The document discusses the key aspects of the endocrine system, including that endocrine glands secrete hormones directly into the bloodstream, hormones act on target organs through receptors, and the neuroendocrine reflex involves both nerve and hormonal input. It also classifies hormones as peptides, amines, or steroids and explains their mechanisms of action and feedback regulation.

3. The Endocrine System
VS 223
Dr. Noland

4. Endocrine Glands
• Secrete their product directly
into bloodstream
• Known as “ductless” glands

6. Hormones
• Act on target organs due to specific
receptors located on the target
plasma membrane

7. Neuroendocrine Reflex
• Nerve input on the afferent end
• Hormonal input on the efferent end
• Suckling reflex
• Induced ovulation in cats, rabbits

8. Endocrine Glands
• Discrete gland - Adrenal gland
• Organ – Duodenum
• Combo of Exocrine/Endocrine -
Pancreas

9. Classification of Hormones
• Peptides – chains of amino acids
–Most hormones
• Amines – tyrosine derivatives
–Catecholamines, T4
• Steroids – cholesterol derivatives
–Gonadal hormones and adrenal
cortical hormones

10. Mechanisms of Action
• Hormones circulate in the
bloodstream and bind with
target organ cell receptors to
affect a change in the target cell

11. Hydrophilic
Hormones
Peptides and
Catecholamines

12. Lipophilic Hormones
Steroids and Thyroid

13. Hormonal
Action

14. Feedback Regulation