Biological Foundations of Adult Sexual Development

Sexual development does not begin in adulthood or when a person has their first sexual experience. Sexual development begins before birth. Hormones are passed from the mother to the child and chromosomes make the determination of whether a fetus will develop into a male or a female. This is when the journey to sexual development embarks. Both biological and sociological influences can determine a person’s sexual identity.

Biological influences, often called hormones, are the chemical forces that help to influence sexual development. Hormones are produced in several different glands throughout the body and are secreted to different parts of the body as needed to allow sexual activity to take place.  Hormones are responsible for many of the body’s functions and assist in the process of homeostasis.

Hormones cause chemical reactions to occur in within the body. These chemical reactions influence the behavior of a person. For instance, “most diseases occur to the over or under secretion of hormones by their respective glands. For example, hyposecretion of insulin by the ß cells of the Islets of Langerhans of the pancreas” (Sexual Differences- The biological process of sexual differentiation, The social process of sexual differentiation, para. 3).

Steroids are sex hormones that control sexual behaviors. Steroids cause sexual changes within humans, such as puberty. The female menstrual cycle is caused by hormones. Sexual hormones are made from a chemical reaction initiating in the male and female sex organs and in the adrenal glands. “For example, estrogen is the primary female sex hormone and it is responsible for promoting secondary sexual characteristics in females” (Sexual Differences- The biological process of sexual differentiation, The social process of sexual differentiation, para. 3). Hormone releases effect cells to cause a reaction to occur. This reaction produces the desired results of that hormone.

Hormones react with proteins and cholesterol to for receptors. Specific hormones released by the thyroid and pituitary glands promote specific behaviors. This behavior is more notable in women than in men. Women have more noticeable changes in sexual behavior, such as puberty, premenopause, menopause, and perimenopause. Levels of hormones and the way that these hormones are displayed in physical and psychological behavior are drastically different during each of these stages. Women experience psychological behavioral differences such as anxiety, impatience, earnestness, and intolerance. Some women also exhibit symptoms of depression during these hormonal changes. “Such personality traits have been observed in men also under various circumstances. This could be directly related to the changing hormones in the body. The hormones have the capability of affecting the neurons in the brain cells and causing certain behavior patterns” (Sexual Differences- The biological process of sexual differentiation, The social process of sexual differentiation, para. 3).

Women and men exhibit very different hormones. There is a genetic difference between men and women and, because of this, the hormones in each act differently. The first sex differentiation occurs at conception. When chromosomes determine the sex of the baby, hormones begin to create sex organs to fit that gender. “If there is a ‘Y’ chromosome present, then the embryonic gonadal (sex glands) become a penis. If there is no ‘Y’ chromosome present, the human embryo is automatically female. In extremely rare cases, there are embryos that have different combinations of chromosomes, which are called hermaphrodites because they are technically both sexes” (Sexual Differences- The biological process of sexual differentiation, The social process of sexual differentiation, para. 3). This begins the sexual life of a human.

Humans are sexual by nature and continue to change and develop sexually throughout life. Sexuality is displayed in a variety of ways throughout life. Each stage throughout life initiates a new change in human sexuality. Biological and psychological changes come with each hormonal change. Healthy sexual development depends both on biological and behavioral factors.

From birth, biological sexual behaviors are displayed. “The capacity for a sexual response is present from birth. Male infants, for example, get erections, and vaginal lubrication has been found in female infants in the 24 hours after birth” (Masters, Johnson, & Kolodny, 1982). Masturbation has been seen in children as young as 2 years old (Masters, Johnson, & Kolodny, 1982). Sexual behavior increases as children get older, however the behavior is often hidden by age 5 as children begin to realize what is socially acceptable. This suggests that psychological sexual behavior begins at a very young age.

