action potential Flashcards
physiology behind unique characterisics of nervous system
- rapid and specific propagation of signa
- integration, computation
- adaptation
what are neurons named based off of
- shape
- anatomical feature (where in body)
- neurotransmitter
- function
input zone of neurons
dendrites
integration zone of neurons
cell body
point of action potential initiation
axon hillock (trigger zone)
conducting zone
axon
output zone
axon terminal
sensory and motor neuron length
excede a meter
resting membrane potential
-50 to -70
megnitude of membrane potential
depends on degree of sepeartion of opposite charges
less potential- depolarized (less neg inside)
more potential- hyperpolarized (more neg inside)
molecules that can go thorugh the lipid bilayer
hydrophobic molecule- o2, co2, steroid
small (uncharged polar)- h20, glycerol, ethanol
molecules that can go thorugh the lipid bilayer
hydrophobic molecule- o2, co2, steroid
small (uncharged polar)- h20, glycerol, ethanols
is the lipid bilayer a good insulator
yes
what occurs during depolarization
Na and Ca into cell
what occurs during hyperplarization
K out and Cl in
what forms water filled pores
ion channels
what are the conducting and non conducting states of ion channels change called
gating
what do channel gates respond to
changes in membrane potential
ligand binding
mechanical forces
what ion channels are present in the cell body and dendrites and function
various not just na and k
synaptic potential and intrinsic excitability
are ion channels evenly distribbuted in a neuron
no
how does the sodlum gated cahnnel work
there is an activation gate and an incativation gate. the activation gate is closed at first and at threshold it opens rapidly and lets na in. then slow closing of inactivation gate happens and the state is inactivated and then it becomes closed state when the activation gate closes again. inactivated channels cannot reopen. fast activating and fast inactivating
how does the potassium gated channel work
it has a closed and activated state and the openng at the threshold is delayed not rapid like sodium channel. its persistant
threshold
start of action potential, point of no return
what underlies the all or none nature of action potential
the fact that once threshold is reached, the positive feedback of Na channels activation begins and cannot be stopped (point of no return)
what leads to potential reaching 0 mv
explosive depolarixation
what happens when the action potentail reaches its peak
na inactivation gate begins to close and k gate opens
what does membrane repolarixation lead to
na and k channels to return to closed state. both are available to open at next stimulation
what does afterhyperpolarixation (ahp) do
makes it harder to elicit an action potential because the membrane is more hyperpolarized
what is afterhyperpolarization
the little extra dip in membrane potential
strong vs weak signals in all or none
high frequency
different patterns in neuron firing
various ion channles that can induce various firing patterns
how do action potential s not wane in size as potential propogates down the azon
bc it is regenerative
what does the refractory period cause
prevents backward propagation of AP and limits action potential frequency
conduction velocity is defined by
axon diameter
dnesity of na channels
myelin insulation
distance between the nodes of ranvier
saltatory conduction
the jumping of action potentials from one node of ranvier to the next due to myelination of axon
what provides myelin
glial cells
glial cells in CNS and PNS
CNS- oligodendrocyte
PNS- schwann cell
what does myelin consist of
tightly wrapped cell membrane
myelin purpose
lessens the amount of leak across the membrane. myelin does NOT conduct current
chronic pain axon type
unmyelinated thin axon
Aa nerve fibre
proprioception (awareness of movement of body)
contraction of skeletal muscle (ALPHA MOTOR NEURON)
AB nerve fibre
touch
Ag nerve fibre
acute pain (sudden and sharp)
C nerve fibre
chronic or dull pain, temperature, itch
role of nodes of ranvier
regeneration and propagation of action potential
rise and decay
rise- influx of na
decay- k efflux
where is the highest density of na channels
axon hillock
