Biology 202
2004 Second Web Paper
On Serendip

Probably the most important signaling apparatus involved in the nervous system's activities would be water soluble ion channels (pores), which can be opened or closed chemically or electrically. These ion channels usually only let one type of ion flow such as sodium ions due to the charge of the ion and the charge of the surrounding environment. Chemically these ion pores can be opened to permit ion flow by ligands, which are small molecules that attach to receptor proteins in a membrane in order to cause a change in pore conformation. One example is in fast synaptic transmission these chemical ion controlling ligands are either the molecule glutamate or gamma-aminobutyric acid which allow certain ions to flow through the pore, but not others and they are involved in many types of ligand gated ion channel activities. Ion pores however in some signaling cases are controlled by a change in the concentration gradient of ions. The gradient opens and closes the pore to control ion flow. As ions flow through the pore, electrical potentials are changed.

Ion permeability controls differences in electrical potential in order to send a signal is called an action potential. Action potentials can send signals very quickly over a relatively long distance in the body via the projections of neurons(1). They are the skipping of current from one node of ranvier on a neuronal projection to the next node. (2) Some of their roles lie in the control of immediate muscle movements among other things. Action potentials are the most immediate form of signaling and are used constantly by the nervous system in order to function in somatic control. Action potentials occur due to depolarization of the membrane; therefore the speed of action potential propagation is dependent on the speed of depolarization. Action potentials also travel better when there is less membrane capacitance, which is the ability of the membrane to store charge. (2) When discussing action potentials it is very important to discuss resting potential and synaptic potential. Resting potential goes hand-in-hand with action potential. Resting potential is the normal potential of the membrane which can change at anytime, but is the normal membrane state. If the membrane did not have resting potential, action potentials would be unable to occur. Synaptic potential is the term used to describe the release of a neurotransmitter over the synapse once an action potential has reached the end of a neuronal projection. The released neurotransmitter from one neuron travels over the synapse and can then if it comes in contact with another neuron causes changes in the neuron.

While action potentials are clearly a very important signaling method in relation to the nervous system, there are other neurological signaling events which can have a great impact on the body as well which are generally slower or have a lesser impact on other systems in the body than action potentials and rely more heavily on chemicals in their signaling mechanisms. These types of signaling can have a tendency to act more locally, meaning that they do not travel as much as an action potential might. These signaling methods include more chemically based approaches such as interactions between proteins associated with neurons. Chemicals can interact with cells in order to change concentration, conformation, activation, or formation of proteins, ions, etc. (3) There are different receptors which associate with different ligands and in the cell produce different responses. There are countless of different cellular interactions which occur in this way and disruptions in these types of reactions can cause neurological diseases as well such as Alzheimer's disease and perhaps schizophrenia among others.

In short, signaling and chemical interactions are important in understanding how parts of the nervous system interact with other parts of the nervous system and how the nervous system interacts with other somatic systems. By gaining knowledge about the types of signaling that occurs in the nervous system we can assess problems with the nervous system and possibly develop treatments for problems among other uses for this information. However processes of the nervous system are much more complicated than this and each reaction and process is unique, which is why the nervous system is still somewhat of a mystery to us today.

References

2)Nelson Lecture 4

3) Helmreich, Ernst J.M. The Biochemistry of Cell Signaling. New York: Oxford University Press Inc., 2001.


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