AP Biology: Human Body Systems

1. AP Biology: Human Body Systems Endocrine System Renira Rugnath

2. Endocrine System Function: The Endocrine System is in charge of body processes that happen slowly, such as cell growth. Purpose: to secrete hormones, or signal molecules released by glands

3. The endocrine system is a collection of glands that secrete chemical messages we call hormones. • These signals are passed through the blood to arrive at a target organ, which has cells possessing the appropriate receptor. • Exocrine glands (not part of the endocrine system) secrete products that are passed outside the body. • Sweat glands, salivary glands, and digestive glands are examples of exocrine glands

7. Parts of the Endocrine System • The major glands that make up the human endocrine system are the hypothalamus, pituitary, thyroid, parathyroids, adrenals, pineal body, and the reproductive glands, which include the ovaries and testes. The pancreas is also part of this hormone-secreting system, even though it is also associated with the digestive system because it also produces and secretes digestive enzymes. • Although the endocrine glands are the body's main hormone producers, some non-endocrine organs — such as the brain, heart, lungs, kidneys, liver, thymus, skin, and placenta — also produce and release hormones.

8. Exocrine Glands Endocrine Glands • Exocrine glands are duct glands that produce a substance which travels through small tube-like ducts. Its secretions are transported in the ducts directly to an organ or the body surface. Exocrine glands include sweat and oil glands of the skin, intestinal glands, and salivary glands in the mouth. • Unlike exocrine glands, endocrine glands are ductless glands. They secrete hormones directly into the bloodstream, which then travel to the target organs. Hormones help regulate metabolism, water and electrolyte concentrations in cells, growth, development, and the reproductive cycles.

9. The production and secretion of pituitary hormones can be influenced by factors such as emotions and seasonal changes. To accomplish this, the hypothalamus relays information sensed by the brain (such as environmental temperature, light exposure patterns, and feelings) to the pituitary. The Hypothalamus The Pituitary Gland • The hypothalamus, a collection of specialized cells that is located in the lower central part of the brain, is the primary link between the endocrine and nervous systems. Nerve cells in the hypothalamus control the pituitary gland by producing chemicals that either stimulate or suppress hormone secretions from the pituitary. • The tiny pituitary gland is divided into two parts: the anterior lobe and the posterior lobe. The anterior lobe regulates the activity of the thyroid, adrenals, and reproductive glands. Among the hormones it produces are: •growth hormone, which stimulates the growth of bone and other body tissues and plays a role in the body's handling of nutrients and minerals •prolactin, which activates milk production in women who are breastfeeding •thyrotropin, which stimulates the thyroid gland to produce thyroid hormones •corticotropin, which stimulates the adrenal gland to produce certain hormones

10. The pituitary also secretes endorphins, chemicals that act on the nervous system to reduce sensitivity to pain. In addition, the pituitary secretes hormones that signal the ovaries and testes to make sex hormones. The pituitary gland also controls ovulation and the menstrual cycle in women. • The posterior lobe of the pituitary releases antidiuretic hormone, which helps control body water balance through its effect on the kidneys and urine output; and oxytocin, which triggers the contractions of the uterus that occur during labor.

11. Thyroids • The thyroid, located in the front part of the lower neck, is shaped like a bow tie or butterfly and produces the thyroid hormones thyroxin and triiodothyronine. These hormones control the rate at which cells burn fuels from food to produce energy. As the level of thyroid hormones increases in the bloodstream, so does the speed at which chemical reactions occur in the body. • Thyroid hormones also play a key role in bone growth and the development of the brain and nervous system in children. The production and release of thyroid hormones is controlled by thyrotrophin, which is secreted by the pituitary gland. • Attached to the thyroid are four tiny glands that function together called the parathyroids. They release parathyroid hormone, which regulates the level of calcium in the blood with the help of calcitonin, which is produced in the thyroid. Parathyroids

12. Adrenal Glands • Each kidney has an adrenal gland located above it. The adrenal gland is divided into an inner medulla and an outer cortex. The medulla synthesizes amine hormones, the cortex secretes steroid hormones. The adrenal medulla consists of modified neurons that secrete two hormones: epinephrine and norepinephrine. Stimulation of the cortex by the sympathetic nervous system causes release of hormones into the blood to initiate the "fight or flight" response.

