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When an action potential arrives at the end of the pre-synaptic axon (top), it causes the release of neurotransmitter molecules that open ion channels in the post-synaptic neuron (bottom). The combined excitatory and inhibitory postsynaptic potentials of such inputs can begin a new action potential in the post-synaptic neuron.
After a cell has been depolarized, it undergoes one final change in internal charge. Following depolarization, the voltage-gated sodium ion channels that had been open while the cell was undergoing depolarization close again. The increased positive charge within the cell now causes the potassium channels to open.
EPSPs are usually recorded using intracellular electrodes. The extracellular signal from a single neuron is extremely small and thus next to impossible to record in the human brain. However, in some areas of the brain, such as the hippocampus, neurons are arranged in such a way that they all receive synaptic inputs in the same area. Because ...
The signals can only continue along the neuron to cause an action potential further down if they are strong enough to make it past the cell's membrane resistance and capacitance. For example, a neuron with a large diameter has more ionic channels in its membrane than a smaller cell, resulting in a lower resistance to the flow of ionic current.
The first phase of synaptic potential generation is the same for both excitatory and inhibitory potentials. As an action potential travels through the presynaptic neuron, the membrane depolarization causes voltage-gated calcium channels to open.
Stimuli cause specific ion-channels within the cell membrane to open, leading to a flow of ions through the cell membrane, changing the membrane potential. Neurons must maintain the specific electrical properties that define their neuron type.
[2] [3] [4] When receptors in the postsynaptic membrane bind this neurotransmitter and open ion channels, information is transmitted between neurons (A) and neurons (B). [5] To generate an action potential in the postsynaptic neuron, many excitatory synapses must be active at the same time. [1]
Finalized neurotransmitter vesicles are bound to the presynaptic membrane. When an action potential propagates down the motor neuron axon and arrives at the axon terminal, it causes a depolarization of the axon terminal and opens calcium channels. This causes the release of the neurotransmitters via vesicle exocytosis.