AP Biology Copy Aim, Do Now, HW#1 Get classwork handout near late log Aim: What roles do hormones play in negative feedback mechanisms? Do Now (4 min): Answer in complete sentences. (1) What do you think of when you hear the word “feedback”? What are ways you receive feedback in school? (2) How can feedback be negative or positive? Is negative feedback necessarily a bad thing? Bonus: How do we maintain homeostasis by regulating the levels of certain things in our body? Give an example. HW #1: Choose a specific hormone from your Table of Hormones and Functions (from yesterday/Tues, also online). Research, online, its: (1) Function (2) How it is activated in the body (3) The effects it produces (4) Disorders where the hormone does not work. At least 2 paragraphs, include sources at end for full credit.

AP Biology Agenda  Do Now and Review  Announcements – Test 1 MP3, Perf Task 1  Class Notes (10 min)  Negative Feedback  Positive Feedback  Pair Work  Handout Questions  Pair Activity on Colored Paper  Exit Tickets Vocab - Negative Feedback - insulin -Glucagon -Liver -Alpha and beta cells -Glycogen

AP Biology  MP3  Test next Tues/Wed on the Endocrine System – you will be allowed to use ONLY class notes and materials  Performance Task 1 for MP3  Performance Task 1 for MP3 – Lab on Monday, do not miss  entirety of the period  We will review classwork rubric on Monday  Expect MP2 grades to be updated by Sunday night Take out notebook – Transitioning into class notes Announcements

AP Biology Hormones and Homeostasis: FEEDBACK MECHANISMS

AP Biology Negative Feedback  Negative feedback occurs when the output of a system acts to oppose changes to the input of the system.  A thermostat is an example of a negative feedback system. How?

AP Biology A thermostat is a device for regulating the temperature of a system so that the system's temperature is maintained near a desired setpoint temperature. Room temp is below the setpoint Room temp is above the setpoint Room temp increases Room temp decreases Set point is reached Set point is reached

AP Biology Negative Feedback in Biology  Negative feedback also regulates many systems in organisms.  The endocrine system is one example.  This diagram shows a negative feedback loop for stress hormones.  Areas of negative feedback are indicated with a minus sign, (-).

AP Biology Maintaining homeostasis high low hormone 1 lowers body condition hormone 2 gland specific body condition raises body condition gland Negative Feedback Model

AP Biology Controlling Body Temperature high low nerve signals sweat nerve signals body temperature (37°C) shiver dilates surface blood vessels constricts surface blood vessels Nervous System Control Feedback hypothalamus

AP Biology

Blood Glucose Level  Pancreatic Hormones regulate blood sugar level before and after meals.  The LIVER stores excess glucose as glycogen to be used for later.  Islets; clusters of cells in pancreas  Alpha  release GLUCAGON – increases sugar  Beta  secrete INSULIN – decreases sugar

AP Biology What Happens?  Between meals Blood glucose low  Pancreas secretes glucagon  Liver changes glycogen to glucose  glucose sent to target tissues  After a meal Blood glucose high  Pancreas secretes insulin  Glucose goes to the Liver (Glycogen) and goes to Target tissues

AP Biology

liver pancreas liver Regulation of Blood Sugar blood sugar level (90mg/100ml) insulin body cells take up sugar from blood liver stores glycogen reduces appetite glucagon pancreas liver releases glucose triggers hunger high low Feedback Endocrine System Control islets of Langerhans beta islet cells islets of Langerhans alpha islet cells

AP Biology  A positive feedback loop occurs when the output of a system acts to enhance the changes to the input of the system.  One example of a biological positive feedback loop is the onset of contractions in childbirth.  When a contraction occurs, the hormone oxytocin is released, which stimulates further contractions.oxytocin  This results in contractions increasing in amplitude and frequency. End of notes – Prepare for Pair Work! Positive Feedback

AP Biology  Both partners do worksheet. No idle time  After worksheet, in pairs on a sheet of colored paper:  Partner 1: Front side: Draw out what will happen with an individual who has eaten too much soda (with extremely high sugar content) and how their sugar level returns to normal  Partner 2: Back side: Draw out the pathway for an individual who has not eaten all day, and needs energy to perform physical activities. Show how their sugar level returns to normal. How do their cells manage to get energy if they aren’t eating? Pair Work

AP Biology  What makes negative feedback important, and not actually “negative”?  What is our ultimate goal for performing negative feedback. Use an example. Exit Tickets (5 min)