Fine, Ch. 2 Flashcards
resting membrane potential
x
receptor potential
x
pacinian corpuscles
x
synaptic potentials
x
hyperpolarization
x
passive electrical responses
x
depolarization
x
Threshold potential
x
action potential
x
active transporters
x
ion channels
x
electrochemical equilibrium
x
Best way to observe electrical signals in neurons is by
using an intracellular electrode
resting membrane potential is the
negative signal reads upon entering neuron
RMP typically -40 to -90 mV
typical resting membrane potential
-40 to -90 mV
change in resting membrane potential is a
receptor potential
receptor potentials are due to
activation of sensory neurons by external stimuli
XY are for communication between neurons at synaptic contacts
synaptic potentials
potentials that travel along the nerve axon
action potentials
action potentials are used for
LONG RANGE transmission of information
If the potential goes more negative it has
hyperpolarized
hyperpolarizations are xxx responses
passive electrical responses
membrane potential becomes more positive
depolarization
xxx must be met for Action Potential to occur
threshold potential
intensity of a stimulus is encoded by
frequency of APs
receptor potentials amplitude are graded by
magnitude of the stimulus
action potentials amplitude are graded by
they are not graded; the amplitude is of the same level independent of strength of stimulus, provided the threshold is met.
Synaptic potentials amplitude is graded by
number of synapses activated & previous synaptic activity
fundamental problem with neurons
axons are not good conductors
if current pulse is below threshold it will
decay as it moves away from the site of current injection as it leaks from axonal membrane
serve as a booster system to send info over long distances
action potentials at nodes of ranvier
xxx circumvent the leakiness of neurons
action potentials
neuronal signals rely upon
movement of ions across the membrane
cell membranes transmit electrical signals because they (2)
a. are selectively permeable B. differences in ion concentration across the membrane
ion concentration gradients are established by
active transporters (proteins)
selective permeability of membranes is due to
ion channels
ion channels and transporters work…
against each other to generate the various potentials
an electrical potential will be generated when K+
K+ is not the same on the two sides
difference in electrical potential across the membrane results from
potassium ions flow down their concentration gradient
resting membrane potential is maintained by
continual resting efflux of K+
electrochemical equilibrium is
an exact balance between a) concentration gradient of K+ from in > out, b) an opposing electrical gradient that prevents K+ moving across membrane
K+ stops flowing at
electrochemical equilibrium
tiny fluxes in ions do not disrupt chemical electroneutrality because
each ion has a counter-ion of opposite charge
in opposite compartments, Cl:Na is
equal
passive membrane decrement of current flow with distance formula
Vx = Vo e^-x / /\
Vx
voltage response at position x
Vo
voltage change at point where current is injected
e
base of natural logarithms
/\
length constant of the axon
length constant of the axon (/)
where initial voltage Vo decays to 1/e (37%) of its value
/\ length constant formula
(sqrt) (rm / ro + ri)
rm
relative resistance of plasma membrane
ri
relative resistance of intracellular axoplasm
ro
relative resistance of extracellular axoplasm
for optimal passive flow, rm should be x and ri and ro should be x
high; low; low
delays in change in membrane potential upon injection is due to
plasma membrane behaving as a capacitor, storing initial charge.
change in membrane potential at any time formula =
t = V(infinity)(1-e^-t/T)
V(infinity)
steady state value of membrane potential change
small t =
time after current pulse begins
big T
membrane time constant = time when Vt rises to 1-(1/e) or 63% of V(inf).
membrane time constant
time when Vt rises to 1-(1/e) or 63% of V(inf).
formula to calculate Potential decline after current pulse ends
Vt = V(inf) e^-t/T
Equilibrium potential -
potential generated across the membrane at electrochemical equilibrium
nernst equation predicts what
equilibrium potential
nernst equation formula
Ex = (RT/zF) In(Xout)/(Xin)
simplified nernst at room temp
Ex = 58/z log (Xout)/(Xin)
ex
equilibrium potential
R
GAS CONSTANT
T
absolute temp
Z
valence (charge) permeant ion
F
faraday constant (amount of electrical charge contained in one mole of univalent ion)
faraday constant
amount of electrical charge contained in one mole of univalent ion)
what does the nernst equation predict exactly
linear slope of 58 mV per tenfold change in the K+ gradient
K+ conc. higher inside =
negative inside
