1. The Endocrine System and Feedback Loops

2. Body System Review
Nervous System: Recognizes and coordinates the body’s response to the internal and external environment.
ex Brain, spinal cord, nerves
Circulatory System: Moves blood containing oxygen, waste, nutrients and hormones throughout the body.
ex Heart, blood vessels (veins, arteries, capillaries), and blood

3. What is the Endocrine System?
is made up of glands that release their products into the bloodstream. These products deliver messages throughout the body.
Function:
Controls growth, development and metabolism….maintains homeostasis!

4. What is the Endocrine System?
Made up of glands that produce and secrete hormones, chemical messengers
Regulation of growth, metabolism, sexual development
Responses to stress and injury
Maintains homeostasis
Glands are found in different areas of the body.

5. Endocrine Glands – secretions inside the body
Exocrine Glands – secretions outside the body (sweat)
Saliva
Breast Milk
Sweat

6. Glands of the Endocrine System

8. The Master Gland
The hypothalamus and pituitary gland in the brain both work together to control all secretions by all endocrine glands.
The pituitary is called the “MASTER GLAND” because it is near the top of the chain of command.
Tells other glands what to do
It produces a large number of different hormones

9. Endocrine: Chain of Command
The Organs
Endocrine: Chain of Command
Hormones
Alters Cell Activities

10. BIG IDEA:
HORMONES are chemical MESSENGERS that act on
target cells

11. Two Hormone Types: Steroid Hormones
Steroid hormones tell a target cell what to do by telling the DNA inside the nucleus what to do.
Steroid hormones turn a gene on and then the gene tells the cell to make a particular kind of protein.
Examples:
Estrogen, Testosterone, Progesterone
Cholesterol, Aldosterone, Cortisone, Cortisol
(most end with “ONE” or “OL”)

12. Two Hormone Types: 2. Protein Hormones
Protein hormones tell a target cell to activate certain existing inactive proteins.
The protein hormone does this by providing the energy for the activation.
Examples:
Oxytocin, Luteinizing Hormone (LH)
All other hormones not on the steroid list

13. What is a Feedback Loop?
Feedback loops are how the nervous system guides the endocrine system to control body conditions.
Nervous system senses the condition
Endocrine system secretes the hormone to adapt to the condition
Circulatory system carries the hormones to the target cells where they are needed!

14. Negative Feedback The amount of a hormone present and
the effect of the hormone are opposite!
They negatively affect each
other
Ex Blood Sugar Levels

15. Regulation of Blood Sugar
Negative Feedback Loops:
Regulation of Blood Sugar
Insulin and Glucagon help to keep the level of glucose in the blood stable.
Insulin is secreted when high levels of sugar are detected (ex after eating)
Glucagon is secreted when low levels of sugar are detected (ex after exercising)

16. Pancreas—Insulin is secreted
Hormone: Insulin
Eat Food
HIGH Blood Sugar
Pancreas—Insulin is secreted
Insulin stimulates cells in the liver and muscles to absorb sugar from the blood and store it as glycogen or fat.
Blood Sugar DECREASES
Pancreas—Insulin stops

17. Pancreas—Glucagon is secreted
Hormone: Glucagon
Heavy Exercise
LOW Blood Sugar
Pancreas—Glucagon is secreted
Glucagon stimulates the liver to break down glycogen and release glucose back into the blood. It also stimulates the release of fatty acids from stored fats.
Blood Sugar INCREASES
Pancreas—Glucagon stops

18. Positive Feedback The more stimulation a gland receives the
more hormone is produced.
Example: Breast Feeding and Oxytocin
When a mother feeds the baby glands in the breast are stimulated.
Nervous system signals glands to secrete oxytocin.
Oxytocin is a hormone that helps the mother produce more milk.
↑ stimulation = ↑ oxytocin released = ↑ milk production

19. THIS IS AN EXAMPLE OF A FEEDBACK SYSTEM
How does feedback work?
“Like a Thermostat!!!”
./ Set at a certain temperature
./ When the temperature in the room changes the thermostat triggers a heater or
air conditioning system
./ The heater or air conditioning system adjust to the temperature in the room
./ When the thermostat senses that the room has
reached the appropriate temperature, the heater or air conditioner turns off.
THIS IS AN EXAMPLE OF A FEEDBACK SYSTEM
The thermostat sends feedback to the heater and air conditioner s

20. Feedback Systems
In humans the hypothalamus acts like the thermostat of feedback systems and the endocrine glands act like the heater or air conditioner.
Hormones are released or stop being released in response to the messages sent from the hypothalamus.