Circadian change in body temperature over 28 hours in a group of eight young men Lecture 3: What is Homeostasis? Review: Liver cell funcAons Non-­‐alcoholic faEy liver  impaired funcAon Today: Define Homeostasis – Key Concept! NegaAve & PosiAve Feedback Temperature RegulaAon Pancreas regulaAon of blood glucose Insulin Glucagon Diabetes: Homeostasis failure How does diabetes promote a faEy liver? 10/2/15 Biology 118, Autumn 2015, Dr. Karen Petersen Is this an example of homeostasis? Why is homeostasis called a dynamic equilibrium? 1 10/2/15 Body Temperature deg. F Body Temperature deg. F sUpper Tolerance Limit Stress 100 96 Lower Tolerance Limit Stress PosiAve Feedback: Dangerous! 100 96 Lower Tolerance Limit Response moves body in same direcAon (+) as stress. Move variable in opposite (-­‐) direcAon of stress. 10/2/15 Upper Tolerance Limit 106 Time Time Rate of change decreases as variable reaches normal values. 2 Explain these PosiEve Feedback models Explain these NegaEve Feedback models 106 hEps://courses.candelalearning.com/ospsych/chapter/what-­‐is-­‐consciousness/ Rate of change increases as variable reaches tolerance limits. 3 10/2/15 4 What are the parts of this feedback loop? Explain the sequence of events in these loops. What causes the tolerance limits to thermoregulaEon? 10/2/15 5 Explain why this is an example of negaEve feedback 10/2/15 hEp://fog.ccsf.edu/~mmalacho/physio/oll/Lesson1/hstasis.html 7 10/2/15 Compare with Fig. 24.23 in OpenStax A & P 6 Why is homeostasis called a dynamic equilibrium? 10/2/15 hEp://www.ausAncc.edu/apreview/
EmphasisItems/Glucose_regulaAon.html 8 Compare the islet vs acinar cells of the Pancreas Why is plasma glucose (blood sugar) regulated by negaEve feedback? SAm. liver & fat cells to store lipids Normal plasma glucose 70-­‐110 mg/dl of blood Fig. 17.18 10/2/15 hEp://pathology.jhu.edu/pancreas/basicoverview3.php?area=ba hEp://www.vivo.colostate.edu/hbooks/pathphys/digesAon/pancreas/exocrine.html hEp://droualb.faculty.mjc.edu/Course%20Materials/Physiology%20101/Chapter%20Notes/Fall
9 %202011/chapter_6%20Fall%202011.htm Fig. 17.19 But also see Fig. 24.21 & 24.22 SAm. liver & fat cells to release lipids 10/2/15 10 What causes the changes in pancreaEc beta cell mass? Beta cells produce insulin. Glucose Tolerance Test Results GL = glycemic load Explain the difference between Type I & Type II Diabetes 10/2/15 hEp://www.mdpi.com/1660-­‐4601/11/1/1106/htm 11 10/2/15 hEps://www.mc.vanderbilt.edu/root/vumc.php?site=gannonlab 12 Ideas to Review:
How can diabetes lead to a faSy liver? 1.  What is homeostasis? Why is it called a dynamic equilibrium?
2.  What are the benefits of a negative feedback response? In what direction does a variable
change as a result of a negative feedback response to a stress?
3.  What are the benefits of a positive feedback response? In what direction does a variable
change as a result of a positive feedback response to a stress? How can this lead to
homeostasis failure?
4.  Draw 2 graphs to show negative & positive feedback responses over time.
5.  Describe these components of a homeostasis loop: stress, receptor, integrator/controller,
effector, response. Recognize these steps & put them in order, if given a new example.
6.  Describe the difference between the normal range & tolerance limits of a variable such as
core body temperature that is regulated by homeostasis.
7.  Explain the events in the normal regulation of body temperature & plasma glucose.
Does path with red lines show + or -­‐ feedback? 8.  Describe the changes in plasma glucose, beta cell mass in the pancreas & insulin
production, and cellular responses to insulin in Type I & Type II Diabetes.
9.  How does elevated insulin production lead to a fatty liver? Explain key steps in the pathway.
10/2/15 Smith & Adams, 2011 13 AddiEonal Resources 1. 
AusAn Community College. (2009) Glucose regulaAon. Associate Degree Nursing Physiology Review. hEp://www.ausAncc.edu/apreview/EmphasisItems/Glucose_regulaAon.html 2.  Smith BW & Adams LA. (2011) Nonalcoholic faEy liver disease and diabetes mellitus: pathogenesis and treatment. Nature Reviews Endocrinology 7:456-­‐465. hEp://www.nature.com/nrendo/journal/v7/n8/full/nrendo.2011.72.html 3.  Rush University Medical Center. (2015) How the body regulates heat. Health & Wellness, Discover Health. hEps://www.rush.edu/health-­‐wellness/discover-­‐health/how-­‐body-­‐regulates-­‐heat 4.  University of Wisconsin Board of Regents. (2003) Animal physiology: homeostasis. ConnecAng Concepts: InteracAve Lessons in Biology. hEp://ats.doit.wisc.edu/biology/ap/ho/ho.htm 5.  Walter M. (2007) Homeostasis. Human Biology Lab Online. hEp://bioserv.fiu.edu/~walterm/human_online/labs/homeostasis/homeostasis.htm 10/2/15 15 10/2/15 14