Chapter 12: Action Potentials Flashcards
How do the cells of nerve and muscle tissues communicate?
action potentials or graded potentials
action potentials or nerve impulses allow?
communication over short + long distances
graded potentials allow?
communication over short distances only
what is the resting membrane potential that action potentials rely on?
-70 mV
membrane potential
electrical voltage across the membrane
2 basic types of ion channels
leakage and gated
what are leakage channels open to?
more of which?
sodium and potassium
- more potassium than sodium
gated channels respond to?
a direct change in the membrane potential
ligand-gated channels respond to?
examples
a specific chemical stimulus
- ex: sodium, chlorine, calcium, potassium, mechanical pressures
mechanicaly-gated ion channels respond to?
mechanical vibration or pressure
What is the chemical permeability of a resting membrane?
the unequal distribution of potassium ions inside the cell membrane and sodium ions outside the cell membrane in the cell membrane in the ECF
potassium=inside
sodium=outside
typical value for the resting membrane potential?
-70 mV polarized
how id th resting membrane potential determined?
by the unequal distribution of ions across the plasma membrane + the selective permeability of the membrane to Na and K
potassium permeability is ___x more than sodium
100
action potential or impulse is a?
what occurs during action potential?
sequence of rapidly occurring events that decrease and eventually reverse the membrane potential (depolarization)
- then restore it to resting (repolarization)
- during action potential, voltage gated Na + K channels open in sequence
all or none principle
if a neuron reaches threshold, an action potential is always generated
what occurs during hyperpolarization?
b/c not all K gates closed, some remain open shortly
- dont close until resting membrane potential reaches -70 again
refractory period
when can action potential be generated again?
when membrane cant respond to 2nd stimulus
- neuron is unabe to generate another ation potential until original Na and K concentrations are reestablished (restored through Na, K pump)
- Na ions pumped against gradient, K ions pumped in
absolute refractory period
membrane cant respond to 2nd stimulus no matter how strong it is (1-2 ms)
relative refractory period
membrane can respond to 2nd stimulus if its stronger than the 1st
how do local anasthetics and certain neurotoxins (botox) affect the muscle
prevent opening of voltage-gated Na channels so nerve impulses cant pass the obstructed region + reach CNS
saltatory conduction in nerve fiber
myelinated segments of the nerve fiber remain electrically inactive and the impulse jumps from node to node as each area depolarizes
propagation speed of a nerve impulse is related fiber ____ and to _____, not _____
diameter, myelin sheath, stimulus strength
what fibers conduct nerve impulses at the fastest rate? how fast?
large, myelinated, type A, 250 mph or 100 mps
what fibers conduct the slowest nerve impulses?
small diameter, non myelinated, 1 mps
where can a neuron synapse?
cell body, dendrite, another axon
synapse interacts with?
functional interaction btwn 2 neurons or neuron + effector (muscle, gland)
presynaptic neuron transmits____ toward_____
impulse twds synapse
post synaptic neuron recieves ______ from ______
impulse from presynaptic neuron
synaptic cleft
space btwn pre and post synaptic neuron
