University:
Texas A&M University
Course:
BIOL 319 | Integrated Human Anatomy and Physiology I
Academic year:

2021
Views:

231

Pages:

103
Author:

Caroline Mcfarland

Muscle Muscle – Introduction Contractivity is one of the fundamental properties of protoplasm and is exhibited in varying degree by nearly all cell types. In the cells of muscle, the ability to convert chemical energy into mechanical work has become highly developed. Locomotion of multicellular animals, beating of their hearts, and movement of their internal organs depends on muscles of different types. Cardiac muscle Smooth muscle Skeletal muscle Objectives Identify smooth, skeletal, and cardiac muscle on route histological preparations Explain the morphological basis for the different functions of these three types of muscle Distinguish between the modes of excitation of these three types of muscle Four basic types of tissues Epithelium (90% of tumors) Muscular tissue Connective tissue Nervous tissue Where are these basic tissues located? EPITHELIUM CONNECTIVE TISSUE MUSCULAR TISSUE NERVOUS TISSUE Muscular tissue Muscle Function: Generation of contractile force Smooth muscle Distinguishing features: high concentration of contractile proteins actin and myosin arranged either diffusely in the cytoplasm (smooth muscle) or in regular repeating units called sarcomeres (striated muscles, e.g., cardiac and skeletal muscles) Skeletal muscle Striated muscles Cardiac muscle Muscle - Histological identification Skeletal muscle – very long cylindrical striated muscle cells with multiple peripheral nuclei Cardiac muscle – short branching striated muscle cells with centrally located nuclei Smooth muscle – closely packed spindle-shaped cells with a single centrally placed nucleus and cytoplasm that appears homogeneous by light microscopy Myoepithelial cells Muscle Distribution: Skeletal – striated muscles mostly associated with the skeleton Muscle Distribution: Cardiac – striated muscles associated with the heart large artery of lung Muscle Distribution: Smooth – fusiform cells associated with the viscera, respiratory tract, blood vessels, uterus, etc. Smooth muscle Ureter Ductus deferens Types of muscle Skeletal muscle – Voluntary, large and multinucleated cells, striated Cardiac muscle – Involuntary, mononucleated and branched cells, striated Smooth muscle – Involuntary, mononucleated, non-striated Connective tissue layers of skeletal muscle Epimysium - coarse CT Perimysium - less coarse CT Endomysium - delicate CT Perimysium Epimysium Endomysium Tongue, monkey Skeletal muscle nuclei Fasciculi Endomysium Muscle cells skeletal muscle nuclei, Connective tissue of perimysium striations Connective Tissue connects cells (muscle fibers) of skeletal muscle Endomysium Connective Tissue Layers of Skeletal Muscle PERIMYSIUM ENDOMYSIUM Connective Tissue Layers of Skeletal Muscle Endomysium Individual cell Striated Muscle Cardiac Skeletal A “A” Band = dark band Anisotropic = does alter polarized light (Birefringent) “I” Band = light band Isotropic = does not alter polarized light AI AI I A I - Striated Muscle (Skeletal) Repeating A and I bands alone each cell’s length creates repeating sarcomeres A I A I A I Three cells with sarcomeres each Striated Muscle (Skeletal) Sarcomere = structural unit and functional unit of striated muscle = from Z disc (Z line) to Z disc = A band plus two half of I band H band in middle of A band Striated Muscle (skeletal) A Sarcomeres are organized for rapid and highly controlled contraction I Striated Muscle (Skeletal) Thin filament = actin + actin-associated proteins Actin-associated proteins dictate network or bundle creating the Z line Thick filament = myosin Striated Muscle Striated Muscle Note uniform spacing of troponin Striated Muscle Unexplained complexity in skeletal muscle 13 isoforms of myosin 128 isoforms of troponin • Footprints of evolution – fossils – comparative anatomy, morphology and physiology – biological macromolecules • nucleic acids & proteins • document evolutionary history • provide insights into evolution of form and function – life – biomolecules • e.g., cytochrome c in rice & tuna Slides adapted from Dr. Chris Collet Queensland University of Technology Australia Ear bones of mammals (including human) began as reptile jaws This 125-million year old fossil has inner-ear anatomy intermediate (still attached to the jaw) between reptiles and mammals. In the early embryonic stage of modern mammals, the middle ear was still attached to the jaw. • Footprints