Chapter 4 Part 2

Question 1

Membrane Permeability

Answer 1

How easy it is to cross the plasma membrane

Question 2

What will determine membrane permeability for an ion?

Answer 2

On its own, its impossible.

The number of ion channels that are present and available will determine permeability

Question 3

Diffusion Potential

Answer 3

The direction and rate of passive ion movement

Question 4

ASsuming there is an open ion channel, what will determine the diffusion direction and rate for an ion?

Answer 4

Whichever has the higher concentration will determine the direction.
The gradient and how steep the concentration gradient is will determine rate and also how many channels are open.

Question 5

Equilibrium Potential

Answer 5

The balance point between the chemical and electrical driving forces for a specific ion

Question 6

Equilibrium Potential Information

Answer 6

Related to intracellular vs extracellular concentration gradients. Never occurs in living cells, but they do provide reference for how voltage will change if permeability to a ion changes.

Question 7

What process creates these concentration gradients?

Answer 7

The stronger the gradient, the higher the number. Channel Opens=Faster ion will cross. If Sodium and Potassium channel open, Na+ will flow in and K+ will flow out.

Question 8

Equilibrium Potentials for Ions

Answer 8

Membrane Potential depends on the ion. If it was only Potassium or only Sodium, they will both have different numbers that bring the cell to equlibrium

Question 9

Resting Membrane Potential

Answer 9

The sum of all electrochemical forces resulting from both active and passive processes at baseline permeability levels

Question 10

What does equlibrium focus on?

Answer 10

A single ion, but in real neurons, where amny ions can play a role in determining membrane potential

Question 11

Factor determining resting membrane potential of neuron (1)

Answer 11

The uneven ratio of 3Na+ out and 2K+ in by the Na/K pump. Leads to net membrane negativity.

Question 12

Factor determining resting membrane potential of neuron (2)

Answer 12

Presence of intracellular protein anions. These negatively charged proteins contribute aother 2.5%

Question 13

Factor determining resting membrane potential of neuron (3)

Answer 13

Equilibrium potentials of K+ and Na+ at baseline permeability levels. At rest, 25 times more permeable to K+ than Na+, so equlibrium potential heavily biased toward K+

Question 14

What would be the resting membrane potential be if permeability to both Na+ and K+ was equal?

Answer 14

+60 mV + (-94mV) = -34 mV

Question 15

How can neuron communication be observed?

Answer 15

Depolarization

Hyperpolarization

Question 16

Depolarization

Answer 16

-70 mV is polarized. 0 mV is depolarized. We are moving from -70 toward 0. Another word for this is excitation. We have to reach threshold in positive direction.

Question 17

HYperpolarization

Answer 17

Going to be even more polar. Hyperpolarization goes from -70 to numbers even higher. -94 is the max.

Question 18

What mechanisms will lead to depolarization or hyperpolarization of a neuron’s membrane?

Answer 18

The influx of Calcium (High on outside, low on inside) will cause depolarization
HyperPolarize; Open up Potassium channels, which leaves cell and leaves it more negative.

Question 19

Summary of Graded Potentials

Answer 19

A+B creating depolarized spots while C is trying to push everyone toward it.

Question 20

Spatial Summation

Answer 20

We opened two sets of ion channels, Summed ions from two locations. Converge inputs from external sources. THe most we could move with two graded potentials is 10 mV

Question 21

Spatial Summation with A and C

Answer 21

A+C occur and end of balancing the entire summation

Question 22

Temporal Summation

Answer 22

Ion channel being opened over and over. One contact generate multiple graded potentials, having ion from those GP reach threshold.

Question 23

Membrane Threshold

Answer 23

Anything qualifies except voltage gated Na. In Axon Hillock, after we make switch, and voltage gated channels open. -55 mV is when sodium channels open and when are open, they all open.

Question 24

Action Potential

Answer 24

When summation of enough depolarizing graded potentials push the membrane potential above the membrane threshold an action potential occurs. REsult of voltage-gated ion channels

Question 25

Action Potential Phase 1

Answer 25

Voltage gated Na+ channels open. Once open, we are 20x more permeable for sodium. Gates open then timer stops. When stopped, gate closes

Question 26

Action Potential Phase 2

Answer 26

Voltage gated K+ Channel open. Moves back toward a polarized position.

Question 27

Action Potential Phase 3

Answer 27

K+ (-35 mV for these channels) slowly close. We hyperpolarize for a short amount of time

Question 28

Action Potential Characteristis

Answer 28

Large Depolarization
‘All or nothing” amplitude (With stronger and stronger stimulus, there will be more action potential). Very short duration and very long distance, .