Muscle Tissue and Function
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Transcript of Muscle Tissue and Function
Human Anatomy, Larry M. Frolich, Ph.D.
Muscle Tissue and Function1. Muscle Cell Architecture and Function
2. Mechanics of muscle contraction—the “sliding filament” model and role of actin and myosin proteins
3. Types of muscle cells
4. Motor Units
Human Anatomy, Larry M. Frolich, Ph.D.
Muscle Cells and Neurons
are unique to animals
have “excitable” membranes that transmit action potentials
allow for rapid large-scale movements
Motor Unit is one motor neuron plus the muscle cells that it stimulates (or synapses with)
Human Anatomy, Larry M. Frolich, Ph.D.
Muscle cell or muscle “fiber” is composed of myofibrils which contain sarcomeres or contractile “units”
Human Anatomy, Larry M. Frolich, Ph.D.
Muscle fibers are cells—visible to naked eye as fibers in meat, chicken, fish
Sarcolemma is muscle cell membrane—”excitable” so has action potentials just like neurons
Because cell is large, T-tubules carry action potential—ionic depolarization—into internal parts of cell
Sarcoplasmic reticulum releases calcium which triggers actin-myosin protein filaments to contract
Muscle cells
Sequence of events Motor Neuron to Muscle contraction at cellular level (from the Brain Top to Bottom) [link]
Human Anatomy, Larry M. Frolich, Ph.D.
Molecular Basis of Muscle Function
Actin-Myosin “sliding filament” model
EXPLAINS: MUSCLE SHORTENING MUSCLE FORCE GENERATION OR
“CONTRACTION”
Human Anatomy, Larry M. Frolich, Ph.D.
Mechanics of Contraction (the sliding filament model)
Action potential or depolarization of membrane triggers Ca release which causes actin and myosin to “slide” causing whole cell to“contract”
Fig. 10.4
Human Anatomy, Larry M. Frolich, Ph.D.
How actin-myosin complex (sarcomere)shorten muscle
• Ca triggers cross-bridges to form from myosin “thick” filament to actin “thin” filament•Cross-bridges “row” or “reach” for next binding site on actin “thin” filaments
Human Anatomy, Larry M. Frolich, Ph.D.
From Actin-Myosin to Whole Muscle
Human Anatomy, Larry M. Frolich, Ph.D.
Skeletal Muscle Tissue(each skeletal muscle is an organ)
Cells Long and cylindrical, in bundles Multinucleate Obvious Striations
Skeletal Muscles-Voluntary
Connective Tissue Components: Endomysium-between fibers Perimysium-surrounds bundles Epimysium-surround whole muscle Attached to bones, fascia, skin Origin & Insertion
Human Anatomy, Larry M. Frolich, Ph.D.
Smooth Muscle TissueCells
Single cells, uninucleateNo striations
Smooth Muscle-Involuntary2 layers-opposite orientation (peristalsis)
Surrounds hollow organs, blood vesselsConnective Tissue Component
Endomysium: surrounds cells
Human Anatomy, Larry M. Frolich, Ph.D.
Cardiac MuscleCells Branching, chains of cells Single or Binucleated Striations Connected by Intercalated discs
Cardiac Muscle-Involuntary
Myocardium-heart muscle Pumps blood through vessels
Connective Tissue Component Endomysium: surrounding cells
Human Anatomy, Larry M. Frolich, Ph.D.
Human Anatomy, Larry M. Frolich, Ph.D.
Carciac Muscle Smooth Muscle
Human Anatomy, Larry M. Frolich, Ph.D.
Human Anatomy, Larry M. Frolich, Ph.D.