Action Potentials + Electrolyte imbalance Flashcards
when are the most voltage gated Na channels open?
at the height of depolarization
where in the AP is the K closest to equilibrium?
just passed the deepest point in hyperpolarization
neurons are _____ modulated, not ____ modulated
frequency
amplitude (height always the same, just the amount it fires changes)
go over the membrane potential chart
!!!
why do neurons use a lot of ATP?
because of the NA/K ATPase channels that require energy
A somatogram with lines very close and equally spaced is showing:
firing potential slowly adapting
no adaptation
(tonic pain receptors, big pain stimulus)
A neuron with stimulus but no AP means?
the neuron adapted
what does the somatogram of a adapted neuron look like?
fire fire fire, break, fire fire fire
what is a neuron that just keeps firing at a continuous rate called?
tonic
what are equilibrium potentials?
depending of the charge of the ion tells you its directionality
what is ohms law?
calculates relationship between current, resistance and voltage in a circuit
what is the equation for ohms law?
V=I*R
what is conductance?
ability of a material to carry current (inversely proportional to resistance)
what ensures the AP goes in a unidirectional manner?
propagation of AP by local NA current
what determines conduction velocity?
length constant (lambda) divided by the time constant (tau)
what is the time constant?
the amount of time it takes following injection of current or the potential to change to 63% of its final value
(how quickly the cell membrane can depolarize in response tot an inward current or how quickly it can hyperpolarize in response to outward current)
what is the equation for the time constant?
T=RC
(time=resistancecapacitance)
what happens if membrane resistance or capitance is high?
time increases
this means it will take longer for cell to de/hyperpolarize (if take longer to depolarize then conduction velocity will decrease)
what is the length constant?
distance from the site of current injection where the potential has fallen by 63%
(indicates how far along a depolarizing current will spread down the axon)
what kind of axons have lower internal resistance?
bigger ones
what does low time constant high length constant cause?
nerve with high conduction velocity
what are the two mechanisms that increase conduction velocity?
increasing diameter of nerve
myelinating the nerve
why does myelination increase conduction velocity?
increase resistance, decreases the membrane capacitance, decreasing the time constant
what effect do nodes of ranvier have on conduction?
cause saltatory conduction (jumping of AP across the non-mylinated portions)