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Lecture 17

Lecture 17-Muscle(I)

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Biological Sciences
Catherine Nash

Lec 17 MUSCLE-I • Types of muscles SKELETAL • attached to bones or our skeleton by collagen known as tendons ○ positions and moves the body or appendages(locomotion) • only these contract to a signal from somatic m motor neuron • cannot initiate own contraction • Origin ○ point of muscle-bone attachment closest to trunk • Insertion ○ is usually more mobile and is the point of muscle bone attachment more distal or distant from the trunk • Flexor and Extensor muscles ○ Flexor muscles brings bones closer together like biceps and extensor muscles moves bones away from each other ○ antagonistic muscles groups are flexor and extensor pair having opposite effect(when one muscle contracts the other one relaxes) • What are skeletal muscles composed of ○ muscle fibers!!!!!!!!!w ○ group of muscle cells function together and have many nuclei and are arranged in parallel ○ connective tissue encases lots of fibers together ○ groups of adjacent fibers are contained in fasicles  (collagen, elastic fibers, nerves and blood vessels are found between the fasicles) ○ COMPONENTS OF MUSCLE FIBERS myofibrils, which contain thick and thin filaments(myosin and actin) - the contractile machinery •arcolemma = Cell membrane •Transverse tubules (T-tubules) = Invaginations of the sarcolemma •Sarcoplasm = Cytoplasm (contains mitochondria and glycogen for muscle contraction) Sarcoplasmic reticulum (SR) = Modified endoplasmic reticulum - Wrapped around myofibrils - releases Ca during muscle contraction •Mitochondria : provides ATP for muscle contraction
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