Feedback and Homeostasis Vocab terms to define Feedback

Feedback and Homeostasis • Vocab terms to define: – – – – Feedback mechanism Dynamic equilibrium Stimuli Homeostasis Pancreas Insulin Guard cells • Review book: Read pg 29 -32 questions 42 -53 completed on loose leaf paper

BELLWORK 1. Read pages 29 -31 in your review book on FEEDBACK and HOMEOSTASIS. 2. Read and discuss QUIETLY the ESSENTIAL question below with your table partner (be prepared to explain if called upon): • During hot weather and vigorous exercise, people sweat. As the water on their skin evaporates, the water molecules absorb heat energy. • Explain why this process is important to the individual.

Dynamic Equilibrium • Our bodies are constantly responding and adjusting to external and internal stimuli, causes small changes in our body temperature, blood sugar level, etc. • Involves interactions between cells and body organs or systems. • All living things must maintain homeostasis in order to survive, otherwise disease or death can result. We refer to these small changes as dynamic equilibrium. This allows us to maintain homeostasis (internal balance or stability). • EX. Human body temp is 37 C; if temp is altered, processes that keep us going will begin to fail

Dynamic Equilibrium • Constant small corrections that keep internal environment w/in stable limit BODY TEMP BLOOD SUGAR LEVEL AFTER MEAL TIME

FEEDBACK MECHANISMS • Involves a cycle in which the output of a system “feeds back” to either modify or reinforce an action. • Closely regulated by the nervous system and endocrine system (using hormones) of the body to Maintain homeostasis • Let’s watch: • http: //www. brainpop. com/health/bodysys tems/homeostasis/ • http: //www. learnerstv. com/animation. php ? ani=241&cat=Biology

TYPES OF FEEDBACK MECHANISM 1. Positive Feedback Mechanism – Change in system causes greater change or response Stimulus: A contraction pushes the baby’s head against the base of the uterus. Positive Feedback Reaction: Pressure on the base of the uterus causes stronger contractions. Response: Baby is born and the feedback cycle ends.

2. Negative Feedback • considered negative because the original signal is lowered or shut off Stimulus Negative Feedback Reaction Response

Examples OF FEEDBACK MECHANISM EX: Thermostat FURNACE KICKS OFF Ex. Body Temperature Stimulus: Brain senses a drop in blood temperature. ROOM COOLS DOWN Negative Feedback: Warmer blood triggers brain to turn-off shivering. ROOM WARMS UP FURNACE KICKS ON Reaction: Nerve message sent to muscles to start shivering. Response: Heat is generated that warms the body and blood.

Example 3: Glucose levels in the blood 1. Blood sugar regulation by insulin (secreted by pancreas) § insulin -- a hormone (chemical messenger); lowers blood sugar 2 major ways: – Takes glucose into our cells to be used as fuel in cell respiration from our blood – Converts excess glucose to glycogen (animal starch) and stores it in our liver and muscles § glucagon -- convert glycogen back to glucose 2. The failure to maintain blood glucose homeostasis results in diabetes. Video: Insulin, Glucose and you http: //www. youtube. com/watch? v=ae_j. C 4 FDOUc http: //bcs. whfreeman. com/thelifewire/content/chp 50/5002 s. swf

Ex #4: Plants regulating water loss • Guard cells in plants opening and closing the stomate to prevent water loss • Stomate- allows for exchange of water vapor (and gases) out of the leaf

Body Systems for Maintaining Homeostasis in multicellular organisms 1) Excretory System - regulates the chemistry of body’s fluids while removing harmful wastes 2) Nervous System - uses electrical impulses to regulate body functions 3) Endocrine System - produces hormones (chemical messengers) regulating their behavior of the body 4) Immune System -stands guard with a set of defenses that protect the body from foreign invaders and disease