Transcript MuscleTissueFunction

Muscle Tissue and Function
1. 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 largescale 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 cells
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
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:
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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
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Long and cylindrical, in bundles
Multinucleate
Obvious Striations
Skeletal Muscles-Voluntary
Connective Tissue Components:
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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 Tissue
Cells
Single cells, uninucleate
No striations
Smooth Muscle-Involuntary
2 layers-opposite orientation (peristalsis)
Surrounds hollow organs, blood vessels
Connective Tissue Component
Endomysium: surrounds cells
Human Anatomy, Larry M. Frolich, Ph.D.
Cardiac Muscle
Cells
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Branching, chains of cells
Single or Binucleated
Striations
Connected by Intercalated discs
Cardiac Muscle-Involuntary
Myocardium-heart muscle
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Pumps blood through vessels
Connective Tissue Component
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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.
Human Anatomy, Larry M. Frolich, Ph.D.