Describe how neurones communicate with each other. How do psychiatric drugs exploit this system?
The neurone is the operative element of the nervous system, and enables communication with other neurones which in turn detail different messages throughout the nervous system and indeed other neurones#. There are many varieties of neurone, and their are specific function determines their exact size and shape.# As demonstrated in 'The Physiology of Behaviour' - Neil R. Carlson - the neurone is comprised of four main structures; the soma, the dendrites, the axon and the terminal buttons. The soma (cell body) contains the nucleus, whose shape varies according to the function of the neurone. The dendrites "serve as important recipients" of the messages that are conveyed between neurones#, and these messages are transmitted across the synapse - "the junction between the terminal button of an axon and the membrane of another neuron"#. The axon "carries information from the cell body to the terminal buttons"# through the process of action potential. The terminal buttons are the stem like forms at the end of the branches of the neuron, and these "secrete a chemical called a transmitter substance"# or a neurotransmitter - it is these which are effected by drugs, whether it be in an excitatory or inhibitory way. It is also the terminal buttons which determine, through the secretion of these chemicals, whether an action potential takes place.
The action potential is a process in which the information is conducted by means of a electrochemical process. This means that the involvement of chemicals results in a electrical signal, an upsurge of electrical activity formed by a depolarising current. So that when the depolarisation reaches approximately -55mV a neuron will launch an action potential; the threshold has to be reached in order for an action potential to take place, and therefore if this threshold is not reached no action potential will occur. Through the process of diffusion the balance of two opposing forces is retained. That is to say that the high concentration of the positive potassium ion, K+, within the intercellular fluid is forced out of the axon through diffusion due to its high concentration, yet the high positive charge "outside of the cell with respect to the inside"# causes K+ to be driven back into the axon and the ions' positions remain unchanged.
The same can be said of the negatively charged Chloride, Cl-, which is in a high concentration within the extracellular fluid. This too transported through diffusion force, but into the axon. However, again due to the negative charge within the cell, Cl- is sent back into the extracellular fluid. "Again, two opposing forces balance each other."# However, positively charged Sodium, Na+. Na+ is, too, in extensive concentration outside the axon so is forced into the cell, but as the inside of the cell is positively charged "Na+ is not prevented from entering the cell"# as the...