3/25 Daily Catalyst Pg. 98 Feedback Loops
 1. Give an example of positive feedback in the
human body.
 2. What type of tissue functions to bind other
tissues.
 3. How is vasodilation and vasoconstriction
part of thermoregulation?
3/25 Class Business Pg. 98 Feedback Loops
 Quiz #25 on Friday
 Report card extra credit
 Tutoring available after school
3/25 Agenda Pg. 98 Feedback Loops
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Daily Catalyst
Class Business
Thermoregulation essay
Feedback Loops gone wrong!
Homework: Gills in Fish and Lungs in humans
Question
 Reptiles are ectotherms and cannot self regulate their internal
body temperatures. Because of this, many reptiles must move
around to find warm or cool areas. Dan the reptile has just woken
up and is freezing, even though he's pretty fat. How could he
become warm again?
A: The hypothalamus sends impulses to his sweat glands.
B: The hypothalamus sends impulses to his muscles to make him shiver
C: He gets up and walks to a rock in sunlight
D: He knits himself a sweater
Essay Prompt
Answer key
 Feedback Loops
 Negative feedback loops:
communication loop between the
body and the brain.
Blood Clots
 In homeostasis:
 Why do not bleed to death every time we cut ourselves?
 Blood Clots!
Blood Clots
 Key Point #1:
 Endothelium is damaged
 (Lines the cavities and organs)
 Key Point #2:
 Clotting factors convert fibrinogen into FIBRIN
 A protein
 Forms the clot
 How is blood clotting an example of positive
feedback?
 Key Point #3 (on your own)
Blood Clotting
 Does this cascade go as planned every time??
 NOPE!
 Key Point #4: Hemophilia
 Caused by –
 Prevents the body from making clots
 Can bleed to death or have internal bleeding easily 
Blood Clotting
 What happens if there is TOO much positive
feedback?
 Lack of homeostasis
 Key Point #5: Thrombus
 A blood clot that forms within a blood vessel and
prevents the flow of blood.
 Can be spontaneous
Diabetes
 In negative feedback, works to inhibit the original
stimulus.
 At homeostasis, blood glucose is around 90 mg/100 mL
 To maintain homeostasis, insulin is released from the
pancreas to lower blood sugar levels BY taking sugar
into the cells for cellular respiration (remember glycolysis)
 Our body is not always at homeostasis.
Diabetes
 Key Point #6: Diabetes is caused by lack of insulin or
decrease in response to insulin in specific tissues.
 Key Point #7: When there is the stimulus of high
glucose levels, the body, by negative feedback works
to lower the blood sugar levels.
Diabetes
 Key Point #8: Type I
 Key Point #9: Type II
In summary
 The control of blood sugar (glucose) by insulin is
another good example of a negative feedback
mechanism. When blood sugar rises, receptors in the
body sense a change . In turn, the control center
(pancreas) secretes insulin into the blood effectively
lowering blood sugar levels. Once blood sugar levels
reach homeostasis, the pancreas stops releasing
insulin.
 Key Point #9: How is diabetes an example of negative
feedback loops?
Work Time
 Complete the following problems on page#98 in your
notebooks. Will be checked tomorrow!
 1,4.7,8,9,10 and evolution connection.