Chapter 10 Notes
Chapter 10 Notes 80887 - BIOL 3150 - 001
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This 10 page Class Notes was uploaded by Abigail Towe on Thursday October 1, 2015. The Class Notes belongs to 80887 - BIOL 3150 - 001 at Clemson University taught by Tamara L. McNutt-Scott in Fall 2015. Since its upload, it has received 55 views. For similar materials see Functional Human Anatomy in Biological Sciences at Clemson University.
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Date Created: 10/01/15
Chapter 10 Muscle Tissue and Organization 0 There are 3 types of muscle tissue 0 smooth 0 cardiac o skeletal I over 700 skeletal muscles in body 0 These 3 muscles work to allow movement of body movement within body and movement throughout body 0 There are fibers within muscles that exhibit specific characteristics 0 excitability responsiveness I reaction to stimuli I uses chances in electrical charges across the permeable membrane to signal internal events to cause muscle contractions o contractility cell shortens I stimulation causes tension within cells to initiate contractile elements and the cells shortens o elasticity cell recoils to original shape I when the tension is removed the contracted muscle returns to its original length 0 extensibility I contraction of opposing muscle leads to muscle to extend in length 0 Anatomic microscopic characteristics of skeletal muscle 0 striated I due to the size and density differences between thin and thick filaments o elongated with peripherally located nuclei 0 long cells that are usually in length of the muscle 0 skeletal muscles 0 composed of the 4 primary tissue types 0 attaches to one or more bones o shape various Functions of Skeletal Muscle Tissue 0 body movement 0 bones move when skeletal muscles contract 0 also pulls on tendons that are attached to bone 0 the movement is highly coordinated because muscles functions are coordinated with bones and joints 0 maintenance of posture 0 because skeletal muscles are attached to bones it helps stabilize joints and maintain postureposition the postural muscles work continuously while awakeconscious when a person is unconscious their skeletal muscles relax because skeletal muscles are voluntary 0 temperature regulation 0 muscle activity creates heat byproducts as a waste as energy is used 0 storage and movement of materials 0 sphincters throughout digestive tract to allow movement when necessary of materials 0 support 0 muscles arranged in sheetslayers gt protects organs and supports their weight within the abdomen Structural Organization of Skeletal Muscle o skeletal muscles are formed by layers of muscle fibers blood vessels nerves connective tissue sheets 0 the CT sheets surround fibers and aid in connecting muscles to bone myofilaments gt myofibrils gt muscle fiber muscle cell gt fascicles gt muscle endomysium wraps around muscle fibers perimysium wraps around fascicles epimysium wraps around the muscle myofilaments actin myosin o actin thin filaments I subunit G actin polymerizes to form F actin I two regulatory proteins troponin and tropomyosin o these proteins regulate the attachment of myosin head to Gactins o while tropomyosin coiled protein covers Gactins myosin cannot bind to Gactin therefore muscle contraction is inhibited o troponin controls the position of tropomyosin troponin is regulated by calcium concentrations in sarcoplasm 0 when the concentration of calcium increases troponin chances conformation shape gt tropomyosin cannot block gt Gactins are uncovered so that myosin can bind gt contraction occurs 0 myosin thick filaments I structure a tail with two heads o tail points toward center o heads point toward edges Muscle Attachments 0 muscles can attach through tendons in two different ways 1 tendons in the form of thick cordlike structures a located at the end of a muscle the connective tissue merges to form a fibrous tendon cord b example in elbow 2 aponeurosis sheet of tendon a the tendon is a sheet that s thin and flattened b example bottom of foot Blood vessels and nerves o epimysium blood vessels and nerves pass through this layer 0 perimysium in this layer blood vessels and nerves are directed to go to specific compartments 0 the blood vessels lymphatics and nerves travel in a neurovascular bundle together through these layers 0 controlled by nerves of somatic nervous system 0 the somatic NS is part of the peripheral NS associated with skeletal muscle voluntary control 0 as efferent and afferent nerves 0 voluntary I motor neurons stimulate muscle contractions through axons of nerves I neuromuscular junctionjunction between axon and muscle fiber 0 