Basis of Neuron / Action Potential Flashcards
Effects of myelin on size
smaller diameter but still efficient
What types of fibers are unmyelinated?
pain fibers (type C fibers)
myelin and capacitance
decreases capacitance
less charge needed to propagate signal
Nerst potential
point at which electric potential and concentration gradient offset each other
*no current is flowing at Nerst
Where is calcium normally? Why?
calcium is normally stored outside cells
store it outside since it has many effects on cells once inside
Total current of a ion channel depends on:
total conductance (this stays fixed)
open probability of a channel
driving force across the channel
Difference between K+ and Na+ channels
K+ channels are slower to open and close
Since K+ channels close slowly, what do we get?
continued outward diffusion of K+ ions
leads to hyperpolarized / relative refractory state
When is absolute refractory state?
occurs when Na+ channel is in its inactive state
at the peak of the action potential
3 steps of synaptic transmission
1) action potential reaches axon terminal and opens Ca2+ channels
2) Ca2+ enters pre-synaptic cell and causes vesicles containing neurotransmitters to fuse to cell membrane and release into synapse
3) Neurotransmitters signal ligand-gated Na+ channels to open in post-synaptic cells and start potential
3 ways to turn off synaptic transmission
1) reuptake of neurotransmitter (active transport)
2) degradation of neurotransmitter by enzymes
3) diffusion of neurotransmitter away from synaptic cleft (passive)
ionotrophic receptor
receptor itself is an ion channel and is quick
metabotropic receptor
triggers secondary cascade which eventually causes an ion change
ex: G-coupled protein receptors (cAMP)
slower
When does Ca2+ peak?
after the action potential
action potential at axon terminal signals the influx of Ca2+ into cell
curare drug
blocks Ach receptors
changes the postsynaptic current
