Membrane Potential and Action Potential

Question 1

What is the membrane potential?

Answer 1

The electrical charge accross the cell membrane.

Question 2

What is the Resting Membrane Potential?

Answer 2

When the membrane has a charge of approximately 70 millivolts. This is due to the negative Charge of large proteins in the intracellular matrix and because the Na+/K+ pump removes 3 Na ions and replaces then with 2 k ions. This results in a net loss of positive ions.

Question 3

What is a voltage gated channel?

Answer 3

A channel that opens in response to a change in membrane potential.

Question 4

What is a chemically gated channel?

Answer 4

The channel is opened when a specific protein or chemical binds to a receptor site on the channel. This is not dependent on membrane potential.

Question 5

What is a chemically gated channel?

Answer 5

The channel is opened when a specific protein or chemical binds to a receptor site on the channel. This is not dependent on membrane potential.

Question 6

What is depolarization?

Answer 6

When a stimulus is applied to a cell resulting in the membrane potential becoming more positive.

Question 7

What is Na+ responsible for?

Answer 7

Depolarization

Question 8

What is hyperpolarization?

Answer 8

When the cell membrane becomes more negative than it’s resting potential?

Question 9

What is repolarization?

Answer 9

A return to resting membrane potential.

Question 10

What is responsible for hyperpolarization?

Answer 10

Slow to close K+ channels or CI-.

Question 11

What is responsible for repolarization?

Answer 11

K+

Question 12

What is a graded potential?

Answer 12

When a stimulus results in only a localized depolarization of the membrane potential. This will radiate out from the initial site of depolarization and weaken over time. There will be no response from the cell. This helps us filter out unimportant stimuli.

Question 13

What is an action potential?

Answer 13

A stimulus causes the entirety of a cell to respond and there is no decrease in intensity as the change in membrane potential propagates accross the cell.

Question 14

What is a threshold response?

Answer 14

The point at which a stimulus causes on event to occur.

Question 15

What is a sub-stimulus?

Answer 15

A stimulus that doos not achieve an action potential.

Question 16

What is a super threshold stimulus?

Answer 16

A stimulus that is significantly higher than a throsheld response and will generate can action potential. How over the magnitude above the threshold has no effect on the intensity of the action potential.

Question 17

What is the absolute refractory period?

Answer 17

There is no possibility for another action potential as the ions are in flux.

Question 18

What is relative refractory?

Answer 18

A strong enough subsequent stimulus con trigger another action potential.

Question 19

What is Salutalory Conduction?

Answer 19

Only occuring in myelinated neurons, this is when an impulse jumps below con the nodes of Ranvier, resulting in only a small. section of the membrane depolarizing. This speeds up the propagation Of action potentials.

Question 20

What is the role of the Ca++ ion?

Answer 20

When an action potential reaches the end of on axon, voltage gated channels are opened leting Ca++ in. This triggers the release of secretory vesicles. This results in the exocytosis of neurotransmitters into the synaptic cleft. These neurotransmitters will diffuse toward another neuron creating graded potentials. When added together, it results in an action potential propagating to the post synaptic cell.

Question 21

What is the role of acetylcholinesterase and monoaminoxidase?

Answer 21

They are enzymes that break down acetylcholine and norepinephrine, thus ending neurotransmitter activity and the triggering: of additional action potentials.

Question 22

What is an excitatory postsynaptic potential?

Answer 22

A local depolarization of a post synaptic membrane which brings a neuron closer to the action potential threshold.

Question 23

What causes an EPSP?

Answer 23

A stimulus, such as the binding of a neurotransmitter to a receptor, results in the opening of voltage gated Channels for Na+ and K+ ions.

Question 24

What is an inhibitory post synaptic potential?

Answer 24

A local hyperpolarization of the post synaptic membrane that drives a neuron alway form the action potential threshold.

Question 25

What causes an IPSP?

Answer 25

This is be caused by a neurotransmitter binding to a channel and allowing CI -

Question 26

What is a Temporal summation?

Answer 26

Two excitatory stimuli close in time will have a combined effect and trigger on action potential

Question 27

What is a Spatial summation?

Answer 27

Two simultaneous stimuli at different locations in the membrane will have a combined effect, triggering an action potential or cancelling each other out.