2-18 - Kin 310 Muscle Structure and Function How are...

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Kin 310 – February 18, 2010 Muscle Structure and Function How are muscles formed? How do muscles contract? What are the different muscle fiber types? How does fiber type affect performance? Muscles: Structure 3 Basic Types o Cardiac o Smooth o Skeletal Skeletal Muscle Made of: Muscle Fibers o Muscle fibers are made up of myofibrils which contain “contractile” o Proteins form “muscle” FASCIA (connective tissue) o Heath that “wraps” layers of skeletal muscle o You want to release FASCIA that has gotten stuck. Doing so will ease movement o Provides “sliding and gliding” environment for muscles and transmits movements from muscle to the bones they are attached to o Epimysium (outer) Layer of connective tissue/fascia around the entire muscle (all the bundles) EPI = outer o Perimysium (middle) Tissue surrounding individual buncdles of muscle fibers PERI = middle o Endomysium (inner) Tissue between individial fibers EMDO = inner o Connective Tissue: Tendons “Non-stretchy fascia” Intramuscular connective tissue merges with dense connective tissue at each end of the muscle to attach it to bone Think of Achilles tendon Stronger/tougher than muscle Small tendon can withstand tension developed by large muscle Nerves Blood Supply
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Arteries/veins parallel the muscle fibers Lots of branches/networks in the endomysium Capillaries o On average: 3-4 per muscle fiber o Athletes: 5-7 per muscle fiber o Implications for performance? Deliver more blood, that way you have more oxygen to extract, so you can train harder and longer To improve performance: More capillaries How much do you need? It depends… o Some muscles may need 100x more blood during maximal exercise than at rest! How do muscles contract? The nuero-muscular system Nerve Supply Nerves are both motor and sensory o Motor nerves are responsible for movement Enter and exit with blood vessels Motor Nerve/Motor Neuron Nerves which exit the spinal cord and innervate (activate) muscle Each motor nerve has a job o Motor Unit Single motor nerve on all the fibers it innervates is called a motor unit The ratio of muscle fibers innervated by a single motor nerve is determined… “All of None Law” A muscle fiber contracts maximally or not at all Which means that… o A motor unit contracts maximally or not at all Muscular Contraction o Motor nerves activate the low-threshold motor units first, then the higher threshold units Low pain threshold means that little things hurts, high pain threshold makes it easier to work through pain What’s a low threshold motor unit? Units that produce
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This note was uploaded on 12/04/2011 for the course KIN 310 taught by Professor Stanforth during the Spring '06 term at University of Texas.

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2-18 - Kin 310 Muscle Structure and Function How are...

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