suzanne d'anna1 muscular tissue. suzanne d'anna2 types of muscle tissue l skeletal l...
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Suzanne D'Anna 3
Skeletal attached to bones, skin, deep fascia, or
other muscles voluntary control striated , alternating light and dark bands
along length of myofibrils many nuclei Functions:
- movement - posture - respiration
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Cardiac located only in the heart striated, single nucleus, branched fibers with
intercalated discs involuntary control by autonomic nervous
system regulation of heart rate is primarily due to
hormones and neurotransmitters no regeneration capability propels blood through blood vessels
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Smooth
located in hollow organs, skin attached to hair follicles, etc.
no striations, single nucleus, spindle-shaped fibers
involuntary control by autonomic nervous system
some regeneration
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Functions of Smooth Muscles
mix and propel food though GI tract regulate flow of blood by changing diameter of
lumen contraction of urinary bladder, gallbladder,
and spleen, expels urine, bile and blood control sphincter muscles control muscles of eye contraction of arrector pili muscles
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Multiunit Smooth
muscle fibers are not well organized occur as separate fibers rather than
sheets found in irises of eye, walls of blood
vessels
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Visceral Smooth
composed of sheets of spindle-shaped cells
in contact with one another more common type found in hollow visceral organs capable of stimulating each other display rhythmicity due to self-exciting
fibers - responsible for peristalsis
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Peristalsis
wavelike motion occurs in various tubular organs helps force contents of these organs
along their lengths
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Contraction of Smooth Muscles
acetylcholine and norepinephrine also affected by hormones slower to contract - slower to relax can maintain a forceful contraction longer
than skeletal with same amount of ATP can change length without changing
tautness
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Muscle Fibers
many muscle fibers are enclosed in a delicate connective tissue sheath called endomysium
several sheathed fibers are wrapped in perimysium in bundles called fascicles (10 -100 fibers)
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Muscle Fibers (cont.)
many fascicles are joined together by even tougher covering called epimysium
fascia covers entire muscles which lead into tendons which attach to bones
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Individual Muscle Fiber (single cell)
sarcolemma
- plasma membrane covering of muscle cell
sarcoplasm
- cytoplasm of a skeletal muscle cell
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Individual Muscle Fiber (cont.)
sarcoplasmic reticulum
- network of membranous channels
- within sarcoplasm (corresponds to endoplasmic reticulum)
- surrounds each myofibril
- channels run parallel to myofibril
- stores calcium which is necessary for muscle contraction
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Individual Muscle Fiber (cont.)
transverse tubules
- fingerlike inward invaginations or channels of sarcolemma
- extend from membrane and pass through the fiber
- open to outside of the muscle fiber
- contain extracellular fluid
- carry action potentials to sarcoplasmic reticulum
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Individual Muscle Fiber (cont.)
cisternae
- enlarged portions of sarcoplasmic reticulum
- lie on either side of transverse tubules
- near region where actin and myosin overlap
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Individual Muscle Fiber (cont.)
myofibrils
- long ribbon-like organelles
- lie parallel to one another myofilaments
- thread-like structures within myofibrils (contain two types of protein filaments)
actin (thin & light) and myocin (thick & dark)
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Actin and Myosin
appear as light (thin) and dark (thick) bands
arrangement of these fibers produces the characteristic striations of a skeletal muscle fiber
slide past each other causing muscle cells to contract
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Actin
located primarily within light areas (I bands) during muscle contraction actin filaments slide
farther into A bands attached to the Z lines at end of I bands Z lines extend across muscle fiber enabling
adjacent myofibrils to lie side by side segment between two Z lines is called a
sarcomere
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Sarcomeres
repeating units composed of filaments inside myofibrils
do not extend the entire length of the muscle fiber
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Characteristics of Muscle Tissue
excitability contractility extensibility elasticity
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Excitability(irritability)
ability to respond to stimuli generate action potentials or impulses stimuli that initiate action potentials in
muscles are neurotransmitters neurotransmitters are released by axon
terminals of neurons
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Contractility
ability to contract and shorten to generate a force
muscles contract in response to action potentials
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Extensibility
ability to be stretched or extended when pulled
with pairs of skeletal muscles - one muscle is contracted while the opposing one is usually stretched
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