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44 Cards in this Set
- Front
- Back
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What is muscle derived from?
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-mesoderm!
-muscle forms from fusion of myoblasts -myoblasts that don't form muscle fibers make satellite cells |
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What is the function of muscle cells in general?
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-contraction
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Which types of muscle are striated?
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-skeletal
-cardiac |
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What do the terms myocyte and myofiber describe?
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-a muscle cell
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Sarcolemma
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-muscle plasma membrane
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Sarcoplasm
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-cytoplasm of a muscle cell
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What are general muscle properties?
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-electrical excitability
-contractability -extensibility -elasticity |
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What are the functions of skeletal muscle?
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-movement and breathing
-posture -surrounds and supports soft tissue -heat production -guards orifices |
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Where is skeletal muscle located?
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-it is ubiquitous
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How is skeletal muscle controlled?
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-voluntary
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Can skeletal muscle regenerate after injury?
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-not very easily
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Organization of skeletal muscle cells
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-does not consist of individual cells
-each muscle is made up of many fascicles -fascicles are made of many muscle fibers (can be very long and have multiple nuclei) -muscle fibers are made up of myofibrils |
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Myofibrils
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-contain myofilaments (actin, myosin)
-produce cross-striation in skeletal muscle -contained within sarcoplasm -have regular striations called sarcomeres |
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Muscle fibers
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-cytoplasm is called sarcoplasm
-mitochondria and sarcoplasmic reticulum surround each myofibril -nuclei are located peripherally (near satellite cells) |
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Satellite cells
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-important in muscle regeneration after injury
-can't recognize them histologically |
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What does skeletal muscle consist of?
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-striated fibers held together by CT (endomysium, perimysium, epimysium)
-CT carries blood vessels, lymphatics, nerves -extends beyond the fleshy part of the muscle to formtendons and aponeuroses |
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Endomysium
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-encloses each muscle fiber
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Perimysium
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-encloses each bundle of fibers
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Epimysium
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-encloses the whole muscle
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Histologic Features of Skeletal Muscle
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-each fiber=one cell
-fibers are long, striated and multinucleate -nuclei are peripherally located |
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Contractile apparatus proteins
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-Contractile: generate contractile force
-actin, myosin -Regulatory: act as a switch to see if muscle will contract or not -troponin, tropomyosin -Accessory: maintain alignment of thin and thick filaments -tropomodulin, myomesin, desmin |
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F-actin
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-thin filament
-polar -made of many G-actin molecules -binding sites for myosin -associated tropomyosin and troponin |
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Tropomyosin
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-forms filaments that run in the groove between F-actins
-during rest, hide the myosin binding site on actin |
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Troponin
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-3 subunits
C: binds calcium T: binds tropomyosin and anchors troponin I: bind actin to inhibit actin-myosin interaction |
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Myosin
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-thick myosin
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A-band
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-dark stripe in H&E
-location of myosin (thick filament) -M-line is in the center -H-band appears along the middle of the A-band when muscle stretches |
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M-line
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-where thick filaments are attached in the A-band
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H-band
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-appears in the middle of the A-band when muscle stretches
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I-band
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-light stripe in H&E
-location of actin (thin filament) -Z-disc is a dark line through the middle of the I-band |
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Z-disc
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-dark line through the middle of the I-band where actin filaments attach
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Function of Smooth Muscle
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-movement of internal organs
-slow, prolonged contraction -moves things through hollow organs -helps maintain blood pressure -able to secrete CT matrix |
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Location of smooth muscle
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-walls of hollow visceral organs
-found in almost every organ.... |
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Histological Features of Smooth Muscle
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-not striated
-individual thin fiberrs with tapered ends -single, cigar-shaped, central nucleus -fibers are densely packed together |
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Can smooth muscle regenerate?
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-Yes, in response to injury
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Multiunit smooth muscle
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-fibers act independently (similar to skeletal muscle)
-fewer gap junctions -under nervous control (well innervated) |
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Visceral Smooth muscle
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-fibers act together as a functional unit (similar to cardiac muscle)
-many gap junctions -contract spontaneously -form sheets or bundles |
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Cardiac Muscle Functions
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-movement of heart
-rhythmic, unfaltering contraction -intrinsic spontaneous contraction |
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Heartbeat conduction
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-initiated, regulated and coordinated by conducting cells
-conducting cells are organized into nodes and conducting fibers (Purkinje fibers) |
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Cardiac Muscle Cellular Organization
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-heart consists of cardiac muscle
-it is striated: -contains sarcomeres -has distinct, individual cells -attached by intercalated discs |
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Is cardiac muscle voluntary?
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-No
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Intercalated discs
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-adhering junctions: contractile myofilamennts are attached
-gap junctions: allow passage of ions to establish electrical connection |
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Histologic Features of Cardiac Muscle
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-striations are present
-fibers branch and interconnect -nuclei are centrally located and there is usually one per fiber -each fiber has a sheath of CT |
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Purkinje Fibers
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-specialized cardiac muscle cell
-conduct electrical signals to coordinate heart contractions -larger diameter and paler pink cytoplasm than cardiac muscle fibers -reduce electrical resistance -increase electrical conduction speed |
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Sarcomere Ultrastructure in Cardiac Muscle
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-myofibrils are similar to skeletal muscle in that they form banding patterns
-have sarcomeres and intercalated discs -T-tubules are located at the Z-line (instead of teh A-I junction as in skeletal muscle) -Sarcoplasmic reticulum forms dilatations only on one side of the T-tubule to form diads (not triads) -gap junctions |
