Muscle Tissue

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Histology (Alb) Lecture 5 - Exam 2
Marissa Alvarez
Fichas por Marissa Alvarez, actualizado hace más de 1 año
Marissa Alvarez
Creado por Marissa Alvarez hace más de 7 años
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Muscle Tissue Main Function? Terminology? Main Function: CONTRACTION to generate MOTION (muscle must span a joint to achieve this) Terminology: Sarco- or Myo- to refer to muscle components e.g. sarcolemma sarcoplasmic reticulum endomysium
Muscle Types SKELETAL MUSCLE weak or strong? fast or slow? discontinuous or continuous? voluntary or involuntary?
Muscle Types CARDIAC MUSCLE weak or strong? fast or slow? discontinuous or continuous? voluntary or involuntary?
Muscle Types Smooth Muscle weak or strong? fast or slow? voluntary or involuntary?
Development of skeletal muscle fibers Satellite cells? Satellite cells are the source of muscle REGENERATION after injury
Muscle Tissue Endomysium? Perimysium? Epimysium? Endomysium: separates muscle fibers Perimysium: contains bundles of muscle fibers Epimysium: covers the muscle
Organization of skeletal muscle What does each black box represent? Ep: epimysium P: perimysium En: endomysium B: blood vessels C: capillaries
Depiction of Muscle FIBER
Organization of skeletal muscle: What does each arrows indicate?
Skeletal muscle banding pattern in H&E histological section: What does each black box represent?
Myosin = Thick Filament Actin = Thin Filament Z line to Z line = Sarcomere (H is in middle of A) (Z is in middle of I) Myosin attaches to A bands) Actin attaches to I bands at Z line
Changes in widths of bands during contraction: What does the contracted state look like for I,Z, A, & H? During contraction, the actin and myosin filaments interact. The acting are pulled toward the center of the myosin filaments. As a result the sarcomeres shorten (Z bands brought closer together). In the fully contracted muscle, the ends of actin myofilaments overlap, the H zones disappear, and the I band becomes very narrow. *A band remains unchanged
Changes in widths of bands during contraction: What does the relaxed/rest state look like for I,Z, A, & H? Actin and myosin filaments lie side by side *A band remains unchanged
Changes in widths of bands during contraction: What does the stretched state look like for I,Z, A, & H? I band and H band grow wider (Z band pulled farther apart) *A band is unchanged.
What is two elements are involved in contraction? Distance actin filaments can travel? How many cycles are necessary for full contraction? Contraction involves: repeated binding-movement-release cycles between the myosin heads and actin filaments The distance the actin filaments can travel during a single stroke is ~10 nm. HUNDREDS of cycles are necessary for FULL contraction.
What membrane system controls contraction? How does it regulate contraction? Where is calcium stored? Special internal membrane system called: TRIADS control muscle contraction by regulating CALCIUM RELEASE Ca is stored in sacs of sarcoplasmic reticulum
What are T-tubules? At what junction do T-tubules occur at? What two elements do T-tubules form triads with (HINT: two of the same thing)? T-tubules (orange) are invaginations of the sarcolemma (plasma membrane) In MAMMALIAN skeletal muscle: T-tubules occur at the A/I junction T-tubules form triads with two terminal cisternae of the sarcoplasmic reticulum
Where are triads located in frogs? In humans? Note that triads are at the Z-line in frogs whereas in humans they are at the A-I junction (indicated by *)
Neuromuscular junction: What two main steps occur at the neuromuscular junction? 1. Nerve impulse triggers RELEASE of ACh into synaptic cleft. ACh binds to ACh receptor on sarcolemma of motor end plate, triggering the muscle IMPULSE. 2. The muscle impulse SPREADS quickly from sarcolemma to T-tubules and Ca is released from TERMINAL CISTERNAE of sarcoplasmic reticulum.
What is indicated by the arrows and what is located here that is involved in the neuromuscular junction? Motor end plates (arrows) demonstrated by silver impregnation ACh receptors are located on sarcolemma of motor end plate
What fibers are involved with the cardiac muscle and conduction system?
Compare Skeletal & Cardiac muscle Tissues: Fiber characteristics (2 things to compare)? Nuclei characteristics? Innervation?
What are the arrows pointing at? Cardiac muscle with visible striations: Pointing to INTERCALATED DISKS
What are the arrows pointing at? Arrows: Intercalated disks (CARDIAC muscle) N: Nuclei of myocytes F: Fibroblasts
Cardiac muscle: Intercalated disk What do the blue boxes represent? FA: Fascia adherens D: Desmosome G: Glycogen M: mitochondria N: Nexus (gap junction) SR: Sarcoplasmic reticulum T: Triad or Tubule (not 100% sure - he did not define in powerpoint)
Cardiac muscle T-tubule system: Can you identify all of the filling in the picture? **T-tubules run at Z-lines (middle of I) Sarcoplasmic reticulum is less developed
Purkinje fibers are modified cardiac myocytes interconnected by gap junctions (electrical synapses).
Smooth Muscle Voluntary or involuntary? Controls? Found? Slow continuous involuntary contraction Controls peristaltic motions of tubular structures Found in larger blood vessels, the GI system, ureter, bladder, reproductive systems and many other locations
What is type of muscle tissue is shown? Two layers of SMOOTH muscle (wall of the gut)
Smooth muscle ultrastructure What is indicated at the arrows? (all the same thing at white arrows) Thick (myosin) filaments indicated at white arrows!
Smooth muscle contraction Relaxed form? (surrounded by?) Surrounded by contractile filament
Smooth muscle contraction Contracted form? (Surrounded by?) Surrounded by contractile filament
What type of muscle tissue is this? What is the arrow and black box indicating? Smooth muscle tissue "corkscrew appearance"
EXAM Question: Identify this tissue A. Skeletal Muscle B. Connective Tissue C. Cardiac Muscle D. Smooth Muscle C. Cardiac Muscle
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