4-26-11

Yunsu Yu

4 Ways that We Regulate Our Internal Environment:

1. Homeostasis: (Review from yesterday...)

• Steady state. While there are large external fluctuations, our homeostatic mechanisms take those in and make them smaller fluctuations.
  

• Although we use homeostasis, there are still changes but in ranges that are tolerable=dynamic state.

2. Negative/Positive Feedback:

• Negative Feedback: When something is too much and it turns off.---think of a thermostat, you set it to 72 degrees and when it gets too hot inside, the thermostat turns on and when the temperature goes over 72, it turns off because it is too hot at the moment.----"on and off" switch.
• Positive Feedback: Process that intensifies-makes even more---"on and on more" switch.
  
• Usually negative feedback is used especially in our bodies, but positive feedback is still present.

3.Thermoregulation: maintenance of internal body temperature.

• we are endotherms, we make our own heat from metabolism: sum of chemical reaction=heat.
  
• ectotherms use the sun for heat. Ex:Reptiles.
• Heat loss is regulated by hair, fur, migration, huddling, clothing, sweating, and panting.
• When we get cold our blood vessels constrict near the surface this is what causes shivering and goosebumps. ---this leads to a decrease in exchange from environment.
• Our brains are the control center. This is the thermostat of our bodies and uses Negative feedback when needed.
  

4.Osmoregulation: control of the gain or loss of water and dissolved solutes.

• Gain water from drinking or eating
  

• Through urinating, breathing, and perspiring we lose water. ---the kidneys help regulate this!
  

When someone has a fever should you lower it?

• It depends: sometimes a fever is good because it kills bacteria growth and speeds up the repair of damaged tissue. (100-102 degrees)
  
• But can also be harmful because it damages body proteins and you can die. (104 degrees and over.)
• Fever-caused by "pyrogens" these raise the body temperature.
  

The Excretory System: Kidney, Skin, Lungs..etc

1. Kidneys are the main organs. They filter blood and take out the "bad" stuff.

• We have 2 kidneys that are smaller than your fist and are located in the lower back.

• They contain tubules, capillaries. Throught the tubules blood enters and it filtrates water, glucose, salts, and amino acids.
• Waste products need to be excreted: urea, extra water, extra salt . (sweat)
• The four Processes of the Kidney:
  

1. Filtration: Small things only enter the tubule.
2. Reabsorption: Water and solutes are returned. Take back what we want.
3. Secretion: Specific substances are removed from blood-2nd chance to get everything-drugs go through here (medicine.)
4. Excretion: Urine exits body. Leftover waste.
   

We then took a look at the kidney and labeled the parts:



HW: Design a QUiZ due May 12th

Do UP. 53-57 due Thursday

Do Up. 7-11 due Thursday

NO SCHOOL TOM SO SLEEP IN!

next scribe: Kristen M.