Biol 2420 Week 8
Biol 2420 Week 8 BIOl 2420
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This 3 page Class Notes was uploaded by Aurora Moberly on Sunday February 21, 2016. The Class Notes belongs to BIOl 2420 at Southern Utah University taught by Dr. Paul Pillitteri in Winter 2016. Since its upload, it has received 41 views. For similar materials see Human Physiology in Biology at Southern Utah University.
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Date Created: 02/21/16
Test 3 3/4/16 Goal: 95 Skeletal Muscle System - Three layers of connective tissue in the muscle belly: - Epimycium: Wrapped around the entire muscle belly, outermost layer - Perimycium: Connective tissue that divides the muscle cells into bundles called fascicles - Endomycium (Basal Lamina): Layer of connective tissue wrapped around each individual muscle cell - All three layers of the connective tissue together are called the Parallel Elastic Component - Two functions of the Parallel Elastic Component: Protection, elasticity to produce force - Tendons: Attach muscle to bones, know as the Series Elastic Component, help to generate force when the muscle is stretched - Muscle Cell: - Sarcolemma: Muscle cell membrane - Skeletal muscle cells are multinucleate (one cell contains multiple nuclei) - Skeletal muscles cells are striated due to the arrangement of proteins in the cell - Muscle cells will run the entire length of the muscle - Looking down the barrel of the muscle cell there are many cylinders called myofibrils - Myofibrils: Bundles of proteins - Two main proteins: Myosin and Actin - Myosin is the thick protein/filament, appears as a dark patch on the myofibril - Actin is the thin protein/filament, appears as a light patch on the myofibril, overlaps with myosin - Creates a Z line/disk that attaches with other proteins - Sarcomere: Functional unit of skeletal muscle that extends from one Z line to the next Z line, contracts the muscle - All myofibrils sacromeres are lined up creating striation on the muscle cell, provides a unified and evenly distributed contraction - Myosin Filament: - Made up of many individual myosin molecules - Myosin molecule has a tail and two heads - Each head has two binding sites: Actin Binding Site (Attaches to the actin filament) and Myosin ATPase Site (Bind ATP and breaks it for energy use) - Once the head breaks ATP it holds onto ADP + P the head is now said to be energized - All the tails of the myosin filament point to the middle and the heads point to the ends - Actin Filament: - Actin molecules strung together in a helix formation - Each actin molecule has a binding site for myosin - Regulatory proteins on the helix: Tropomyosin and Troponin - Tropomyosin: Wraps itself around the actin filament so it covers over the binding sites so it can’t bind with the myosin - Troponin: Has three parts to it T IBinds to actin) T (Tinds to tropomyosin) T C (Binds calcium ions) - Troponin holds onto both the actin and tropomyosin but when calcium binds to TCit causes the troponin shape to change and pulls the tropomyosin off the myosin binding sites to allow myosin to bind to the actin - T-Tubules: Tube extensions of the cell membrane that dive deep into the cell, function is to spread the action potential deep down into the cell - Sarcoplasmic Reticulum (SR): Highly branched membranous sac, its function is to store and release calcium ions - The action potential from the T-Tubules sparks the SR to release the calcium ions - Contraction (Twitch) of a Muscle (Sliding Filament Mechanism): - Excitation-Coupling-Contraction-Relaxation - 1. Stimulus from motor neuron - 2. Action potential initiated and spreads down the sarcolemma - 3. Action potential travels down the T-tubules to hit the SR ++ - 4. SR releases Ca - 5. Ca++ binds to troponin - Troponin shifts tropomyosin to uncover the binding sites on actin - 6. Energized myosin head binds to actin (cross bridge formation) - 7. Myosin head pulls actin across myosin filament - Shortens sarcomere - Spends energy and releases ADP and P - 8. New ATP binds, cross bridge detaches and re-cocks - As long as calcium is present the steps 6-8 will be repeated to create the contraction - Relaxation: - 1. Ca++ is actively pumped back into SR ++ - 2. Ca is removed from troponin - 3. Tropomyosin moves to cover actin-binding sites - 4. Cross bridge cannot form, muscle relaxes to resting length - Muscle Properties: - All or None: In terms of a muscle twitch when the calcium is released from the SR there will be enough to bind with all the troponin and all the binding sites will be uncovered - Treppe: If we allow the muscle to relax and stimulate immediately after we can get a greater force because all of the calcium hasn’t been taken back up to the SR by the time the second stimulation has started - Twitch: -Latent Period: Time between action potential generated on the membrane and when the cell begins to generate force - Contraction Phase: Beginning of force generation to the peak of force generation - Relaxation Phase: Peak of the force generation till the muscle cell is completely relaxed - Motor Unit: How the nervous system is wired to your muscle cells - One muscle cell will only have one neuron innervating it - One neuron will innervate many muscle cells through branching - Motor unit is one motor neuron and all the cells that it innervates
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