Announcements

• Lab this week: Frog Reflexes– Review information on lab webpage

• Friday Quiz– Topics

• Thermoregulation and • Glucose Homeostasis and • Frog Reflexes

– Format• Powerpoint slides on screen• Multiple-multiple choice: choose all correct responses• Fill in the blank• About 10 questions

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?

• How does glucose get into “sinks?”

Activates some enzymes, inactivates others

GLUT-4

Peptide hormone

Exercise via an undescribed mechanism

+

T1DM =beta cells fail to produce adequate insulin (5%)T2DM = target cells “resistant” (less responsive) to insulin

↑ plasma glucose →↑insulin secretion→↑glucose uptake into cells →↓ plasma glucose

Fig. 16.07Identify sensors, afferent pathway,integrator,efferent pathway,effectors

How is insulin secretion affected if plasma glucose is lower than set point?

Which cell types have insulin receptors?

Fig. 16.01

=sink

Abs

orpt

ive

Pha

se

Neurons don’t have insulin receptors, but do have Glucose transporters (not GLUT-4)

=GLUT-4

Absorptive Phase

Post-Absorptive Phase

?

The Integrator integrates multiple inputs

Glucose uptake, Storage, Lipogenesis

WHY?

Another hormone that regulates plasma glucose concentration

Glucagon prevails during post-absorptive phase

Transition from absorptive to post-absorptive phase?

Fig. 16.10

EPI, yet another horomone inglucose homeostasis

Glucose-counterregulatory controls

(oppose effects of insulin)

GlucagonEpinephrineCortisol (permissive effect)Growth hormone (permissive effect)

Who Cares?

A Case Study

• On our website at• http://webs.wofford.edu/davisgr/bio342/oggt.htm

Oral Glucose Tolerance Test

• Overnight fast, no beverages other than water

• Fasting blood sample• Ingest 75 grams glucose• Blood samples every 0.5

hours for 3-5 hours• Plot plasma glucose

concentration over time• Compare curves

60

Stress,Emergency (fight or flight)

Effect onBeta cells

Effect on Alpha Cells