By the time a child reaches 10 years old, he or she has realized the social difference of males and females (Thorne, 1993). This type of social organization is known as homosocial. Increases in masturbation occurs during this period. “About 40% of the women and 38% of the men in a sample of college students recall masturbating before puberty” (Bancroft, Herbenick, & Reynolds, in press). Sexual attraction and sexual fantasies also begin during this stage of sexual development.

Puberty occurs in adolescents, usually between the age of 13 and 19 years old. Puberty is the period of sexual development that is associated with the maturing of the gonads and genitalia. Psychological sexual behavior, whether acted upon or only imagined, spikes during this period. “These changes begin as early as 10 years of age to as late as 14 years of age, and include rises in levels of sex hormones, which may produce sexual attraction and fantasies. Bodily changes include physical growth, growth in genitals and girls' breasts, and development of facial and pubic hair” (Thorne, 1993). This phase of sexual development makes adult sexual interactions possible (Udry, 1988).

Sexual development continues into adulthood. The decision making process involved in sexual activity often does not develop until adulthood. Sexual experimentation takes on a new role in adult sexual relationships. “Couples report engaging in a variety of sexual activities in addition to vaginal intercourse, including oral-genital sexuality (70% of married men and 74% of married women), anal intercourse (27% and 21%), and hand-genital stimulation. Many adults continue to masturbate even though they are in a long-term relationship; 17% of married men and 5% of married women masturbate at least once a week” (Laumann et al., 1994).

Later in adulthood, women experience menopause as their body’s hormone levels change again. Similarly, men experience a hormone change known as andropause (Lamberts, van den Beld, & van der Lely, 1997) This period begins around age 50, but can begin as early as 40. In this period, the body experiences a decrease in hormone levels specific to each gender. While lubrication may be necessary for regular sexual activity, this does not stop sexual activity. If a person remains active, his or her sexual life can last beyond age 70 (AARP, 1999).

Human sexuality is a developmental process that continues throughout life. This process is birthed at conception and does not end until death. These biological and psychological processes influence the behaviors-both emotional and physical- of humans. Hormonal changes develop the sexual appetite and ability of each human. Each stage of life displays a unique level of sexual maturity, beginning at birth and ending with late adulthood. These hormones influence sexual identity, ability, and behaviors. Hormone levels create both the ability and the desire for sexual action.

References:

American Association of Retired Persons. (1999). AARP/Modern Maturity sexuality study. Atlanta, GA: NFO Research, Inc.

Bancroft, J., Herbenick, D., & Reynolds, M. (In press). Masturbation as a marker of sexual development. In J. Bancroft (Ed.), Sexual development. Bloomington, IN: Indiana University Press.

Laumann, E. O., Gagnon, J. H., Michael, R. T., & Michaels, S. (1994). The social organization of sexuality: Sexual practices in the United States. Chicago: The University of Chicago Press.

Lamberts, S. W. J., van den Beld, A., & van der Lely, A.-J. (1997). The endocrinology of aging. Science, 278, 419-424.

 Masters, W. H., Johnson, V. E., & Kolodny, R. C. (1982). Human sexuality. Boston: Little, Brown

Net Industries. (2010). Sex Differences. Retrieved from http://psychology.jrank.org/pages/574/Sex-Differences.html

Thorne, B. (1993). Gender play: Girls and boys in school. New Brunswick, NJ: Rutgers University Press.

Udry, J. R.. (1988). Biological predispositions and social control in adolescent sexual behavior. American Sociological Review, 53, 709-722.

Neurological Processes

Biological and neural psychologies both have a common goal: to discover the biological reasoning for mental disorders. These areas in psychology are extremely important. In order to medicate and hope for a cure for certain mental deficiencies, scientists must first research these deficiencies. Scientists must fully understand the chemical and biological reasoning behind the disorder if they hope to reverse the damage done to the brain.

