Homeostasis and Feedback

Homeo = Similar Stasis = State

Definition: Maintaining a stable internal environment within a narrow range - keeps proper function of enzymes for metabolic processes

•Involves all organ systems!

What needs to be regulated?(Only need to write what is in bold)

• Nutrients – oxygen, glucose, proteins etc.• Electrolytes – salts (muscle contractions nerve

transmission)• Waste concentrations – CO2, urea (nitrogen

wastes), bile• pH• Temperature• Pressure/volume – gases in blood, lungs

Video Homeostasis

http://www.bbc.co.uk/schools/gcsebitesize/science/add_aqa_pre_2011/homeo/homeosts.shtml

How to regulate(top chart left side)

• Set point – what is the desired range?• Sensors – structures including receptors on

target cells that will monitor levels relative to set point

• Controller – determine if levels are within set point range and what response is necessary to return to range

• Effector – parts of body that physically make the change to return to set point range

Negative Feedback(write in comparing -/+ space below chart)

• change from the normal range is opposed (thus negative)

• brings it back within optimal range and decreases the chaos in the body

• Most systems in body are negative feedback • Examples – body temperature, blood sugar

Thermostat Analogy

Body Temperature(right side of chart)

Set Point: 98.6 degrees F (37 degrees C)

Sensors: sensory nerves

Controller: hypothalamus area in brain sends signals to muscles via nerves

Effector: muscles, sweat, blood vessels (hot/cold details on next slide)

Effectors:

EX. Body Temperature Effectors When Cold (don’t need to copy this)

• Muscles/circulatory constrict peripheral blood flow body sacrifices fingers and toes to save your internal organs

• Muscles at follicles raise hairs (goose bumps),• Skeletal muscles contract (shiver) generate heat• Heart rate slows to keep blood concentrated in core

body• Skeletal muscle adjust body curls up fetal position

Positive feedback(write in comparison space under chart)

• Reinforces the original stimulus – pushing conditions further from the normal

• Less common as it can get out of control and will not stop until stimulus is removed (the bleeding stops)

• Increases chaos in body systems• Examples – blood clotting and child birth

Clotting signals continue until clot is complete and bleeding stops

Next Steps1. Read blood sugar article individually2. Answer the 9 questions at the end of the article on the BACK of the graphic organizer page OR write on separate paper to staple to the graphic organizer3.Complete the bottom chart on the graphic organizer (challenging) turn in at end of class4.Complete Osmosis and Diffusion Practice

Due Tuesday