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There are three types of muscle tissue: skeletal, cardiac, and smooth. Skeletal muscle is striated and voluntary, composed of bundles of fibers surrounded by connective tissue layers. Each fiber contains myofibrils which are made up of thin actin and thick myosin filaments in a repeating sarcomere pattern, allowing for contraction. Motor neurons stimulate muscle fibers at the neuromuscular junction, transmitting action potentials that trigger calcium release and excitation-contraction coupling to cause contraction.
Lec25
- 1. Muscle OverviewThree types of muscle tissue are skeletal, cardiac and smoothMuscle contraction depends on two types of myofilaments – actin and Myocin
- 3. SKELETAL MUSCLE ORGANA WHOLE MUSCLE CONSISTS OF A LARGE NUMBER OF MUSCLE FIBERS (CELLS) , PLUS CONNECTIVE TISSUE WRAPPINGS,BLOOD VESSELS, AND NERVE FIBERS.
- 4. SKELETAL MUSCLE ORGANTHE OUTERMOST LAYER, WHICH ENCIRCLES THE WHOLE MUSCLE ORGAN, IS THE EPIMYSIUM.IT IS COMPOSED OF CONNTECTIVE TISSUE.
- 5. SKELETAL MUSCLE ORGANTHE NEXT LAYER IS THE PERIMYSIUM.IT SURROUNDS GROUPS OF 10 TO 200 MUSCLE FIBERS, SEPARATING THEMINTO BUNDLES CALLED FASCICLES.
- 6. SKELETAL MUSCLE ORGANTHE DEEPEST LAYER IS THE ENDOMYSIUM. IT SURROUNDS EACHMUSCLE FIBER SEPARATING ONE FROM ANOTHER. IT IS COMPOSED OF LOOSE CONNECTIVE TISSUE.
- 7. SKELETAL MUSCLE ANATOMYA MUSCLE FIBER OR CELL ISELONGATED, MULTINUCLEATED, AND IS STRIATED.
- 8. Parts of a Muscle
- 10. SKELETAL MUSCLE CELL ANATOMY
- 11. Internal structure of skeletal muscle cellNucleus: Contain the genetic material of the cellSarcolemma: Plasma membrane of muscle cellSarcoplasmic Reticulum: The endoplasmic reticulum of the muscle cellT Tubule: Invagination of the Sarcolemma project deep into Muscle cells interiorTerminal cisternae: Serve as specialized reservoirs for Ca ionsTriad: Consist of one T-Tubule laying between two terminal cisternae Mitochondria: The site of ATP synthesisMyofibril: Bundle of contractile filaments
- 12. Myofibrils StructureMyofibrils -cylindrical structures within muscle fiberAre bundles of protein filaments Two types of myofilamentsActin filaments (thin filaments)Myosin filaments (thick filaments)At each end of the fiber, myofibrils are anchored to the inner surface of the sarcolemmaWhen myofibril shortens, muscle shortens (contracts)
- 13. Myofibrils StructureMYOFIBRILS ACCOUNT FOR ABOUT 80% OF THE CELLULAR VOLUME OFA SKELETAL MUSCLE FIBER. THEY ARE THE CONTRACTILE ORGANELLE OF SKELETAL MUSCLE FIBERS.
- 14. Myofibrils StructureWITHIN THE MYOFIBRIL, ARE THICK AND THINMYOFILAMENTS.THESE MYOLFILAMENTS ARE ARRANGED IN A REGULAR PATTERN, A SARCOMERE,WHICH PRODUCES A REPEATINGSERIES OF DARK AND LIGHT BANDS.
- 15. The Thick Filament (Myosin)Consists of the protein called myosin.A myosin molecule is shaped a bit like a golf club, but with 2 heads.The heads stick out to form the cross bridgeMany of these myosin molecules stick together to form a thick filamentEach head contains two binding sites, one for actin and one for ATP.
- 16. Thin Filament (Actin)The thin filament consists of a protein called actin. It compose of actin subunit twisted into double helical chain. Actin has specific binding site to which the myosin head bindsThe thin filament also contains tropomyosin. The position of tropomyosin cover the binding sites on the actin during unstimulated muscleThe third component is troponin. Attached along the tropomyosin strand.Which expose the binding site of actin to myosin
- 17. Arrangement of MyofilamentThe arrangement of thick and thin myofilaments forms light and dark alternating bands (striation). A band: Dark region, correspond to the length of thick filamentI band: light region, only thin filaments, correspond to distance between adjacent thick filamentsIn the middle of the light band is the Z-line: Protein disc anchor the thin filamentsThe repeating unit from one Z-line to the next is called the sarcomereH zone: Light stripe in the center of the dark (A) band, region between thin filamentsM line: Line in the center of H zone, Protein connect myosin filamentsSarcomere: Contractile unit, extends from one Z line to the next, include the entire A band and half I band on each side of A band
- 18. MYOSIN
- 20. SARCOMERE
- 21. MOTOR UNITA MOTOR UNIT IS A MOTOR NEURON AND ALL OF THE MUSCULE CELLS IT INNERVATES.
- 22. THE NUMBER OF MUSCLE FIBERS PER MOTOR UNIT MAY BE AS HIGH AS SEVERAL HUNDRED OR A FEW AS FOUR.MOTOR UNITSTIMULATION OF A SINGLE MOTOR UNIT CAUSES A WEAKCONTRACTION OF THE ENTIRE MUSCLE, OR A NUMBER OF MOTOR UNITS MAY CAUSE A STRONG CONTRACTION OF THE ENTIRE MUSCLE.
- 23. NEUROMUSCULAR JUNCTIONCONSISTS OF:1. THE AXON TERMINAL: The distal end of an axon, contains neurotransmitter substance within synaptic vesicles2. SYNAPTIC CLEFT: The space between the axon terminal and the folded region of the muscle cell membrane3. THE MOTOR END PLATE: The folded portion of the sarcolemma
- 26. Excitation contraction couplingTransmission of action potential along transverse tubules (T tubules)T tubules action potentials caused release of Ca ions inside the muscle fiber.Ca ions caused contractionOverall process called Excitation Contraction Coupling
- 27. Neuromuscular transmissionAction Potential through motor nerve fiberAxon TerminalOpening of Voltage gated Calcium channelsEntry of Calcium ions from Extracellular fluidOpening of vesicles & release of AchThe function of neuromuscular junction is to transmit the impulses from the nerve to the muscle.
- 28. When the impulses are transmitted from nerve to the muscle, a series of events occur in the neuromuscular junction:Release of acetylcholine Action of acetylcholine Binding with receptors Miniature end plate potential Destruction of acetylcholine Synaptic cleftPassage of AchPostsynaptic membraneBinding of Ach with Receptor and formation of Ach-Receptor complexOpening of the ligand gated sodium channels & entry of sodium ions from ECFDevelopment of end plate potentialMuscle FiberGeneration of Action PotentialExcitation contracting couplingMuscular contraction