13. The adrenal cortex produces several steroid hormones in three classes: mineralocorticoids, glucocorticoids, and sex hormones. Mineralocorticoids maintain electrolyte balance. Glucocorticoids produce a long-term, slow response to stress by raising blood glucose levels through the breakdown of fats and proteins; they also suppress the immune response and inhibit the inflammatory response.

14. The Gonads • The pineal body, also called the pineal gland, is located in the middle of the brain. It secretes melatonin, a hormone that may help regulate the wake-sleep cycle. • The gonads are the main source of sex hormones. In males, they are located in the scrotum. Male gonads, or testes, secrete hormones called androgens, the most important of which is testosterone. These hormones regulate body changes associated with sexual development, including enlargement of the penis, the growth spurt that occurs during puberty, and the appearance of other male secondary sex characteristics such as deepening of the voice, growth of facial and pubic hair, and the increase in muscle growth and strength. Working with hormones from the pituitary gland, testosterone also supports the production of sperm by the testes. • The female gonads, the ovaries, are located in the pelvis. They produce eggs and secrete the female hormones estrogen and progesterone. Estrogen is involved in the development of female sexual features such as breast growth, the accumulation of body fat around the hips and thighs, and the growth spurt that occurs during puberty. Both estrogen and progesterone are also involved in pregnancy and the regulation of the menstrual cycle. The Pineal Glands

15. Pancreas • The pancreas contains exocrine cells that secrete digestive enzymes into the small intestine and clusters of endocrine cells (the pancreatic islets). The islets secrete the hormones insulin and glucagon, which regulate blood glucose levels. • After a meal, blood glucose levels rise, prompting the release of insulin, which causes cells to take up glucose, and liver and skeletal muscle cells to form the carbohydrate glycogen. As glucose levels in the blood fall, further insulin production is inhibited. Glucagon causes the breakdown of glycogen into glucose, which in turn is released into the blood to maintain glucose levels within a homeostatic range. Glucagon production is stimulated when blood glucose levels fall, and inhibited when they rise.

16. Diabetes results from inadequate levels of insulin. Type I diabetes is characterized by inadequate levels of insulin secretion, often due to a genetic cause. Type II usually develops in adults from both genetic and environmental causes. Loss of response of targets to insulin rather than lack of insulin causes this type of diabetes. Diabetes causes impairment in the functioning of the eyes, circulatory system, nervous system, and failure of the kidneys. Diabetes is the second leading cause of blindness in the US. Treatments involve daily injections of insulin, monitoring of blood glucose levels and a controlled diet.

17. Relationships • Integumentary System: By releasing hormones to activate the skin cells/glands • Skeletal System: The thyroid in the endocrine system produces the hormone calcitonin. Calcitonin decreases the concentration of calcium in the blood by acting with bone to inhibit its breakdown. The less bone that is reabsorbed the less calcium moves into the blood. So the level of calcium in the blood decreases. On the other hand, the parathyroid secretes parathyroid hormone which increases the concentration of calcium in the blood. The PTH stimulates the osteoclasts to increase the breakdown of bone. Cells in our bodies are very sensitive to changing amounts of calcium in the blood. With too much or too little calcium in the blood cells do not function correctly and for example the heart could stop. • Muscular System: One way the endocrine system works with the muscles is through the release of glucose. When your muscles need energy, a signal will be sent to your brain to release more insulin from your pancreas, which will create more energy to be available for use. Glycogen will be pumped out by your liver if you are in need of energy stores. Also read more about the fight or flight response.

