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276 Cards in this Set
- Front
- Back
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Muscle comprises _____ % of total body weight
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35-45%
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muscle is fromed of _____cells specialized for contraction possessing _______ containing ______ & _______
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differentiated cells, contractile filaments containing actin and myosin
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shape of muscle cells
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elongated
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are muscle cells polar
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yes, ordered polarity w/ contraction along major axis
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muscle possesses an ____ membrane which propagates ____& initiates ________
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excitable, impulse, contraction
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muscle is derived from _______ so has close assoc. w/ __________
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mesoderm, CT
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can muscle regenerate
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to varying degrees
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3 types of muscle
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skeletal, cardiac, smooth
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which muscles are striated
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skeletal and cardiac
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which musches are voluntary
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only skeletal
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which muscles are regenerative
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skeletal is regenerative, smooth is moderately regenerative, cardiac is not
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type of contraction of skeletal muscle
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strong, quick, discontinuous, voluntary
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type of cardiac muscle contraction
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strong, quick, continuous, involuntary
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type of smooth musch contraction
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weak, slow, involuntary
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Skeletal muscle is not merely a tissue, it is an _______ containing ___, ____,&_____
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organ, CT, blood vessels and nerves
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skeletal muscle cells AKA
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fibers
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skeletal muscle fibers are ______ packed, _____ organized, and exhibit ______ metabolic activity
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densely, highly, high
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why do skeletal muscle have high metabolic activity
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lots of mitochondria w/ enriched blood and nerve supply
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shape of skeletal muscle
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cylindrical and elongated
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are skeletal muscle multinucleate
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yes
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Skeletal muscle fibers from a morphological and funcational ________
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syncytium
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Sk. mus., fibers have diameters of ___-____ and lengths from less than ____ to more than ______
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diameter=10-100 micrometers
length=<1mm->30cm |
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Skeletal muscle fibers types, (often all types are present in given muscle)
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red (slow twitch), white (fast twitch), & intermediate
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Fiber types (red, white & int,) vary in content of ____, relative enrichment of _______ and various metabolic ___ as well was capacity for ____
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myoglobin, mitochondria, enzymes, rate of contraction
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what is myoglobin
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carries O2 similar to hemoglobin
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what does epimysium cover
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entire muscle
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what is epimysium made of and what is it often called
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dense CT layer, rich in collagen, elastic and reticular fibers, called fascia
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what does perimysium divide muscle into
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smaller fxnal units=fasicles
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endomysium divides fascicles into______
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fibers
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endomysium is rich in _____&_______ and provides pathways for ___&___ to supply muscle fibers
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collagen & reticular fibers, capillaries and nerves
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what is a skeletal muscle fiber formed by
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fusion of myoblasts (10-100micrometers in diameter)
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are all nuclei in skeletal muscle fibers myoblasts
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no- satellite cells
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what are skeletal mm satelite cells
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myoblastic stem cells
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where can skeletal mm satellite cells be found
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under endomysium (1-2% of visible nuclei) adjacent to sarcolemma
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sketal mm satelite cells exhibit ____proliferative capactiy reflecting ___ ability of skeletal m.
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high, regenerative
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what are the 2 types of fibers in skeletal m.
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extrafusal & intrafusal
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what are extrafusal and intrafusal muscle involved in
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extrafusal- contraction, intrafusal-reg. of contraction
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what innervates extrafusal skeletal m.
