BIO-121 Lab 13 Homeostasis 3 PDF

Lab 11 - Homeostasis BIO-121  Homeostasis Homeostasis is the maintenance of a relatively constant internal environment by an organism, or even by a single cell. Even as external conditions change, internal conditions stay within a narrow range. Internal...

Lab 11 - Homeostasis BIO-121  Homeostasis Homeostasis is the maintenance of a relatively constant internal environment by an organism, or even by a single cell. Even as external conditions change, internal conditions stay within a narrow range. Internal state is often described as one of dynamic equilibrium because internal conditions tend to fluctuate above and below a certain value.  Negative Feedback Negative feedback is the primary mechanism that keeps a variable close to a set point. At least two components. A sensor - detects changes in the environment. A control center - directs a response to return conditions to normal levels. When the pancreas detects high blood glucose levels, it secretes insulin, which causes cells to take up glucose. Blood glucose levels return to normal (set point). Negative Feedback Mechanism  Mechanical Example A home heating system illustrates how a more complex negative feedback mechanism works. The thermostat is set to 68 degrees Fahrenheit, the set point. The thermostat also has a thermometer, which is a sensor to detect room temperature above or below a set point. The thermostat also has a control center. Turns furnace off when the room is too hot. Turns furnace on when the room is too cold.  Mechanical Example In a typical negative feedback mechanism, there is a fluctuation above and below normal. When the furnace is off, the room cools. When the furnace is on, the room warms. Human Example: Regulation of Body Temperature The hypothalamus of the brain serves as the sensor and control center for body temperature. When body temperature is above normal: The control center causes blood vessels near the skin to dilate. Increased blood flow near body surface allows heat to dissipate. Sweat glands are activated by the nervous system so that evaporation helps lower body temperature. Human Example: Regulation of Body Temperature 2 When body temperature falls below normal: The control center causes blood vessels near the skin to constrict. This conserves heat. If body temperature falls even lower, nerve impulses are sent to skeletal muscles, and shivering occurs. Shivering generates heat, and body temperature gradually rises. Negative feedback prevents change in the same direction. Regulation of Body Temperature Figure 11.12 Access the text alternative for these images Positive Feedback Positive feedback. Brings about a greater change in same direction. Blood clotting: Activated platelets initiate clotting process and release factors that stimulate further clotting. Involved in processes with a definite cutoff point. Woman giving birth: Contractions get stronger until birth occurs. Homeostasis and Body Systems: The Transport Systems The Transport Systems. Cardiovascular system conducts blood to and away from capillaries. Exchange of gases, nutrients, and wastes occurs. Interstitial fluid, which bathes cells of the body, is refreshed by exchanges with blood. Oxygen and nutrients move into tissue fluid from the blood. Carbon dioxide and wastes move from tissue fluid into the blood. Regulation of Tissue Fluid Composition Figure 11.13 Access the text alternative for these images The Maintenance Systems The respiratory system adds O2 and removes CO2. The digestive system takes in and digests food to provide nutrients. The liver, an organ that assists in digestive process, regulates blood composition, removes toxins, and makes urea. Kidneys regulate blood volume, salt balance, pH regulation, and waste removal. The Support Systems The Support Systems. The integumentary, muscular, and skeletal systems protect internal organs. Integumentary system also produces vitamin D. Skeletal system also stores minerals, produces blood cells. The Control Systems The Control Systems. The nervous system and endocrine system work together to function to control other body systems and maintain homeostasis. Sensory receptors send signals to the control centers in the brain. Control centers direct the effectors, muscles, and glands to become active. Muscles cause immediate changes. Endocrine glands secrete hormones that bring slower changes. Disease 1 A disease is an abnormality in the body’s normal processes that significantly impairs normal function. Major causes include blood vessel issues, cancers, infections, inflammatory conditions. Systemic disease. Affects entire body or several organs. Localized disease. Restricted to one part of the body. Disease 2 Acute disease. Occurs suddenly. Usually short duration. Chronic disease. Long term. Develops slowly. Cancers are a group of disorders in which the usual controls of cell division fail, resulting in the production of abnormal cells that invade and destroy healthy tissue.