Membrane Potential Flashcards

1
Q

What are excitable cells?

A

Cells capable of generating action potentials on stimulation including neurons and muscles

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2
Q

Give the definition of an action potential

A

A short-lasting event in which the electrical membrane potential of a cell rapidly rises and falls

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3
Q

What is membrane potential?

A

The difference in voltage between the interior and exterior of a cell

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4
Q

what is electrochemical equilibrium?

A

A combination of the voltage gradient and the concentration gradient of an ion

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5
Q

What drives the flow of any ion through a membrane channel protein?

A

The electrochemical gradient for that ion

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6
Q

What is equilibrium potential?

A

The membrane potential at which there is no net flow of the ion, can be calculated by the Nerst equation

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7
Q

What determines the resting membrane potential?

A

Potassium, because resting channels in animal cells are selective for potassium only

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8
Q

Define depolarization

A

Making the membrane potential less negative, the cell interior becomes less negative

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9
Q

What is depolarization dependent on?

A

Inward current of positive charges

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10
Q

Define hyperpolarization

A

Makes the membrane potential more negative, the cell interior becomes more negative

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11
Q

What is hyperpolarization dependent on?

A

The outward current of positive charges

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12
Q

What are some properties of action potentials?

A

Stereotypical size and shape, propagating, all or nothing

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13
Q

Describe upstroke of an action potential

A

Upon stimulation, inward current depolarizes the membrane to threshold causing rapid opening of Na+ channels but does not reach the Na+ equilibrium potential (65mV)

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14
Q

Describe repolarization of an action potential

A

Repolarization is the combined effect of Na+ channels closing and K+ channels opening

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15
Q

What is undershoot/hyperpolarization?

A

The K+ channel conductance remains higher than at rest a while making it approach the K+ equilibrium potential

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16
Q

What is the absolute refractory period?

A

A period in which another action potential cannot be elected no matter how large the stimulus because the Na+ channels are closed when the membrane potential is depolarized and will remain closed until repolarization

17
Q

What is the relative refractory period?

A

An action potential can be elected only if a larger than usual inward stimulus is provided because the membrane potential is closer to the K+ equilibrium and further from the threshold

18
Q

How long does the relative refractory period last?

A

Brings at the end of the absolute refractory period and contained until the membrane potential returns to resting levels

19
Q

What is the accommodation refractory period?

A

Occurs when the cell membrane is held at a depolarized level such that the threshold potential is passed without firing an action potential because the Na+ channels close and remain closed

20
Q

How can an action potential be propagated?

A

By the spread of local currents to adjacent areas of the membrane which are depolarized to threshold

21
Q

How can conductance velocity while propagating an action potential be increased?

A

Increasing fiber size to decrease the internal resistance, myelination

22
Q

Where are action potentials generated on an axon?

A

Only at nodes of ranvier which increases conductance

23
Q

Define saltatory conductance

A

When the action potential jumps from one node to the next

24
Q

What do inhibitory neurotransmitters do to a post synaptic membrane?

A

Hyperpolarize the membrane

25
Q

What do excitatory neurotransmitters do to the postsynaptic membrane?

A

Depolarize the membrane