henry tanner: 1900’s – “angels and shepherds”. the endocrine system chapter 10: 257-265...
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Henry Tanner: 1900’s – “Angels and Shepherds”
The Endocrine System
Chapter 10: 257-265
276-278
Hormones and Homeostasis…Of Course!“Homeostasis depends on the
precise regulation of the organs and organ systems of the body. The Nervous and Endocrine Systems are the two major systems responsible for that regulation.”
Nervous vs. EndocrineAxons relay the
message directly to target
Fast/Short Acting
Homeostatic “Rescue”
Blood delivers message to widespread targets
Slow/Long Lasting
Adaptation – Training Effect
Chemical Signals (Ligands):Autocrine: Released from one type
of cell – targets the same type of cellProstaglandins - inflammation
Paracrine: Released from one cell – targets a neighboring cell without being transported in the bloodNitric Oxide in blood vessels
More Ligands:
Endocrine: released into the blood for distant target tissuesInsulin: Pancreas – Muscle
Neurohormones: Released by nerves into the bloodAntidiuretic Hormone (ADH):
Posterior Pituitary - Kidney
Last But Not Least…Neuromodulators: Released by nerves
to modulate the activity of neighboring nerves
Neurotransmitters: Released by nerves to signal activity in neighboring nerves / tissues
Pheromones: Released into the air to attract mates…
Let’s Look Closely…
Page 258: Examples of ChemicalSignals
At The Target Cell:Intracellular Recepters: Ligand
able to diffuse into cell – receptor in cytosol (enzymes) or nucleus (DNA – RNA synthesis)
Membrane Bound Receptors: Ligand activates receptor – initiate intracellular responses
Responses:Channels open/close
Acetylcholine – Na+ ChannelsEnzymes Activated
Glycogenolysis enzymesG-Proteins Initiated
Activate chemical signals: cAMPDNA/RNA synthesis
A Closer Look at Blood Glucose Homeostasis:Who Cares (About Blood Glucose)?
The Brain Does (45% of all Glucose used by the brain)
What are Normal Fasting Levels?70-100 mg/dl blood
What are Normal Fed Levels?120-180 mg/dl
Glucose
Muscle10%
BRAIN45%
Glycolysis20% (RBC)
Other25%
FoodGluconeogenesis
Glycogenolysis
Hypoglycemia: A Homeostatic Emergency!
Eat!Make New Glucose:
GluconeogenesisBreak Down Stored Glycogen:
Glycogenolysis
Sustaining the Fast: (Non-Feed Options)Glucagon: A Pancreatic Hormone that
acts on liver cells: Glycogenolysis, Gluconeogenesis,
LipolysisGlucocorticoids: Adrenal medulla
hormone that acts on liver, fat, muscle cells: Lipolysis, Gluconeogenesis
Fasting and Insulin:Fasting HypoglycemiaHypoglycemia Glucagon
and Glucocorticoids
INSULIN
Hypoglycemia
Glucagon
Glucocorticoids
Response to StarvationDecrease Insulin: Conserves
Glucose for the brainIncrease Glucagon/Glucocorticoids:
Mobilizes stored glycogen/fats to maintain energy and glucose
NET EFFECT: Stable Blood glucose for the BRAIN
INSULIN
GLUCAGON
Hormones During Fasting
After Feeding (Twinkies?)
Increased Blood GlucosePancreas Secretes InsulinInhibits: Glucagon and
GlucocorticoidsNET EFFECT: Increase glucose
uptake by muscles and fat cells for use and storage
INSULIN
GLUCAGON
Hormones after Feeding
One Last Exercise Application: Muscles Need
Lots of FuelGlucose is
Important in Brief Intense Exercise
We don’t Feed During Exercise
Exercise is a Homeostatic Emergency!Sympathetic Nervous System
Activated!Decreases InsulinIncreases “Mobilizing
Hormones: Glycogenolysis, Gluconeogenesis Stimulated
But Wait! How does Glucose get into the muscles???
EXERCISE stimulates Glucose Transporters and Glucose Uptake Without Insulin!
Which Means:Glucose can get into muscle cells Glucagon/Glucocorticoids can
maintain glucose mobilization and supply
We don’t need to eat while we work!
Exercise and DiabetesNIDDM: Regular activity improves
the “receptor problem”May be the most important
treatment (prevention?) for NIDDM!!IDDM: Exercise reduces the amount
of insulin needed: May pose the risk of hypoglycemia
This wraps up our semester
long journey
It’s beenFUN!