Chapter 9-11 Muscular System PDF

1 Chapter 9 Myology- Study of the Muscles 4 characteristics 1. excitability 2. contractibility 3. extensibility 4. elasticity Main Functions: 1. movement 2. support 3. body temperature maintenance 4. guards openings (orifices) Types of muscles: - smooth...

1 Chapter 9 Myology- Study of the Muscles 4 characteristics 1. excitability 2. contractibility 3. extensibility 4. elasticity Main Functions: 1. movement 2. support 3. body temperature maintenance 4. guards openings (orifices) Types of muscles: - smooth - cardiac - skeletal Gross Anatomy: 3 concentric layers of connective tissue 1. epimysium dense irregular connective tissue; surrounds entire skeletal muscle; separates the muscle from surroundings 2. perimysium divides the muscles into compartments (containing bundles of fibers called fascicles); contains blood vesicles and nerves 3. endomysium surrounds each muscle fiber; binds fibers to each other - satellite cells between endomysium & muscles fibers; repairs damaged muscle fibers Tendon Neuromuscular Junction site of chemical communication between synaptic terminal of a neuron and skeletal muscle fibers Microanatomy: - sarcolemma - sarcoplasm - differ from regular cells: a. muscle cells (fibers) long 100mm b. multinucleated- 100; embryonic cells fuse to create muscle cells; myoblasts that don’t fuse become satellite cells in adulthood c. contain indentations in the membrane forming tubule network; transverse or T. tubule conducts electric impulse Myofibrils (100-1000) located in the sarcoplasm - length extends entire length of muscle - shortencause contractions - surrounded by mitochondria & glycogen molecules - myoglobin reddish pigment similar to hemoglobin stores O2 until needed for mitochondria Sarcoplasmic Reticulum- membrane sleeve that helps control contractions of individual myofibrils Myofibrils consist of myofilaments (bundles): a. actin- thin filaments b. myosin- thick filaments Summer 2018  2 c. troponin d. tropomyosin e. titin Sarcomere- smallest functional unit of the muscle fibers a. Z discs/ lines- separate sarcomeres b. A-band - dark area; thick filaments overlapping thin filaments c. M-lines- protein molecules adjoin thick filaments (page 246) d. H-zone- zone of thick filaments in the center of A-band e. I-band- zone of thin filaments Motor neurons- neurons that stimulate muscle tissue Synaptic vesicles- membranes sacs containing neurotransmitters acetylcholine Synaptic cleft- space between axon terminal & sarcolemma All or none principle - once a threshold stimulus is reached, muscle fibers of a motor unit (motor neuron & muscle fiber) will contract to its fullest capability or not at all Muscle atrophy & Hypertrophy: 1. disuse atrophy 2. denervation atrophy 3. hypertrophy 2 types of skeletal muscle fibers: 1. red muscle fibers high myoglobin content smaller in diameter; increase mitochondria & blood supply 2. white fibers (fast) low myoglobin, bigger diameter; low mitochondrial content & blood supply Fibers: Type 1  slow twitch, slow oxidative, fatigue resistance, high Myoglobin, high mitochondria & blood supply, high capacity to produce ATP aerobically, red, contraction velocity is slow & very resistant to fatigue Type 2 fast twitch, fast glycolytic, fatigable fibers, low myoglobin, low mitochondria & few capillaries, high amount of glycogen, white, generate ATP anaerobically, contraction are strong and fast-fatigable Type 2A(intermediate) fast twitch, fast oxidative and fatigue resistance, high myoglobin, high mitochondria & capillaries, ATP aerobic metabolism, contraction are fast, fatigue resistance, occurs infrequently Abnormal Muscle Contractions: 1. Spasm- any involuntary contraction of large groups of muscle 2. tremor- rhythmic involuntary, purposeless contraction of opposing muscle groups 3. fasciculation- involuntary, brief twitch of a muscle visible under the skin 4. fibrillation- involuntary, brief twitch of a muscle not visible under the skin Organization of muscle fibers: 4 patterns of the fasicle arrangement 1. parallel- parallel to the longitudinal axis of the muscle 2. convergent- based over a large area with a common attachment site 3. Pennate- one or more tendons run thru the body of the muscle - unipennate muscle on the same side of the tendon - bipennatemuscle on both sides of the tendon 4. circular or sphincter muscles- concentric around the opening Summer 2018  3 Summer 2018  4 origin insertion action primary actions: 1. prime movers agonists, contraction are responsible for a particular movement 2. synergist assist prime movers, prevent movement by stabilizing the joint 3. antagonist muscle who’s action oppose the agonist if agonist flexion, the antagonist produces extensions 4. fixators stabilizes the origin of the prime mover so it is efficient Names of the skeletal muscles: 1. directional indications a. rectus - straight parallel fibers run along axis of body b. transversus- fibers that run across c. obliques- run at an angle to long axis 2. unusual structure features ( # of insertion & origins) a. biceps- 2 tendons of origin b. triceps- 3 c. quadriceps- 4 3. shape a. trapezius- trapezoid b. deltoid- triangular c. rhomboideus- rhomboid d. orbicularis- circular e. longus- long f. longissimus- longest g. teres- long and round h. brevis- short i. magnus- big j. major- bigger k. maximus- biggest l. minor- small m. minimus- smallest 4. location a. externus or superficial- visible at body surface b. internal or profundus- internal c. extrinsic- muscles that position or stabilize an organ d. intrinsic- operate within an organ 5. muscle that identify their origins and insertion a. genioglossus chin + tongue = genio + glossus 6. names that include flexor, extensor, retractor, indicate the primary function of the muscle 7. Except for the platysma & diaphragm all skeletal muscles include the term “muscle”. Summer 2018