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alpha motoneurons
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what does intrafusal muscle include
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nuclear bag and chain fibers
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what is the prinicpal cytoplasmic component of the muscle fiber
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myofibrils
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are myofibrils branched
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no they are rods
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how far do myofibrils extend
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full length of fiber
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what are myofibrils composed of
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sarcomeres (fxnal units of skeletal and cardiac contractile apparati)
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what are sarcomeres limited by
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Z-line on each end
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what are myofibrils composed of
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2 myofilaments: actin and myosin
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what is the principal contractile protein of thin myofilaments
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actin
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what does actin consist of
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pair of helically entwined polymers (F-actin) of the globular (G-actin)
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Actin is assoc w/ the globuler _______ and the filamentous ______
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troponin, tropomyosin
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toponin and tropomyosin conver _____ dependency on the ______ interaction
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Ca++ ACTIN-MYOSIN INTERACTION
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What makes up troponin complex
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TnC, TnI, TnT
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What does TnC bind
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Calcium
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what does TnI bind
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actin
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What does TnT bind
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tropomyosin
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What color are Type I fibers
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red
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what color are type II fibers
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white
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what fibers have more glycogen
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type II
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what fibers are slow oxidative and fatigure resistant
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type I
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Myosin is held in register by crosslinkages of the protein ______ &______at the _______
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myomesin & C=Protein at M-Line
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the "head" portion of myosin confers ______ activity and possesses _____
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ATPase, actin binding site
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how are myosin arranged
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polarized, antiparallel, with head and tail
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A bands= "___ band" is ____ with ____ but stain darkly with most stains
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dark band, anisotropic with polarized light
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what does the A band contain
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6 thin myofilaments surround each thick myofilament, the filaments overlap and interdigitate
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I bands= ______ w/ polarized light, appear ____ stain w/ most stains
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isotropic, lightly
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what do I bands contain
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only thin filaments
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H bands=have _____ central regions w/in _____
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light, A bands
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what do H bands consist of
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thick filaments only
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Where are M lines
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center of H bands
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how do M lines appear
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narrow and dark
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how are M line formed
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from cross-connections of adjacent thick filaments by myomesin and C Protein
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Z-disks (lines) are dense regions bisecting each____
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I band
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Z lines contain _______ which binds to _______ and anchorms them to the _____ with the assistance of ______
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a-actinin, thin filaments, Z line, nebulin
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What large elastic cytoskeletal protein is assoc w/ Z line
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titin
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where do titin span? what does it form? what does it contribute to?
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spans Z line to M line, foms elastic lattice, contributes to passive elasticity of sarcomere
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what surrounds sarcomere at Z line attaching it to the sarcolemma
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desmin
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what stabilizes a-actinin /actin interaction @ Z-line
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nebulin
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During contraction, thick and thin filaments do not _______ but _________
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not shorten but overlap more
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_____ slide past _____ resulting in greater penetration into _____ which themselves remain a constant length
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thin filaments slide past thickfilaments, A band
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_____ and ______ decrease in length as _____ are drawn closer together
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I bands and H bands, Z disks
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cell membrane of muscle fiber AKA
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sarcolemma
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sarcolemma is invested with an external ______________
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basal lamina
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a single muscle fiber may have ____#___ of nuclei
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thousands
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where are the nuclei of a muscle fiber located
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in the periphery of the fiber beneath the sarcolemma
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cytoplasm of muscle fiber =
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sarcoplasm
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sarcoplasm hsa many ______
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mitchondria
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special form of sER of muscle fiber
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sarcoplasmic reticulum
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principle role of sarcoplasmic reticulum
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sequester Ca++ during contraction
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sarcoplasmic reticulum is rich in _______ which binds to Ca++
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calsequestrin
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a depolarization signal is transferred from the sarcolemma to the interior of the fiber via ________
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T-tubules
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In response to depolarization the sarcoplasmic reticulum releases _____ sequestered in the_______ into the cytoplasm
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Ca++ , terminal cisternae
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The release of Ca++ enables the interaction of ____ and ____ resulting in shorteing of the ______ and muscle contraction
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actin & myosin, sarcomere,
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Sarcolemma depolarization is linked to muscle at a structure called the _______
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triad
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what are the membranous units of the triad
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1 T-tubule + 2 terminal cisternae
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the transverse tubule is a tubular invagination of the _____