when muscles move it uses anaerobic produces lactic acids and aerobic mechanisms 0 lactic acids make you sorefatigue so the more fit you are the less pain you will have Microscopic Anatomy of Skeletal Muscle 0 some myoblasts fuse together during embryonic development gt multinucleated skeletal muscle the myoblasts that don t fuse gt satellite cells 0 they differentiate when repairs or regeneration of injured skeletal muscle has to take place 0 review sarcomeres gt myofilaments gt myofibrils gt muscle fiber muscle cell gt fascicles gt muscle 0 myofibrils long cylindrical and extends the entire length of muscle fiber 0 myofibrils shorten as myofilaments change position during contraction o the plasma membrane of skeletal muscle fibers sarcolemma the plasma sarcoplasm o connective tissue runs in vessels sarcoplasmic reticulum stores calcium 0 calcium is the ghost signal for contraction o transverse T tubule runs perpendicular to the fibers and the sarcoplasmic reticulum connects to these tubules 0 serves as the communication link on the inside and within the muscular junc on o triadcommunication link between sarcoplasmic reticulum and T tubules Histoloy Lab Part Slide 45 w g V m a wquot 39 T 5 ll llll I l jlts li u ll mm l l all 3 l l l 56 l E Sarcoplasm V Mitochondria 7 Openings into transverse tubules Triad Transverse T tubule Terminal cisternae Sarcoplasmic reticulum Sarcomere Organization 0 multiple sarcomeres gt myofibril o sarcomeres are the functional contractile unit of skeletal muscle fibers o sarcomere distance between 2 Z linesdiscs o made up of o A band dark band 0 I entire thick filament I some of thin filament lbandthtband I contains thin filament only 0 thick filaments I H zone central region of A band 0 only thick filaments I M line center of H zone o thin protein that runs down center of H zone 0 attachment site for thick filament o stayed aligned during contraction 0 thin filaments I Z line thin protein structure attachment site for thin filaments Contraction of Skeletal muscles 0 Sliding Filament Theory interactions between filaments cause them to slide over each other to cause contraction of muscles 0 O sarcomere shortens because it s the distance between Z discs and the Z discs in the thin filaments change position as the thin filament moves past thick filaments thick filaments DO NOT move thin filaments move toward M line centrally to bring Z lines closer together Summary thin and thick filaments remain the same length I thin filaments move past thick filaments o contraction occurs when the nerve impulse traveling along a motor neuron reaches the neuromuscular junction to stimulate a muscle fiber 0 motor neurons control many muscle fibers motor unit I fine motor units wiggling fibers usually 4 muscle fibers associated I gross motor units kicking leg muscle fibers are spread out All or None Principle all of the fibers under the motor neuron s control contract or none do there is resting tension in skeletal muscles because some motor units remain activated even when a muscle is at rest This serves to keep muscle firm healthy and ready to respond to stimulation I motor units are stimulated randomly I they assist to stabilize position of bones stabilize joints and maintain posture o muscle tension the force exerted by a contracting muscle on some object 0 load weight reciprocal force exerted by an object on a muscle 0 muscle contraction types 1 isotonic changes length of muscle a can be concentric contractions or eccentric contractions i concentric muscles shorten to generate force ii eccentric muscles elongate in response to greater opposing force 2 isometric contraction generates force without changing length of muscle 0 the physiology of muscle contraction Synaptic knob Sarcolemma Neuromuscular junction Myofibril A nerve impulse triggers release of ACh from the synaptic knob into the synaptic cleft ACh binds to ACh receptors in the motor end plate of the neuromuscular junction initiating a muscle impulse in the sarcolemma of the muscle ber 2 As the muscle impulse spreads quickly from the sarcolemma along Ttubules calcium ions are released from terminal cisternae into the sarcoplasm Active sites blocked 5 When the impulse stops calcium ions are actively transported into the sarcoplasmic reticulum tropomyosin recovers active sites and filaments passively slide back to their relaxed state Active site Thin filament 4 Thick filament Myosin heads pivot moving thin filaments toward the sarcomere center ATP binds myosin heads and is broken down into ADP and PI Myosin heads detach from thin laments and return to their prepivot position The repeating cycle of attach pivot