Action Potential

4. Understand how lidocaine (local anesthetic) works.

they block the voltage gated sodium channels in neurons. if these channels cannot open then action potentials cannot be produced in the neuron. as they block action potentials then there is no signal going to the central nervous system.

1. Be able to differentiate between polarization, depolarization, hyperpolarization and repolarization.

Polarization: any state whent he membrane potential is other than 0mV Depolarization: membrane becomes less polarized Repolarization: membrane potential returns to the resting membrane potential following a depolarization. hyperpolariztion:

5. Understand what the absolute and relative refractory periods are and what causes them to occur.

REFRACTORY PERIODS Right after the action potential the cell tired and less excitable. ABSOLUTE REFRACTORY PERIOD its the time where the sodium gates are opening and it is responding to a stimuli. during this time a second stimuli cannot affects the gates because this gate is busy. RELATIVE REFRACTORY PERIOD occurs right after absolute refractory period. a second action potential is possible if it is a large stimulus sodium gates reset but potassium gates open

Potassium Voltage-gated Channel

When membrane is resting: K+voltage gated channel is closed During depolarization: Closed Repolarization: open Hyperpolarization: closing

The Voltage-gated Sodium Channel

When the membrane is resting: Activation gate is closed Inactivation gate is open During depolarization: Activation gate is open Inactivation gate is open After one Millisecond:(Repolarization Activation gate is open Inactivation gate is closed Hyperpolarization: activation gate closed Inactivation gate open

7. Be able to describe what causes multiple sclerosis.

caused by autoimmune attack of myelin scarring forms where the myelin is damaged inflammation causes degeneration of axons results in tingling, numbness, balance and coordination problems, gradual paralysis

Know what the "all-or-none" law states.

excitable cells respond to a stimulus completely or not at all.

3. Know what an action potential is

rapid, large change in membrane potential conducted over entire membrane magnitude does not diminish as it moves its comes when gates response reaches threshold.

6. Understand what saltatory conduction is and how it occurs, including the role of nodes of Ranvier, myelination, Schwann cells, and oligodendrocytes.

saltatory conduction only happens in myelinated axons and it is used to perform action potentials. nodes of ranvier are gaps in the myelin where the voltage gated sodium and potassium channels are. this is where action potential occurs. myelinated areas of the axon cannot receive action potential. this makes the message go faster.

2. Be able to describe a graded potential. How is it triggered? What are its characteristics?

small change in membrane potential triggered by opening or closure of gated ion channels spread by passive current flow doesnt spread far

Know what channels and changes in ion permeability are involved in its generation on the nerve membrane.

with dramatic increase in sodium depolariztion occurs. then repolariztion occurs which makes sodium become less permeable and increases K+ permeablility to return membrane to normal levels