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sarcolemma
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the T-tubule penetrates into the ________, perpendicular w/ ______
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sarcoplasm, myofibrils
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the t-tubule is alighned w/ the _______
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A-I band jxns
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the terminal cisternae is part of the _______
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sarcoplasmic reticulum
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what is the attachment step of contraction
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not active step, In the absence of ATP (but w/ Ca++) the conformation of the myosin head allows for tight interaction w/ actin "rigor configuration"
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During step 2 of the contraction cycle "release" what happens
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ATP binds the S1 fragment of myosin head resulting in dissociation of myosin head from actin
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what causes step 3 of contraction "bending"
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ATP hydrolyzed to ADP + Pi, both remaining w/ myosin head. Head pivots and aligns w/ adjacent actin monomer
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what causes step 4 of contraction : "force generation"
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"power stroke" Ca++ dep. phase. bound Pi and ADP release from myosin head and cross-bridge forms between myosin and actin
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During step 5 of contraction "reattachment" the ____ undergoes conformational change, resulting in tight interaction of _______ & ______
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myosin head, actin & myosin
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During reattachment interaction of actin and myosing causes what
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pulling of actin filament toward center of sarcomere, shortening it
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what happens to contraction cycle when ATP is not available
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bind of actin and myosin is stabilized (Step I attachment)and rigor mortis occurs after death
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_____ the source of energy for skeletal muscle contraction is formed from ______ by several processes
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ATP, ADP
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How is ATP formed in white (fast) fibers
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ATP is generated by anaerobic glycolysis resulting in buildup of lactic acid
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How is ATP formed in red (slow) fibers
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ATP is generated by oxidated phosphorylation
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How else is ATP formed
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ATP is formed from transfer of phosphate in creatine phosphate to ADP in rxn catalyzed by phosphocreatine kinase
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Skeletal muscle is __ dep, and occurs in what 3 phases
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Ca++,
depolarization and Ca++ release, activation of actin by calcium, relaxation |
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depolarization and calcium release triggers binding of ____ & ______
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actin & myosin
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pathway of depolarization in skeletal muscle
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sarcolemma @ motor-ene plate (AKA myoneural jxn)->T tubules->myofibrils
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Where is Ca++ released into the cytosol in skeltal muscle
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at A-I jxns via voltage reg. channels in SR terminal cisternae
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In the resting state, the ____-bind sites on actin are covered by _______
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myosin, tropomyosin
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_______ is also bound to actin hindering ______ binding
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Troponin I, actin/myosin
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In active state, binding of Ca++ by _______ resulting in conformation change interrupting the _______ interaction
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troponin C, TnI/actin
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what happens when TnI and actin separate
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tropomyosin shifts unmasking myosin binding sites
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when does relaxation occur in skeletal muscle
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when Ca++ conc in cytoplasm is reduced and TnC loses its bound Ca++, tropomyosin returns to resting state
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what is relaxation dep. upon
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ca++ pump in sarcoplasmic reticulum, translocating Ca++ from cytosol to inner surface of SR membrane where they are sequesterred by calsequestrin
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what does the motor unit consist of
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a neuron and the skeletal muscle fibers it innervates
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all muscle fibers obey the _______ law
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all or none
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muscle fibers of the same motor unit contract in ______
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unison
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The force generated by a muscle is dependent upon what
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the # of motor units undergoing contraction at the same time
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In Fine coordination muscles (i.e. ocular, digital) one nerve can only innervate ____ muscle fibers
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one to 3
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in muscle used for coarse movement, (i.e. postural muscles) 1 nerve can innervate how many muscle fibers
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hundreds
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each muscle fiber has how many motor end plates
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1
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motor end plate AKA
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myoneural jxn, neuromuscular jxn
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3 components of motor end plate
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axon terminal, synaptic cleft, muscle fiber
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at the motor end plate the nerve axon ____- and ________ with the sarcolemma to form _____
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expands and invaginates, jxnal folds
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On the presynaptic jxnal fold there are many _____- containing ______
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synaptic vesicls containing Ach
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Depolarization of the nerves causes _______ of the contents of the ______, spilling Ach into the synaptic cleft
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exocytosis, synaptic vesicles
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Ach in synaptic cleft activates ____ on ______ resulting in ______ of the muscle fiber membrane and contraction
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receptors, sarcolemma, depolarization
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____ innervation of ____ muscle is provided in part by muscle spindles
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sensory, skeletal
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muscle spindles are _____ organs (________)
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sensory, stretch receptors
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shape of muscle spindles
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elongated and fusiform
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what is muscle spindle bound by
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CT capsule enclosing a fluid-filled space containing 8-10 modified muscle fibers referred to as intrafusal fibers
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what fibers is the muscle spindle surrounded by
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normal skeletal fibers (extrafusal)
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the muscle spindle is anchored via the ______ to the _____ &_______ of adjacent fibers
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capsule, perimysium & endomysium
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Innervation of muscle spindles consists of ____ &______ nerve fibers
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sensory (afferent) and motor (effered)
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2 types of nerve endings of afferent nerves
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annulospiral endings, flower spray endings
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what type of nerve fibers have annulospiral endings
