Membrane Potential

Question 1

What are excitable cells?

Answer 1

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

Question 2

Give the definition of an action potential

Answer 2

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

Question 3

What is membrane potential?

Answer 3

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

Question 4

what is electrochemical equilibrium?

Answer 4

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

Question 5

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

Answer 5

The electrochemical gradient for that ion

Question 6

What is equilibrium potential?

Answer 6

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

Question 7

What determines the resting membrane potential?

Answer 7

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

Question 8

Define depolarization

Answer 8

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

Question 9

What is depolarization dependent on?

Answer 9

Inward current of positive charges

Question 10

Define hyperpolarization

Answer 10

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

Question 11

What is hyperpolarization dependent on?

Answer 11

The outward current of positive charges

Question 12

What are some properties of action potentials?

Answer 12

Stereotypical size and shape, propagating, all or nothing

Question 13

Describe upstroke of an action potential

Answer 13

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

Question 14

Describe repolarization of an action potential

Answer 14

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

Question 15

What is undershoot/hyperpolarization?

Answer 15

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

Question 16

What is the absolute refractory period?

Answer 16

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

Question 17

What is the relative refractory period?

Answer 17

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

Question 18

How long does the relative refractory period last?

Answer 18

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

Question 19

What is the accommodation refractory period?

Answer 19

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

Question 20

How can an action potential be propagated?

Answer 20

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

Question 21

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

Answer 21

Increasing fiber size to decrease the internal resistance, myelination

Question 22

Where are action potentials generated on an axon?

Answer 22

Only at nodes of ranvier which increases conductance

Question 23

Define saltatory conductance

Answer 23

When the action potential jumps from one node to the next

Question 24

What do inhibitory neurotransmitters do to a post synaptic membrane?

Answer 24

Hyperpolarize the membrane

Question 25

What do excitatory neurotransmitters do to the postsynaptic membrane?

Answer 25

Depolarize the membrane