Module 2 Flashcards
Define the following properties of ion channels:
gating:
activation:
inactivation:
gating: occupation of a receptor (ligand gating), mechanical forces, change in potential (depolarization)
activation:
inactivation:
Differentiate between the properties of electrotonic conduction, conduction of an
action potential, and saltatory conduction
electrotonic conduction-
conduction of an action potential-
saltatory conduction-
Identify regions of a neuron where each
type of electrical activity may be found.
electrotonic conduction-
conduction of an action potential-
saltatory conduction-
electrotonic conduction-
conduction of an action potential-
saltatory conduction-
Understand the principle of the voltage clamp and how it is used to identify the ionic selectivity of channels.
Clamps Vm at fixed level (prevents fluctuations) to measure currents in cell
Does NOT measure action potential
ONLY Depolarization opens voltage gated Na channels
Inward ionic current is negative. Outward current is positive
TTX and Saxitoxin- blocks Na current. Only outward current (K) present
TEA blocks K current (only inward current (Na) present
Contrast the gating of ion-selective channels by extracellular ligands, intracellular
ligands, stretch, and voltage.
.
Know the properties of voltage-gated Na+, K+, and Ca2+ channels, and understand
that voltage influences their gating, activation, and inactivation.
.
Understand how the activity of voltage-gated Na+, K+, and Ca2+ channels generates
an action potential and the roles of those channels in each phase (depolarization,
overshoot, repolarization, hyperpolarization) of the action potential.
Resting- Polarized. Na gate closed. K closed -90mV
Depolarization- (towards 0) Na gates open. Na rushes in.
Overshoot- (positive) in large nerve fibers, goes beyond zero level to +35mV
repolarization- (toward RMP) Na+ channes close. K channels open more. K moves out
hyperpolarization- (away from 0)
Contrast the mechanisms by which an action potential is propagated along both
nonmyelinated and myelinated axons.
speed depends on size and myelination
Predict the consequence on action potential
propagation in the early and late stages of demyelinating diseases, such as multiple
sclerosis
.
Describe the functional role of myelin in promoting saltatory conduction,
contrasting the differences between the CNS and PNS.
.
Write the Nernst equation, and indicate how this equation accounts for both the
chemical and electrical driving forces that act on an ion.
.
Based on the Nernst equilibrium potential, predict the direction that an ion will
take (follow) when the membrane potential
a) is at its equilibrium potential
Potential inside the membrane
+ if ion diffusing inside -> out is neg
- if ion diffusing inside -> out is pos
Based on the Nernst equilibrium potential, predict the direction that an ion will
take (follow) when the membrane potential
b) is higher than the equilibrium potential
.
Based on the Nernst equilibrium potential, predict the direction that an ion will
take (follow) when the membrane potential
c) is less than the equilibrium potential.
.
List values in a typical non-excitable cell for the membrane potential, for:
ENa
EK
ECl
ECa
ENa-
EK-
ECl-
ECa-
# Define the concepts of electrochemical equilibrium and equilibrium potential, and give internal and external ion concentrations.
.
Be able to calculate an equilibrium potential for that ion using the Nernst equation.
Contrast the difference in EK (the
Nernst potential for K+) caused by a 5 mEq/L increase in extracellular K+ with
the change in ENa (the Nernst potential for Na+) caused by a 5 mEq/L increase in
extracellular Na+.
.
Explain how the resting membrane potential is generated and calculate membrane
potential by using the Goldman-Hodgkin-Katz equation.
.transfer of incredimbly small # of ions through membrane
K+ naturally diffusing out -94mV
Na+ naturally diffusing in +61mV (but lower permeability) [-86 overall]
Na-K Pump -4mV
Overall net membrane potential -90mV (mostly diffusion)
Given an increase or
decrease in the permeability of K+, Na+, or Cl-
, predict how the membrane
potential would change.
.
Define, and identify on a diagram of a motor neuron, the following regions:
dendrites, axon, axon hillock, soma, and an axodendritic synapse.
.
Describe ionic basis of an action potential.
normal -90mV resting potential
sudden depolarization to +35mV
rapid repolarization back to -90mV
Describe the ionic basis of each of the following local graded potentials: excitatory
post synaptic potential (EPSP), inhibitory post synaptic potential (IPSP), end plate
potential (EPP) and a receptor (generator) potential.
.
Contrast the generation and conduction of graded potentials (EPSP and IPSP)
with those of action potentials.
.
Contrast the cell-to-cell spread of depolarization at a chemical synapse with that at
a gap junction based on speed and fidelity (success rate).
.
At the chemical synapse,
contrast the terms temporal summation and spatial summation.
.