of evolution – fossils – comparative anatomy, morphology and physiology – biological macromolecules • nucleic acids & proteins • document evolutionary history • provide insights into evolution of form and function – life – biomolecules • e.g., cytochrome c in rice & tuna Slides adapted from Dr. Chris Collet Queensland University of Technology Australia You can learn a lot about humans from studying animals • Footprints of evolution – fossils – comparative anatomy, morphology and physiology – biological macromolecules • nucleic acids & proteins • document evolutionary history • provide insights into evolution of form and function – life – biomolecules • e.g., cytochrome c in rice & tuna Slides adapted from Dr. Chris Collet Queensland University of Technology Australia Introduction: Pathways Of Protein Evolution Protein Evolutionary Trees Introduction: Pathways Of Protein Evolution • Point mutation – change of function to meet changing requirements • Duplication – simplest mechanism of evolving new proteins – functional divergence of duplicates to meet new requirements in biochemical pathways • Exon shuffling – creating novel proteins for new pathways of development • Alternate splicing – protein diversity from existing genes Exon Shuffling And Mosaic Proteins If structural = functional modules then – modules (domains) can be moved around genome – fulfill new functions – proteins show a mosaic history Exon Shuffling and Mosaic Proteins Many proteins are modular – units derived from many sources Alternate Pathways Of Transcript Splicing • Different exons may be joined to produce a related set of mRNAs encoding a small family of related proteins – protein isoforms • Splicing patterns often tissue-specific • Related proteins may perform similar, not necessarily identical, functions in different types of cells • Splicing is the norm in elks as a means of producing diversity Unexplained complexity in skeletal muscle 13 isoforms of myosin 128 isoforms of troponin Cell Structure of Skeletal Muscle Myofiber = multinucleated cell Myofibrils Sarcomere – Z Line (α-actinin) – I Band (actin, tropomyosin, troponins) – A Band (myosin, overlaps actin) – H Band (myosin with no overlap of actin) H Cell Structure of Skeletal Muscle Individual cells attached by endomysium Individual cell Cell Structure of Skeletal Muscle Cell Structure of Skeletal Muscle Skeletal Muscle Wall Paper Skeletal Muscle Sarcomeres shorten to create contraction Skeletal Muscle Remember the Intermediate Filaments on Epithelium Structural support of epithelial desmosomes and hemidesmosomes Intermediate Filaments – Function in Muscle Cells Myofibril organization – Muscle cells Cell = Contraction of the Sarcomere Thin Filament Actin (F-actin) Tropomyosin Troponin T - attaches to tropomyosin C - binds calcium ions I - inhibits actin-myosin interaction Contraction of the sarcomere Thick Filament (myosin) Contraction – Troponin-C binds calcium – Conformational change in – Tropomyosin exposes the binding site of actin – Myosin binds actin – ATP → ADP yielding energy and movement of myosin head (motor), sliding of filament results Calcium Regulation Transverse (T) tubule (invagination of sarcolemma) transmit depolarization of membrane deep into the cell Sarcoplasmic reticulum (SER of cell) release Ca++ for contraction – then recovers Ca++ after contraction Triad = (T tubule and two ends of SER) Calcium Regulation TRANVERSE (T) TUBULE The transverse tubule (T tubule) is a cell membrane modification to transmit the action TRIAD = (T TUBULE + potential deep within TWO ENDS OF SER) the cell to stimulate local scarcoplasmic reticulum to release Ca++ T tubule = invagination of the cell membrane Calcium Regulation Transverse Tubule Stimulation of Muscle Cells Innervation of Skeletal Muscle Motor end-plate: Synaptic cleft Acetylcholine and receptor Junctional Folds Junctional folds are cell membrane modifications of skeletal muscle cells to increase surface area of synapse Innervation of Muscle Slide HISTO007 skeletal muscle cells Nerve – muscle interface at the motor end plates Note the motor end plates in several skeletal muscle cells Innervation of Muscle Innervation of Muscle Innervation of Muscle Innervation of Muscle Innervation of Muscle Innervation of Muscle Sensory Innervation of Muscle Muscle Fiber / Cell Muscle Spindle Innervation of Muscle Muscle Spindle Muscle Spindle Intracapsular fibers 136 Tongue Muscle spindle Muscle spindles Intrafusal fibers inside the capsule capillaries nerve