18. Nervous System: The endocrine system is responsible for the regulation of hormones in the body. It works with nervous system by stimulating the brain to release hormone to stimulate glands like thyroid glands to secrete thyroid hormones. They also work together to maintain homeostasis. • Digestive System: When we digest carbohydrates, they are transformed into sugars. The pancreas, part of the endocrine system, produces the hormone insulin to regulate how fast the sugars are broken down; therefore, insulin regulates the amount of sugar in the blood in a certain amount of time (the blood glucose level). • Cardiovascular System: The cardiovascular system consists of the heart and blood vessels, from the largest veins and arteries down to the smallest capillaries. It also circulates hormones that are released by the endocrine system--a system of glands--throughout the body. Hormones function by producing their effects only when they attach to a suitable target receptor. Even though hormones circulate freely throughout the cardiovascular system, aside from the target receptors, the rest of the body's systems are essentially unaffected by their presence. The following 10 kinds of glands form the endocrine system. All secrete their hormones into the cardiovascular system at large. • Lymphatic System: The endocrine system releases cortisol with can make substances that increase your immunity.

19. Respiratory System: Both the endocrine and respiratory systems are dependent on each other. For example, there are certain hormones like adrenalin, which is released by the adrenal glands, which help to stimulate the respiratory activity. Also, some endocrine hormones have an effect on the dilation of the alveoli, or the respiratory passages. This can affect the amount of oxygen that the lungs absorb. • Urinary System: The endocrine system (specifically pituitary gland and adrenal gland (cortex)) secrete hormones (ADH - antidiuretic hormone & aldosterone) which cause the kidneys to reabsorb salt. This, in turn, causes the kidneys to increase water re-absorption. All of this increases blood volume, which increases blood pressure. • Reproductive System: The endocrine system sends out hormones which control your fertility and periods after puberty, so the endocrine system really controls the reproduction system.

20. Evolutionary Development • Most animals with well-developed nervous and circulatory systems have an endocrine system. Most of the similarities among the endocrine systems of crustaceans, arthropods, and vertebrates are examples of convergent evolution. The vertebrate endocrine system consists of glands (pituitary, thyroid, adrenal), and diffuse cell groups scattered in epithelial tissues. • More than fifty different hormones are secreted. Endocrine glands arise during development for all three embryologic tissue layers (endoderm, mesoderm, ectoderm). The type of endocrine product is determined by which tissue layer a gland originated in. Glands of ectodermal and endodermal origin produce peptide and amine hormones; mesodermal-origin glands secrete hormones based on lipids.

21. In order to answer this question we must all understand what the organs are that make up the endocrine system. The hypothalamus is the master control found in the brain at the base of the optic chiasm. The hypothalamus releases a hormone in the pituitary gland, controls the balance of water, sleep, temperature, appetite, blood pressure and such. There is much more but that is a start..... Hormones! Homeostatic conditions also vary across the body - for example, a high acidic level must be maintained in the stomach, this level is maintained by the hormone Gastrin, which is released when the stomach is stretched by food, this hormone targets the production of HCl (Hydrochloric Acid) in the stomach Homeostasis

22. Another, possibly the most important homeostatic condition is water, which can be maintained by the hormone ADH (anti-diuretic hormone) which controls how permeable the distal convoluted tubules and collecting tubules are, the increase of permeability makes the water that would usually go straight into the urine go back into the body, this lowers water loss and increases urine concentration. this hormone is only released when the body is dehydrated, but when the body has too much, this is removed from the body and most of the water that would be reabsorbed into the body is just removed in the urine. Hormones send messages to different organs and organ system to turn on/off speed up/slow down activities of those tissues This is the main way we maintain homeostasis actually, since the endocrine system releases chemicals known as hormones. These hormones are sent via the blood to specific spots in the body to control things like blood sugar, heart rate, etc.

23. WORK CITED • Answers. (2013). WikiAnswers. Retrieved from http://wiki.answers.com/ • Farabee, M.J. (2001). THE ENDOCRINE SYSTEM. Retrieved from http://www.emc.maricopa.edu/faculty/farabee/biobk/biobookendocr.html#Other%20Endocrine%20Organs • Grallator9. (2010). The Endocrine System. YouTube. Retrieved from http://www.youtube.com/watch?v=Ry5fTZfZHIs • Nemours. (n.d.). KidsHealth. Retrieved from http://kidshealth.org/parent/general/body_basics/endocrine.html# • The Endocrine System: A Control Device. (2008). ThinkQuest. Retrieved from http://library.thinkquest.org/07aug/01618/endocrine.html