Transcript homeostasis and feedback with video clip

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/scie
nce/add_aqa_pre_2011/homeo/homeosts.shtm
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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 Steps
1. Read blood sugar article individually
2. 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 organizer
3. Complete the bottom chart on the graphic
organizer (challenging) turn in at end of class
4. Complete Osmosis and Diffusion Practice
Due Tuesday