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type 1a
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Annulospiral endings wind around the center of _____ & ____ fibers
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nuclear bag and nuclear chain
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annulospiral endings respond to _________
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rate of stretching
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flower spray endings are on what type of fibers
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type IIa
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where do flower spray endings terminated
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on either side of annulospiral endings
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what do flower spray endings respond to
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duration of stretching
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what do efferent nerves consist of
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gamma 2 and gamma3 efferent axons
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what happens when efferent nerves are stimulated by over-contractions of the muscle
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depolarize intrafusal fibers to counteract muscle stretching
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tapping patellar tendon stretches the quadriceps femoris muscle and its _____
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muscle spindles
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The ____ nerves innervating the intrafusal fibers sned impulses to the spinal cord signaling a ________ of intrafusal fibers
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afferent, stretch
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In the spinal cord the ______ synapse with _____ nerves that travel in both ______ and _____ motoneurons back to both extrafusal and intrafusal fibers causing contraction
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afferent, efferent, alpha and gamma,
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The "_____ loop" causes the ______ reflex and is a measure of _____ fxn
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reflex, knee jerk, CNS
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Cardiac muscle contracts _____, ____ &______
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spontaneously, rhythmically, continuously
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cartiac muscle is modulated by ______ &_______ nervous stimuli
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endocrine and autonomic nervous
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Cardiac muscle is located w/in the _____ of the heart and within proximal portions of the _____- &_____
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myocardium, aorta & vena cava
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Cardiac muscle is under _____ control
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involuntary nervous
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Are cardiac muscle fibers a synctial network
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no, individual cells
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do cardiac muscle of regenerative capacity
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almot none, replace w/ CT scar
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the sarcoplasm of heart muscle contains more ____, ___ and ____ than skeletal muscle
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glycogen, lipid, mitochondria
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How does heart muscle contract and relax
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same steps as skeletal muscle
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how many nuclei does cardiac muscle have and where
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1 or 2 central
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does cardiac muscle branch
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yes
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is cardiac muscle striated
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yes
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what are cardiac muscle cells lined by
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external (basal) lamina
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_____ and _______ are esp. enriched at poles of nucleus in region called _______ in cardiac muscle
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mitochondira, glycogen granules, sarcoplasmic cone
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purpose of cardiace muscle in whorled pattern
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enables myocardium to wring out blood from chambers of heart
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CT element are between cardiac muscle fibers (like endomysium) and support a rich ______ that supports ______ of tissue
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rich capillary bed, high metabolic activity
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cardiac muscle cells are joined by ______ which provided _____ & ______
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intercalated discs, mechanical & electrical cellular coupling
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what parts of intercalated discs have jxns specializations
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transverse and lateral
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3 jxns of transverse portion of intercalated discs
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fascia adherents, maculae adherents (desmosomes), gap jxns
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what jxn does the lateral portion of intercalated disc possess
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gap jxn
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fascia adherents is analogous to _______- of epithelia to which _______ attach
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zonula adherens, actin filaments
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purpose of fasciae adherents in intercalated discs
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anchor site for sarcomeres nearest to the end of the cells
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purpose of maculae adherents (________) in intercalated discs
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desmosomes, bind cells to prevent separation during contraction
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Gap jxns form the portion of the intercalated disc that lies in a place ____ to the ____ of the cell
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parallel to the long axis
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Purpose of gap jxns in intercalated discs
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direct electrical communication between cells
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which has larger T tubules, skeletal or cardiac muscle
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cardiac
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cardiac T tubules are lined w/ ________
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external lamina
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is the sarcoplasmic reticulum is cardiac muscle well developed
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`no poorly developed
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Each cardiac cell T tbuble is asso. w/ _#_terminal cisterns forming _____ instead of ____
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1, dyads instead of triads
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Dyads are located at the ____ in cardiac muscle rather than the A-I jxns in skeletal muscle
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Z lines
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cardiac muscle contains many ____, and ____ mitchondria than skeletal muscle
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more, larger
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Sarcoplasmic reticulum in heart contributes to ___
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dyads
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sarco. reticulum in cardiac mm leak _____ into the _____ at a slow and constant rate contibuting to the ______
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ca++, sarcoplasm, automatic rhythm
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where are mitochondria in cardiac mm
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parallel to the I bands
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where are atrial granules found
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in atrial cardiac muscle cells (otherwise these cells are identical to other cardiac mm cells)
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atrial granules contain the precursor _____ which is secreted in response to an increase in ______
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atrial natriuretic peptide, blood pressure
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Atrial natriuretic peptide causes excretion of _____ in uring reducing the workload of the heart by modulation of _____, _____, and _____
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salt,
BP, blood volume, cardiac output |
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how does nervous innervation affect cardiac mm
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speed up or slow down intrinsic beat
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cardiac mm are innervated by branches of _____ & ____ nervous systems, which terminate where?
