1. The Endocrine System: An Overview
Ch. 9a

2. What Do Hormones Do?
Adrenaline Rush
Feeling Dehydrated
Being in love

3. The Endocrine System Second messenger system of the body
Uses chemical messages (hormones) that are released into the blood
Hormones control several major processes to maintain homeostasis
Reproduction
Growth and development
Mobilization of body defenses
Maintenance of much of homeostasis
Regulation of metabolism
Slide 9.1
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4. Quick Quiz
What is one major function of the Endocrine System?

5. Hormone Overview
Hormones are chemicals produced by specialized cells located in glands
Cells secrete hormones into extracellular fluids
Blood transfers hormones to target sites
These hormones regulate the activity of other cells
Slide 9.2
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6. The Chemistry of Hormones
Amino acid-based hormones
Proteins
Peptides
Amines
Steroids – made from cholesterol
Prostaglandins – made from highly active lipids

7. Mechanisms of Hormone Action
Target Cells (or organs)
Hormones specifically affect certain tissues or organs
Target cells must have specific protein receptors
Hormone binding influences how the cells work
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8. Quick Quiz What are hormones? What do hormones do?
What is a target cell (or organ)?

9. Effects Caused by Hormones
Changes in plasma membrane permeability or electrical state
Synthesis of proteins, such as enzymes
Activation or inactivation of enzymes
Stimulation of mitosis
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10. Steroid Hormone Action
Diffuse through the plasma membrane of target cells
Enter the nucleus
Bind to a specific protein within the nucleus
Bind to specific sites on the cell’s DNA
Activate genes that result in synthesis of new proteins
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11. Steroid Hormone Action
Figure 9.1a
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12. Nonsteroid Hormone Action
Hormone binds to a membrane receptor
Hormone does not enter the cell
Sets off a series of reactions that activates an enzyme
Catalyzes a reaction that produces a second messenger molecule
Oversees additional intracellular changes to promote a specific response
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13. Nonsteroid Hormone Action
Figure 9.1b
Slide 9.9
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14. How Do Feedback Loops Work?
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15. Control of Hormone Release
Negative Feedback
Maintains hormone levels in the blood
A stimulus or low hormone levels in the blood triggers the release of more hormone
Hormone release stops once an appropriate level in the blood is reached
Slide 9.10
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings

17. Quick Quiz
Explain how negative feedback works using any of the following examples:
Thirst
Home Heating System
Sweating
Or, your own example

18. Hormonal Stimuli of Endocrine Glands
Endocrine glands are activated by other hormones
Figure 9.2a
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19. Humoral Stimuli of Endocrine Glands
Changing blood levels of certain ions stimulate hormone release
Figure 9.2b
Slide 9.12
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20. Neural Stimuli of Endocrine Glands
Nerve impulses stimulate hormone release
Most are under control of the sympathetic nervous system
Figure 9.2c
Slide 9.13
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21. Now that you know…
Now that you’ve got an overview of the endocrine system, its time to put that knowledge to work
Endocrine System Project Time
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