Download Lecture 27 (Hormones) OBJ*s by Dhruv Raj!

Lecture 27 (Hormones) OBJ’s by Dhruv Raj!
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Explain the concept of balance between tissue needs for fuel and fuel availability.
• Metabolic Homeostasis = bodies metabolic needs at normal or minimum requirements
• Normal blood glucose is 80-100mg/dl
• Avg Body needs 190g of Glucose, out of that
• Brain needs 150
• Other tissues/cells want 40g
• Our body accomplishes this with what we eat (carbs/proteins/fats..)
• If too much is available, the body will store it for future use rather than have it
go to waste or leave via urine/fecal route
Explain how the metabolic hormones insulin and glucagon can either stimulate or inhibit
systems to modify cellular homeostasis.
• Insulin is released when we eat food, about 45mins-1hr later insulin levels peak bc the
glucose is in bloodstream. Insulin will direct that glucose to cells if they need it, or liver
for storage (major function), or direct it fat cells for Triglyceride storage. Insulin will
inhibit glycogen breakdown.
• Glucagon is released when blood glucose levels fall below 60mg/dl. It directs the liver to
break down glycogen and release glucose to bloodstream for use. If the glycogen
storage is low then it starts GLUCONEOGENESIS (make new glucose with lactate,
glycerol, amino acids) Glucagon inhibits glycogen storage.
Explain the concept of counter-regulatory hormones, using insulin and glucagon as an
example.
• Counter regulatory hormones are those work against each other. Their actions are exact
opposite. They don’t work together; when one is active the other is inactive. This is all
true for insulin/glucagon.
Describe changes in glucose levels, insulin levels, glucagon levels and nitrogen levels in the
blood over 3-4 hours following a high carbohydrate meal versus a high protein meal.
• High Carb Meal: Since glucose = carbs, there will be a ton of glucose in bloodstream
which will call for Insulin to come and direct the glucose to liver for storage, muscles for
metabolic use..etc During this meal GLUCAGON is not activated!
• High Protein: Protein = No glucose, even though there isn’t glucose, the insulin levels do
peak just a little bit (in 1 hr), but they fall rapidly so once they fall, the Glucagon then is
active and will direct the liver to break glycogen into glucose and release it to the
bloodstream for bodily use. Note: the insulin being active for a short time is only within
one hour, in this case its 3-4 hours so by that time the insulin levels have already
dropped and Glucagon is in action.
Explain the relationship between endocrinology and metabolism.
• Endocrinology is a field which deals directly with hormones, metabolism and the bodily
functions activated/deactivated by these. During metabolism the endocrine system will
react in a way that it promotes homeostasis. It can do this by releasing certain
hormones such as Epinephrine/Norepinephrine, Insulin/Glucagon and many others. Its
job is to make sure the body doesn’t run low on things or doesn’t have too much of
stuff!
Explain how the relative levels of insulin versus glucagon following a meal determine the flux
of dietary fuel molecules through the various metabolic pathways.
• If insulin levels are high it means there is too much glucose, which will activate systems
like Glycogen Synthesis.
Lecture 27 (Hormones) OBJ’s by Dhruv Raj!
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Glucagon levels being high will activate glycogen breakdown. It also activates
gluconeogenesis.
• Explain how metabolic pathways can be stimulated or inhibited by glucagon signaling, using
glycogen synthesis and glycogen breakdown as an example.
• Glucagon signaling will stimulate Glycogen breakdown while it will inhibit Glycogen
storage. It makes sense that to free up glucose for the body we want pathways to be
active that will increase glucose levels and deactivate those that decrease glucose levels.
• Explain in general signal transduction by insulin.
• Beta cells signal insulin production/release when blood glucose is high, the insulin then
binds to the Insluin receptor on cell membrane (cell/brain/muscle). This leads to the
receptor phosphorylating via ATP, this receptor Autophosphorylates. A lot of
phosphorylation happens inside the cell!! Left and right stuff is phosphorylating 
• Glut 4 receptors help in taking in glucose after the protein which makes them
active/open is ….. Phosphorylated!!
• Protein Phosphatase 1 is activated to undo Glucagon-dependent/PKA (protein Kinase A)
proteins and then it activates gene transcription
• Key point: Insulin Dephosphorylates Phosphorylase kinase so the glycogen degradation
can be stopped.
• Explain the fight or flight response to epinephrine that elicits metabolic changes in glycogen
breakdown in muscle versus liver.
• During flight/fight we need as much glucose as possible for the body to utilize so we can
run from a lion,dog,bigfoot..whatever is after us. To run/think our brain and skeletal
muscles need lots of glucose. It would make sense that Epinephrine would have a
stimulatory effect on Glycogen Breakdown (MORE GLUCOSE)
• Its effect is similar to that of Glucagon
• How Epi does this: it binds to beta receptors to activate PKA , and also binds to alpha
cells to signal the start of Glycogen breakdown
• Compare and contrast glycogen breakdown during exercise versus during stimulation by fight
or flight hormones.
• The function for both is the same: Have more glucose available
• The difference is in their signal pathway:
• Epinephrine activates cAMP which then activates PKA—which acts through
Glycogen Phosphorylase a
• Exercise: works via nerve impulses (Increase in Ca2+ levels), Myosin ATPase is
activated which activates Adenylate Kinase which acts on Glycogen
Phosphorylase b
• Define the roles fo glucagon-like peptides 1 and 2 in the regulation of glucose homeostasis.
• I don’t even think Dr. Brown mentioned these! If he did, too bad I wasn’t paying
attention.
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Here are some other important details about this lecture:
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Insulin is made in Beta cells, it travels via the Hepatic portal vein to its acting zones
o When glucose levels come back to normal it is degraded in liver, kidney, or skeletal
muscle
Glucagon is Alpha cells (gucagon has an a in it, so alpha-a)
Lecture 27 (Hormones) OBJ’s by Dhruv Raj!
Major DETAIL:
 Insulin Dephosphorylates for its activity, turn on glycogen synthesis, turn off glycogen
breakdown
 Glucagon phosphorylates for its activity, turn off glycogen synthesis, turn on glycogen
breakdown
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Insulin is only signaled if blood glucose is HIGH
Glucagon can be signaled by CNS, or other factors depending on the state of the body.
If I miss something, please let me know! Thanks!