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

Psychology 07.28.13

Today in the Intro to Psychology class I went over good practices in experiments, specifically in reference to psychological experiments.  Randomly assigning participants to either the experimental or control group can help insure that both groups are similar. Not telling participants which group they are in eliminates bias on their part, having  both the participants and the experimenter in the dark is called a double blind study and this eliminates bias on both parts. An important thing to note about psychology is that a review board has to okay any experiments, the benefits must outweigh the risks and participants must sign informed consent. Participants must also be able to leave the study at anytime without negative consequences.

Lesson 3 starts out with an introduction into how long modern humans have been around as compared to other humans. Modern humans have existed for the last 200,000 years, before that were Neanderthals, homo-erectus and homo-habilus. Homo habilus, the first humans, lived from about 2.4 to 1.4 million years ago. Our closest relative would be the Neanderthals and we actually interbred with them before they died off around 28,000 years ago so many of us have Neanderthal DNA. Our closest living relative is the chimp, with whom we share about 98% of our DNA, the other 2% is what makes us uniquely human. These changes happened over a long period of time due to mutations and natural selection, in other words, we evolved.

The changes to our brains is probably what makes us most human. Our brains are bigger than our ancestors and the most differences between our brains and theirs is in the frontal lobe. Having a bigger brain did not come without consequences, childbirth is more painful because of larger skulls and we need more food to fuel our brains.

There is a section on DNA structure, from the nucleotides Thymine, Adenine, Guanine, Cytosine to the 23 chromosomes that make up our DNA. Also it is not the amount of DNA but the sequence that makes us more complex, in fact some amoeba's have more DNA than than anything else on earth. Only about 2% of our genome actually codes for proteins (these portions are called genes), most of the rest regulates which genes are activated, but some of this remaining 98% we're not really sure as to what its purpose is. Alleles are versions of genes, for example my dad has the allele for colorblindness where as my mom does not, so being that this allele only exists on the x chromosome (of which I have 2) I have one allele for colorblindness and one for normal vision. Luckily for me the colorblindness allele is recessive which means that I would need two in order to be colorblind. However this also means that there is a 50/50 chance my daughters will also carry the colorblindness allele and 50/50 chance that any sons I would have would be colorblind. Why? Because males have an x and a y chromosome so they only get one chance at a good allele, where as the x chromosome from my mom allows me to recognize all the colors males don't have a second x chromosome to cancel out or hide the colorblindness allele. This is why more men than women are colorblind, for a woman to be color blind her father would have to be colorblind and her mother would have to carry the colorblind allele.

Psychology 07.26.13

I'm going through Udacity's Introduction to Psychology so here are my notes. Psychology is a field of science that explores the questions of why we do what we do. Psychology covers a wide area, from developmental psychologists who study why children acquire different skills at different times to industrial psychologists who review workplace dynamics to create a more productive environment, the classic image of a Freudian character asking a patient how that made them feel is only a small part of what psychologists do.

Lesson 2 is about research methods. The first part of the lesson is about correlations. Let's say that the price of pickles went up 2 dollars and the price of milk went up 1 dollar, so looking back we can see that as the price of pickles goes up so does the price of milk. So if we were to plot the data points on the price of pickles to milk we would likely see a correlation. However, that does not mean that one caused the other, the price of milk could be going up because of the economy or higher fuel prices, pickles could be in higher demand recently or a million other things could have affected the price. Correlation does not imply causation.

To determine whether one thing causes another is often more difficult than plotting points on a graph. One way is through an experiment. A good experiment starts with a testable hypothesis. I want to know what the best time to feed my girls vegetables is, I've noticed that they tend to eat more vegetables if they have them before meals or as snacks. So my hypothesis is, My girls will eat more of their vegetables if they are fed to them before their meals. Now I set up my experiment, I will feed my children vegetables before meals one week, during meals another week and after meals another week.. The independent variable (the one I will manipulate) in this experiment is the time they are fed vegetables. I will measure how much they eat by how much is left afterwards making quantity remaining my dependent variable. To ensure that my data actually measures what I want it to measure I will control the time of day they eat, what vegetables are served, and what the environment is while they are eating (tv on or off, living room or kitchen), these are my control variables. If in fact they do eat more when they are fed veggies before meals I will have proved my hypothesis. The difference between a hypothesis and a theory is that a theory encompasses many proven hypothesis to come up with an idea that ties them all together. Saying for example that evolution is a theory is really saying that it is the best explanation we have for all the data and proven hypothesis currently available to us.  As an aside, during my hypothetical experiment I recorded measurable data (how much of the veggies were left), if I wanted to know how much my kids like veggies I would have to find a way to measure "liking a food" liking something is a construct in that we know what someone means when they say they like something but it isn't a quality that we can measure. So we use operational definitions, in this case we could say kids will eat more of the foods they like so we will measure how much they eat.