Hormones, Heredity, and Human Behavior July 14, 2011 BEH 225 Why do people behave the way they do? What makes us tick? While our environment molds some of who we are, much more comes from heredity and hormones. Genes passed on to us from our parents make up heredity, and glands throughout the body produce hormones. As generations progress, new psychological and behavioral traits are earned and learned. This paper will explain hormones and the endocrine system, glands associated with the endocrine system, behavior genetics, and evolutionary psychology.
The endocrine system is the system of the body in which releases hormones into the bloodstream. The hormones then cause different reactions within the body, and these reactions shape part of human behavior. There are seven glands within the body, which are the pineal gland, thyroid and parathyroids, the pancreas, pituitary gland, gonads, and adrenal glands. Each gland produces diverse hormones, and each hormone has a specific effect on the body, be it mood, energy, or sexual needs (Morris and Maisto, 2002).
The pineal and pituitary glands are located in the center of the brain. The pineal gland is in the center of the brain, regulates activity levels throughout the day, and secretes melatonin, which controls the body’s sleep wake cycles. Lack of melatonin in the body causes what is known as “jet lag”, which occurs when the body’s proper sleep cycle is interrupted. The pituitary gland lies on the underside of the brain, and produces the largest number of hormones in the body, thus called the “Master Gland”.
This gland influences blood pressure, contractions during childbirth, milk production, sexual behavior and interest, growth, and hydration (Morris and Maisto, 2002). The thyroid is located below the voice box, and produces thyroxin, which regulates the body’s metabolic rate, thus controlling how thin or fat, or lazy or energetic a person is. Hyperthyroidism and hypothyroidism are diseases caused by too much or too little thyroxin. Hyperthyroidism is characterized by insomnia, fatigue, agitation, and problems focusing on tasks.
Hypothyroidism often causes a person to sleep a lot, but the person is still tired. The parathyroids are located within the thyroid, secrete parathormone, and controls levels of calcium and phosphates in the body. The parathyroids are also involved with controlling excitability levels (Morris and Maisto, 2002). The pancreas is located between the stomach and small intestine, and secretes insulin and glucagon to balance blood sugar levels in the body.
When the pancreas does not work properly, a person may be diagnosed with diabetes mellitus, which is more commonly known simply as Diabetes (Morris and Maisto, 2002). People with diabetes suffer from extreme thirst, fatigue, lack of or increased appetite, and a myriad of other symptoms if their condition is not controlled properly with diet, exercise, and medications (if needed) (Steadman’s Concise Medical Dictionary, 2001). The gonads are the male and female reproductive organs, the testes (males) and ovaries (females).
The testes and ovaries produce androgens (testosterone) and estrogens, these hormones affect aggressiveness, mood, and sexual interest and behavior. Higher levels of these hormones have been shown to promote aggressiveness in both sexes (Morris and Maisto, 2002). The last glands are the adrenal glands, which are located above the kidneys, and have an inner core and an outer layer. The inner core is called the adrenal medulla, and the outer layer is known as the adrenal cortex. These parts work together to condition our bodies to handle stress.
Blood pressure rises, pupils dilate, and heart rate quickens when the adrenal glands release epinephrine and norepinephrine into the bloodstream to trigger the body’s sympathetic nervous system. This causes what is known as the fight or flight response when a person is in danger (Morris and Maisto, 2002). Genetics control another part of why we do the things we do, and are given to us at birth through chromosomes from our parents. Genetics determine the traits, such as hair and eye color, and influence some things that may occur in our lives, such obesity and blood pressure disorders.
Behavior genetics is the study of how the genetics we receive from our parents affects our behavior. The goal of understanding behavior genetics is to decipher how genetics affects memory, intelligence, emotions, personality, and psychological disorders (Morris and Maisto, 2002). Evolutionary psychology works alongside genetic behavior to help psychological professionals understand how the mind works, and what pushes us to do certain things, such as why a serial murderer decides upon that life path. Evolutionary psychology promotes the theory of natural selection.
Natural selection implies that certain traits are ingrained into all human beings, and these traits suggest that people, who are strong and adapt well, will be the ones to survive and pass on their traits to following generations (Morris and Maisto, 2002). REFERENCES Morris, C. G. , & Maisto, A. A. (2002). Psychology: An introduction (12th ed. ). Upper Saddle River, NJ: Prentice Hall. Dircx, J. , M. D. (ed). (2001) . Steadman’s concise medical dictionary for health professions (4th ed. ). Dayton, OH. Lippincott Williams &Wilkins.