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sympathetic and parasympathetic, terminating near (not on) muscle cells
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where is the initiating stimulus for contraction in cardiac mm
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sinoatrial node
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the SA node delivers the stimulus to modified cardiac m. fibers in the _____ of the ventricles and eventually to the _____
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endocardium, Purkinje fibers
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Purkinje fibers communication w/ many ordinary cardiac m cells via _____
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gap jxns
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where are Purkinje fibers located
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atrioventricular bundle of His
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Are Purkinje fibers bigger or smaller than reg cardiac m cells
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bigger
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Purkinje fibers have large # of ____
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gap jxns
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Purkinje fibers have a lower content of ____ and a higher content of _____
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lower myofibrils, higher glycogen
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smooth muscle is mostly assoc w/ _____ organs
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hollow
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smooth muscle occurs in ____ or _____ at ____ angles
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sheets or layers at rt. angles
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what control smooth m
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autnomic nervous system
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how does contraction rate of smooth m. compare to skeletal m.
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smooth m. contracts 10x more slowly
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smooth muscle can maintain contraction of _____ periods of time
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extended
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smooth m can contract up to ____% of length
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75
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does smooth muscle have T tubule system
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no
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is smooth m striated
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no
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smooth muscles ranges in length from ____ (small blood vessels) to ______ (pregnant uterus)
|
20 micrometers to 500 micrometers
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2 types of smooth m based on fxn
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unitary/visceral smooth m, multi-unit smooth m.
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where is unitary visceral smooth m,
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in the walls of hollow viscera (intestinal walls, bronchi, ureters, uterus, fallopian tubes)
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Unitary/visceral Smooth m is richly innervated by the ______ serving mainly to __________
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autonomic nervous system, increase or decrease levels of spontaneous contraction
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how else are unitary/visceral smooth m contractions initiated
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nerve action, stretch, irritation
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unitary/visceral smooth muscle have many ____ between cells serving to________
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gap jxns, propagate wave of depolarization
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where does multi-unit smooth m. occur
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iris of eye, walls of some large arteries, ductus deferens
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______ activity _____ controls multi-unit smooth muscle fibers
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autonomic, precisely
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contractions of multi-unit smooth m. is typically initiated by _______
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neural discharge
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multi-unit smooth m. cells are not _____ or not well-_____ electrically
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coupled, coupled
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electrical properties of multi-unit smooth m. cells are influenced by both ______-&________
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hormones & autonomic neurotransmitters (epinephrine and norepinephrine)
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shape of smooth muscle
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spindle shaped
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location of nucleus in smooth m
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central
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color of cytoplams in smooth m
|
eosinophilic
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smooth muscles occur in bundles of _____ size
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varying
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bundles of smooth m. can be ____ oriented (as in arteries)
|
helically
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most of sarcoplasm of smooth m. is occupied by ________ which insert into ______
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actin filaments, dense plaques
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where are cytoplasmic organelles confined to in smooth m.
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conical regions at ends of central nucleus
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Smooth m. nucleus have a _____ shape and is deeply _____ in longitudinal sectiong through smooth m. fibers
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cork-screw, indented
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is actin and myosin organized into myofibrils in smooth muscle
|
no
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contractile myofilaments actin and myosin are attached to _____&____ densities in smooth muscle
|
peripheral plaques and cytoplasmic densities
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how are actin and myosin aligned in smooth m
|
obliquely to the longitudinal axis of SMCs
|
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Intermediate filaments of SMCs are:
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desmin (non-vascular SMCs) and vimentin (vascular SMCs)
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intermediate filaments are anchored to _____ in SMCs
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cytoplasmic densities
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do SMCs have troponin
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no replaced by caldesmin and calponin
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dense plaques (cytoplasmic densities) of SMCs are comparable to _______
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Z discs
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dense plaques (cytoplasmic densities are enriched w/ _____ and serve as primary sites of _______
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alpha-actinin, filament attachment
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Sarcolemmal vesicles AKA
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caveolae
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Sarolemmal vesciles (caveolae) are present where in SMCs
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along periphery
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fxn of caveolae in SMCs
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uptake and release of Ca++
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Why does SMC contraction occur more slowly and last longer than skeletal muscle contraction?
