PHIS 206 Lecture Notes - Lecture 29: Adrenal Gland, Parathyroid Gland, Circadian Rhythm
2 May 2018
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Lecture 29: Intro to Endocrine Physiology
Definitions
• Endocrine System
o Collection of ductless endocrine glands scattered throughout the body
• Endocrine Agent
o Chemical signal that travels via the bloodstream to find its target - a hormone
• Endocrinology
o The study or medical specialty concerned with homeostatic adjustments or
interventions made by hormones
Hormones
• Solubility
o Hormones vary in solubility → and this solubility affects how it executes its
function
• Receptors
o Hormones can only exert their actions in tissues that have proper receptors for the
hormone
o Makes sense → it would be a waste for hormones to go to every body part and try
their luck
• Solubility & Receptors
o H2O-soluble hormones target receptors on the membrane of cells
o Lipid-soluble hormones find receptors inside of cells (cytosolic receptors)
What Do Hormones Do?
• Tropic hormones
o Primary function is to regulate the secretion of another hormone from a different
endocrine gland
o Regulate secretion of hormone from other endocrine gland
• Alter Protein Function
o Fast-acting hormones typically work by changing the behavior of existing protein
machinery -- The duration of the action is short
• Regulate Protein Synthesis
o Slow-acting hormones usually work by causing more or fewer proteins to be
synthesized -- The duration of the action is long
Complexity
• A single endocrine gland can secrete multiple hormones
• A single hormone can be secreted by multiple glands
• A single hormone may work on many types of cells, having differing effects in each
The Lesser Science View
• Many Players
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