Chemical Signals Maintaining Homeostasis

Chemical Signals Maintaining Homeostasis - CHEMICAL SIGNALS...

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CHEMICAL SIGNALS MAINTAIN HOMEOSTASIS 8.1: Importance of the Endocrine System BASIC HOMEOSTATIC MECHANISM: Stimulus: change in external environment that you can detect Receptor: detects stimulus Message: message is sent to coordinating centre Coordinating centre: processes information and chooses appropriate response Message: message to effector with response Effector: carries out instructions Response: the change Feedback: tells response to stop. Hormones are chemical messengers released by the body that affects cells in other parts of the body Endocrine hormones are hormones produced by cells which is released directly through the bloodstream (ex: insulin, ADH) Exocrine hormones are hormones produced by cells which is released through a duct or tube (ex: gastric glands, sweat glands) Endocrine hormones are carried via the circulatory system Hormones are classified based on their activation site: hormones like insulin and epinephrine are non-target hormones since they work on all cells while hormones like parathyroid hormone are called target hormones since they regulate calcium levels in the body Antagonistic hormones are hormones that counteract the effects of opposing hormones. An example of antagonistic hormones is: insulin decreases blood glucose levels while glucagon increases blood glucose levels Protein vs. Steroid Hormones: Cells may have receptors for one hormone but not the other The # of receptors found on individual cells vary For example, the receptors of liver and muscle cells have a lot more receptors for insulin and less receptors at less active locations such as bone and cartilage cells Two types of hormones: steroid and protein
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Steroid hormones are produced from cholesterol, a lipid compound which is made of 4 rings composed of C,H and O; soluble in fat and not in water (ex: progesterone, testosterone, male/ female sex hormones) Protein hormones are made of varying chains of amino acids, soluble in water (ex: insulin and growth hormone) Steroid Hormones (ex. Testosterone): 1. Steroid hormones diffuse from capillaries into the interstitial fluid and then into target cells. 2. They attach to specific receptor molecules found on target cells. 3. Hormone-receptor complex moves into the nucleus and attaches to DNA. 4. Once the hormone is inside the cytoplasm of the target cell, it activates a specific gene in DNA initiating protein synthesis by sending a message to ribosomes to produce a specific protein. Protein Hormones (ex. Insulin): 1. The protein hormone attaches to specific receptor molecules on the outside of the cell membrane of the target cell. 2. This forms a hormone-receptor complex that activates the production of an enzyme called adenylyl cyclase which then converts ATP into cyclic AMP (cyclic adenosine monophosphate). 3.
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This note was uploaded on 02/05/2011 for the course PHYS 1010 taught by Professor Tomkirchner during the Spring '11 term at York University.

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Chemical Signals Maintaining Homeostasis - CHEMICAL SIGNALS...

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