Quiz 5 Flashcards
Graded potentials
passive (electrotonic)
degrade with distance and time
variable amplitude/duration
positive or negative sign
sub-threshold: no AP
can summate to reach threshold
Action Potentials
Active
no decrement with distance (maintains same amplitude)
All-or-none: fixed duration
Supra-threshold
cannot summate
Common features between graded and action potentials
voltage changes in membrane
propagate down neuron- process: axon/dendrite
transient events
axon terminal
output structure of one neuron
dendrite
input structure of another neuron
ligand-gated ion channel=
iontropic channel
depolarization
membrane more positive to rest (Excitatory Post Synaptic Potential- EPSP)
increases likelihood of firing an AP
Na could yield EPSP
hyperpolarization
membrane more negative to rest (inhibitory post synaptic potential- IPSP)
moves further from firing an AP
K/Cl could yield IPSP
If neurotransmitter opens a receptor and increases Na permeability, then…
NA flows in, Vm would become more positive, towards Ena
If neurotransmitter opens a receptor and increases K permeability, then…
K flows out, Vm becomes more negative, toward Ek
Passive
decreases in strength as they spread away from point of origin
Graded potentials are passive…
they decrease in amplitude with distance and time
Temporal Summation
summation over short time, getting us to threshold for an AP
Spatial Summation
2+ roughly simultaneous PSPs from different locations sum up across space
ligand
something that can bind
Voltage Na channels open ___ in response to depolarization, causing
fast
Na+ ions to rapidly flow in
K channels open ____ in response to depolarization, causing
slow
K ions to flow out
activation
opening of a channel
depolarization to open, hyperpolarization to close
De-activation
closing of a channel
Inactivated
open channel but it is blocked
Na+ channels are blocked
potentials must be slightly depolarized
blocking needs time (delayed)
nothing can flow through when blocked
Step 1 of AP
resting membrane potential
Step 2 of AP
depolarizing stimulus
Step 3 of AP
membrane depolarizes to threshold; NA channels open fast and K channels open slow
Step 4 of AP
rapid Na entry depolarizes cell
Step 5 of AP
Na channels block and K channels open
Step 6 of AP
K flows out of cell into ECM
Step 7 of AP
K channels remain open, addition K ions leave cell, hyperpolarizing the cell, Na channels close
Step 8 of AP
K channels close, less K ions leak out of cell
Step 9 of AP
Cell returns to resting ion and membrane permeability
Na opening of Na channels is ____ feedback and is stopped by _____
positive
blocking
threshold
state of being where one channel type behavior outstrips the other
Na permeability briefly outstrips K permeability
refractory period
unwilling/unable to fire action potential
because Na channels are blocked
Myelination
provides insulation with little gaps (nodes) and isolation from other axons
Na/K channels are located in ___ and not under ____ this allows for____
nodes
myelin
saltatory conduction
saltatory conduction
potential jumps from node to node, allowing quicker propagation
propagation
local current flow
Synapse
point of connection between two neurons
basic mechanism of communication between neurons or to effector
Electrical synapse
result of gap junctions
bi-directional signaling
direct electrical coupling
second cell mirrors first cell
Chemical synapse
synaptic cleft= gap between neurons
anterograde (forward direction)
signals pre to post-synaptic
axon terminal contains mitochondria, ER, and vesicles
vesicles loaded with NT that bind to membrane and release into synaptic cleft
