1. Homeostasis of Plasma Glucose Concentration
Normal physiological range: mg/dl
Set point?
Plasma glucose concentration = glucose entering the plasma – glucose leaving the plasma
What are the mechanisms that regulate plasma glucose concentration?
What are the components of the negative feedback loop:
Glucose receptors?
Afferent pathway?
Integrator?
Efferent pathway(s)?
Effector organ(s)?
Phases: *absorptive, *post-absorptive, and fasting

2. Fig
=sink
Absorptive Phase
16.01.jpg

3. Fig
Glucose Sparing
16.02.jpg
Post-absorptive phase

4. Major Points Absorptive phase lasts ~ 4 hours
During absorptive phase, energy needs provided by recently digested food
During absorptive phase, excess is converted to stored fuel
During post-absorptive phase, energy need met by release of stored fuels
Fasting defined as greater than 12 hours after previous meal (some say 24 hrs)
Fasting for several days has little effect on plasma glucose levels

5. The Issues How do cells “know” which fuel to “burn?”
How do cells “know” when to synthesize glycogen or lipids and when to break down glycogen or lipid?
What is responsible for the transitions from the absorptive and post-absorptive states?

6. Islets of Langerhans

7. Which cell types have insulin receptors?
Activates some enzymes, inactivates others
Which cell types have insulin receptors?

8. Fig. 16.01 Absorptive Phase =sink
16.01.jpg
Neurons don’t have insulin receptors, but do have Glucose transporters

10. Post-Absorptive Phase
Fig
Absorptive Phase
16.04.jpg
Post-Absorptive Phase

11. Fig
Id sensors, afferent pathway, integrator, efferent pathway, effectors
How is insulin secretion affected if plasma glucose is lower than set point?
16.07.jpg