1. The Endocrine System

2. How will you learn about the endocrine system?
Introductory lecture
1 to 2 classes
Poster project completed in groups of 2 or 3
Student driven learning
4 to 5 classes
Poster sessions
Present your poster to the class just like it’s done in the biotech and medical industries.
2 classes
No dissection for this system

3. Introduction to the Endocrine System Story time……

4. Overview
What are the two systems that are in charge of controlling and coordinating the other systems in the body?
Nervous system
Endocrine system

5. Nervous System
Controls all activities that must happen quickly over a short period of time.
Movement of skeletal muscles
Organ activity (smooth muscles)
Digestive system
Esophagus
Stomach
Intestines

6. Endocrine System
Controls all activities that happen slowly and/or over a long period of time.
The activity of the pituitary gland (the control center of the endocrine system) is controlled by the nervous system.
Allows the endocrine system to respond to stimuli from the environment.
Controls the body using compounds called “Hormones.”

7. Endocrine System
All physiologic events that occur in the body are influenced by the endocrine system:
There are no cell types, organs, or processes that are not influenced by hormones.
The endocrine system has a hand in regulating every single major process that goes on in our bodies.
All "large" physiologic effects are mediated by multiple hormones acting together:
Normal growth from birth to adulthood.

8. Hormones, Receptors, and Target Cells
Hormones: chemical compounds secreted into the blood stream by one type of cell which effect the functioning of other types of cells.
The affected cells can be located close to or far away from the cells producing the hormones.
The affected cells are called “target cells.”

9. Hormones, Receptors, and Target Cells
Example
“Hormone A” moves through the body via the blood stream.
In doing so, “Hormone A” comes into contact with essentially every cell in the body.
Only specific cell types are affected by “Hormone A.”
Why are there only certain “target cells” that “Hormone A” affects? Why doesn’t the hormone affect all cells with which it comes in contact?

10. Hormones, Receptors, and Target Cells
Hormone A
Good fit
Bad fit
Hormone A
Does not
Bind to
Receptor
Hormone A
Binds to
Receptor
Two different receptors
Causes a
Change to
Occur
Cells
Target cell for Hormone A
Not a target cell for Hormone A

11. Agonist vs. Antagonist
Agonist: Molecules that bind to a receptor triggering a biological event to occur in the cell.
Antagonist: Molecules that bind to a receptor and block the binding of an agonist, but fail to trigger a biological event.

12. Agonist vs. Antagonist Agonist bound and causing a biological event.
Same receptor
Agonist bound and causing
a biological event.
Antagonist bound, not causing
a biological event and blocking
the agonist from binding.

13. Control of Hormone Levels
Hormone concentration in the blood stream is determined by three factors:
Rate of production
Production of hormones is the most highly regulated aspect of endocrine control.
It is mediated by positive and negative feedback loops.
Rate of delivery
high blood flow delivers more hormone than low blood flow.
Rate of elimination
Body eventually metabolizes and excretes hormones.

14. Control of Hormone Levels
Feedback Loops
Positive feedback loops exist in the endocrine system.
Negative feedback loops are far more prevalent.
What is a negative feedback loop?
When the product of a given process inhibits further production of that product.
Production of “Product A” inhibits further production of “Product A.”
Can you think of an example in everyday life? Hint: You all have at least one in your house!
Thermostat
Controls the heat in your home.

15. Thermostat: Negative Feedback Loop
A thermostat has a set point.
This is the temperature you would like the air in your house to be.
A thermostat controls a furnace which produces heat.
When the furnace produces enough heat to increase the air temperature above the set point of the thermostat, the thermostat is triggered and shuts off the furnace.
Heat is giving “negative feedback” to the source of heat.
When temperature drops back below the set point, negative feedback is gone, and the furnace comes back on.

16. Negative Feedback Loop
Electricity
Furnace
Current Temp.
68º
Furnace On
HEAT

17. Negative Feedback Loop
Electricity
Furnace
Current Temp.
69º
Furnace On
HEAT

18. Negative Feedback Loop
Electricity
Furnace
Current Temp.
70º
Furnace
Off
HEAT

19. Negative Feedback Loop
Electricity
Furnace
Current Temp.
69º
Furnace On
HEAT

20. How does this compare to endocrine negative feedback loops?
Example
Generation of thyroid hormones.
The thyroid is one of the many glands associated with the endocrine system.
The amount of thyroid hormone produced is negatively controlled by the concentration of thyroid hormone in the blood.

21. Thyroid Hormone: Negative Feedback Loop
Hypothalamus
Neurons
(TRH)
Pituitary Gland
(TSH)
Thyroid Gland
(Thyroid Hormone)

22. Poster Project
In groups of 2 or 3 research an endocrine gland and at least one associated disorder.
Create a poster with various pieces of required information.
Present the poster to the class: “poster sessions.”
Will be graded as a test and will be the only assessment for this unit.