Scheys: Action potential and signal propagation

What is graded potential?

Small change in Vm, either depolarizing or hyperpolarizing

What is action potential?

Rapid depolarization/repolarization cycle when threshold Vm is reached

Ions moving through open channels will cause a change in voltage across membrane. Voltage-gated channels will open when the membrane potential reaches what?

A threshold value

What is a stimulus?

Something that elicits a local change in ion channel permeability

Example of stimulus

Molecule binding to receptor or sensory stimulus like light, touch, pressure, etc

What is graded potential?

Change in membrane potential caused by a change in current

What determines the graded potentials amplitude or duration?

Proportional to stimulus strength

Graded stimulus only affects membrane locally, therefore what happens to the charge as it travels further from the initial depolarization site?

The charge dissipates

Action potential is "All-or-none" meaning what happens if the threshold is reached?

If the threshold is reached, action potential fires and the amplitude will be the same for every action potential

What's the difference between Na+ and K+ channels once they are activated by depolarized?

Na+ channels open and closes rapidly, K+ channels open and close slowly

What is the absolute refractory period?

A second response is not possible regardless of strength or duration(Na+ channels are inactivated)

What is the relative refractory period?

A second response can be elicited but requires a stronger stimulus(membrane is hyperpolarized)

What is the refractory period in general?

Time following an action potential during which a second stimulus CANNOT generate another action potential

What does the speed of signal propagation in neuron depend on?

Diameter, myelination, expression of voltage gated channels

The larger the diameter of axon, the _____ the speed

faster (less resistant to local current)

What does myelination do?

Insulates axon and prevents leakage of charge

What is saltatory conduction?

Action potentials appear to "jump" from one node to the next as they propagate along the myelinated axon

What are the effects of demylelination?

Speed of action potential is reduced in unmyelinated area, spiking frequency is reduced, complete inhibition of conduction, and generation of impulses from neighboring fibers or mechanical forces

Leakage of charge from one demyelinated neuron can activate an action potential in ____?

Neighboring neurons

What is a demyelinating disease in the CNS?

MS

What is a demyelinating disease in the PNS?

Guillain-Barre

What causes spiking patterns?

If a neuron remains depolarized above threshold then multiple AP will be generated and will then become dependent upon expression of multiple channels and refractory periods

Does AP affect concentration gradients?

Ion concentrations in ICF and ECF are not appreciably changed by an AP

What is the target of local anesthetic?

The cytoplasmic side (inside cell) of V-gated Na+ channels and maintains inactive state

I don't want to make cards on the effect of pH on effectiveness of local anesthetic sorry

its okay hannah <3