Neuroscience: The structure of the Brain and its Development
A WORKBOOK and Demonstration text, the practical guide for the study of the complexities of the human brain.
By: Dr.LR Crouch
Parts of the Human Brain
A publication of TRI Country Psychological Service & Consulting Co., LLC
TCC Company-psychological and Integrative Healing Specialities
Table of Contents:
Part I, Structures of the Brain, Page 1
Part II, Cognitive functionaing, Page 10
Part III, Personality and the Brain, page 14
Part IV, Physical Development, page 29
Part V, Cognitive Development, page 37
Part VI, References
Structure of the Human Brain
It has been said that the human brain is the most complex structure in the universe and that In many ways it is one of the final frontiers in science. This three-pound organ is the basis of our intelligence, center of our senses, controller of our behavior and prompter of movement. It is in essence the source of all the qualities that make us human. The brain is made up of many parts all working together to provide for a functioning human being. There are approximately one hundred billion nerve cells in the brain. Although this is a conveniently round number it may underestimate the number of possible cells. Some nerve cells such as granule cells are so numerous in some parts of the brain that scientist now are inclined to revise the estimate much higher. (Amen, 2014)
Neurons contain the cell body, axons and dendrites. Messages generally come from the dendrites and leave through the axons with modification of the messages occurring in the cell body. The dendrites are relatively short and extremely numerous. There may be as many as 100,000. There is usually a single axon which can be quite long, in humans up to a meter in length. Unlike the dendrites the axons contain no DNA and are thus incapable of synthesizing needed molecules. These must be sent through the axons from the cell body. At the end of each axon is a terminal bud containing the synaptic vesicles which release neurotransmitters. One of the core components of the neuron system are the dendrites.
The dendrites receive a signal which is transmitted to the cell body. As the signal travels its strength diminishes. Signals arrive from the different dendrites and receptors on the cell body Itself and eventually arrive at the axon hillock and initial axon segment. These are located at the point where the axon is connected to the cell body. It is here that the magnitude of the signals, and the effects of inhibitory and excitory signals are evaluated in some fashion and a spike of biolectric charge (action potential) either occurs or it doesn't. Unlike what occurs in the dendrites the impulse that travels down the axon does not weaken with distance. It travels In an undiminished state to the terminal bud where a neurotransmitter is released into the synaptic cleft where a receptor on another cells dendrites receives the chemical signal. This is the classic form of interneuronal communication, but it has now been found that dendrites can sand messages to axons and axons to other axons and in fact almost any possible combination is possible. (Hunt, 1982)
HEIRACHIAL SECTION OF THE BRAIN
The human brain still contains and is influenced by structures that we share in common with our most primitive ancestors and which continue to exert an important influence on our behavior. MacLean believes that the human brain developed hierarchally and contains three sections in the form of layers. Each of these layers has a separate function and differs in terms of its evolutionary development. He calls this a triune theory of brain structure and he asserts that instead of a single brain we have three. The innermost parts of the brain we share with our primitive ancestors, while the outermost part of the brain is uniquely human. (McDonald, 2006)
R-complex
At the center of the brain is the most basic section, the reptilian or R-complex. It is called this because it is the part of the brain that we as humans share with all other vertebrates including fish and reptiles. Included are the brain stem, spinal cord, medulla and pons, hindbrain, and neural chassis. In addition to certain reflexes, motor activities, and the regulation of the autonomic nervous system, it is believed that ritualistic behaviors, aggression, territoriality, and the specific behaviors that make each animal unique reside here. Also found in this part of the brain are specific forms of nest building in birds, and the construction of beaver dams. (MacLean, 1985)
Limbic system
The next level is the mammalian brain or limbic system. While the R-complex focuses on species preservation, the limbic system houses our emotional experiences. Most experts in the field of social science take the position that emotions are learned responses. However, studies of the brain indicate that emotions are centered in the limbic system and for this reason have a physiological basis. The removal or stimulation of parts of the limbic system cause changes in emotional functioning.
During surgery on the brain, specific locations can be electrically simulated to provide a better understanding of the functioning of different regions. Stimulation of the septal areas results in pleasurable feelings. Stimulation of the hippocampus and amygdala result in rage, fear, and discomfort. Patients will self-stimulate the septal area but not the hippocampus or amygdala. It has been proposed that the pleasure and pain centers are at opposite poles of the limbic system, each with the capacity to overrule the others. The emotions centered in this section of the brain are not isolated but are related to the rest of the brain through neural connection and the actions of the neurotransmitters. Cocaine for instance, elevates the abstract characteristics. The emphasis is always on the perceptual. If you ask a child at this stage to tell you how a dog and a cat are the same they will focus only on physical characteristics such as the fact that they both have fur or tails. They are unlikely to provide a more abstract similarity such as the idea that they are both mammals or animals. The child can categorize only according to a single attribute. They seem to not understand the logical rule that asserts that the number of objects in a subcategory cannot exceed the total number of objects. If you show a child in the pre-operational stage a bouquet of roses which contains 5 red roses and 3 white roses and ask which type of rose is more numerous the child can respond correctly. If you ask if there are more red roses or more roses they will say there are more red roses. This is because they are incapable of thinking both in terms of roses and non-roses and red roses and white roses. This ability is called combinatorial thinking and it is not achieved until the child reaches the concrete operations stage. The child at this stage tends to group objects together not because they logically belong together but because of often irrelevant characteristics. Dogs and cats are thought to go together because the child likes both of them. During the second part of this stage the child begins to think In classes and can begin to see some relationships at least at a simplistic level. They can us some number concepts and even though they still can classify objects only according to one attribute they can do this much more efficiently.