Ionic Currents and the Electrochemical Gradient Flashcards
Name the gradient that is due to chemical concentration:
Chemical gradient
Name the gradient that is due to electrical charge:
Electrical gradient
Name this gradient:
A difference in concentration between the inside and outside of a neuron.
Chemical gradient
Name this gradient:
The membrane potential (Vm) that arises from the excess of ionic charge (either negative or positive) inside the neuron.
Electrical gradient
Chemical gradient:
The difference in concentration creates a ____ ____ between the inside and outside.
diffusion force
Chemical gradient:
The direction of movement is always from ___ to ___ concentration.
high to low
Electrical gradient:
An ____ ____ is generated that either repels ions apart (similar charge) or attracts ions together (opposite charges).
electrostatic force
Electrical gradient:
The direction of movement is governed by the polarity of the ___, relative to the polarity of the ____…
ion; neuron
When the polarity of the neuron is NEGATIVE:
- Cations will be pulled?
- Anions will be repelled?
Cations: In
Anions: Out
When the polarity of the neuron is POSITIVE:
- Cations will be repelled?
- Anions will be pulled?
Cations: Out
Anions: In
What is the concentration gradient on the inside and outside of Na+?
Outside: High
Inside: Low
What is the concentration gradient on the inside and outside of K+?
Outside: Low
Inside: High
Neuronal rest potential:
Normal polarity = ___
Negative
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?
Zero
Nernst Equilibrium
There will be an ionic current as long as (Vm – E) is not equal to?
Zero
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?
In
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?
1) Depolarizes; Less
2) Hyperpolarizes; Greater
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?
Out
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?
1) Deploarizes; Greater
2) Hyperpolarizes; Less
3) Hyperpolarizes; Inward
To induce an ionic current across the neuronal membrane, what normally varies is?
The membrane conductance to a particular ion
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…
Open; Signals
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
Low; Open
In synaptic neurotransmission, the amplitude of the postsynaptic response is determined by the change in ____ ____, triggered by neurotransmitter binding to its ____ receptors
membrane conductance; postsynaptic
