NAS L1&L3 Flashcards
What is an electrical signal?
Change in balance of positive and negative charges
How is an electrical signal generated?
By transfer of ions through ion channels
Conc of K+ in and out of cell?
Inside: 100 high
Outside: 5 low
Conc of Na+ in and out of cell?
Inside: 15 low
Outside: 150 high
Conc of Ca2+ in and out of cell?
Inside: 0.0002 low
Outside: 2 high
Conc of Cl- in and out of cell?
Inside: 13 low
Outside: 150 high
What maintains ionic gradients?
Na+/K+ pump. Exchanges Na+ from inside out and K+ from outside in, against conc gradients. Ca2+ pump transports Ca2+ out of cell. These pumps operate in the background continuously, over long time periods. Constant K+ efflux will lead to significant change in conc. PUMPS MAINTAIN CONCS OVER LONG TERMS NOT FOR CONTROLLING Em.
What is resting membrane potential?
Voltage inside a cell.
What is the RMP for neurons?
-65mV
What determines RMP?
Leak channels, ion movement is passive. Non-gated (leak) - set Em for resting membrane.
There is an excess of negative charge inside.
How does RMP remain stable?
By the movement of ions across the membrane.
At RMP how much Na influx and how much K efflux?
Na influx = K efflux
What factors influence movement of the ions?
Chemical gradient = unequal ion distribution and electrical force = if attracted/repelled by voltage inside cell.
When electrical and chemical influence balance there is no net movement of ions.
What controls ion movement across a resting membrane?
Present of ion channels.
Non-gated: K, Na channels
Therefore membrane has permeability to each ion. Permeability is in part dependent on number of channels for that ion.
Nernst - equilibrium potential of an ion…
the voltage at which equilibrium of ions takes place depends on permeability and conc gradient.