Medication for mental disorders has only become available through the research done by biological and neural psychologists. Research must be done not only on global levels, but also within each individual patient. "Mental health professionals use psychological testing, interviews, questionnaires, and patient history to determine first, if a change in the neurotransmitter system is present, then second, what neurotransmitters are involved" (Carver, J., 2006). Medication can only be administered to a patient after this individual research has been conducted.

Regulating behavior is an important aspect in the treatment of people with mental disorders. This can be done with the use of excitatory and inhibitory postsynaptic potentials, receptors, and synaptic transmission. Stimulation of the presynaptic cell causes a change in the resting potential. This is called postsynaptic potential. Excitatory postsynaptic potential occurs when the stimulation causes the current in the cell to be more positive than it already is, while inhibitory postsynaptic potential occurs when the stimulation causes the current in the cell to be more negative that it already is (Wickens, A., 2005).

The axon hillock is located inside of the neuron and is between the axon and the cellular body.  Here, there are nerve impulses. These nerve impulses cause electrical movement inside the synapses. This movement is called synaptic transmission (neurotransmission). Synaptic transmission enables communication between neurons in the brain. "All experiences, such as thoughts and feelings, and all actions, are the results of neurons generating nerve impulses" (Wickens, A., 2005). The portion of the cell that connects with transmitters or molecules is called the receptor. The receptor causes psychological changes.

There are several primary neurotransmitters that influence brain function and behavior. Noradrenalin (also known as norepinephrine), serotonin, gamma-amino butyric acid, glutamate, acetylcholine, and dopamine make up these primary neurotransmitters. Noradrenalin “is both a hormone and a neurotransmitter. As a hormone, secreted by the adrenal gland, it works alongside epinephrine / adrenaline to give the body sudden energy in times of stress, known as the ‘fight or flight’ response. As a neurotransmitter, it passes nerve impulses from one neuron to the next” Purse (2010, para. 1).

Dopamine is a neurotransmitter that influences several functions in the brain. It creates intense feelings of happiness in humans and is “a chemical substance, a neurotransmitter, found in the brain that regulates movement, balance and walking” UK HealthCare (2007, Dopamine, para. 30). Dopamine influences behavior and thought processes. Dopamine helps to influence feelings of motivation, reward, sleep, and mood regulation (Wickens, A., 2005). Like Dopamine, Serotonin is responsible for mood regulation and sleep. The factor that makes Serotonin different from Dopamine is that Serotonin also helps to regulate body temperature and sexual drive. This small factor makes Serotonin distinctly important to the human body.

Gamma amino butyric acid (also known as GABA), “acts at inhibitory synapses in the brain by binding to specific trans-membrane receptors in the plasma membrane of both pre and post synaptic neurons” (Sahley, B., 2002). Like Dopamine and Serotonin, Gamma amino butyric acid regulates sleep. What makes it unique is that it also regulates anxiety.  Glutamate is “the most common neurotransmitter in the brain” (National Institutes of Health/National institute on Drug Abuse, n.d.). Glutamate helps to regulate cognitive functions. Acetylcholine “is a very effective deliverer of sodium ions, which stimulate muscle contractions and excites nerves. An increase in acetylcholine causes a decreased heart rate and increased production of saliva, as well as readying the muscles for work “(ISCID Encyclopedia of Science and Philosophy, 2008).

In order to understand mental disorders, scientists must first understand what causes these disorders. Neurotransmitters play a large role in the formation of these disorders. If scientists can understand these neurotransmitters, there is a better chance they can understand the disorders. Neurotransmitters are chemicals within the body that enable communication between cells. If there is a problem with a neurotransmitter, this communication is slowed, skewed, or cut off completely. This is how mental illnesses are formed.

