Undergraduate – Graduate Muscle Lecture Series

Larry Johnson, Professor Veterinary Integrative Biosciences Texas A&M University College Station, TX 77843 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. 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 Muscle Function: Generation of contractile force

Distinguishing features:

high concentration of contractile Smooth muscle proteins and arranged either diffusely in the cytoplasm Striated muscles (smooth muscle) or in regular repeating units called (striated muscles, e.g., cardiac and skeletal muscles) Cardiac muscle Muscle - Histological identification

Skeletal muscle – very long Dilator muscle of iris cylindrical striated muscle cells with multiple peripheral nuclei Myoepithelial cells

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 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 - coarse CT - less coarse CT - 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 Skeletal Cardiac

A I

“A” Band = dark band Anisotropic = does alter polarized light A (Birefringent) I “I” Band = light band Isotropic = does not alter polarized light

A

I

Polarized Light Micrograph Of Human… High-Res Stock Photography ...www.gettyimages.com Striated Muscle (Skeletal) Repeating A and I bands alone the cell’s length creates repeating sarcomeres A I A I A I A I Striated Muscle (skeletal)

A I

Sarcomeres are organized for rapid and highly controlled contraction Striated Muscle (Skeletal) = structural unit and functional unit of striated muscle 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 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 Based on scientific research, what three characteristics

do these mammals all have in common… 2. Mammary with these mammals?

glands 1. Hair

3.Special inner ear bones 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 Sarcomere – Z Line (α-actinin) – I Band (actin, , H ) – A Band (myosin, overlaps actin) – H Band (myosin with no overlap of actin) Cell Structure of Skeletal Muscle

Individual cell Individual cells Cell Structure of Skeletal 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 - attaches to tropomyosin C - binds calcium ions I - inhibits actin-myosin interaction Thick Filament (myosin) of contraction Sliding filament theory of contraction of the sarcomere

Contraction (know five steps) 1. Troponin-C binds calcium 2. Troponin changes shape causing conformational change in tropomyosin exposing actin binding site 3. Myosin binds actin and released inorganic phosphate inducing 4. Movement of myosin head (motor, power ) and sliding of actin filament in relation to the myosin filament 5. ATP  ADP and inorganic phosphate binds to myosin head cocking it Contraction of the sarcomere Contraction of the sarcomere http://www.youtube.com/watch?v=gJ309LfHQ3M

https://www.youtube.com/watch?v=0kFmbrRJq4w

Calcium Regulation

Transverse (T) tubule (invagination of ) 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 TRIAD = (T TUBULE + TWO ENDS OF SER) Calcium Regulation Transverse Tubule

Stimulation of Muscle Cells Innervation of Skeletal Muscle

Motor end-plate: Synaptic cleft and receptor Junctional Folds 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 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) http://www.youtube.com/watch?v=pbTah5NVOtU&feature=r elated 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 – Fascia Adherens – Maculae Adherens – Gap Junctions - Lateral Portion Cardiac Muscle

Intercalated Disc Cardiac Muscle Intercalated Disc Fascia Adherens Maculae Adherens Gap Junctions Lateral Portion

Intercalated discs 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 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 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

Many illustrations in these VIBS Histology YouTube videos were modified from the following books and sources: Many thanks to original sources!

Bruce Alberts, et al. 1983. Molecular of the Cell. Garland Publishing, Inc., New York, NY. Bruce Alberts, et al. 1994. Molecular Biology of the Cell. Garland Publishing, Inc., New York, NY. William J. Banks, 1981. Applied Veterinary Histology. Williams and Wilkins, Los Angeles, CA. Hans Elias, et al. 1978. Histology and Human Microanatomy. John Wiley and Sons, New York, NY. Don W. Fawcett. 1986. Bloom and Fawcett. A textbook of histology. W. B. Saunders Company, Philadelphia, PA. Don W. Fawcett. 1994. Bloom and Fawcett. A textbook of histology. Chapman and Hall, New York, NY. Arthur W. Ham and David H. Cormack. 1979. Histology. J. S. Lippincott Company, Philadelphia, PA. Luis C. Junqueira, et al. 1983. Basic Histology. Lange Medical Publications, Los Altos, CA. L. Carlos Junqueira, et al. 1995. Basic Histology. Appleton and Lange, Norwalk, CT. L.L. Langley, et al. 1974. Dynamic Anatomy and Physiology. McGraw-Hill Book Company, New York, NY. W.W. Tuttle and Byron A. Schottelius. 1969. Textbook of Physiology. The C. V. Mosby Company, St. Louis, MO. Leon Weiss. 1977. Histology Cell and Tissue Biology. Elsevier Biomedical, New York, NY. Leon Weiss and Roy O. Greep. 1977. Histology. McGraw-Hill Book Company, New York, NY. (http://www.nature.com), Vol. 414:88,2001. A.L. Mescher 2013 Junqueira’s Basis Histology text and atlas, 13th ed. McGraw Internet images and videos on biological presentations Next time

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