Henry Tanner: 1900’s – “Angels and Shepherds”

The Endocrine System Chapter 10:

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 v s. Endocrine Axons 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 cell Prostaglandins - inflammation Paracrine: Released from one cell – targets a neighboring cell without being transported in the blood Nitric Oxide in blood vessels

More Ligands: Endocrine: released into the blood for distant target tissues Insulin: Pancreas – Muscle Neurohormones: Released by nerves into the blood Antidiuretic 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 Chemical Signals

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+ Channels Enzymes Activated Glycogenolysis enzymes G-Proteins Initiated Activate chemical signals: cAMP DNA/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? mg/dl blood What are Normal Fed Levels? mg/dl

Glucose Muscle 10% BRAIN 45% Glycolysis 20% (RBC) Other 25% Food Gluconeogenesis Glycogenolysis

Hypoglycemia: A Homeostatic Emergency! Eat! Make New Glucose: Gluconeogenesis Break Down Stored Glycogen: Glycogenolysis

Sustaining the Fast: (Non- Feed Options) Glucagon: A Pancreatic Hormone that acts on liver cells: Glycogenolysis, Gluconeogenesis, Lipolysis Glucocorticoids: Adrenal medulla hormone that acts on liver, fat, muscle cells: Lipolysis, Gluconeogenesis

Fasting and Insulin: Fasting Hypoglycemia Hypoglycemia Glucagon and Glucocorticoids INSULIN Hypoglycemia Glucagon Glucocorticoids

Response to Starvation Decrease Insulin: Conserves Glucose for the brain Increase 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 Glucose Pancreas Secretes Insulin Inhibits: Glucagon and Glucocorticoids NET 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 Fuel Glucose is Important in Brief Intense Exercise We don’t Feed During Exercise

Exercise is a Homeostatic Emergency! Sympathetic Nervous System Activated! Decreases Insulin Increases “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 Diabetes NIDDM: 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 been FUN!