Resting, Action Potential, Synaptic Transmission X Flashcards
Absolute Refractory Period
All Na+ channels inactivated until after membrane potential back to resting
Relative REfractory Period
During hyperpolarization when still closing K+ cells make I difficult but not impossible to have action potential
Depolarizing after-potential - what, why
B/C K+ slowly diffusing out of T-Tubles in skeletal muscle
Factors the modify threshold potential
K & Cl permeability - inhibitory
# Na+ Channels i.e. local anesthetics
Rate of depolarization ( if too slow, inactivation gates have time to close before AP fired)
Charge movement
Current
See other slide
Factors that increase rate of action potential propagation
inc. Cell diameter (most significant)
inc. Resisting membrane resistance
inc. # of Na+ channels present
presence of myelin
dec. Capacitance
inc. length constant
Saltatory Conduction
Discontunous - jumping from on node to another
Ability of tissues in the heart to allows actiona potentials to propagate in wrong direction can cause…
cardiac arrhytmias
Effect of Charge movement and Current on action potential
charge movement - positive into cell & current - negative/inward = positive or less negative threshold
OPPOSITE TRUE TOO
charge movement positive into cell & current - positive/outward = negative of less positive threshold
OPPOSITE TRUE TOO
EPP larger than ESPS b/c
EPP can reach voltage that exceeds amount to produce action potential in muscle while ESPS are small and need many to have effect. THEREFORE you can have an action as soon as you want it.
Neuropeptides - a.k.a, fxn
Neuromodulators
From dense core visicles.
Act pre or post synaptically
longlastin, complex effects
Temporal v Spatial summation
S - Many inputs at same time in different locations, meet up elsewhere and combine or cancel out
T - many inputs fired in rapid succesion - larger postsynaptic response
End plate potential - def
membrane potential developed in post-synaptic muscle fiber
Structure of gap junction
One synapse per fiiner, although a single motoneuron may innervate up to 2000 muschle fibers
Events leading to transmission at chemical synapse
AP reaches
Ca2= enters. Synap[tic vesicles fuse to presynaptic membrane.
Contents(transmitters) released.
Transmitters bind to post synaptic membrane receptors
directly coupled channels open, causing AP or Inhibition on muscle
Desensitization - explain
If ACh remains bound to ACh receptors for prolonged time, those channels will close (desensitize). This is prevented by use of enzyme, acetylcholine-esterase.
