Bioelectricity Flashcards
2 main cations that create bioelectricity of a neuron
Na+ and K+
how is membrane potential created
- high Na+ conc (135-145mM) and low K+ conc (3.5-5mM) outside cell and low Na+ conc (12mM) and high K+ conc (150mM) inside cell created charge difference between two sides of membrane
typical RMP for living neurons
-70mV
ion channels at RMP
most Na+ channels are closed; Some K+ channels are open
how is RMP maintained?
Na+/K+ pump (ATPase) shifts 3 Na+ out and 2 K+ in
ion channels
large proteins that form within the lipid bilayer to enable charge movement. highly selective
changes in membrane potential
resting, depolarised, repolarised/hyperpolarised
ion channels at depolarised RMP
Na+ channels open, Positive charges move IN, depolarised (less negative)
ion channels at repolarised RMP
K+ channels open, Positive charges move OUT, charge moves towards RMP
ion channels at hyperpolarised RMP
K+ channels open, Positive charges move OUT, charge moves past RMP
threshold potential
-59mV, minimum local potential that triggers an action potential, cell is depolarised
action potential
+30mV, temporary maximum depolarisation propagates along the axon without losing amplitude, cell is depolarised then repolarised
steps of action potential propagation
- stimulus triggers stimulus-gated Na+ channels to open and allow inward Na+ diffusion. This causes the membrane to depolarise
- as the threshold potential is reached, voltage-gated Na+ channels open
- as more Na+ enters the cell through voltage-gated Na+ channels, the membrane depolarises even further
- the magnitude of the AP peaks at +30mV when voltage-gated Na+ channels close
- repolarisation begins when voltage-gated K+ channels open, alloowing outward diffusion of K+
- after a brief period of hyperpolarisation, the resting potential is restored by the Na+/K+ pump and the return of ion channels to their resting state
conduction of AP down axons
relies on spread of depolarising electrical signal along the axon to activate the next set of voltage-gated Na+ channels
refractory period
time during which another AP cannot be passed down the same nerve, affects frequency of APs