Resting Potential & Action Potential Flashcards
define
ion channel
an opening (pore) formed by 4-6 membrane spanning protein molecules embedded in cell membrane
the diameter of an ion channel determines ____
ion selectivity
what is gating?
the property of ion channels to open & close depending on changes in cell membrane
functional states of ion channels
- closed & activatable (at rest)
- open (active)
- closed & non-activatable (refractory, inactive)
types of gated ion channels
- ligand (chemical transmitor)
- phosphorylation
- voltage
- mechanically
resting membrane potential is determined by ____
non-gated ion channels (always open)
what is the typical RMP?
-70mV (-40 to -90mV)
depolarization
mV
> -70mV (more positive)
hyperpolarization
mV
< -70mV (more negative)
what channels are active at RMP?
- leak channels
- Na/K pump
describe the actions of ion channels during RMP
- more K non-gated channels than Na channels (K leaks out, some Na leaks in)
- Na/K pumps 3Na out, 2 K in
- creates more negative inside
ion distribution in motor neuron at rest
- ECF: Na+, Cl-
- ICF: K+, organic anions (-)
define
equilibrium potential
what would happen if each ion was able to move in or out of cell in absence of the others
equilibrium potential: Na+
+55mV
Na+ would enter
equilibrium potential: K+
-75mV
K+ would exit
equilibrium potential: Cl-
-60mV
Cl- would enter
permeability is determined by ____
number of non-gated ion channels present in the membrane
the permeability of (Na/K) is higher than (Na/K)
K>Na
the concentration gradient is maintained by the ____
Na/K pump
the Na/K pump sends ____ Na+ out and ____K+ in
3Na out, 2K in
why is RMP closer to the equilibrium of K?
- more K goes out, some Na goes in
- closer to K equilibrium of -75mV
the Na/K pump moves ions ____ their concentration gradient
against
