Neurons, Synapses, Signaling Flashcards
What did Luigi Galvini discover
the role of electricity in nerves by observing frog muscle, proposed the theory of animal electricity
what did Galvani conclude from his frog experiments
in an animal there is a particular machine capable of generating disequilibrium = animal electricity
What is a membrane potential
the voltage across a cells plasma membrane
when does the resting potential occur
when the neuron is not sending signals
how to neurons transmit information
via changes in membrane potential = action potentials
what ion channels are open at rest
K+
when is a cell at equilibrium/equilibrium potential
when both electrical and chemical forces are balanced
which way does K+ diffuse
out of cell down the concentration gradient
where do negative charges build up
along the inner membrane, creating an opposing electrical force
how are ions located in neurons
neurons maintain a certain concentration gradient across their membranes which is different for each ion
What does Na+/K+ ATPase do
maintain resting membrane potentials by maintaining na and k gradient by pumping 3 na+ out and 2 k+ in
how much energy does Na/K ATPase use
20-30% of body’s resting enrgy, 60% of brains neuronal ATP
What drug targets ATPase
Digoxin and Oubain blocks it
How can you find the equilibrium potential
by knowing the concentrations of an ion (like K) inside and outside the cell
What is depolarization
when the cell is more positive than resting potential
which way does K flow during depolarization
out of the cell
which way does K flow at equilibrium
equal rates in and out
what is hyperpolarization
when the cell is more negative than resting potential
where does K flow during hyperpolarization
into the cell
what causes the membrane potential to change
flow of ions
do ions have their own equilibrium potential
yes
what functions as a resistor
ion channels, slow current
what acts as a capacitor
phospholipid cell membranes, store charge, once saturated then allows current to flow
what do the resistor and capacitor result in
neurons respond with a delay
what are graded potentials
changes in polarization where the magnitude of the change varies with the strength of the stimulus
can graded signals be propagated through great distances
no
what needs to happen to generate an action potential
depolarization above a certain threshold resulting in a massive change in membrane voltage
what are three characteristics of APs
constant magnitude
all or none
may transmit over longer distances
why do APs arise
because some ion channels are voltage gated, opening or closing when the membrane potential passes distinct levels
what structure receive signals
dendrites
what happens to signals after they are received
graded and funneled to stoma (cell bodY)
where does the stoma extend into
cone-shaped axon hillock
what is the function of the axon hillock
site of AP generation
what is the axon
a longer extension that transmits APs
What occurs in the resting state
Na and K channels are closed
What occurs during slow depolarization
slowly brought to threshold
what occurs during depolarization
Na channels activated, Na flows into the cell, positive feedback loop ensures a rapid rising phase of the action potential
what occurs once the AP peaks, during repolarization
Na channels close, slower K channels open, K flows out of the cell leading to the falling phase
what occurs at hyperpolarization
cell goes to Ek, Na channels are reset, Na is pumped out and K pumped into neuron, K channels close
what happens during refractory period
time it takes to return to resting potential, second AP cannot be generated
how are APs conducted
an electrical current spreads and depolarizes neighbouring region of the axon membrane, causing cycle to repeat
how is the AP prevented from travelling backwards
Na channels are inactivation behind the zone of depolarization
What direction do APs travel
toward synaptic terminals
where might APs back propogate
to stoma/dendrites
how does the axon diameter affect the speed of the AP
increased diameter = increased speed
what is the myelin sheaths function
insulates vertebrate axons, speeding up the AP
what are myelin sheaths made of
glia in CNS, schwann cells in PNS
where are APs formed in myelinated neurons
nodes of ranvier = gaps in sheath where Na channels are found
what is saltatory conduction
APs jump between nodes of Ranvier
