Copyright 2010. PEER.tamu.edu How have you changed over the past year? What has caused those changes? How do you think you will change in the next few years? The Endocrine System regulates, coordinates and controls: Growth and development. Male and female development. How your body uses energy. Levels of salts and sugars in your blood. The amount (volume) of fluid in your body. Appetite. Many other body functions. The Endocrine Glands are the organs of the Endocrine System. They produce and secrete (release) Hormones. They are located all over your body. Gland What it Regulates Pituitary “Master Gland” that regulates all other Endocrine Glands, also releases growth hormone Thyroid Metabolism, body heat, bone growth Parathyroids Use of Calcium and Phosphorous Hypothalamus Links nervous system to endocrine system Adrenal Response in emergency or stressful situations, metabolism, blood pressure, salt balance Pancreas Blood sugar Ovaries Production of eggs; female characteristics Testes Production of sperm; male characteristics Thymus Parts of the immune system The answer is Hormones! Hormones are chemical messengers that are secreted (released) from glands into the blood and affect cells in another part of the body. Hormones only work on certain cells, called target cells. The target cells have special receptors that “recognize” the hormones and allow them to influence that cell. Target Target Cell Cell for for Hormone Hormone A A Target Cell for Hormones A and B Hormone A Target Cell for Hormone B Hormone B These receptors recognize the hormones. They “fit” like a lock and key. External stimuli by way of nerves from the sensory organs in the nervous system Internal stimuli by way of nerves and other hormones from inside the body Brain reacts by way of secretions from neurons in hypothalamus (neurohormones) Brain also reacts by way of nerves from hypothalamus and brainstem “Autonomic Nervous System” What is the difference between nerve and hormone control? Why both kinds of controls? Discuss your answers. •Remember, external means coming from outside of your body and internal means coming from inside of your body. Stimulus: You hear a loud noise A large dog runs toward you, growling and barking You eat a large candy bar You have not eaten in six hours You have strep throat A chain of events occur that lead from the stimulus to the response. Negative feedback means that when enough hormone is in the body, the body stops producing the hormone until it is needed again. You eat. Glucose (sugar) in the blood increases. Increased glucose is detected by receptors that notify the brain. It sends a message to the pancreas to produce insulin. Pancreas stops making insulin. Blood glucose level drops as it is removed by the cells. Insulin tells muscle and liver to take up glucose from the bloodstream and use it for energy or store it for later. Brain reduces appetite. Diabetes In the case shown in this picture, the body produces insulin but the target cells become resistant and unresponsive to it. Diabetes can also be caused by the body not producing enough insulin. The glucose does not enter the muscle and liver cells like it should and it builds up in the blood causing complications. A few hormone systems are positive feedback systems: The pituitary gland sends a signal by way of the hormone oxytocin to the uterus causing contractions. The pressure of the fetus on the cervix sends a signal back to the brain which then stimulates the release of more oxytocin. This causes more contractions. The fetus pushes harder on the cervix. More oxytocin is released. The system continues until birth occurs. When normal functions lose their negative feedback control, many times disease is the result. An example: •Neurons in the hypothalamus secrete thyroid releasing hormone (TRH), which stimulates cells in the anterior pituitary to secrete thyroid-stimulating hormone (TSH). •TSH binds to receptors to cells in the thyroid gland, stimulating thyroid hormones, which affect all cells in the body. •When blood concentrations of thyroid hormones increase above a certain level, TRH-secreting neurons in the hypothalamus are inhibited and stop secreting TRH. •If this process is disrupted, the Thyroid keeps producing hormones and hyperthyroid disease ensues. Do you know where each hormone comes from, where it acts, and what the action is? Guess first, then click each to find out. Progesterone Insulin Adrenaline Testosterone Thyroxine Cortisol Estrogen Done Where it comes from: Adrenal Gland Where it acts: heart, blood vessels, eyes What it does: stimulates heart rate, increases blood pressure, dilates pupils Causes "Adrenaline Rush” A 'fight and flight' hormone. It is released in high stress conditions or in excitement or fear. Loud noise, high temperature etc. may also trigger its release since these are also high stress situations. Return to hormones slide • Where it comes from: ovary (where an egg was released) • Where it acts: uterus • What it does: controls menstruation in women and plays a role in pregnancy. • One of the components of birth control pills Return to hormones slide Where it comes from: thyroid gland Where it acts: most cells of the body What it does: controls the rate of metabolic processes (how energy is used) in the body and influences physical development People may not produce enough of this hormone and get a condition known as hypothyroidism. They can take thyroxine to treat this condition. Return to hormones slide Where it comes from: testicles Where it acts: body-hair cells, muscle, reproductive structures What it does: stimulates development of male sexual characteristics Testosterone is a steroid and has been administered to athletes in order to improve performance. This is considered to be a form of doping in most sports and is a very dangerous practice. Females also produce small amounts of testosterone in their ovaries that affect muscle development and other body Return functions. to hormones slide Where it comes from: ovary Where it acts: breast tissue, reproductive structures in female What it does: stimulates development of female sexual characteristics Estrogen levels may be related somehow to migraine headaches in women. Return to hormones slide Where it comes from: outer part of adrenal gland Where it acts: multiple tissues What it does: mental stimulation, breaks down fat and protein to glucose, antiinflammation It is usually referred to as the "stress hormone" as it is involved in response to stress and anxiety. Return to hormones slide Where it comes from: Insulin is produced in the pancreas Where it acts: liver, muscle, and fat tissue What it does: Insulin causes cells to take up glucose (sugar) from the blood, storing it in the liver and muscle, and stopping use of fat as an energy source. Problems with insulin production or use in the body can lead to diabetes. Return to hormones slide What are the functions of the Endocrine System? Name 5 Endocrine Glands and what they do. What are hormones? How do hormones work? Name some hormones and what they do. At what times in your life do you think your Endocrine System is most active?