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When an action potential reaches the end of a neuron, it triggers the release of neuotransmitters such as epinephrine (sympathetic) or achetylcholine (parasympathetic).
Once you have the action potential made from the influx of Na traveling down the axon depolarizing it. The action potential reaches the axon terminals, the depolarization causes Ca2+ to enter the cell and that causes the release of the neurotransmitters out of the axon terminals and into the dendrites of the next axon to continue the signaling pathway.
When it reaches the nerve impulse threshold, the next neuron will fire..
duriing action potential, whall na+ doors are open it reaches threshold. -55mvolts
When an action potential reaches the knoblike terminals at an axon's end, it triggers the release of chemical messengers called neurotransmitters. Within 1/10,000th of a second, the neurotransmitter molecules cross the synaptic gap and bind to receptor sites on the receiving neuron-as precisely as a key fits a lock.
if the graded potential of threshold size reaches a trigger zone
The actional potential would not reach the axon terminals.
From dendrites to cell body to axon to axon terminals, in case of nerve cells.
A synapse and an action potential have a flip-flopping cause and effect relationship, in that an action potential in a presynaptic neuron initiates a release of neurotransmitters across a synapse, which can then subsequently potentially trigger an action potential in the axon of the postsynaptic neuron, which would then cause release of neurotransmitters across a following synapse.
Single action potentials follow the "all or none" rule. That is, if a stimulus is strong enough to depolarize the membrane of the neuron to threshold (~55mV), then an action potential will be fired. Each stimulus that reaches threshold will produce an action potential that is equal in magnitude to every other action potential for the neuron. Compound action potentials do not exhibit this property since they are a bundle of neurons and have different magnitudes of AP's. Thus compound action potentials are graded. That is, the greater the stimulus, the greater the action potential.
It is a difference in charge supplied by ion position. In resting potential the tendency is for the inside of the cell membrane to have a negative ionic charge, while the outside of the membrane has a positive charge. The change, back and forth in these two charge potentials is the conduction of charge down the neuron and is called the action potential.
Depolarization occurs when a stimulus opens sodium channels which allow more sodium to go into the membrane making it less negative and more positive (toward reaching threshold). An action potential can only occur once the membrane reaches threshold which means it has reached the level needed through depolarization. An action potential is a brief reversal in polarity of the membrane making the inside more positive and the outside more negative, the reverse occurs again once the membrane reaches resting potential.