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!