Neurochemistry is the analysis of organic compounds, neurotransmitters and neuro-migration and pathfinding. It includes amino acids and their combinations such as dipeptides (two amino acids), tripeptides (three amino acids), polypeptides (short chains) and proteins (long chains).
Neurochemistry is needed to understand the mechanisms of neurotransmitters, drugs, alcohol and medications. It also help provide the medications to treat many disorders and conditions.
The classic image of a scientist looking through a microscope is an apt description of histology. It includes the traditional tasks of tissue cultures, preservation and staining techniques. The more modern tasks of chemical fixtures, freezing, dehydration, infiltration and embedding are also part of histology. But recent developments include DNA replication, antibodies and immunohistochemistry.
To discover the cellular structure of the brain, Camillo Golgi created a unique silver nitrate staining technique that allowed Santiago Ramón y Cajal (the father of neuroscience) to examine the structure of central nervous system cells. This led to more evidence that nerves are not single fibers (continuous) but are a series of neurons with multiple synapses (contiguous).
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This research method builds on both the correlational and experimental methods. The focus is on how we grow the become who we are. Since we are not born with complete adult capabilities, the developmental approach looks at all of the contributing factors to our growth.
There are two experimental designs that are typical of developmental research. Children can be measured over their lives. This longitudinal design requires a huge investment in time (years) and in resources (money). It’s expensive to measure people every year for 20 or 30 years. Subjects are not always available, move away, or become uninterested. Researchers move on to other topics, and in some cases get old and die.
The other alternative is a cross-sectional design. Instead of following the same people over time, people from several age groups are tested at the same time. Children, teens, adults and the elderly can be tested on the same day, using the same materials. This method is fast, efficient and cheap.
The downside is that we are guessing that these children will grow up to be like these teens. And that these teens will grow up to be like these adults. Researchers compromise by doing the cross-sectional studies first and following up with an occasional longitudinal study.
Longitudinal studies often start with a general concept or principle, like intelligence, and try to reduce it to a simple explanation. In contrast to this deductive method, cross-sectional studies are often inductive. They gather lots of data and try to discover a general principle.
In order to explore the brain, early research would often destroyed a portion of the brain and then observe the outcome. The purposeful destruction of a cell or group of cells is called ablation.
Napoleon Bonaparte had heard of Gall’s phrenology and asked (ordered) his scientists to find out if it was true. They chose Jean Pierre Flourens to do the research. Flourens was a new doctor but an accomplished researcher. He decided that the best way to understand the human brain was to start with animals.
Using rabbits and pigeons, he set about his task in a systematic fashion. Flourens ablated (destroyed) a portion of the brain and observed the effect. He selected an area and then watched to see if the rabbit still hopped.
In a broader sense, Flourens showed that removal of the cerebellum impaired coordination, and that destroying the medulla oblongata causes sudden death. Similarly, removal of one hemisphere impairs perception and function of the other side (left hemisphere runs right side).
Flourens proved that different regions of even small-brained animals do have different functions but that fine point discriminations were not possible.
Flourens major contribution was to show that the scientific approach was more useful than the correlational method. Finding similarities is a start but an experimental investigation is even better.
Today we use ablation to destroy select heart or brain cells that are misbehaving. In addition to heart anthemia and epilepsy, ablation is used to destroy tumors and cancers.
Although you’re probably not working with rabbits and pigeons, remember Flourens when you are troubleshooting a computer problem or repairing your yard’s sprinkler system. What happens if I do this? What happens if I do that?
Correlation is a necessary component of causation. You observe two things and try to figure out a relationship. Your conclusions are limited because you can’t prove anything with a correlation but it’s a good place to
Correlations don’t prove causation. A can cause B but it is just as likely that B causes A. And it is equally likely that C caused both A and B.
Franz Gall gives us two examples. Gall was a comparative anatomist. He used the skull size of animals as his independent variable (input) and musket balls as his dependent variable (outcome measure). He took skulls of different sizes and poured the musket balls (lead shot) into each.
He reasoned that the more lead shot a skull could hold, the larger its skull was and the larger its brain. And larger the brain, the smarter the animal would be. Gall was mostly right.
There is a minimum size required and a maximum. At some point it is not the size of the brain but how it is constructed that matters. But it wasn’t a bad guess. There is a correlation there, at least in the middle region.
Gall’s next correlational study was between the bumps on the head and the mental abilities of people. He thought of the brain as a muscle that gets bigger the more it is used. As it gets bigger, it would push out the skull. So if you mapped the topography of the skull, you’d know from the outside what was going on inside. Gall called this process cranioscopy. Everyone else called it phrenology.
Although the scientific community didn’t ascribe to it, for over 100 years, phrenology was used by the general public to describe people. Using phrenology made you feel smart, educated and scientific. It also fit so well with people’s prejudices that it could and was used to discriminate against people they didn’t like.
Phrenology supported stereotypes that were cultural, national and racial. Something was wrong if your eyes were large or small, close together or far apart. You were lazy if your nose was too wide. You were conceited if your nose was too narrow. It was a one-stop shop for prejudice.
Correlations are still used today. You can’t randomly assign children to parents or people to geographical locations. But you can explore child abuse, obesity, diet, job advancement, leadership and the impact of television.
Galen agreed (about 500 years later) that Aristotle had the correct organ but argued that his methodology was wrong. Galen recommended dissection.
Dissection (the Latin word dissecare means to cut to pieces) is the detailed analysis of a structure by cutting it into smaller discrete segments.
From his observations he concluded that the heart is the center of life. It is comprised of tough muscles tissue, and has many nerves attached to it. Also, it expands when active or when experiencing emotion. Clearly, it must be the center of thinking and emotion.
As a mnemonic, remember that Aristotle watched the chickens and Galen dissected them for dinner. Actually, Galen dissected monkey and pigs but it is a good way to remember the difference.
We don’t dissect animals much any more. There is no need. The video simulations and practice dummies do an amazing job of teaching surgical skills.
