“The beginning of wisdom is to call things by their right names.” 11/14/2018 Title: Anat & Phys 11/28/06 Objectives: To learn about the physiology of muscles. Class Topics Muscle physiology Connective Tissue Coverings All or none principle Neuromuscular junction Innervation Myofibril Contraction “The beginning of wisdom is to call things by their right names.” Chinese proverb Wednesday, November 14, 2018 5:07 PM
Class Assignments Lab - Reaction Time 11/28/06 Read 197-212 12/4/06 11/14/2018 Class Assignments What By When Lab - Reaction Time 11/28/06 Read 197-212 12/4/06 Due this class period Due next class period Due in the future
Connective Tissue Coverings 11/14/2018 Connective Tissue Coverings Fascia - broad band of collagen-based connective tissue Tendons - connective tissue connecting muscle to bone connects in the periosteum for strength Aponeurosis - fascia of one muscle attaching to that of another muscle
Connective Tissue Coverings 11/14/2018 Connective Tissue Coverings Epimysium - surrounding each muscle closely Perimysium - divides the muscle into fascicles around each bundle of muscle fibers Endomysium - surrounding each muscle fiber
11/14/2018 From: http://www.shef.ac.uk/~toa/js/histolo/cell_sha/maintext.htm From: http://www.bmb.psu.edu/courses/bisci004a /muscle/musc-img/fasicle.jpg
Skeletal Muscle striated all or none response 11/14/2018 Skeletal Muscle striated all or none response if a muscle fiber is exposed to a stimulus (electrical or nervous) it will contract to its full extent How can we have smooth movements?
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Neuromuscular Junction 11/14/2018 Neuromuscular Junction Each muscle fiber is connected to a nerve fiber - motor neuron Where they join is called the neuromuscular junction one nerve cell may have several junctions with one muscle cell and even several muscle cells nerve cells send messages to muscle cells by releasing neurotransmitters chemicals that have receptors in muscle cells that stimulate contraction - acetylcholine Wisconsin Online - Animation
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11/14/2018 From: http://www.people.virginia.edu/~dp5m/phys_304/figures/synapse_2.jpg
11/14/2018 Innervation 1:10 Eye muscles 1:1000 Leg muscles
Muscle fibers each fiber represents 1 muscle cell some organelles 11/14/2018 Muscle fibers each fiber represents 1 muscle cell some organelles Nuclei, sarcoplasmic reticulum, sarcolemma, ribosomes, mitochondria mostly myofibrils filaments that contain myosin and actin proteins and the location of contraction Myosin - thick filament Actin - thin filament
Contraction Terminology 11/14/2018 Contraction Terminology A band - myosin filaments - dark area of myofibril I band - actin filaments - light area of myofibril Z line - Where actin filaments connect together (middle of I band) H zone - non overlap area Sarcomere - area from Z line to Z line
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From: http://www.biology.eku.edu/RITCHISO/301notes3.htm 11/14/2018 From: http://www.biology.eku.edu/RITCHISO/301notes3.htm
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11/14/2018 Contraction Overview Filaments on myosin and actin merge causing muscle fibers to converge Myosin - 2 protein strands with globular proteins (heads) sticking out that can react with active sites of actin to form cross bridges Actin/troponin/tropomyosin Actin – contains active site used to bond with myosin Tropomyosin – resting position for myosin heads Together with troponin Troponin – bond to calcium ions Changes shape to expose actin active sites Together with tropomyosin
Contraction step by step 11/14/2018 Contraction step by step Stimulation - acetylcholine released from motor neuron Muscle fiber stimulation by acetylcholine & calcium ions are released from the sarcoplasmic reticulum Calcium ions bind to troponin molecule Troponin molecules change shape causing tropomyosin to rotate and expose active sites on the actin molecule
Contraction step by step 11/14/2018 Contraction step by step Cross bridges form between actin (active sites) and myosin filaments (globular proteins) Actin filaments slide along myosin filaments (ATP used) due to a swivel action of myosin globular protein Muscle fiber shortens as contraction occurs Wisconsin Online - animation Texas A&M University - animation
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