Transcript GlucoseHomeostasis1

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 10:30
Name on top edge, back side of paper
Answer 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 11:30
Name on top edge, back side of paper
Answer 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
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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
Phases:
absorptive,
post-absorptive, and fasting
Plasma
Glucose
Calories
consumed
?
?
6am
Noon
6pm
MN
6am
Noon
6pm
MN
6am
Noon
Overlay absorptive and post-absorptive phases on the graph
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:
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Glucose receptors?
Afferent pathway?
Integrator?
Efferent pathway(s)?
Effector organ(s)?
Muscle
Adipose
Liver
Nervous
Other
Absorptive
Phase
Fig. 16.01
Lipoprotein Lipase
=“sinks”
Entry requires
Glut-4 transporters
Once inside, glucose is
converted to something else,
thereby maintaining a
concentration gradient
for facilitated diffusion of
glucose into cells.
Exercise (via an undescribed mechanism)
increases the number of glucose
transporters in muscle cell membrane
Peptide hormone
GLUT-4
Activates some enzymes, inactivates others
↑ plasma glucose →↑insulin secretion→↑glucose uptake into cells →↓ plasma glucose
Diabetes mellitus:
T1DM =beta cells fail to produce adequate insulin (5%)
T2DM = target cells “resistant” (less responsive) to insulin
Identify sensors,
afferent pathway,
integrator,
efferent pathway,
effectors
Fig. 16.07
How is insulin secretion
affected if plasma
glucose is lower than
set point?
Which cell types have
insulin receptors?
Liver
Typical vasculature: Artery-Arteriole-Capillary-Venule-Vein-Heart
Islets of Langerhans
Alpha cells secrete glucagon
Beta cells secrete insulin
Delta cells secrete somatostatin
Hepatic
portal
Route
of blood
system
Artery-Arteriole-Capillary in digestive tract-Portal Vessel- Capillary in liver-Venule-Vein-Hea
Factors that influence Insulin Secretion
Thinking
about food, aroma,
?
and other Incretins
WHY?
The Integrator
integrates multiple
inputs
FF
Glucose
uptake,
Storage,
Lipogenesis