3: Resting and Action Potentials Flashcards
What ions have the most influence on plasma the membrane?
K+, Na+, Cl-
Leak channels
always open and work when cell is at rest
What ion has the most leak channels?
K+
Gated ion channels
open and close because of stimulus
Voltage gated ion channel
channels open or close due to voltage changes
Inactive state of voltage gated channels
forced rest, only some cells have
What ions are the most common voltage gated channels?
Na+, K+, Ca+2
Ligand gated ion channels
open due to a NT or hormone binding to receptor
Mechanoreceptors
respond to a mechanical stimulus (pressure, stretch)
Thermoreceptors
respond to temperature changes
Chemoreceptors
respond to chemical changes
Na+/K+ pump
pumps out 3 Na+ and pumps in 2 K+, creating a positive charge outside the cell
What ion have the most influence of RMP?
K+
Depolarization
change in membrane potential in the positive direction
Repolarization
return of the membrane potential toward RMP
Hyperpolarization
the membrane potential become more negative than RMP
Graded potentials
small local changes in membrane potential
What causes the decrease in magnitude over time of GPs?
electrotonic conduction
Excitatory postsynaptic potentials
GPs that bring the membrane potential closer to threshold and more likely to fire an AP
Inhibitory postsynaptic potentials
GPs that take the membrane potential away from threshold and make the cell less likely to fire an AP
End-plate potential
GPs in skeletal muscle cells caused by ACh binding onto poststynaptic membrane ion channels
Receptor potential
GPs in sensory receptor cells caused by mechanical or chemical stimuli from internal or external environment
Steps of AP
- At RMP, high Na+ outside cell and high K+ inside cell
- large enough GP causes Na+ channels to open and Na+ rushes inside cell, depolarizing cell to a more + voltage
- Na+ channels slowly close, K+ channels open and K+ rushes out of cell, repolarizing MP
- K+ continue to leave cell via leak and voltage gated channels and return to RMP once voltage gated K+ channels close
Refractory period
excitable cells cannot produce APs
Absolute refractory period
cannot generate AP no matter now large the stimulus
Relative refractory period
a stronger than threshold (suprathreshold) can generate an AP
Ionophore toxicity
make cell membrane permeable to ions, usually feed additives for cattle, nor suitable for horses
Channelopathies
genetic mutations altering ion channel function
