gated K+ channel- __ gate with __stages. Increase of voltage opens the gate (slow activation) approximately when Na+ channels become inactivated.

A

1, 2

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11
Q

what is the action potential activation treshold?

A

-50mV

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12
Q

What is Plateau in action potential?

A

This pause is critical to heart function, as it allows the atrial cardiomyocytes to complete their contraction that pumps blood into the ventricles before the impulse is transmitted to the cells of the ventricle itself.

K channels open more slowly during the phase

13
Q

what is the refractory period?

A

is a period in which a cell cannot generate action potential. There are two main types of refractory period:

The absolute refractory period is the time during which a nerve cell is unable to fire a new action potential. It occurs when sodium channels are inactivated after the initial depolarization

The relative refractory period is a critical concept in neurophysiology. It occurs immediately after the absolute refractory period and allows a second action potential to be generated, but only if the stimulus is strong enough