Neurochemistry
Neurochemistry is the study of the neurochemicals that influence the functions of neurons within the body. Neurotransmitters are the "chemical communicators" involved in signaling and they are organic molecules that participate in neural activity. Neurotransmitters are substrates that must fit into its receptors. Since receptors have certain shapes, and polarities, only a few similar molecules can activate each individual receptor. Human bodies communicate by sending chemical information from one neuron to another. The neurons communicate by sending neurotransmitters across the synapse.
This image shows the structure of a neuron. The dendrite is the area that receives the signal and sends it down the axon to the axon terminal. Structures like the Myelin sheath and Schwann cells speed up the signal as it travels down the axon. Neurons connect from axon terminal to dendrite, so when one neuron ends, another begins, and the synapse is located between them.
Synapses
A synapse is the area where two neurons connect and transfer information from one to another. This process of sending information is known as a nerve impulse. The synapse itself is made up of three main parts; the pre-synaptic neuron, the synaptic cleft, and the post-synaptic neuron.
An action potential is what starts this signaling process; however, the electrical signal brought about by an action potential cannot cross the extracellular fluid in the synaptic cleft. But chemical messengers can. Therefore, the electric signal must signal a chemical signal to take place to pass on the message from one neuron to another. The electric signal travels down the neuron from the dendrite to the axon terminal.
This electric signal causes the voltage gated Ca+2 channels to open and allow Ca+2 to rush into the cell. The Ca+2 that rushes in binds to the protein Calmodulin and activates it. Calmodulin is an intermediate molecule that serves as a second messenger.
Calmodulin then proceeds to activate protein kinase II. Protein kinase II then phosphorylates the protein Synapsin. Synapsin is what causes the synaptic vesicles to release their neurotransmitter into the synaptic cleft. Synapsin causes the synaptic vesicles to fuse to the membrane and open their contents into the synaptic cleft. This process is known as exocytosis.
The neurotransmitters then cross the synaptic cleft from the pre-synaptic neuron to the post-synaptic neuron and bind to the membrane proteins on the post-synaptic neuron. This causes ion channels to open and change the potential of the neuron and causes an action potential to start in the dendrite.
An action potential is caused by a difference in charge between the inside and outside of a nerve cell. At rest, there is very low Na+ concentration inside the cell and a very high Na+ concentration outside of the cell with a little K+ inside the cell. This causes the cell to have a negative electric potential (-70mV) at rest.
To start an action potential, ion channels open up and Na+ rushes in. The cell then becomes positive inside and negative outside, so the little bit of K+ that was inside of the cell rushes out. This electric signal is then sent down the axon until it reaches the axon terminal and another synapse occurs. In order to restore the cell to its negative potential and prepare it to receive another signal, sodium potassium pumps move 3 Na+ out of the cell and 2 K+ into the cell, leaving it negative inside compared to its surroundings.
Neurochemistry is the study of the neurochemicals that influence the functions of neurons within the body. Neurotransmitters are the "chemical communicators" involved in signaling and they are organic molecules that participate in neural activity. Neurotransmitters are substrates that must fit into its receptors. Since receptors have certain shapes, and polarities, only a few similar molecules can activate each individual receptor. Human bodies communicate by sending chemical information from one neuron to another. The neurons communicate by sending neurotransmitters across the synapse.
This image shows the structure of a neuron. The dendrite is the area that receives the signal and sends it down the axon to the axon terminal. Structures like the Myelin sheath and Schwann cells speed up the signal as it travels down the axon. Neurons connect from axon terminal to dendrite, so when one neuron ends, another begins, and the synapse is located between them.
Synapses
A synapse is the area where two neurons connect and transfer information from one to another. This process of sending information is known as a nerve impulse. The synapse itself is made up of three main parts; the pre-synaptic neuron, the synaptic cleft, and the post-synaptic neuron.
An action potential is what starts this signaling process; however, the electrical signal brought about by an action potential cannot cross the extracellular fluid in the synaptic cleft. But chemical messengers can. Therefore, the electric signal must signal a chemical signal to take place to pass on the message from one neuron to another. The electric signal travels down the neuron from the dendrite to the axon terminal.
This electric signal causes the voltage gated Ca+2 channels to open and allow Ca+2 to rush into the cell. The Ca+2 that rushes in binds to the protein Calmodulin and activates it. Calmodulin is an intermediate molecule that serves as a second messenger.
Calmodulin then proceeds to activate protein kinase II. Protein kinase II then phosphorylates the protein Synapsin. Synapsin is what causes the synaptic vesicles to release their neurotransmitter into the synaptic cleft. Synapsin causes the synaptic vesicles to fuse to the membrane and open their contents into the synaptic cleft. This process is known as exocytosis.
The neurotransmitters then cross the synaptic cleft from the pre-synaptic neuron to the post-synaptic neuron and bind to the membrane proteins on the post-synaptic neuron. This causes ion channels to open and change the potential of the neuron and causes an action potential to start in the dendrite.
An action potential is caused by a difference in charge between the inside and outside of a nerve cell. At rest, there is very low Na+ concentration inside the cell and a very high Na+ concentration outside of the cell with a little K+ inside the cell. This causes the cell to have a negative electric potential (-70mV) at rest.
To start an action potential, ion channels open up and Na+ rushes in. The cell then becomes positive inside and negative outside, so the little bit of K+ that was inside of the cell rushes out. This electric signal is then sent down the axon until it reaches the axon terminal and another synapse occurs. In order to restore the cell to its negative potential and prepare it to receive another signal, sodium potassium pumps move 3 Na+ out of the cell and 2 K+ into the cell, leaving it negative inside compared to its surroundings.
This short crash course video will explain the overall concept of synapses. It really is excellent and worthwhile to watch!
Sources
Brain Synapses and Neurotransmitters - Alzheimer's Association. (n.d.). Retrieved May 27, 2015, from https://www.alz.org/braintour/synapses_neurotransmitters.asp
Human Diseases and Conditions. (n.d.). Retrieved May 23, 2015, from http://www.humanillnesses.com/Behavioral-Health-A-Br/Brain-Chemistry-Neurochemistry.html
Neurochemistry. (n.d.). Retrieved May 26, 2015, from http://gabyramirezchemistryhonors.weebly.com/
Neuroscience For Kids. (n.d.). Retrieved May 27, 2015, from https://faculty.washington.edu/chudler/synapse.html
Synapses. (n.d.). Retrieved May 26, 2015, from http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/S/Synapses.html