fibroblasts Types of Fibers in Skeletal Muscle Red (Slow, Oxidative) – High Myoglobin – High Cytochromes/ Mitochondria – Posture, flight muscle in birds Types of Fibers in Skeletal Muscle White (Fast, Glycolytic) – Low Myoglobin – Fewer Mitochondria Types of Fibers in Skeletal Muscle Intermediate (Fast, Oxidative, and Glycolytic) Cardiac Muscle Cardiac Muscle is Striated Muscle Differences From Skeletal Muscle – Mononucleated vs. Multinucleated – Central vs. Peripheral Nuclei – Diad vs. Triad Cardiac Muscle is Striated Muscle Intercalated Disc – Fascia Adherens – Maculae Adherens – Gap Junctions - Lateral Portion Cardiac Muscle Intercalated Disc Intercalated Disc Fascia Adherens Maculae Adherens Gap Junctions Lateral Portion Intercalated discs Cardiac Muscle Intercalated Disc Cardiac Muscle is Striated Muscle Cardiac Muscle Cardiac Muscle – Diad located at Z line Diad = (T tubule + one end of SER) Cardiac Muscle Cardiac Muscle Cardiac Muscle has Organized Contractions PURKINJE FIBERS Heart Internodal connections Cardiac Muscle has Organized Contractions Purkinje Fibers Cardiac Muscle Purkinje Fibers Cardiac Muscle Purkinje Fibers Nexus (gap junction) Smooth Muscle Cell organization Myofilament organization Intermediate filaments and fusiform dense regions Smooth Muscle Smooth Muscle MUSCULAR ARTERY Smooth Muscle Arrector Pili Muscle in Skin Smooth Muscle Has a PAS + basement membrane Smooth Muscle Actin Myosin Smooth Muscle Intracellular caveolae (cell membrane modification) Smooth Muscle Excitation-Contraction Coupling Smooth Muscle Smooth Muscle Smooth Muscle Regeneration of Muscle Cardiac – None Skeletal – Some Smooth - Lots Muscle Striated - Smooth Summary of Muscle shapes and excitations of types Cell membrane modifications: characteristic and contribute of that characteristic on the function of the cell or organ in which the modification is found. -------------------------------------------------------------------------------------------------------------------------------- Modification 1. Microvilli Characteristic Function in cell or organ projections off surface of cell membrane increase surface area (absorption/phagocytosis, macrophage) 2. Brush border uniform projections off surface of cell membrane increase surface area (absorption intestine) 3. Cilia has basal bodies to anchor and axoneme for movement 4. Stereocilia very long branched microvilli ciliary action to move mucus in lungs increase surface area of epididymis/ hair cells in hearing in ear 5. Cells interdigitation interdigitating of lateral borders to increase surface area for fat/lipid absorption in intestine Cell membrane modifications: characteristic and contribute of that characteristic on the function of the cell or organ in which the modification is found. -------------------------------------------------------------------------------------------------------------------------------- Modification 6. Marginal fold 7. Enfolded basal CM Characteristic Function in cell or organ endothelial cell projection into lumen protects the cell junctions of endothelium lines up mitochondria /striated cell appearance increase surface area for electrolyte transport (kidney) 8. Secretory (intracellular) canaliculus enfolded cell mem. of parietal cell allows HCl release within cell limits but outside CM 9. Intercullular canaliculus lateral border and between two hepatocytes allow production and transport of bile separate from blood 10. Osteoclast ruffered border base produces microenviroment of low Ph Digest bone and cartilage Cell membrane modifications: characteristic and contribute of that characteristic on the function of the cell or organ in which the modification is found. -------------------------------------------------------------------------------------------------------------------------------- Modification 11. Junctional folds Characteristic enfolded skeletal cells at nerve junction 12. Transverse tubule enfolded cell membrane 13. Intracellular caveolae 14. Exocytotic vesicle increase surface area for nerve transmission carry depolarization deep within striated muscle cells Smooth Muscle Excitation-Contraction Coupling discharges secretion/add membrane protein to CM 15. Apocrine secreted produce 16. Flagellum enfolding on surface of SM cells Function in cell or organ merocrine secretion of proteins (casein in milk) cell membrane released with produce (lipid) lipid secreted in milk cells grow form centriole motility of spermatozoa

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