Electrophysiology of Neurons Flashcards
electrical potential is the difference in the
concentration of charged particles between one point and another
electrical potential is a form of potential energy that can
produce a current
does resting membrane potential have the same charge across the plasma membrane?
no it varies
how much potential does resting membrane potential have?
much less than a flashlight battery
an electrical current is a flow of
charged particles from one point to another
sodium ions generate a current in the body from the
flow of ions with potassium through gated channels in the plasma
gated membrane channels can be opened and closed by what?
various stimuli
from the gated membrane channels being opened and closed this allows what?
cells to turn electrical currents on and off
ligand-gated ion channels can open when what binds to the receptor?
the appropriate chemical (neurotransmitter)
voltage-gated ion channels open and close in response to what?
changes in the membrane potential
stimulation of a neuron causes what?
local disturbances in membrance potential
local potential is what kind of change in voltage?
short-range
four characteristics what distinguish a local potential
graded
decremental
reversible
excitatory
graded varies in
magnitude according to the strength of the stimulus
decremental gets weaker
as they spread from the point of origin
reversible if the stimulation
ceases
diffusion out of the cell quickly returns the membrane voltage to its resting potential
reversible
excitatory
polarize a cell and make a neuron more likely to produce an action potential
step one of action potential
arrival of local potentials at axon hillock depolarizes membrane
step two of action potential
depolarization must reach threshold
critical voltage required to open voltage-regulated gates
step three of action potential
Voltage-gated Na+ channels open, Na+ enters and depolarizes cell
Opens more channels resulting in rapid positive feedback cycle as voltage rises
in step three an action potential
is produced
step four of action potential
Na+ channels are inactivated and close
Voltage peaks
Membrane polarity is reversed
step 5 of action potential
Slower-voltage gated K+ channels open
Outflow of K+ repolarizes cell
step 6 of action potential
K+ channels remain open for a time
Membrane briefly hyperpolarized
More negative than RMP
step 7 of action potential
RMP restored as all voltage-gated channels go back to closed states
Na+ leaks into cell
K+ leaks out of cell
Sodium-potassium pump keeps working
in the all-or-none law action potential will occur when a
stimulus reaches the threshold
in an all-or-none law, if a stimulus depolarizes the neuron to threshold,
the neuron fires at its mox voltage
with distance, nondecremental
do not get weaker
in a nondecremental, the last action potential at the end of a nerve fiber is
just as strong as the first one in the trigger zone
in irreversible, if a neuron reaches threshold, the action potential
goes to completion
irreversible cannot be stopped
once it begins
refractory period is a period of time after a nerve or muscle cell
has not responded to a stimulus in which is cannot be re excited by a threshold stimulus
in an absolute refractory period no stimulus of any strength
will trigger a new potential
in a relative refractory period is it possible to
trigger a new action potential, but only with an strong stimulus
if an axon is unmyelinated
continuous conduction
continuous conduction is the uninterrupted
wave of electrical excitation all along the fiber
in myelinated axons, an action potential at one node of ranvier causes
an action potential in the next node
myelinated axons perform
saltatory conduction
saltatory conduction creates
jumping or leaping
saltatory conduction cannot conduct a signal in continuous mode because
voltage-gated ion channels are too scarce in the myelin-covered internodal segments
myelinated axons are ____________ than unmyelinated axons
much faster
