Untitled document for biology PDF

Preview

Summary

for learing biology...

Description

Most communication between neurons occurs at a specialized structure called the synapse. A synapse is an area where two neurons come close to one another that they are able to pass chemical signals from one cell to another They are not connected but separated by microscopic small spaces called the synaptic cleft. The presynaptic neuron is where the signal is initiated while the postsynaptic neuron receives the signal. In the presynaptic neuron, there are chemical signals called neurotransmitters that are packaged into small sacs called vesicles. When the presynaptic neuron is excited by the action potential it causes the vesicles to fuse with the presynaptic membrane and release their contents into the synaptic cleft. Once there are in the synaptic cleft neurotransmitters interact with receptors on the postsynaptic membrane. They bind to these receptors and cause an action to occur in the postsynaptic cell. The neurotransmitter molecule must be cleared from the synaptic cleft. Some of them will drift away through diffusion. In some cases, the neurotransmitter is taken back up in the presynaptic neuron in process of reuptake. Once back in the presynaptic neuron the neurotransmitter can be recycled and reuse. In some cases, enzymes break down the neurotransmitter within the synaptic cleft than the component parts of the neurotransmitter...