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The Endocrine System and Feedback Loops LSHS Science Department CA Biology Standard 9c KM/ rev YM CA Standard 9c Students know how feedback loops in the nervous system and endocrine systems regulate conditions in the body. Body System Review Nervous System: Recognizes and coordinates the body’s response to the internal and external environment. ex Brain, spinal cord, nerves Circulatory System: Moves blood containing oxygen, waste, nutrients and hormones throughout the body. ex Heart, blood vessels (veins, arteries, capillaries), and blood What is the Endocrine System? Endocrine System • is made up of glands that release their products into the bloodstream. These products deliver messages throughout the body. Function: • Controls growth, development and metabolism….maintains homeostasis! What organs make up the system? • Glands – Specialized organs that produce and secretes hormones What are hormones? • • Chemical messengers that alter the activities of cells in other parts of the body Hormones do this by binding target cells (cells that have receptors for a particular hormone) Glands and Hormones A. Pituitary Gland—the “Master” gland • • B. Pancreas • C. Reproduction Testes (male) • F. Produces adrenalin (epinephrine) to evoke “fight or flight” response Ovaries (female) • E. Produces insulin and glucagon to help regulate blood sugar levels Adrenal Gland • D. Recognizes info and regulates endocrine system Hypothalamus (above pituitary): Helps control pituitary gland Reproduction Thyroid Gland • Regulates metabolism Sweat Glands? **not endocrine glands** F. What is a Feedback Loop? Feedback loops are how the nervous system guides the endocrine system to control body conditions. • Nervous system senses the condition • Endocrine system secretes the hormone to • adapt to the condition Circulatory system carries the hormones to the target cells where they are needed! The Organs Hormones Alters Cell Activities What is a Feedback Loop? Feedback loops are how the nervous system guides the endocrine system to control body conditions. • Nervous system senses the condition • Endocrine system secretes the hormone to • adapt to the condition Circulatory system carries the hormones to the target cells where they are needed! Negative Feedback The amount of a hormone present and the effect of the hormone are opposite! They negatively affect each other Ex Blood Sugar Levels Negative Feedback Loops: Regulation of Blood Sugar Insulin and Glucagon help to keep the level of glucose in the blood stable. Insulin is secreted when high levels of sugar are detected (ex after eating) Glucagon is secreted when low levels of sugar are detected (ex after exercising) Hormone: Insulin Eat Food HIGH Blood Sugar Pancreas—Insulin is secreted Insulin stimulates cells in the liver and muscles to absorb sugar from the blood and store it as glycogen or fat. Blood Sugar DECREASES Pancreas—Insulin stops Hormone: Glucagon Heavy Exercise LOW Blood Sugar Pancreas—Glucagon is secreted Glucagon stimulates the liver to break down glycogen and release glucose back into the blood. It also stimulates the release of fatty acids from stored fats. Blood Sugar INCREASES Pancreas—Glucagon stops Positive Feedback The more stimulation a gland receives the more hormone is produced. • Example: Breast Feeding and Oxytocin • When a mother feeds the baby glands in the breast are stimulated. • Nervous system signals glands to secrete oxytocin. • Oxytocin is a hormone that helps the mother produce more milk. ↑ stimulation = ↑ oxytocin released = ↑ milk production How does feedback work? “Like a Thermostat!!!” Set at a certain temperature When the temperature in the room changes the thermostat triggers a heater or air conditioning system The heater or air conditioning system adjusts to the temperature in the room When the thermostat senses that the room has reached the appropriate temperature, the heater or air conditioner turns off. THIS IS AN EXAMPLE OF A FEEDBACK SYSTEM The thermostat sends feedback to the heater and air conditioner Feedback Systems In humans the hypothalamus acts like the thermostat of feedback systems and the endocrine glands act like the heater or air conditioner. Hormones are released or stop being released in response to the messages sent from the hypothalamus.