3A Resting Membrane And Action Potentials (Electrophysiology I) Flashcards
Must exist across membranes of cells for the signals to be sent to any cells
electrical potential
electrical potential difference between the intracellular and extracellular fluid
membrane potential
electrochemical state of the cell at rest; no net movement of any ions across the cells
resting membrane potential (rmp)
rapid changes in the membrane potential that spread rapidly along the nerve fiber membrane
action potential
RMP of a large nerve fiber
-90mV
formation of RMP depends on:
- concentration gradient or concentration difference of an ion
- permeability of the ion across the cell membrane
main workforce responsible for establishing concentration gradients of K and Na
sodium potassium pump
concentration of Na and K intracellularly
Na = 10mEq/L K = 140mEq/L
concentration of Na and K extracellularly
Na = 142mEq/L K = 4mEq/L
K moves out of the cell to equalize the concentration and diffuses extracellularly through what channel?
potassium leak channel
moving out of K out of the cell causes the cytoplasm of the cell to be
electronegative since anions( negatively charged) the only ions left
exact point where the K moving out of the cell due to concentration gradient, equals the K moving back into the cell because of the electrical gradient
Equilibrium or Nernst Potential
electrical potential needed to attract K back into the cell to balance the concentration gradient
-94mV
used to calculate the diffusion potential when the membrane is permeable to SEVERAL DIFFERENT IONS
goldman equation
Keeps cells in “ready state” to fire an action potential
resting membrane potential
threshold potential
-55mV
channel that causes both depolarization and repolarization
voltage gated sodium channels
2 gates of voltage gated SODIUM channels
- activation gate - near the outside
* inactivation gate - near the inside
channel that increases rapidity of repolarization
voltage gated potassium channel
T/F: it is usually not possible without first repolarizing the nerve fiber in order for Na channels to open again
TRUE
Stages of Voltage gated Sodium Channels
- Resting stage -90mV
- Activation stage -90mV to +35mV
- Inactivation stage +35 to -90mV
Stages of Voltage gated potassium channels
- Resting stage
2. Slow Activation
period when voltaged gated sodium channel closes and the voltage gated potassium channels open
repolarization stage
stage wherein reestablishes the normal negative resting membrane potential
repolarization stage
excess exit of potassium which leads to the potential being more negative than the RMP
hyperpolarization
this is where the RELATIVE REFRACTORY PERIOD occurs, membrane potential returns to RMP throught the normal action of N/K pump
RECOVERY
stage wherein absolute refractory period occurs
repolarization
this is where the membrane returns to its Resting membrane potential
repolarization
the transmission of the depolarization process along the nerve or muscle fiber
impulse
recite the PROPAGATION OF ACTION POTENTIAL
clue: 1st step-VGNC opens
VGNC opens –> positive charges move through the nerve –> positive feedback occurs –> VGNC’s adjacent areas open –> propagation of the action potential –> VGKC opens slowly –> repolarization –> return to RMP
principle in which the voltage must be high or equal to that of the threshold potential in order for an action potential to occur
ALL OR NOTHING PRINCIPLE
where a stimulation does not generate enough voltage to stimulate the NEXT AREA OF THE MEMBRANE
subthreshold potential
the spread of the depolarization stops at this point
subthreshold potential
this begins at the upstroke until the end of the downstroke of the action potential or repolarization
ABSOLUTE REFRACTORY PERIOD
voltage gated sodium channels are inactivated at this point and no amount of stimulus will activate it
absolute refractory period
action potential cannot be elicited at his time regardless of the stimulus strength
absolute refractory period
an action potential can be elicited at this period but stimulus should be greater than the threshold potential
RELATIVE REFRACTORY PERIOD
also known as CONTINUOUS CONDUCTION
non-saltatory conduction (applies the all or nothing principle)
slower conduction velocity
non-saltatory period
faster conduction velocity
saltatory period
conduction that involves activation of adjacent voltage-gated sodium channels
non-saltatory conduction
conduction that increases velocity of nerve transmission in myelinated fibers as much as 5- to 50- fold
saltatory conduction
electrical insulator absent –> charges leak out –> decrease in voltage –>adjacent channels not stimulated –> action potential stops
non-saltatory conduction
action potential goes through fewer voltage-gated Na channels –> faster transmission of impulse + energy conserved –> subsequent activation of succeeding nodes
saltatory conduction
this membrane potential change is responsible for the start of an action potential
threshold potential
T/F: resting membrane potential is solely dependent on the equilibrium potential of potassium
false
T/F: during hyperpolarization, a cell cannot be stimulated to form an action potential
false
