Test 2 Flashcards
Two things that dictate membrane potential
of channels per ion; # of ions
Resistance
a channel is an impedance to an ion
Membrane Capacitance
membrane stores a charge because the ions cannot pass through
Internal Axial Resistance
as the amplitude spreads along the surface it decreases; why there is a graded potential; leak channels decrease the effect as time goes on
why does the membrane capacitance take the form of a inverse exponent curve?
kind of clogs the channels up
lambda gives?
how far from a stimulus site will a Vm be detectable
soma
contains nucleus, mitochondria, ER
dendrites
branch extensively; receive signals from other neurons
axon
transmits singals to other neurons
transport molecule
have central pores that open to 1 side of membrane at a time; undergoes comformational changes; SLOW
ion channnels
increase the permeability of the PM to ions; opne to both sides of the membrane at a time; FAST
neuroglia
provide supportive scaffolding for neurons; some produce chemicals that guide neuron connection; other insulate neuron processes
neurons
excitable nerve cells; transmit electrical signals
axon terminal
secretory region of neurotransmitters
Why do nerve cells need to be maintained?
many diseases use retrograde transport to cause neuron malfunction
depolarization
inside of cell becomes +
hyperpolarization
inside of cell becomes more -
repolarization
inside of cell back to -70mV
EPSP
depolarization
IPSP
hyperpolarization
Why do graded potentials decrease with distance?
leak channels
ion channels for graded potential
Cl- Na+ K+ (less frequent)
why are graded potentials bidirectional?
the local currents that are created depolarize adjacent membrane areas and allow the wave of depolarization to spread
Depolarization Phase
voltage gated Na+ channels open to allow in
Repolarization Phase
Na+ channels close and K+ open to allow in
Hyperpolarization Phase
K+ channels close and leak channels bring the cell back to -70mV
Absolute Refractory Period
second AP cannot be generated; Na+gates are inactivated
Relative Refractory Period
second action potential can be generated with a stronger stimulus; some Na+ gates closed, some inactivated
consequences of refractory period
all-or-none principle; frequency coding; unidirectional propagation
threshold
minimum depolarization necessary to induce the regenerative mechanism for the opening of Na+ channels
