The Endocrine System

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

Introduction to the Endocrine System

Story time……

Overview

• What are the two systems that are in charge of controlling and coordinating the other systems in the body?– Nervous system– Endocrine system

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

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.”

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.

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.”

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?

Hormones, Receptors, and Target Cells

Good fit Bad fit

Hormone A

Two different receptors

Target cell for Hormone A Not a target cell for Hormone A

Cells

Hormone ABinds toReceptor

Hormone ADoes notBind to

Receptor

Causes aChange toOccur

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.

Agonist vs. Antagonist

Agonist bound and causinga biological event.

Antagonist bound, not causinga biological event and blocking

the agonist from binding.

Same receptor

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.

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.

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.

Negative Feedback Loop

Furnace

Electricity

68º FurnaceOn

HEAT

Current Temp.

Negative Feedback Loop

Furnace

Electricity

69º FurnaceOn

HEAT

Current Temp.

Negative Feedback Loop

Furnace

Electricity

70º FurnaceOff

HEAT

Current Temp.

Negative Feedback Loop

Furnace

Electricity

69º FurnaceOn

HEAT

Current Temp.

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.

Thyroid Hormone: Negative Feedback Loop

Hypothalamus Neurons

Pituitary Gland

Thyroid Gland

(TRH)

(TSH)

(Thyroid Hormone)

Poster Project

1. In groups of 2 or 3 research an endocrine gland and at least one associated disorder.

2. Create a poster with various pieces of required information.

3. Present the poster to the class: “poster sessions.”

4. Will be graded as a test and will be the only assessment for this unit.