6.1_ Anatomy of the Endocrine system_ Essential Human Anatomy and Physiology I with Lab- Keck.pdf

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8/20/20206.1: Anatomy of the Endocrine system: Essential Human Anatomy and Physiology I with Lab- Keck2/9the excitability of the other neurons. In contrast, the endocrine system (seeFigure6.1) utilizes hormones, chemical messengers, that are typically released directly intothe bloodstream. Once in the bloodstream, hormones interact with cells throughoutthe body.The nervous system reacts quickly to external and internal stimuli, but the endocrinesystem tends to react somewhat slower. It takes time for a hormone to travel throughthe circulatory system to its target organ. Cells that can react to a hormone havespecific receptors, which combine with the hormone in a lock-and-key manner.Therefore, certain cells respond to one hormone and not to another, depending onthe cell’s surface receptors.Ahormoneis defined as an organic chemical produced by one set of cells thataffects a different set of cells. Hormones are chemical messengers that influence themetabolism of the recipient cell. Hormones are chemical messengers sent throughthe body produced and utilized by the endocrine system. All hormones have aspecific organ/gland of origin, a specific target organ/gland or organs/glands, and aspecific action. Many hormones are proteins that are coded for by genes andsynthesized within the cytoplasm at the ribosomes. Eventually, hormones arepackaged into vesicles at the Golgi apparatus and are secreted at the plasmamembrane.There are two main categories of hormones: peptide hormones and steroidhormones.Peptide hormonescan be derived from proteins, peptides, orcatecholamines. Peptide hormones activate existing enzymes in the cell. Peptidehormones tend to act relatively quickly but for a short period of time.Steroid hormonesare derived from cholesterol by a series of metabolic reactions.Steroids act more slowly than peptides because it takes more time to synthesizenew proteins than to activate enzymes that are already present in the cell. These

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Endocrine System, Anatomy of the Endocrine system

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