Psychology 08.01.13

So over the last few days I have been working on Lesson 3 "The Biology of Behavior". Last post I talked about colorblindness which is a trait controlled by one gene. There are, however, many traits that are controlled by multiple genes such as eye color or height, these are called polygenic traits.  Traits are not just affected by genes but also by the environment. Identical twins can posses very different traits because of their life choices, if one overeats and smokes while the other doesn't  they are going to look very different. Epigenetics is the study of how our environment can turn different traits on and off. There is a study about two genetically identical mice whose mothers were fed different diets while pregnant, one high in methyl groups and one without. The end result was that one mouse came out obese and yellow while the other was normal and brown. These mice have the same genotype but different phenotypes. The same principals hold true for personality traits, there is a gene that is referred to as the warrior gene, this gene was thought to cause aggressive behavior but as it turns out many people have the gene without displaying aggressive behavior. In fact it takes an abusive childhood coupled with the Monoamine Oxidase A (warrior gene) to cause the more aggressive personality, making this an excellent example of how the environment can affect the gene expression.

The next part of Lesson 3 had to do with the nervous system. The nervous system can be broken down as into the Central and Peripheral nervous systems. The central nervous system consists of the brain and spinal cord while the peripheral accounts for all the other nerves. The peripheral system can be broken into the somatic and autonomic systems, the autonomic system controls functions like heart beat, breathing, digestion etc... the somatic is responsible for voluntary functions. Both of these systems have motor and sensory nerves. The autonomic nervous system has both a sympathetic and parasympathetic nervous system.   The sympathetic nervous system is responsible for the fight or flight response, when activated it does things like dilate the pupils, increase heart rate, inhibit digestion and relax the bronchi to make taking in more oxygen possible. When the parasympathetic nervous system is activated it has the opposite effect, the pupils and bronchi are restricted, heart rate is slowed and digestion is stimulated.

There are two types of cells that make up the nervous system, Glial cells and Neurons. Glial cells provide structural support and remove debris while Neurons process and transmit information. There are three different types of neurons; sensory, motor and interneurons, the interneurons connect neurons to one another. Below is a very rough drawing of a neuron. The Soma is the center of the cell and contains the nucleus. Branching off of the soma are the Dendrites, dendrites connect to other neurons and are the receivers for the cell. The axon transmits the electrical charge (when a neuron fires) to the terminal buttons, the mylin sheath (not present on all neurons) helps to speed up this process. The terminal buttons release neurotransmitters to neighboring neurons and the process repeats. Neurotransmitters can be either inhibitory or excitatory, excitatory neurotransmitters increase the chance that a neuron will fire while inhibitory ones decrease that chance. So to put it all together lets say an excitatory neurotransmitter is received by the dendrites of a neuron, if enough are received the neuron will fire off an electrical signal that runs down the axon and tells the terminal buttons to release more neurotransmitters once they do the cycle repeats with the next neuron.

Neuron