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slower rate of ATP hydrolysis
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As in skeltal muscle, SMC contraction results from ____ & _______ interaction
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actin and myosin
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Are SMC thick and thin filaments arranged into sarcomeres?
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no, this only happens in striated muscle
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____, ____ and _____ insert into the dense plaques in SMCs
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actin, myosin & intermediate filaments
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when the SMC contracts, ____ pulls on the dense plaques, causing a ruffling of the cell and a ______ shaped nucleus
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actin, corkscrew-shaped
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SMC contraction cycle is stimulated by _________
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transient increase in cytosolic ca++
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Step I of SMC contraction: _____ binds to _____ altering its conformation
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Ca++ , calmodulin
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Step 2 of SMC contraction: ca++/calmodulin complex activates _______which leads to _______ of light-chains of myosin
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myosin light-chain kinase, phosphorolates
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Step 3 of SMC contraction: phophorolated globular head then interacts w/ ____, stimulating _______ resulting in contraction
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actin, myosin ATPase
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As long as the _______ remains phosphorolated, the contraction cycle will continues
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light-chains of myosin
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Step 5 of SMC contraction: _____ of myosin prevents ____ binding resulting in relaxation
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dephosphorylation, actin
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2 types of contractile non-muscle cells
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myoepithelial cells, myofibroblasts
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where are myoepithelial cells located
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between the epithelium and basal lamina of certain types of glands and in ductal portions of glands
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purpose of myoepithelial contraction
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assist in expression of glandular material
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myoepithelial cells are similar in ____ to SMCs but possess a _______ morphology w/ multiple ______
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shape, basket-like, processes
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where doe myoepithelial cells arise from
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ectoderm
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where do SMCs arise from
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mesoderm
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contractile apparatus and cycle of myoepithelial cells is comparable to that of ______
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SMCs
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in lactating mammary glands, ____ contractions is initiated by _____
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myoepithelial, oxytocin
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in lacrimal glands ____ contaction is initiated by _____
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myoepithelia, acetylcholine
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myofibroblasts resemble ____ but possess high amounts of ____ and ____ facilitating contraction
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fibroblasts, actin & myosin
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what may myofibroblasts contribute to
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wound healing contracting to decrease size of defect
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Duchenne muscular dystrophy (DMD) is a ____-linked (most common in ________), ____ genetic defect
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sex-linked, young men, recessive
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DMD results in _____ synthesis of ______
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decreased, sarcolemmal protein dystrophin
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pathological signature of DMD
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replacement of degenerating skeletal muscle fibers w/ fatty and fibrous CT
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DMD may also affect ____ muscle
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cardiac
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DMD result in death in most ppl by age ___
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20
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Myostatin mutation causes _____
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skeletal muscle hypertrophy
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what is the myostatin mutation commonly observed in
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mice and cattle- 1 human case
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Myostatin mutation does what to myostatin
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loss of function of gene
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What is myostatin
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GDF-8, growth factor regulating size of muscles beginning in utero
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Pathological results of myostatin mutation
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hypertrophy of skeletal muscle, also expressed in heart (cardiomyopathy)
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Myasthenia gravis is a ____ disease where ______ blocks ____ of the ______
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autoimmune, antibodies block Ach receptors of motor-end plates
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Myasthenia gravis pathological characteristics
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gradual weakenings of skeletal muscles esp. those most used( extraocular, tongue, facial expression, etc.)
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Clinical symptoms of myasthenia gravis
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high circulating titer of antibodies to Ach receptros
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why might myasthenia gravis be fatal
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respiratory compromis resulting in pulmonary infection
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What is botulism caused by
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food poisoning (Clostridium botulinum)
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What does Clostridium botulinum do
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inhibit Ach release at motor-end plates
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Clinical signs of botulism
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muscle paralysis, vomiting, visual disorder and death if untreated
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what does the golgi tendon organ monitor
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tension developed in muscle
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what does golgi tendon organ consist of
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afferent fibers
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what does golgi tendon organ prevent
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damage during excessive forcer generation
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GTO stimulation results in _____ of muscle via _______ inhibition of ______
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reflex relaxation, interneuronal, alpha-motoneurons
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