Lecture 3 - Electrophysiology of the Cell Membrane Flashcards
what is a chemical/concentration gradient?
the energy provided by the difference in concentration moving from a high concentration to a low concentration across a plasma membrane
what is an electrochemical gradient?
the energy associated with moving charged molecules across the membrane when a membrane potential exists (Na+, K+ and CI-)
what is the concentration of Na+ outside the cell?
high
what is the concentration of K+ outside the cell?
low
what is the concentration of Na+ inside the cell?
low
what is the concentration of K+ inside the cell?
high
what is the concentration of Cl- outside the cell?
high
what is the concentration of CI- inside the cell?
low
what is the number for resting membrane potential?
-70mV
what does the Z represent in nersts equation?
valence charge
e.g Na+ will have valence charge of +1
what is the potential difference across the cell membrane generated by?
principally generated by the Na+/K+ATPase
what does the Na+/K+ATPase pump in and out?
pumps out 3Na+ for every 2K+ in
what is the relationship between resting membrane potential and equilibrium potential?
RMP is largely an outward K+ mediated equilibrium potential modified by a much smaller inward equilibrium potential for Na+ ions
how is resting membrane potential maintained?
K+ and Na+ are moved against their concentration gradient by energy from ATP
what is the relationship between resting membrane potential and ATP?
ATP sets up the RMP for every cell but this can be changed by the use of other ions or the opening/closing of channels
what is hyperpolarisation?
the change in membrane potential to become more negative
what is depolarisation?
the change in membrane potential to become less negative (more positive)
what is repolarisation?
the change in membrane potential to return back to resting membrane potential (more negative)
what is a local potential?
passive change in membrane potential that is caused by the flow of current across the membrane by small local ion fluxes (channel openings) that occurs when synapses are active
-can depolarise and hyperpolarise
what is the relationship between local potentials and RMP?
local potential can change without changing RMP as the movement of a few ions is localised to only a small area at any given time
what is passive/local potential decay?
local potentials decay from the point of origin (Vo) along the length constant
what is the relationship between local potentials and time summation?
local potentials summate in time as temporal summation and spatial summation
what is length constant?
the distance the voltage decays to 37% of its original size or Vo
what is an action potential?
actively propagated depolarization that spreads from the point of origin and typically down the axon to the axon terminal to trigger communication with the next neuron in the sequence
what does it mean that an AP is an all or nothing response?
AP must meet the threshold (usually 10mV depolarised from RMP) to generate an AP, if the threshold is not met then no AP will be propagated
is an AP regenerative?
yes as it is propagated without decreasing amplitude
what is the advantage of low axial resistance?
passes the current down the axon more easily
what is the disadvantage of a small axon?
results in a much quicker voltage decay because of intrinsic/physical factors of the internal resistance
