Homeostasis

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Homeostasis

• Objectives
• Significance of homeostasis
• Positive and negative feedback

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Disruption of Homeostasis
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Disruption of Homeostasis
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Disruption of Homeostasis
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Disruption of Homeostasis

• Polycystic Kidney Disease

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Disruption of Homeostasis
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• Start here

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Two ways to maintain homeostatis

• Negative feedback
• Positive feedback

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Negative Feedback example body temperature
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Q1 compare response to original stimulus

• Answer
• The response by the effectors is antagonistic
  (opposite) of the stimulus
• Stimulus body temp ?
• Response body temp ?

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Q2 homeostasis restored? How do you know?

• Answer
• Yes, because the response counteracts the
  stimulus
• Brings back balance

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Positive Feedback example labor contractions
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Q3 compare response and stimulus in positive
feedback

• Answer
• The response acts to heighten or increase the
  stimulus
• Stimulus ? distortion of uterus
• Response ? distortion and contraction of
• uterus

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Q4 Is homeostasis restored in this example? How
do you know?

• Answer
• No, homeostasis is continually disrupted
• This is a good thing in this case b/c returning
  to homeostasis would cause the birthing process
  to stop.
• The positive feedback loop will continue until
  birth is complete.

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Lots of examples of negative feedback loops, few
positive loops

• Blood glucose pages ____
• Blood clotting pages _____
• Blood calcium level pages ______
• Female reproductive cycle pages ____

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About Drinking Water

• One glass of water shuts down midnight hunger
  pangs for almost 100 of the dieters studied in a
  University study.
• Lack of water is the 1 trigger of daytime
  fatigue.
• 9-10 glasses of water a day could significantly
  ease back and joint pain for up to 80 of
  sufferers.

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More water stuff

• A mere 2 drop in body water can trigger fuzzy
  short-term memory, trouble with basic math, and
  difficulty focusing.
• Drinking 5 glasses of water daily decreases the
  risk of colon cancer by 45, breast cancer by 79
  and one is 50 less likely to develop bladder
  cancer.

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Cellular homeostasis

• Every level of organization within the body must
  maintain homeostasis

Phospholipid Bilayer
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Diffusion

• Diffusion is the movement of molecules from a
  higher concentration to a lower concentration.
• The difference in concentration of two solutions
  is called the concentration gradient
• Demonstration food coloring in water
• ttp//www.biosci.ohiou.edu/introbioslab/Bios170/di
  ffusion/Diffusion.html

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Diffusion across membranes

• Molecules that dissolve in lipids can cross the
  lipid bilayer through diffusion. Example O2
  CO2 H2O

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Osmosis

• Think back to solutions solutes and
  solvents
• Osmosis is the process by which water molecules
  diffuse across a cell membrane from an area of
  lower solute concentration to an area of higher
  solute concentration.
• Direction of movement depends on relative
  concentrations of solutions.

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Direction of movement into cells

• Hypotonic to the cytosol
• solution outside the cell is less concentrated
  than inside the cell
• water moves into the cell
• Hypertonic to the cytosol
• solution outside the cell is more concentrated
  than inside the cell
• water moves out of the cell
• Isotonic
• concentrations are equal
• http//www.tvdsb.on.ca/westmin/science/sbi3a
  1/Cells/Osmosis.htm

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What about the molecules that cant pass through
the membrane freely?

• Glucose, Na, Ca, K and lots of other molecules
  need to get into and out of the cell but cant
  get through the lipid bilayer
• They must use the proteins embedded in the lipid
  bilayer and this takes type of transport takes
  energy

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Now apply this knowledge to come up with a
logical conclusion for the homeostasis and sports
drink lab

• Putting it altogether research how your body
  maintains homeostasis when you become dehydrated.
  Why do you feel thirsty?

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Active Transport

• Transport Notes
• Active Transport Movie 1
• Active Transport Movie 2

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Predicting water movement

• http//www.mhhe.com/biosci/esp/2001_gbio/folder_st
  ructure/ce/m3/s3/cem3s3_3.htm