Ionic Currents and the Electrochemical Gradient

Question 1

Name the gradient that is due to chemical concentration:

Answer 1

Chemical gradient

Question 2

Name the gradient that is due to electrical charge:

Answer 2

Electrical gradient

Question 3

Name this gradient:

A difference in concentration between the inside and outside of a neuron.

Answer 3

Chemical gradient

Question 4

Name this gradient:

The membrane potential (Vm) that arises from the excess of ionic charge (either negative or positive) inside the neuron.

Answer 4

Electrical gradient

Question 5

Chemical gradient:

The difference in concentration creates a ____ ____ between the inside and outside.

Answer 5

diffusion force

Question 6

Chemical gradient:

The direction of movement is always from ___ to ___ concentration.

Answer 6

high to low

Question 7

Electrical gradient:

An ____ ____ is generated that either repels ions apart (similar charge) or attracts ions together (opposite charges).

Answer 7

electrostatic force

Question 8

Electrical gradient:

The direction of movement is governed by the polarity of the ___, relative to the polarity of the ____…

Answer 8

ion; neuron

Question 9

When the polarity of the neuron is NEGATIVE:

• Cations will be pulled?
• Anions will be repelled?

Answer 9

Cations: In
Anions: Out

Question 10

When the polarity of the neuron is POSITIVE:

• Cations will be repelled?
• Anions will be pulled?

Answer 10

Cations: Out
Anions: In

Question 11

What is the concentration gradient on the inside and outside of Na+?

Answer 11

Outside: High
Inside: Low

Question 12

What is the concentration gradient on the inside and outside of K+?

Answer 12

Outside: Low
Inside: High

Question 13

Neuronal rest potential:

Normal polarity = ___

Answer 13

Negative

Question 14

Whenever the two gradients are opposite, the net flow of an ion across the membrane will be ___ when the strength of the electrical gradient exactly matches the strength of the chemical gradient.

This statement is know as?

Answer 14

Zero

Nernst Equilibrium

Question 15

There will be an ionic current as long as (Vm – E) is not equal to?

Answer 15

Zero

Question 16

The electrochemical gradient for Na+: (Vm – ENa).

Given the normal intracellular and extracellular concentrations of Na+,
ENa = +55 mV.

Let’s say that the resting potential is -65 mV …
then, |(Vm-E)| = 120 mV.

The electrochemical gradient will therefore cause Na+ to flow?

Answer 16

In

Question 17

Relative to the rest potential of -65 mV:

1) As Vm ______ (the magnitude becomes less), the electrochemical gradient for Na+ (Vm - ENa) becomes?
2) As Vm ______ (the magnitude becomes more), the electrochemical gradient for Na+ becomes?

Answer 17

1) Depolarizes; Less

2) Hyperpolarizes; Greater

Question 18

The electrochemical gradient for K+: (Vm – EK)

Given the normal intracellular and extracellular concentrations of K+,
EK = -80 mV.

Let’s say that the resting potential is -65 mV
then, |(Vm-E)| = 15 mV.

The elctrochemical gradient will therefore cause K+ to flow?

Answer 18

Out

Question 19

Relative to the rest potential of -65 mV:

1) As Vm _____ (the magnitude becomes less), the electrochemical gradient driving the outward flow of K+ becomes?
2) As Vm _____ (the magnitude becomes more), the electrochemical gradient driving the outward flow of K+ becomes?
3) As Vm _____ to greater than EK (-80 mV) the flow of K+ will reverse, and now becomes?

Answer 19

1) Deploarizes; Greater
2) Hyperpolarizes; Less
3) Hyperpolarizes; Inward

Question 20

To induce an ionic current across the neuronal membrane, what normally varies is?

Answer 20

The membrane conductance to a particular ion

Question 21

The membrane conductance is dependent upon how many ion channels are ____, and this is controlled by ____ that will open and close the gate in ion channels…

Answer 21

Open; Signals

Question 22

At synaptic junctions, the conductance of the postsynaptic membrane to ions is normally very ____ … signal transduction via ligand activation of the postsynaptic receptors will ____ certain ion channels to provide a selective increase in conductance to one or two ions

Answer 22

Low; Open

Question 23

In synaptic neurotransmission, the amplitude of the postsynaptic response is determined by the change in ____ ____, triggered by neurotransmitter binding to its ____ receptors

Answer 23

membrane conductance; postsynaptic