The Endocrine System and Feedback Loops

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? 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 is the Endocrine System? Made up of glands that produce and secrete hormones, chemical messengers Regulation of growth, metabolism, sexual development Responses to stress and injury Maintains homeostasis Glands are found in different areas of the body.

Endocrine Glands – secretions inside the body Exocrine Glands – secretions outside the body (sweat) Saliva Breast Milk Sweat

Glands of the Endocrine System

The Master Gland The hypothalamus and pituitary gland in the brain both work together to control all secretions by all endocrine glands. The pituitary is called the “MASTER GLAND” because it is near the top of the chain of command. Tells other glands what to do It produces a large number of different hormones

Endocrine: Chain of Command The Organs Endocrine: Chain of Command Hormones Alters Cell Activities

BIG IDEA: HORMONES are chemical MESSENGERS that act on target cells

Two Hormone Types: Steroid Hormones Steroid hormones tell a target cell what to do by telling the DNA inside the nucleus what to do. Steroid hormones turn a gene on and then the gene tells the cell to make a particular kind of protein. Examples: Estrogen, Testosterone, Progesterone Cholesterol, Aldosterone, Cortisone, Cortisol (most end with “ONE” or “OL”)

Two Hormone Types: 2. Protein Hormones Protein hormones tell a target cell to activate certain existing inactive proteins. The protein hormone does this by providing the energy for the activation. Examples: Oxytocin, Luteinizing Hormone (LH) All other hormones not on the steroid list

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

Regulation of Blood Sugar 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)

Pancreas—Insulin is secreted 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

Pancreas—Glucagon is secreted 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

THIS IS AN EXAMPLE OF A FEEDBACK SYSTEM 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 adjust 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 s

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.