BIOL 122 Chapter 17: The Endocrine System Part 1
BIOL 122 Chapter 17: The Endocrine System Part 1 BIOL 122
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This 3 page Class Notes was uploaded by Bridget Notetaker on Thursday February 4, 2016. The Class Notes belongs to BIOL 122 at University of Southern Indiana taught by Dr. Pilcher in Spring 2016. Since its upload, it has received 11 views. For similar materials see Human Anatomy & Physiology II in Biology at University of Southern Indiana.
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Date Created: 02/04/16
Chapter 17: The Endocrine System (Part One) Thursday, January 21, 2016 4:15 PM One of two control systems in body that are charged with homeostasis (second is nervous system) Both endocrine and exocrine glands are secretory Differences: Presence/Absence of ducts Secretion onto tissue surface vs. into the ECF/blood Exocrine glands (sweat and sebaceous gland -‐s)presence of ducts The liver is a type of exocrine gland Contains bile Endocrine glands: lack ducts, release hormones into ECF, then make their way into the blood, then circulates in blood so it can have its effect Mechanism of control for nervous system are neurotransmitters released at synapses Endocrine system uses hormones Nervous system responds quickly Hormones have to be released through endocrine glands, circulate through the blood and find target cells before they can have an effect; response takes longer Nervous system has effects of short duration Endocrine system effects last longer Hormones continue to have their effect until the hormone molecules are removed from the blood stream by the liver or kidney and sometimes by the lungs Hormones are chemical substances secreted into the blood that regulate the metabolic function of other cells in the body Target cells = those cells with receptors for hormones ADH targets the kidney ADH changes the composition of urine Hormones are chemical substances secreted into the blood that regulate the metabolic function of other cells in the body Target cells = those cells with receptors for hormones ADH targets the kidney ADH changes the composition of urine Water-‐soluble hormone -‐sproteins, peptides, most am -acoid derivatives Lipid-‐soluble hormone -‐ssteroid hormones, thyroid hormones (an a-‐acido derivative) The two chemical classes of hormones influences how the hormone is circulated in the blood, how long it lasts in blood before its broken down or removed, the site of the location of receptors on the target cell Lipids don’t mix with water, making them hydrophobic Carbs and proteins are w-telruble and do mix with water, making them hydrophilic Two layers of phospholipids form the cell membrane (bilayer), protein groups scattered throughout, carbohydrate groups are primarily on the outer surface Transport of lip-‐soluble hormones Steroid hormones, thyroid hormones etc Small, hydrophobic molecules Need binding proteins for transport through blood Longer half-‐life due to "protection" by binding proteins Most hormones are bound to binding proteins but some are unbound or free hormones Free hormone molecules will interact with target cells Removal of free hormones from blood: Broken down by hydrolytic enzymes in blood Hydrolytic -‐ breaking down of molecule by water Bound to water-‐soluble conjugation molecules Products excreted in urine or bile Transport of water-‐soluble hormones Proteins, peptides, most am-incoid derivatives Hydrophilic Small molecules dissolve in blood stream Larger molecules may require binding protein In general, short -felif Most broken down by: Proteins, peptides, most am-incoid derivatives Hydrophilic Small molecules dissolve in blood stream Larger molecules may require binding protein In general, short -felif Most broken down by: Hydrolysis (proteases) in blood Target cell (using lysozymes after endocytosis) Others have longer h-lile due to: Stabilization by sugar grou--s glycoproteins Modification at terminal ends (target of proteases) Binding to binding proteins Location of receptors For water soluble hormones, the location of the receptor is on the surface of the target cell Membrane -‐bound receptor with binding site specific for that hormone For lipid soluble hormones, the location of the receptor is well within the target cell Nuclear receptor Patterns of hormone secretion Chronic secretion (long term) Chronic hormone secret-‐ioa n relatively stable concentration of hormone is maintained in the circulating blood over a relatively long period. This pattern is exemplified by the thyroid hormones Acute secretion (short term, sudden onset) Acute hormone secretio -‐na hormone rapidly increases in the blood for a short time in response to a specific -flur example, insulin (the blood suga-regulating hormone) secretion following a meal. Note that the size of the stimulus arrow represents its strength. A smaller stimulus does not activate as much hormone secretion as a larger stimulus Episodic secretion (secreted in episodes) Episodic hormone secretion -‐ a hormone is stimulated so that it increases and decreases in the blood at a relatively consistent time and to roughly the same amount. Examples are the reproductive hormones regulating menstruation
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