Action Potential Flashcards
What is an action potential?
A process in which neurons are dynamically changing their membrane potentials as they communicate with another
Is Na always going in to out of neurons?
In
Is Cl normally going in or out of neurons?
In
What is local potential?
Change in potential difference in a small portion of the neuron (dendrite)
How can local potentials be generated?
At synapses or by sensory stimuli in the periphery
what are local potentials?
Reversible
Graded
Excitatory or inhibitory
Additive
What does graded mean in terms of local potentials?
depends on amount strength and length of the stimulus
What is depolarization?
resting membrane potential becomes less negative -> depolarization
What is hyperpolarization?
resting membrane potential becomes more negative
What is threshold?
Membrane potential that must be reached for an axon to send an electrical signal
What is summation?
Integration of signals that determines if an action potential will fire
What does excitatory mean in terms of signals?
Likely to fire an action potential
What does inhibitory mean in terms of signals?
Prevents the firing of an action potential
What do signals depend on?
The receptor a neurotransmitter binds to
Glutamate- excitatory, passes cations
GAB- inhibitory, passes anions
what is spatial summation?
Multiple dendrites stimulated at once
What is temporal summation?
One dendrite stimulated several times over time
An action potential will only be initiated when…
A “threshold potential” of -55 mV is reached at the axon hillock
What happens to local potentials that fail to reach threshold?
They will dissipate over time
Which channels open faster Na or K?
Na opens and closes faster
How are Na channels controlled?
Voltage gated
How are K channels controlled?
Voltage gated
What is the refractory period?
The ability for a patch of membrane to fire an action potential is altered
What is the absolute refractory period?
Na channels have not yet returned to resting state; cannot be reactivated
what is the relative refractory period?
Membrane is hyperpolarized, stronger signal is necessary to re-fire an action potential
How do action potentials move faster?
Myelin
What does myelin do?
Insulates the axon, preventing current leak, guaranteeing travel of longer distances and speeding up conduction
Refresher: what is myelin produced by in the CNS?
Oligodendrocytes (myelinate multiple axons)
Refresher: what is myelin produced by in the PNS?
Schwann cells (myelinate single axon)
If the current cant move through myelin how is a signal transmitted?
Nodes of ranvier
What is saltatory conduction?
When the ion influx “speeds” through myelinated portion of axon without being lose, initiating an action potential at the adjacent node of Ranvier
