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Unformatted text preview: Muscles Muscle o Smooth o Cardiac o Skeletal Require continuous stimulation by nerves Two types Type I- Slow Twitch Type II- Fast Twitch Action at Neuromuscular Junction o Alpha motor Neuron produce one NT (Acetylcholine- ACH) is excitatory o Neuromuscular junction Highly fluid Aging, lots of collagen desposition, tissue damage o NT released, binds to Nicitinic receptor on NMJ o Denervation serious problem with aging Sarcopenia o Loss of muscle mass and muscle function (loss of type II fast twitch fibers) o Causes: Changes in muscle structure Chronic diseases (and Medications taken by elders to treat) Statens taken to lower LDLs and cholesterol, causes muscle weakness Disuse atrophy Malnutrition (muscle fibers are proteins, takes lots of energy to make proteins) General Changes o Decrease in muscle weight relative to body weight o Decrease in muscle mass and volume Muscle mass ~ Muscle force generations (?). Recently been suggested there is no correlation, more innervation A-MN innervating muscle fibers Avg 30-40% loss of muscle mass and volume between ages 30-80 o Muscle atrophy Look at number and size of muscle fibers (Type I and II). Type II number and size decline significantly. Past age 70, not many type II fibers left Type I number decline, size is normally maintained When animals are calorically restricted, this does not occur. Preserves muscle fibers o Decrease in Force generated 20% loss of muscle strength by 70 50% loss past age 70 (sarcopenia) Anti gravity muscle fibers are effected the most (quads, hip extensors, ankle DF, Lats, Triceps) reason for elderly falls. drop attack just fall down due to loss of force generated in antigravity muscles o Extensive proliferation of tubular system Normal T tubules extend deep into muscle fiber , surrounded by sarcoplasmic reticulum (contains lots of Ca 2+ ) AP goes down T tubule Causes SR to release Ca 2+ which end result is muscle contraction Aging- T tubule pushed away, harder to initiate contraction o Irregularity and streaming of Z lines Improper anchoring of Z lines So interaction of myosin and actin, so limited bridge formation Therefore force generated will decline significantly Do not see this in calorically restricted animals o Satellite cells Stem cells of muscle fibers. Ability to induce regeneration if tear Decline with aging Maintained in calorically restricted animals o Multinucleation Skeletal muscle fiber cells are multinucleated During embryonic development, many cells fused together becoming a single cell Still multinucleated, but less nuclei than younger individuals Comparision of Old skeletal Muscle fiber and Young skeletal muscle fiber o Very little difference in dynamic properties o Current thinking is a difference in the Innervation ratio of nerves Muscle force o One leg stand by Richard Bohannen...
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This note was uploaded on 02/25/2012 for the course ECO 101 taught by Professor Staff during the Fall '10 term at Texas State.
- Fall '10