AP Biology—Unit 9

 Definition: maintaining a stable internal environment.  Fluctuates within the bounds of “normal.”  Feedback mechanisms to control homeostasis

 Positive Feedback—an increase in a variable triggers a mechanism that amplifies the variable  Negative Feedback—an increase in a variable triggers a response that counteracts the initial change

 Thermoregulation—regulation of body temperature  By what feedback loop do animals regulate body temperature, positive or negative?  What are some adaptations that help organisms regulate their temperature?

 Define the following types of INTERCELLULAR COMMUNICATION:  Endocrine Signaling  Paracrine  Synaptic

 Endocrine System—sum of all the cells and tissues that secrete hormones  Endocrine Glands—secrete hormones directly into body fluids. They do not have ducts.  Hormones—chemical signals that cause a response in a target cell.  Water-Soluble (Hydrophilic)—cannot go through plasma membrane, so bind to receptor proteins  Lipid-Soluble (Hydrophobic)—diffuse through plasma membrane and bind to intracellular receptor

Signal Transduction Review!!!

 One hormone can have different effects on different target cells.

Gutsman

 Both an Endocrine and Exocrine gland  Endocrine—_________________________________ (i.e. pituitary, thyroid, etc.)  Exocrine—secretes “stuff” that goes into a duct (i.e. liver, salivary gland)

 Exocrine—Secretes Pancreatic Juice through the Pancreatic Duct to the Small Intestines  Pancreatic Juice Contains—  Bicarbonate—buffers stomach acid  Digestive Enzymes

 Endocrine—regulate blood glucose by negative feedback  Beta cells—make Insulin  Insulin tells cells to take in sugar  Increased insulin causes decrease in blood sugar  Alpha Cells—make Glucagon  Glucagon tells cells to convert glycogen to glucose  Increased glucagon causes increase in blood sugar

 Steps:  Eat—Blood sugar increases  Insulin increases—cells take in glucose which decreases blood sugar  Liver converts excess glucose to glycogen  Blood sugar decreases, and so insulin decreases  As blood sugar begins to dip, glucagon increases and tells liver to convert glycogen to glucose  Blood glucose increases

 Homeostasis: Regulating Blood Sugar Movie Homeostasis: Regulating Blood Sugar Movie  Draw a diagram of the feedback system that controls blood sugar levels!

 Prostagladins (local regulators) and Estradiol and Oxytocin (hormones) regulate the contractions of the uterus  Oxytocin forms a positive feedback loop— uterine contractions stimulate the secretion of more oxytocin

 Kidneys—filter blood; maintain water balance  Parts of Nephron—functional unit of kidney  Glomerulus / Bowman’s Capsule  Proximal & Distal Convoluted Tubules  Loop of Henle  Collecting Duct  Processes  Filtration  Reabsorption  Secretion  Excretion

 Antidiuretic Hormone (ADH)  Produced by hypothalamus  Receptor cells in hypothalamus sense osmolarity in the blood (more solutes/salts = higher osmolarity)  If osmolarity increases, ADH is released  ADH binds to receptor proteins on the cells in the collecting duct of nephron  This increases permeability of these cells for water— causing water to be reabsorbed into the blood  Result = more water in blood = decrease in osmolarity

 Aldosterone  Produced in Adrenal Glands  Stimulated by cascade of events between renin and angiotensin when blood pressure and / or blood volume decreases in artioles that supply blood to glomerulus  Aldosterone acts on distal tubule and collecting duct  Increases reabsorption of Na + and water = increase in blood volume = increase in blood pressure