Ch 9 Skeletal Muscular System 09 02 2010 19 16 00 Three types Skeletal Cardiac Smooth Function Excitability respond to stimulus Contractibility shorten and exert tension Extensibility can contract even when stretched Elasticity rebound length Skeletal Muscle Produces movement Maintains posture and position Supports soft tissues Guards orfices Maintain body temperature Organization The organ Groups of fibers within a muscle fasicles Inside the fascles are the muscle fibers or cells Organ fascicle fiber myofibrils myofilaments Connective Tissue layers Epimysium outer layer covers the whole muscle organ Perimysium covers the fascicle find blood vessels and nerves Endomysium surrounds the muscle fibers cells Contain the muscle and have the nerves and arteries within them Converge to form tendons muscle to bone attachment o Flattened is an aponeuroses o Interwoven into periosteum and bone Features of skeletal muscles Large cylindrical muscle fibers Multinucleated Striated Voluntary Satellite cells help in repair limited but possible Sacrolemma is the membrane Sacroplasm is the cytoplasm A muscle fiber Myofibrils in sacroplasm all red dots Blue nuclei multi An abundance of mitochondria Membrane sacrolemma Invagination of sacrolemma is transverse tubules which carry electrical impulses nerve impulses Inside myofibrils are myofilaments Myofibrils surrounded by sacroplasmic reticulum o Internal membrane system one myofibril is as long as fiber and is attached to sacrolemma cisterna swollen parts of reticulum near t tubules Myofilaments Sacromere one unit in a myofilament o Goes from z line to z line Thin filament actin red lines o Have active site on them Thick filament myosin purple lines o Has a tail and head o Moveable head A band band where thick filaments reach only thick o Bumps on a band heads of myosin M line the middle where actin and myosin meet in the sacromere I band thin filaments Z line boundaries of the sacromere Cross bridges head of myosin Sliding filament theory Requires presence of calcium and ATP Explains how a muscle fiber exerts tension Active sites of actin filaments o And head of myosin filament Cross bridge head of myosin to active site of actin o Attach pivot detach return o Attach when calcium and atp is present o Detach when calcium and atp is not present o Elasticity make muscle go back to original shape Happens to all sacromere in one cell at a time Skeletal mucle fascicle fiber myofibril myofilament sacromere Skeletal muscle innervation Stimulated by a nerve fiber at a neuromuscular junction Motor nerve from a cell body Sends it down axon to neuromuscular synapse Synaptic terminals have small vesicles that release Ach a neurotransmitter Stimulate motor end paltes causing an action potential impulse a a acetylcholinesterase breaks down Ach understand summary of events o contraction Ach is released binding to receptors Action potential reaches t tubules Sacroplasmic reticulum releases Ca2 Active site exposure cross bridge binding Contraction begins o End contraction Ach removed by AChE Sacroplasmic Reticulum recaptures Ca2 Active sites covered no cross bridge interaction Contraction ends Relaxation occurs passive return to resting length Move towards m line when contracting and a band shortens Motor units One axon to one group of muscle cells Contraction all motor unit are active Muscle tone resting o Some motor units are active causing muscles to be tense but no movements o Maintain body position Muscle hypertrophy muscle becomes enlarges o Muscle repeated stimulated o Increase in number of myofibrils o Increase amount of mitochondria o Tension increases Muscle atrophyo Muscle is not stimulated o Muscle becomes smaller o Muscle tone is decreased flaccid low muscle tone o Cause by lack of nerve input or disuse Shapes of Muscles Parallel muscle fascicles are lined up parallel to one another and a tendon at each end Convergent base of muscles wide and converge down to a single tendon o Lots of movements pennate fibers are at an angle o Multiple or single tendons uni bi or multio The angle of the tendons cause for different types of movement Circular muscle around an orifice o Contract smaller and smaller radius o Relaxed larger Terminology pg 253 Terms indicating action Terms indicating direction Term indicating specific region Specific o Buccinator trumpeter o Risorious laughter Origin o Bicep two head etc Shape o Deltoid triangle etc Axial musculature Arises and inserts onto the axial skeleton Poisitions head and vertebral column Moves rib cage thus assits in brething 60 of muscles Appendicular musculature Stabilizes components of the appendicular skeleton Axial Skeletal muscles know name origin insertion action and innervation Refer to ch 12 Muscles of the head and neck o Strap muscles just know names and origin and insertion o Cranial nerves Veretebral column Abdominal Pelvic floor 09 02 2010 19 16 00 09 02 2010 19 16 00