Checkpoint:  Heredity and Hormones

        The influence on heredity and hormones play a major role on a person’s behavior.  Traits are passed from generation to generation, and though upbringing and environment allow for some modifications in how those genes may or may not be expressed, the traits have already predetermined some things.  Hormones have been identified as having noticeable control of physical and mental processes as well.  

        Hormones are of significant importance.   Hormones are your body's chemical messengers. They travel in your bloodstream to tissues or organs. They work slowly, over time, and affect many different processes, including:  growth and development, metabolism, sexual function, reproduction and mood (Medline Plus, 2010).  Hormones are powerful and it only takes a tiny amount to cause big changes in cells or even your whole body.  Endocrine glands, which are special groups of cells, make hormones.  The major endocrine glands are the thyroid, pineal, pituitary, adrenal glands and pancreas. In addition, men produce hormones in their testes and women produce them in their ovaries (Medline Plus, 2010).  The thyroid gland produces thyroxin which is the hormone responsible for regulating metabolism which plays a part in how much energy one has at a particular time.  When the thyroid overproduces thyroxin, a person will experience several symptoms, some being insomnia, fatigue, and depression.  On the contrary when the thyroid does not produce adequate amounts of thyroxin, one will want to sleep all of the time.  The pineal gland is a tiny gland located in the middle of the brain.  This gland secretes the hormone melatonin.  Melatonin regulates the sleep-wake cycle; is this hormones is unstable a person can experience feelings of “jet-lag”.  A person’s pituitary gland is known as the “master gland” and has the largest effect on the body of all the endocrine glands.   It produces and secretes many hormones that travel throughout the body, directing certain processes stimulating other glands to produce different types of hormones.  The pituitary gland controls biochemical processes important to our well-being.  There are several hormones secreted by the pituitary.  Prolactin stimulates milk production from the breasts after childbirth to enable nursing.  Growth hormone (GH) stimulates growth in childhood and is important for maintaining a healthy body composition and well-being in adults.  In adults it is important for maintaining muscle mass as well as bone mass.  It also affects fat distribution in the body.  Adrenocorticotropin (ACTH) stimulates the production of cortisol by the adrenal glands.  Cortisol, a so-called "stress hormone" is vital to our survival.  It helps to maintain blood pressure and blood glucose levels.  Thyroid-stimulating hormone (TSH) is responsible for stimulating the thyroid gland, which regulates the body's metabolism, energy, growth, and nervous system activity.  This hormone is also vital to our survival.  Another hormone secreted into the body by the pituitary is Antidiuretic hormone (ADH), also called vasopressin, regulates water balance.  If this hormone is not released properly, it can lead to too little hormone (called diabetes insipidus), or too much hormone (called syndrome of inappropriate ADH).  Both of these conditions affect the kidneys.  Diabetes insipidus is different from the more well-known diabetes mellitus (including type 1 and type 2 diabetes), which affects the levels of glucose in our bodies.  The last two hormones secreted by the pituitary are Luteinizing hormone (LH) which regulates testosterone in men and estrogen in women and Follicle-stimulating hormone (FSH) which promotes sperm production in men and stimulates the ovaries to enable ovulation in women.  Luteinizing hormone and follicle-stimulating hormone work together to cause normal function of the ovaries and testes (The Hormone Foundation, 2010).  The adrenal gland is responsible for a person’s reaction to stress, releasing hormones that you can't live without, including sex hormones and cortisol, which helps you respond to stress and has many other functions.  During periods of stress the brain signals the adrenal glands to produce epinephrine or "adrenaline".  Epinephrine increases the rate in which the heart beats.  The increased cardiac output supplies more oxygen to the muscles, putting the body in a heightened state to react.  As a longer term response to stress, cortisol is secreted by the adrenal glands, promoting the release of energy (Medline Plus, 2010).  Norepinephrine released by the adrenal glands also contributes to the increase in heart rate and blood pressure.  The pancreas is located between the stomach and small intestine and is responsible for producing insulin and glucagon.  These hormones work against each other to keep the body’s blood sugar in balance.  Without proper function of these hormones, a person may develop diabetes or hypoglycemia.  The final endocrine glands of importance are the gonads.  Both males and females produce amounts of estrogen and androgens.  In males the testes produce and abundance of testosterone while in females the ovaries produce increased amounts of estrogen.  

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        Scientists have accepted the fact that genes have an effect on more than just physical appearance.  Genes can have an influence on behavior, mood, mental processes, and can mark a predisposition for certain diseases, addictive behavior, and mental disease.  Behavior genetics is the scientific study of the interrelationship of genetic mechanisms and behavior (Behavior Genetics Association, 2010).  Research in behavior genetics has shown that almost all personality traits have both biological and environmental bases.  Behavior genetics is a field in which variation among individuals is separated into genetic versus environmental components.  The most common research methodologies are family studies, twin studies, ...

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