detachreturn slides thick and thin filaments past one another The sarcomere shortens and the muscle contracts The cycle continues as long as calcium ions remain bound to troponin to keep active sites exposed Calcium ions bind to troponin Troponin changes shape moving tropomyosin on the actin to expose active sites on actin molecules of thin filaments Myosin heads of thick filaments attach to exposed active sites to form crossbridges Axonal tamina39 Neurotransmitter released diffuses across the synaptic cleft and attaches quot synapuc to ACh receptors on the sarcolemma cleft 39 Q I Sarcoiemma Tmbule N N 6 Action potential B along the sarcolemma and down the T tubules f 75 from terminal cisternae of SR o I 0 39 2 63quotquot 39 C39azquot ca Tropomyosin blockage restored blocking actin Calcium ions bind to troponin active sitecontraction troponin changes shape removing ends and Caz the blocking action of tropomyosin muscle 39 actin active sites exposed tiber mam Removal of Ca2 by active transport 39 39 into the SR after the action potential ends c820 39 39 39 Contraction myosin cross bridges alternately attach to actin and detach pulling the actin laments toward the center at the sarcomere release of energy by ATP hydrolysis powers the cycling process Copynghi 03 2004 Pearson Education Inc puhlishn as Benjamin Cummings Summary excitationcontraction coupling 1 Neurotransmitter released a diffuses across synaptic cleft b attaches to acetylcholine receptors on the sarcolemma plasma membrane 2 action potential generated is propagated along the sarcolemma and down the T tubules 3 calcium ions bind to troponin a the troponin chances shape conformation b removing the blocking action of tropomyosin c actin active sites exposed 4 myosin bridges alternately attach to actin and detach contraction a pulls actin filaments toward the sarcomere b releases energy by ATP through hydrolysis 5 removal of calcium by active transport into the sarcoplasmic reticulum after the action potential ends 6 tropomyosin blockage restored to block actin active site a now that the actin active site is blocked contraction ends fibers relaxes Tvnes of Skeletal Muscle Fibers 1 slow oxidative SO fibers prolonged contractions a if dominate in muscle red muscle 2 fast glycolytic F0 or FG rapid intense movments a if dominate in muscle white muscle Skeletal Muscle Fiber Organization 0 muscle fibers gt fascicles o the bundle pattern can vary there are 4 different patterns 1 circular a fibers arranged concentrically b examples sphincters orbits mouth anus 2 parallel a fibers are parallal b example rectus abdominis high endurance not very strong 3 convergent a fibers arranged in triangular pattern to meet at common attachment site b example pectoralis major 4 pennate a muscle body has one or more tendons b unipennate all muscle fibers on same side of tendon c bipennate fibers on both sides of tendon d multipennate tendon branches within the muscle Lever Svstems of Muscles o lever rigid bar that moves on a fixed point fulcrum when a force is applied fulcrum joints lever bone load bone or anything you try to move effort provided by muscle contraction mechanical advantage power lever mechanical disadvantage speed lever the site of muscle insertion can affect the force a muscle must generate to move a given load 0 the position of effort fulcrum and load influences amount of force needed Actions of Skeletal Muscle o muscles PULL they cannot push o 3 primary actions 1 prime moversagnoists msucle provides major force 2 antagonists opposereverse particular movement 3 synergists aids agonists a muscle can act as any of these types depends on movement Characteristics of Cardiac Muscle Endomysium 8 Cardiac muscle cell Z discs M arranged in thick bundles within heart wall fibers are straited but shorter and thicker 1 or 2 nuclei per cell numerous mitochondria aid in aerobic respiration forms Yshaped branch to join adjacent msucle fibers via intercalated discs Intercalated disc cardiocyte lntercalated discs Centrally located nucleus Endomysrum M Gap junctions Desmosomes a l 3 r 39 39quot ijj j g 1 1 K it I 39 I t I i I V Mitochondrion Sarcolemma Nucleus Cardiac muscle cell b Characteristics of Smooth Muscle short fusiform shape single central nucleus nonstraited even though smooth muscle has thin and thick filaments they just aren t aligned in a pattern 0 the thin filaments are attached to dense bodies sarcoplasmic reticulum is in small quantity T tubules and Z discs are absent contraction is slow but sustained for an extended period of time involuntary controlled by autonomic nervous system
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