5. Physiology of excitable tissues. Ligand/voltage gated channels, transmembrane/resting potential Flashcards
What are excitable tissues
Muscle and nerve tissue due to their partly electrical response to external stimuli
Excitable cells use electrical signals (fast
changes in ion permeability and membrane
potential) to encode, process and transmit
information.
What is an excitable membrane (DEF)
They are membranes that react to stimuli with selective change in their ionic permeability
What is a diffusion potential - mV
( Potential difference)
Caused by the diffucsion of ions
Created when a charged solute diffuses down its concentration gradient
ONLY CREATED IF MEMBRANE PERMEABLE TO THAT ION
Created by movement of only a FEW ions
What is equilibrium potential of a particular ion
- Net flow through a membrane for a fiven ion is equal to zero
- When the flow of ions moving along conc grad, equalizes w flow of ions moving along electrochemical gradient
The equilibrium potential is the diffusion potential that exactly balances or opposes the tendency for diffusion down the concentration difference
What happens at electrochemical equilibrium
The chemical and electrical driving forces
acting on an ion are equal and opposite, and no further net diffusion occurs.
How is membrane potential created?
Potential difference between 2 sides of the cell membrane
This is caused by diffusion of ions Na+/K+ pump
What is important in determining membrane potential
permeability of an ion
What equation do you use to calculate equilibrium potential
NERNST
Eion = RT/zF . ln (ion ex)/(ion int)
What equation do you use to calculate membrane potential
GOLMDMANS
bit long to type but includes permeability
What is the electogenic effect of Na+/K+ pump
exports 3 Na+
imports 2K+
For charged solutes, the driving force must consider the conc differecne and electical potential difference
How is driving force calculated
Difference btw the membrane potential and the ions calculated eqm potential
- When the driving force is negative (i.e., Em is more negative than the ion’s equilibrium potential), that ion will enter the cell if it is a cation and will leave the cell if it is an anion.
What is a electrochemical gradient
baso driving force
Difference btw electochemical potentials of ion on both sides of membrane
What causes membrane potential to change
slective change of ionic permeability
when pump activity chnages
proportional changes in conc gradient
What is the result if the electrochemical gradient of an ion has negative value
ion flow will be directed inwards the cells
What ion flow will be larger when
non-selective Na+- К+ channels in
a postsynaptic membrane open?
Na+ flow larger therefore mem will depolarize
BC 5.4 times more sodium will enter the cell than k+ will leave
