Test 1 Flashcards
(45 cards)
Mem excitability
The ability of a cell to generate action potentials. Depends on the presence of specific types of voltage gated ion channels
Action potentials
Brief. Large changes in the electrical potential across the cell mem
Channelopathies
Diseases caused by ion channel dysfunction
Leak channels
Ion channels. Open in the testing unstimulated mem of the cell.
Principle of electro neutrality
Both ic and ec fluid. Total mEq for cations equals total mEq for anions in the ic fluid. And in the ec fluid. There is no charge separation across the cell mem, no resting mem pot exists
Mem polarization
Movement of ions down conc gradient resulting in net charge interior and exterior
Mem pot
Mem voltage. Requires unequal distribution of ions across cell mem and open ion channels in the resting mem of the cell
Equilibrium pot
Diffusion due to conc gradient is balanced by opp movement resulting from electrical pot
Nernst eqn
Ek=(RT/zF)ln[(K+)o/(K+)i]
Ek=61mVlog[(K+)o/(K+)i]
Goldman. Hodgkin. Katz. Eqn
Expanded versions of Nernst. Applicable to men with permeability to more than one ion. Vm=61mVlog[Pk(K+)o+Pna(Na+)o/Pk(K+)i+Pna(Na+)i]
Anions input opp due to -z
Electrochemical gradient
Sum of the electrical gradient (total mem charge distribution) and the chemical (conc) gradient for the ion
Hyper polarized
More negative. (Lowering Ko)
Depolarizer
Less negative. (Raising Ko)
Mem permeability (Pm)
How easily a substance can move through a mem
Mem ion permeability
How easily an ion can move through a member. Determined by the number of open ion channels
Mem conductance (gm)
How easily electric current flows through the cell mem. Units-Siemens (S). Electrical equivalent of permeability. Determined by the number of open channels in the cell mem. Gm=total number channels*single channel conductance
Mem resistance (Rm)
Logical and mathematical inverse of conductance. R=1/g. Units-ohms
Mem current (Im)
Rate of charge (ion) flow across the cell mem. Units-amperes,amps,A
Driving force.
Net electrochemical force acting on an ion. Mem pot-ion equilibrium pot. Vion change=Vm-Eion
Ohms Law
Current = driving force X conductance. V=IR
Postsynaptic pot
Change in postsynaptic ion permeability caused by releases neurotransmitter
Capacitance (Cm)
Cell mem capability to store electrical charge. Units-farads F. Directly related to SA of lipid bilateral of cell mem. Inversely proportional to mem thickness
Length constant
The distance over which deltaVm declines by approximately 63% from the original level. Square root of Rm/Ra
Axial R (Ra)
R to current flow down cylinder
