Neuro Lecture B2 Flashcards
Depolarization
Reduction of resting membrane potential toward less negative potentials (towards zero)
Hyperpolarization
increase in membrane potential from resting value away from zero (toward more negative potentials), tending to reduce excitability
Equilibrium Potential
Membrane potential where there is no net passive transport of a permeant ion into or out of the cell
Electrochemical Gradient
The transmembrane difference in potential energy of an ion due to the combined electrical and diffusion forces acting on it
Ion channel
aqueous porous route (across membrane) within a single large protein or cluster of polypeptide subunits
Membrane Potential
the electrical potential of the interior of the cell measured relative to the exterior (denoted by Vm)
Do small influxes or effluxes of ions greatly shift the electrical potential of the membrane without greatly shifting intra or extracellular ionic concentrations?
yes
Raising K outside does what to the polarization of the cell?
depolarizes
Reducing K+ outside the cell does what to the polarization of the cell?
hyperpolarizes
Examples of Active Ionic Transport
- ATPases —> Ca2+ ATPase
- H+ ATPase
- Na/K ATPase
Symport
Transport proteins use the gradient of one ion or molecule for energy to transfer another molecule in the same direction
what factors affect the membrane potential?
- Type and number of open ion channels
- Amount of current passing through open channels
- Time spend in an open state
How is the probability of channel opening (Po) calculated?
as a proportion of the time the channel spends in an open state to the total time of observation
How can channels that are usually closed in the resting state be gated to open more frequently?
by changes of membrane potential acting on the voltage sensors or by binding of neurotransmitters or second messengers
The total membrane conductance (flow of charged ions) for an ion X will depend on what?
the number of open channels for X.
