HOMEOSTASIS ENDOCRINE SYSTEM THE PANCREAS THE NEPHRON AP

HOMEOSTASIS, ENDOCRINE SYSTEM, THE PANCREAS & THE NEPHRON AP Biology—Unit 9

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

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

Homeostasis � 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?

Homeostasis

Cell Communication Review! � Define the following types of INTERCELLULAR COMMUNICATION: � Endocrine � Paracrine � Synaptic Signaling

Cell Communication Review!

Cell Communication Review!!!

Endocrine System � 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!!! Endocrine System

Signal Transduction Review!!! Endocrine System

� One hormone can have different effects on different target cells. Endocrine System

Endocrine System—Pancreas Gutsman

Endocrine System—PANCREAS � 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)

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

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

Endocrine System—Pancreas

Endocrine System—Pancreas � 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

Endocrine System—Pancreas � Homeostasis: Regulating Blood Sugar Movie � Draw a diagram of the feedback system that controls blood sugar levels!

Endocrine System—Childbirth � 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

Endocrine System—Childbirth

Endocrine—Osmoregulation & Kidneys � 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

Endocrine—Osmoregulation & Kidneys � 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

ADH—Positive or Negative?

Endocrine—Osmoregulation, Blood Pressure, and Kidneys � 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

Aldosterone—Positive or Negative?