Lecture 3 Flashcards
an _____ _______ is generated by the glow of ions through voltae gated channels
action potential
t/f the nervous sustem expresses a rich variety of voltage gaed ion channels
true
t/f the opening of voltage gated ion channels is all or none
true
list the 4 phases of an action potential
rising phase, overshoot, falling phase, undershoot phase
t/f the rising and overshoot phase is potassium dependent
false , it is sodium dependent
t/f the rising and overshoot phase is sodium dependent
true
are sodium channels voltage gated
yes
define threshold potential
voltage at which many of the sodium channels start to open
does sodium move into or out of a cell during the rising and overshoot phase
it goes into the cell
during the rising and overshoot phase does hyperpolarization or depolarization occur
depolarization
is the falling and undershoot phase sodium or potassium dependent
potassium
a potassium channels voltage gated
yes
which opens and closes faster a sodium or potassium channel
sodium
during the falling phase is hyperpolarization or depolarization occuring
hyperpolarization
during which phases are sodium channels inactivated
falling and undershoot phase
can sodium channels pass current if they are inactivated
no
during the falling and undershoot phase if hyperpolarization or depolarization occuring
hyperpolarization
when a cell is returning to resting membrane potential what channels are closing
the potassium channels close
when na channels open and na rushes in this is an example of ______
depolarization
when k channels open , k rushes out this is an example of ______
hyperpolarization
when k channels close it shuts off the hyperpolarizing or depolarizing current?
hyperpolarizing
what did hodkin and huxley want to know
which ions gave rise to an action potential
what is the main point of a voltage current
it measures current at specific voltages
if you hold an axon at 0mv what 3 currents will you see
- very transient capacitative current
- fast transient current inward , rising phase
- delayed sustained current, outward part of the falling phase
what ion is responsible for the transient current
sodium
at the reversal potential is there any net movement of ions
no
what does the reversal potential equal
the diffusional force
what is the name of the chemical that is responsible for blocking sodium
tetrodotoxin (ttx)
t/f ttx block the ouward current
false, ttx only blocks the early inward current
the inward current is dependent on which ion
sodium
is the sustained current sodium dependent
no
the sustained current is dependent on which ion
potassium
what is the name of the potassium channel blocker
tetraethylammonium (tea)
does TEA block early inward currents
no , it only blocks late outward current
if you want to have no action potential which 2 chemicals would you use
tea and ttx
changing the resting potential to a value above threshold produces what 2 effects
- an early influz of sodium into the axon , followed by sodium rapidly coming into the cell.
- a delayed efflus of the potassium slowly leaving the cell
what cause a transient current
an early influz of sodium
what causes a sustained current
delayed efflux of potassium
ion membrane permiability changes with what
voltage
t/f as you hyperpolarize you get more conductance
false, as you depolarize you get more conductance
t/f an increase in sodium permiability inactivates after awhile
true
t/f t/f an increase in potassium permeability inactivates after awhile
false
t/f it is possible to get an action potential during an absoulte refractory period
false
is it possible to get an action potential during the relative refractory period
yes, but unlikely
why isnt it possible to have an action potential during the absolute refractory period
because sodium channels are inactive
during the closed state of a sodium channel is the core open or closed
closed
during the closed state of a sodium channel is the gate open or closed
open
during the inactivated state of a sodium channel is the core open or closed
open
during the inactivated state of a sodium channel is the gate open or closed
open
can current flow in the inactivated state
no
can current flow in the closed state
no
can the closed state of a sodium channel occur when the membrane potential is low
no
can the closed state of a sodium channel occur when the membrane potential is high
yes
when the membrane potential is high and the channel is still shut off what do we call this state
inactive state
t/f the sodium channel only lets in negative ions
false, the sodium channel only lets in postive ions
voltage sensors are composed of lots of positively charged ______ _______
amino acids
if a sodium channel goes from the pore being closed to open , is depolarization or hyperpolarization occuring
depolarization
if a sodium channel goes from the pore being open to closed , is depolarization or hyperpolarization occuring
hyperpolarization
where are action potentials generated
in the axon hillock
the highes expression of sodium channels is in the
axon hillock
what is the cable theory
if you simply inject current into a cable , the voltage will change locally, then die out as ions leak
do action potentials decay
no , they are actively regenerated
how are action potentials propegated
the action potential moves a short distance and triggers the opening of more sodium channels
are action potentials able to go backwards
no
why arent action potentials able to go backwards
because the sodium channels are inactivated
t/f action potentials are bi directional
false , they are unidirectional
what is myelin
an insulative material that prevents current (ions) from leaking out
where are sodium channels located
at the nodes of ranviwe
what does saltatory conduction enable
faster transmission of signals
what is saltatory conduction
action potentials jumping from one node to the next
does continuous conduction invovle an unmylenated axon
yes
t/f myelin is only found in vertebrates
true
name 2 places where mylenated axons are found
optic nerve and motor nerves
name a place where unmylenated axons are found
olfactory nerves
