1. Endocrine system
Human Systems Biology

2. Hormones “Chemical Messengers”
Produced and secreted directly into the blood by endocrine glands
Endocrine gland hormones are spread by blood stream throughout body to target organs (each hormone has a specific target)
Target organs have hormone-receptor proteins that bind to hormones that arrive in blood
Neurotransmitters are different because they send signals between cells

3. Page 65 The main glands in the Endocrine system are: Pituitary Gland
Thyroid Gland
Parathyroid Glands
Adrenal Glands
Pancreas
Ovaries
Testes
Refer to page 65, write a brief function for each gland!

5. Types of Glands Exocrine Glands Endocrine Glands Have ducts
Secrete products into body cavities
E.g. salivary glands secrete salivary amylase enzyme into mouth via salivary ducts
No ducts!
Secrete hormones directly into bloodstream
E.g.
Hypothalamus
pituitary
thyroid
pancreas

6. Salivary Gland
Duct

7. Control of Endocrine Glands
Endocrine glands are controlled by a “cause and effect” feedback system with inputs (reactants) and outputs (products).
This is what maintains “Homeostasis” (balance)
Negative Feedback
Positive Feedback
If the output (i.e. hormone) fed back is increasing the input
If the feed back output opposes the input
Pancreas: See page 66 about blood glucose.
Kidney: See page 64 about ADH.