This preview shows pages 1–3. Sign up to view the full content.
This preview has intentionally blurred sections. Sign up to view the full version.View Full Document
Unformatted text preview: 1 The Muscular System The Muscular System The Muscular System Functions of Muscle s Produce movement s Maintain posture s Stabilize joints s Generate heat s Prefix myo and mys refer to muscle s Prefix sarco refers to flesh Characteristics of Muscles Characteristics of Muscles 3 basic muscle types in the body s Smooth muscle s 1 nucleus; no striations; involuntary s found mainly in the walls of hollow organs s Cardiac muscle s usually 1 nucleus; striations; involuntary s found only in the heart s Skeletal muscle s multinucleate; striated; voluntary s attached by tendons to bones s surrounded & bundled by connective tissue Muscle Fibers Muscle Fibers s Muscle fiber = muscle cell s Fascicles = bundles of muscle fibers s A muscle fiber consists of myofibrils (many filaments) s Each myofibril is made of 2 kinds of proteins filaments s Actin filaments: are thin & light s Myosin filaments: are thick & heavy s Contraction of muscles is due to the movement of these protein filaments Connective Tissue Wrappings Connective Tissue Wrappings of Skeletal Muscle of Skeletal Muscle s Endomysium = s around a single muscle fiber s deepest layer s Perimysium = s around a fascicle of fibers s Epimysium = s covers the entire skeletal muscle s Fascia = s on the outside of the epimysium Skeletal Muscle Attachments Skeletal Muscle Attachments s The epimysium blends into a connective tissue attachments , which may be a/an: s tendon = cord-like structure s aponeuroses = sheet-like structure s Sites of muscle attachment : s Bones & cartilages, and s connective tissue coverings 2 Structure of Muscle Fiber Structure of Muscle Fiber s Sarcolemma = specialized plasma membrane s Nuclei are just beneath the sarcolemma s Sarcoplasmic Reticulum (SR)= s specialized smooth endoplasmic reticulum s stores calcium (Ca++) needed for muscle contractions Structure of Muscle Fiber Structure of Muscle Fiber s Sarcomere = contractile unit of muscle s alternating bundles of actin & myosin filaments give a striated appearance s Cross bridges = paddle-like extension of the myosin filament for attachments to actin filaments s Myosin and actin overlap somewhat s at rest, there is a bare zone that lacks actin filaments Nerve Stimulus to Muscles Nerve Stimulus to Muscles s Skeletal muscles must be stimulated by a nerve(a motor neuron) to contract s Motor unit is composed of: s 1 neuron + the muscle fibers stimulated by that neuron Neuromuscular Neuromuscular Junction Junction s An association site of the motor nerve and muscle cell membrane Neuromuscular Junction Terms Neuromuscular Junction Terms s Motor end plate = receiving muscle cell membrane s Synapse = a point of communication between cells s Synaptic cleft = gap between cells s nerve & muscle do not make contact s filled with interstitial fluid s Synaptic vesicle = vesicles at the end of the motor neuron containing neurotransmitters Neuromuscular Junction Terms Neuromuscular Junction Terms s Neurotransmitter = a chemical released by a neuron to...
View Full Document
This note was uploaded on 05/04/2008 for the course HP 320 taught by Professor Islam during the Spring '08 term at USC.
- Spring '08