EndocrineSystem

EndocrineSystem - Endocrine System Overview The endocrine...

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Unformatted text preview: Endocrine System Overview The endocrine system and the nervous system handle control and coordination of the other systems. Control and coordination involves maintaining homeostasis (constant internal environment) and responding to environmental stimuli. Each system responds to stimuli on differing time and distance scales. Differences The endocrine system differs from the nervous system in the following ways: Time scale Endocrine system acts slowly and over a longer period of time Nervous system acts quickly and over a shorter period of time Distance Endocrine system products circulate throughout the body and act on targets widely separated from each other Nervous system projections travel to specific locations and act in an extremely localized fashion Similarities The endocrine system and the nervous system are similar in the following ways: Chemical signaling Both endocrine and nervous cells produce chemical signals for communicating with other cells Endocrine products are called hormones, while nervous products are neurotransmitters Homeostasis Both systems act to maintain homeostasis Both systems use stimulatory and inhibitory mechanisms Glands Glands are organs that secrete some product. Endocrine glands secrete product directly into the bloodstream. Exocrine glands secrete product via a duct to a body surface (either internal or external). Not all glands are part of the endocrine system Endocrine Cells Not all endocrine cells are collected in discrete glandular organs. Endocrine cells are also located in the walls of the small intestine, stomach, kidneys, and heart. Other cells, such as adipose cells and certain neurons, also have an endocrine function. Chemical Signaling Most cells have some capacity for chemical signaling. Autocrines have an effect on the cell that produces them (self-signaling). Paracrines have an effect on the cells in the local environment (ex. capillary endothelium on pre-capillary sphincters). Neither are examples of hormones. Hormones Hormones are chemical signals that are secreted into the bloodstream. They typically act on targets that are located at a distance from the source. They regulate the metabolic activities of their targets. The effect of a hormone is determined by the receptors at the target and is not intrinsic to the hormone itself. Classes of Hormones Hormones can be classified by chemical structure and include: Amino-acid based: single amino acids, peptides, and proteins. Steroid: lipid derived molecules built from cholesterol Eicosanoids: lipid molecules that usually have localized effects (ex. Leukotrienes and prostaglandins). Action of Hormones Hormones act at the target cell by interacting with a specific receptor molecule....
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EndocrineSystem - Endocrine System Overview The endocrine...

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