Lec11 - FACT OR FICTION ? • YOUR SKELETON REPLACES ITSELF...

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Unformatted text preview: FACT OR FICTION ? • YOUR SKELETON REPLACES ITSELF EVERY 1O YEARS • IT’S A FACT!! BONE IS A LIVING TISSUE! Cells…… Osteoblast • Bone cell capable of synthesizing new bone matrix • Usually found in growing portion of bone Osteocyte • Main cell of mature bone tissue Osteoclast • A multi-nucleate bone destroying cell • Usually found where bone is resorbed during normal growth Bone as a Tissue • Connective tissue with a matrix hardened by minerals ( calcium phosphate) • Individual bones consist of bone tissue, marrow, blood, cartilage and periosteum • Continually remodels itself • Functions of the skeletal system – support, protection, movement, electrolyte balances,acid-base balance, and blood formation Function: 1. Support 2. Protection 3. Movement 4 . Hematopoiesis (manufacture of blood cells) 5. Storage of inorganic salts THE FUNCTIONS OF BONE • Support the body with a by providing a frame • Protect softer tissues by shielding or encasing them • Provide points of attachment for muscles , so that the skeleton can act as levers as forces are generated by muscles. . • Houses blood-producing stem cells , and • Stores inorganic minerals necessary for bioreactions in the body. Also, stored in bone are lipids . Storage of inorganic salts • Mostly calcium phosphate • 70% of weight of matrix Calcium: Needed for • Blood clot formation • Nerve impulse conductor • Muscle contraction HUMAN SYSTEMS MAINTAIN HOMEOSTATSIS Negative Feedback Mechanisms The net effect of the response to the stimulus is the SHUT OFF the original stimulus OR reduce its intensity . Negative Feedback This is the Most common control mechanism! When Levels of hormone in blood or body return to Normal levels homeostasis shuts off loop at the hypothalamus and pituitary ( Most common Negative Feedback Loop) Positive Feedback The initial stimulus does NOT cause a switch to be “shut off”. Rather, a CASCADE of more ON switches in response to the initial response occurs. Examples: Giving Birth and Blood Clotting An Example of Positive Feedback: Giving Birth Bone Homeostasis Parathyroids regulate the homeostasis of blood calcium When blood calcium is low Osteoclasts tap into reserves and Bone is “demineralized” Calcium ions is released into blood Too much calcium in the blood? This hormone causes the deposition of Calcium into the bone matrix by osteoblasts Low Blood Calcium • Parathyroid gland releases parathyroid hormone • Stimulates osteoclasts to resorb Ca++ • Blood calcium rises Feedback Inhibition High Blood Calcium • Inhibits parathyroid gland •...
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This note was uploaded on 12/08/2011 for the course AMY 2A taught by Professor Jamesivey during the Spring '06 term at Riverside Community College.

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Lec11 - FACT OR FICTION ? • YOUR SKELETON REPLACES ITSELF...

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