Lab this Week

Endocrinology of Hormone Supplementation

Write a paragraph in which you 1) identify the major objectives of the paper (the most important questions it addresses), and 2) a concise summary of their most important findings. Bring this text with you to lab, ready to turn in to the lab instructor.

Classes this Week

• Glucose Homeostasis:Ch 16A p.555-567 and Ch 16B.1 p. 569-580

• Endocrinology Chapter 11 A-D, F

1QQ # 3 for 10:30Name on top edge, back side of paperAnswer on blank side of paper.

1. Describe what would happen if a person were injected with a drug that acts like Interleukin-6?

2. How can a feedforward response be distinguished from a negative feedback response?

3. What is the difference between heat stroke and heat exhaustion, and how can they be distinguished by physical examination?

4. How do Tylenol and other NSAIDs minimize a fever?

1QQ # 3 for 11:30Name on top edge, back side of paperAnswer on blank side of paper.

1. Describe what would happen if a person were injected with a drug that acts like Interleukin-6?

2. How can a feedforward response be distinguished from a negative feedback response?

3. What is the difference between heat stroke and heat exhaustion, and how can they be distinguished by physical examination?

4. How do Tylenol and other NSAIDs minimize a fever?

Positive feedback

• Examples of Positive Feedback in Physiology– Heat stroke (diagrammed earlier)– formation of blood clot– menstrual cycling of female sex hormone concentrations– generation of action potentials in nerve fibers– uterine contractions during childbirth

• Each of these examples terminate naturally (self limiting)

• Inherently unstable but some are essential for life!

Glucose Homeostasis

Another detailed example of negative feedback

Graph your daily caloric intake over a 48 hour period

6am 6am6pm 6pmNoon NoonMN MN

Cal

orie

sco

nsum

ed

6am Noon

PlasmaGlucose

?

?

Overlay absorptive and post-absorptive phases on the graph

Phases:absorptive, post-absorptive, and fasting

Homeostasis of Plasma Glucose Concentration

• Why is too much plasma glucose harmful?• 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)?

MuscleAdiposeLiverNervousOther

Fig. 16.01A

bsor

ptiv

e P

hase

Lipoprotein Lipase

Once inside, glucose is converted to something else, thereby maintaining a concentration gradientfor facilitated diffusion ofglucose into cells.

=“sinks”Entry requiresGlut-4 transporters

Activates some enzymes, inactivates others

GLUT-4

Peptide hormone

Exercise (via an undescribed mechanism) increases the number of glucose transporters in muscle cell membrane

Diabetes mellitus: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?

Islets of Langerhans

Alpha cells secrete glucagonBeta cells secrete insulinDelta cells secrete somatostatin

Route of blood

LiverTypical vasculature: Artery-Arteriole-Capillary-Venule-Vein-Heart

?

The Integrator integrates multiple inputs

Glucose uptake, Storage, Lipogenesis

WHY? FF

Thinking about food, aroma,Factors that influence Insulin Secretion

and other Incretins