Luckily, there are medications that can change the way neurotransmitters work. Neurotransmitters can be made to function in a different way to make up for other neurotransmitters that have malfunctioned. "The discovery of synaptic chemical transmission by Loewi provides one of the pivotal points in the history of biological science-not least because it raised the possibility of modifying brain function (and behavior) by the use of drugs that affect neurotransmitters" (Wickens, A., 2005 p. 14). Antidepressants, for instance, can increase the level of extracellular neurotransmitter serotonin.  The Antidepressants prevent the reuptake into the pre-synaptic cell, which increases the level of serotonin available to bind the cell to the postsynaptic receptor (Wickens, A., 2005 p. 14). Changing the way that chemicals interact in the brain helps to reduce or eliminate the effects of several mental illnesses.

"Neurotransmitters control every emotion and thought, memory and learning; they carry the signals between the nerve cells or neurons in the brain. Psychiatric drugs can interfere with just about every step in work of neurotransmitters" (Sahley, B., 2002). Psychiatric drugs can be used in both positive and negative ways. If a psychiatric drug is used when a neurotransmitter problem does not exist, the function of the brain is altered in a negative way and long term effects may be present.

If there is a malfunction with a neurotransmitter, however, psychiatric drugs may assist in therapeutic treatment of the disorder. "When Serotonin is low, we experience problems with concentration and attention. We become scatterbrained and poorly organized" (Carver, J., 2006). Inability to concentrate can make people behave in ways that they normally would not behave. This is seen in students with Attention Deficit Hyperactivity Disorder. Students are unable to concentrate on their school work and very often their grades are effective. This can cause some students to behave inappropriately because they cannot concentrate on school work and need some other outlet. Having low levels of serotonin can be stressful, and that stress can cause depression symptoms and indigestion.

Depression itself can also be caused by low levels of serotonin. "Treatment for depression, as might be expected, involves increasing levels of Serotonin in the brain. Since the mid-eighties, medications have been available to simply target and increase Serotonin" (Carver, J., 2006). Medications such as Sertraline HCI can be used to treat mental disorders such as depression, obsessive compulsive disorder (OCD), anxiety, bipolar disorder, manic depression, post traumatic stress disorder (PTSD), premenstrual dysphoric disorder (PMDD), and panic disorder (Revolution Health, 2010). Sertraline (Zoloft) raises levels of Serotonin in order to regulate the patient’s mood and behavior.

The knowledge of biological psychology has been a wonderful achievement in the history of psychological research. Without this research, psychologists would not have medication to treat people who have mental disorders. The combination of neural and biological psychologies has made great strides in understanding the chemical and biological reasons that mental illnesses occur. In order to achieve a cure or even a treatment, research in these areas must continue. 

References:

Acetylcholine. (2008). ISCID Encyclopedia of Science and Philosophy. Retrieved from

                http://www.iscid.org/encyclopedia/Acetylcholine

           Carver, J., (2006). Medication Treatment of the Chemical Imbalance. Retrieved from

http://www.enotalone.com/article/4119.html

           Carver, J., (2006). Serotonin: From Bliss to Despair. Retrieved from

                http://www.enotalone.com/article/4116.html

           National Institutes of Health/National institute on Drug Abuse. (n.d.). The brain:

understnding neurobiology. Retrieved from

http://science.education.nih.gov/supplements/nih2/Addiction/other/glossary/glossary2.htm

          Purse, M. (2010). Norepinephrine. About.com. Retrieved from

                http://bipolar.about.com/od/glossary/g/gl_norepinephri.htm

          Revolution Health. (2010). Drugs & treatments. Retrieved from

                http://www.revolutionhealth.com/drugs-treatments/zoloft

          Sahley, B., (2002). Understanding Chemical Imbalances. Retrieved on February 17, 2008 from                

                 http://web.ebscohost.com/ehost/detail?vid=4&hid=9&sid=385e984f-4531-405c-99df-d9250955aad9%40sessionmgr2

         UK HealthCare. (2007). D glossary. Retrieved from

                http://ukhealthcare.uky.edu/patient/glossary/glossary-d.htm

Wickens, A. (2005). Foundations of Biopsychology, Second Edition. Prentice-Hall.