AP Unit 4 - Bio185 A&P1 Lecture 03-10 to 11: The Endocrine...

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Bio185 A&P1 – Lecture 03-10 to 11: The Endocrine System Page 1 of 21 Endocrine System Basics Endocrine gland: secretory cells release secretions into extracellular fluid A. Nervous System vs. Endocrine System 1. Similarities: 2. Differences: Nervous System Endocrine System Response: Rapid Delayed Duration of effect: Short-lived Prolonged Targets: Specific neurons, Far-reaching, muscles, glands cells throughout body Location of Signal: Synapse Bloodstream Type of chemical signal: Neurotransmitters Hormones B. What is a hormone? Hormone: chemical messenger (signal) secreted into the bloodstream to reach target cells in other tissues. 1. Amino acid derivatives e.g. epinephrine, thyroid hormones 2. Peptides e.g. insulin, growth hormone 3. Lipid derivatives a. Steroid hormones e.g. testosterone, estrogen b. Fatty-acid based e.g. prostaglandins C. How do hormones work? Target Cells — cells that can respond to a particular hormone Hormone receptor — A protein to which a hormone specifically binds to trigger its actions on a target cell. (1) At the cell membrane = extracellular Targeted by: Amino Acid & Peptide hormones = not lipid soluble Activate a second messenger inside the cell (2) Within the cytoplasm or nucleus = intracellular Targeted by: steroid and thyroid hormones = diffuse through memb. Change gene expression D. How is hormone secretion controlled? Usually by negative feedback 1. “Direct” control — Stimulus: change in composition of extracellular fluid Feedback: Endocrine cells respond to changes produced by the hormone e.g. blood glucose — pancreas detects ↑ glucose releases insulin
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Bio185 A&P1 – Lecture 03-10 to 11: The Endocrine System Page 2 of 21 2. Neural control — Stimulus: Neurons signal endocrine cells to secrete hormone Feedback: Rising hormone level “turns off” neuron e.g. Sympathetic nervous system signals adrenal gland to release epinephrine 3. Hormonal control — Stimulus: Hormone from another endocrine gland Feedback: Level of second hormone feedback to stop secretion of first e.g. hypothalamus secretes releasing - hormones to control anterior pituitary A. Pituitary Gland or hypophysis Connected to hypothalamus by infundibulum Lies in the fossa of the sella turcica 9 peptide hormones 1. Anterior Pituitary or Adeno hypophysis a. Control: Controlled by Hypothalamus Hypothalamus secretes Releasing or Inhibiting hormones (RH or IH) Hypothalamus secretes RH/IH in response to changes in homeostasis b. Hormones that act on other endocrine glands: e.g. TSH c. Hormones that act on non-endocrine targets: e.g. GH Hormone Action Control (Stimulus) Pathology Anterior Pituitary Thyroid-stimulating hormone (TSH) stimulates thyroid to release thyroid hormones RH/IH’s from Hypothalamus Adrenocorticotropic hormone (ACTH)
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This note was uploaded on 04/03/2008 for the course BIOL 185 taught by Professor Harms during the Fall '07 term at Messiah.

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AP Unit 4 - Bio185 A&P1 Lecture 03-10 to 11: The Endocrine...

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