The Influence of the Nervous System on Human Behavior
Basic Human Nervous System
The Nervous System and Human Behavior
The human nervous system is can be viewed in two parts, which include the CNS (central nervous system) and the PNS (peripheral nervous system). The brain and the spinal chord comprise the CNS, whereas the PNS connects the rest of the body, such as vital organs to the spinal chord and the brain.
The neuroanatomical construction is distinctly important, as the architecture of the brain assists in understanding how parts of the brain interact with the rest of the nervous system and influence functional expressions, behavior, and emotions. Although much of the human nervous system is based on biological, chemical, and physiological foundations that most scientists and researchers agree upon, the influence of the brain and its anatomical architecture on function and behavior is highly controversial.
Regardless of the consensus surrounding areas such as the physiology, biology, and chemical reactions, there is a major debate regarding genetics and the role of the nervous system in the development and change of personality. By starting with the construction and general functions of the nervous system, it will provide a foundation to dive deeper into the controversy surrounding the nervous system, specifically the brain and its role in personality and behavior.
Early Development of Nervous System
Construction of the Nervous System
The construction of the nervous system begins in the embryo at about 2 weeks of age. Kalat (2013) suggests during the construction of the central nervous system after 2 weeks, the dorsal begins to thicken, which eventually separates and forms the:
- fore-brain and
- ultimately the spinal cord.
Through the construction of the human nervous system in early development, 5 stages occur in developing neurons in the brain. These 5 stages or processes include:
Ultimately, this is the process of producing cells/neurons, the movement and formation of neurons and glia, development of the axon and dendrite, through to the formation of the synapses between neurons (Kalat, 2013). Upon maturation of the nervous system, several perspectives begin to diverge in the scientific community, as this is the point where the nervous system sustains itself and affects cognitive functioning, learning, and behavior.
It is understood that genetics play a role in the construction and development of the human nervous system. As humans develop, there is an overproduction of neurons and apoptosis is a mechanism to systematically cause cell death to ensure an exact match of incoming axons to receiving cell (Kalat, 2013). Thus, the early stages of construction and development are vital in the normal maturation of humans, as genetic mutations can cause defects and the distortion of chemicals can cause issues such as impairment and learning disabilities. Therefore, as humans develop through adulthood, the nervous system can have profound impacts on their ability to see, hear, learn, and express emotion, among other things.
From birth to 1 year, the weight of the human brain is increased from about 350 grams to 1,000 grams, reaching roughly 1,200-1,400 grams as an adult.— (Kalat, 2013)
Animated Video of Nervous System Development
Human Behavior Genetics Research
According to Vukasović & Bratko (2015), human behavior genetics research offers insight into the vast and complex connections between the nervous system and human personality. There are three main research designs within this field that assist in providing a deeper understanding of this topic and the controversies that have been debated for many of years. The three types of research that Vukasović & Bratko (2015) refer to within human behavior behavior genetics include twin studies, adoption studies, and family studies. This is the foundation of identifying the influence of the nervous system as genetically designed and environmentally modified.
Over the course of many studies on genetically related human personality, utilizing the three broad research designs, Vukasović & Bratko (2015) synthesized the findings of 45 prior studies, offering a meta-analytical analysis and insight into the controversy. As noted in their study, the findings suggest that 40% of an individual’s personality is hereditary and contributed by genetics. This is in line with prior studies, such as Johnson, Vernon & Feiler (2008), where 50 years of genetic research on human personality was analyzed and found similar results among a statistical analysis of these studies.
The findings suggest that 40% of an individual’s personality is hereditary and contributed by genetics.— Vukasović & Bratko (2015)
Gene Mapping of the Brain
The environment also plays a role, but it is still much harder to identify the environment's specific influences on personality variations, with the exception of early development issues including the affects of alcohol, drugs, and other substances consumed by the mother while pregnant. These can cause chemical distortions and lead to issues such as fetal alcohol syndrome, known as FAS.
Going back to the construction and development of the nervous system, apoptosis is a method of killing unneeded cells, based on the match of cells and axons. When a pregnant mother consumes alcohol, it can inhibit the excitation of neurons which would normally be matched to avoid apoptosis, causing behavioral and learning disorders.
Although the evidence from genetically related studies indicate about 40% of human personality is genetically inherited, environmental exposure to various chemicals in-vitro can mutate the normal process of development.
FAS (Fetal Alcohol Syndrome)
It is difficult to identify environmental influences in normally developed individuals. There may not be a clearly defined answer as to the environmental affects on human behavior and personality. Genetically related research does provide enough evidence to state that genetics does play a significant role in the development of human personality and behavior.
Within the confines of various cultures, life experiences, and expectations, it appears that environmental influence on human personality past the early development stage is still unclear. There is a long way to go to establish the environmental affects on individuals and separate these from established genetic factors.
The neuro-anatomical construction is still a vital and important influence on human behavior. The architecture of the brain acts as a road map to assist in understanding how parts of the brain interact with the rest of the nervous system and influence functional expressions, behavior, and emotions. With genetic and environmental factors still being researched, it is difficult to separate these factors and clinical studies will require more intensive technology, resources, and dedicated scientists to solve this mystery. But since we know that the nervous system does play a role in human behavior and that the environment can disrupt the normal development of the nervous system, perhaps 'cracking the code' may not be too far in the future.
Johnson, A. M., Vernon, P. A., & Feiler, A. R. (2008). Behavioral genetic studies of personality: An introduction and review of the results of 50+ years of research. In G. J. Boyle, G. Matthews, & D. H. Saklofske (Eds.), The Sage handbook of personality theory and assessment. Vol. 1: Personality theories and models (pp. 145–173). London, England: Sage.
Kalat, J. W. (2013). Biological psychology (11th ed.). Belmont, CA: Thomson Wadsworth.
Vukasović, T., & Bratko, D. (2015). Heritability of personality: A meta-analysis of behavior genetic studies. Psychological Bulletin, 141(4), 769-785. doi:10.1037/bul0000017