This document provides an overview of the endocrine system and hormones. It discusses the discovery of hormones in 1902 by Bayliss and Starling. It defines hormones and describes the principal functions of the endocrine system in maintaining homeostasis, growth, development, and reproduction. It compares the endocrine and nervous systems and describes different types of cell signaling. It provides details on the major endocrine glands and hormones, hormone classification, mechanisms of hormone action, and feedback control of hormone secretion.

1. ENDOCRINOLOGY

6. Endocrine vs Nervous system Nervous system performs short term crisis management Endocrine system regulates long term ongoing metabolic

7. Types of cell-to-cell signaling Classic endocrine hormones travel via bloodstream to target cells; neurohormones are released via synapses and travel via the bloostream; paracrine hormones act on adjacent cells and autocrine hormones are released and act on the cell that secreted them.

11. The Endocrine System

13. A Structural Classification of Hormones

14. Protein and Polypeptide Hormones: Synthesis and Release

18. Thyroid hormones

20. Synthesis of catecholamines

28. Hormones and their receptors Hormone Class of hormone Location Amine (epinephrine) Water-soluble Cell surface Amine (thyroid hormone) Lipid soluble Intracellular Peptide/protein Water soluble Cell surface Steroids and Vitamin D Lipid Soluble Intracellular

29. A cell is a target because is has a specific receptor for the hormone Most hormones circulate in blood, coming into contact with essentially all cells. However, a given hormone usually affects only a limited number of cells, which are called target cells . A target cell responds to a hormone because it bears receptors for the hormone.

32. Types of receptors

33. G Proteins and Hormone Activity

35. Tyrosine Kinase ( continued )

36. Hormone Effects on Gene Activity

44. Feedback Control of Hormone Production Feedback loops are used extensively to regulate secretion of hormones in the hypothalamic-pituitary axis. An important example of a negative feedback loop is seen in control of thyroid hormone secretion

46. Negative feedback effects of cortisol

48. Feedback control of insulin by glucose concentrations

50. Circadian (chronotropic) control

51. Circadian Clock

56. Parvocellular & Magnocellular Neurosecretory Neurons * * * # # * # Rostral Hyp Medial Basal Hyp

62. Major Endocrine Organs: Pituitary (Hypophysis)

72. Figure 5.2.13 Feedback loops in a typical hypothalamo-hypophyseal axis. The target cell types (shaded area) may be any of those present in the anterior pituitary. They operate in a closed-loop feedback mode to maintain relatively steady plasma levels of the hormones concerned, subject to modifications of the hypothalamic drive by inputs from outside the body (exteroceptive signals), or intrinsic to the brain (pulse-generator). Long-loop and short-loop negative feedbacks involve respectively, the peripheral hormones and the tropic hormones.

76. Control of prolactin

81. Metabolic Action of GH

82. Control of GH secretion

91. Figure 5.2.10 Summary of the pathways involved in control of ADH secretion.

92. Factor affecting ADH secretion

97. Neuro-humeral reflex for OT

98. Anterior pituitary hormones