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69 Cards in this Set
- Front
- Back
Muscle Tissue is specialized for what
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Contraction and relaxation
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Muscle tissue comes from what germ layer
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mesoderm
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What are the three types of muscle tissue
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skeletal, cardiac and smooth
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Skeletal Muscle is derived from what mesoderm origin
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Mesenchyme
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What is skeletal muscle composed of
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Fasciculi, bundles of muscle fibers
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Describe three layers of skeletal muscle CT organization
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1. Epimysium
2. Perimysium 3. Endomysium |
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Def epimysium
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External sheath of dense ct surrounding the entire muscle
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Def perimysium
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Septa (partition) of ct surrounding each fasciculus
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Def endomysium
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Delicate layer of ct surrounding each muscle fiber (cell)
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Def muscle fiber
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a muscle cell
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# of nuclei in skeletal muscle
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multinucleated of various diameter
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Where are the nuclei located in muscle fibers
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periphery
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Each muscle fiber is filled with structural subunits called ________
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Myofibrils
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Myofibrils are composed of what
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Contractile subunits called sarcomeres
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Each saromere is composed of what?
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Each sarcomere is composed of thick and thin filaments
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Skeletal muscle fibers have striations of ______ and _____ bands
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Skeletal muscles have cross striations of dark and light bands
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Dark bands of skeletal muscle are ______?
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A Bands
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Light bands of skeletal fibers are ____?
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I bands
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charac of A band
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The A band is the central portion of the sarcomere
Consists mainly of myosin filaments Portion overlap by actin filaments |
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def I band
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I Band is the segment composed of actin filaments bisected in the midle by the z line
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def z line
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actin filament insert
a segment between the two z lines is a sarcomere |
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def h band
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central rgion of the a band consisting only of the myosin molecules
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def m line
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center of the a band wher two thick filaments are connected to each other
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What are the four main proteins of the muscle?
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1. Actin
2. Tropomyosin 3. Troponin 4. Myosin |
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What are the two types of actin?
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1. G-actin (globular monomers)
2. F-actin (Filamentous polymers, double helix of g-actin wrapped around each other |
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define tropomyosin
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long, thin, homodimer
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What are the three subunits of Troponin?
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TnT (strongly attaches to tropomyosin
TnC (binds Ca2+) TnI (inhibits actin-myosin interaction) |
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Define myosin
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Large complex protein with heavy and light chains
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What does the haevy chain consist of?
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2 thin rod like proteins twisted together with a globulaar head at one end
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composition of light of myosin?
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4 small proteins associated with the head
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Describe the sliding filament hypothesis
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increase in the amount of overlap between the thick and thin filaments. Thin filaments are pulled into the a band, resulting in shortening of the sarcomere
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During contraction, which bands shorten?
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I and H bands
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define stage 1 contraction
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myosin head is tightly bound to the actin (rigor configuration)
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Define stage 2
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ATP binds to the myosin head conformation change uncouples myosin head from actin
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Define stage 3
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Myosin head bends as ATP is hydrolized to ADP
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Define stage 4
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Myosin head binds to actin, releases adp, returns to original unbent conformation and forces movement of the thin filament along the thick filament (POWER STROKE)
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Define stage 5
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Myosin head tightly binds to actin (rigor configuration)
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What regulates contraction
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Ca2+ mus be present for contraction and removed after the contraction
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Define sarcoplasmic reticulum
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Networks around the myofibrils extending from one A-I junction to the next within the a sarcomere, includes terminal cisternae
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Define Terminal cisternae
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Ring like SR channel at the junction between A&I bands
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Define Transverse tubular system (T system)
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1.Numerous tubular invaginations of the the sarcolemna (T tubule)
2.Located between terminal cisternae 3. Contain voltage-sensor proteins |
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Define voltage sensor proteins
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They depolarize adjacent terminal cisternae to release Ca2+
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Define Triad
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Complex of T tubule and two adjacent terminal cisternae
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What do you find at the end on individual muscle fibers
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Axons of motor neurons originated from spinal chord or brainstem
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Define motor end plate (neuromuscular junction)
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Axon terminal covered by thin schwan cell membrane & contains numerous mitochondria and synaptic vessicles contraining neurotransmitters (mostly acetalcholine) has synaptic clegt and junction folds
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Define junction fold
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Fold of the sarcolemma
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Describe process of innervation
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!. action potential reaches motor end plate
2. acetylcholine is released from the axon terminal into the synaptic cleft 3. Neurotransmitters bind the sacrolemma and initiate membrane depolarization 4.Depolarization is propagated along the entire muscle fiber via t-tubule system 5. at Each triad, depolarization stimulates SR to release Ca2+ 6. Initiation of the contraction cycle 7. Cessation of depolarization Ca2+ is actively transported back into SR 8. Muscle relaxes |
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What is a motor unit?
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All the muscles fibers innervated by a single neuron
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Define small motor unit?
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Fine, delicate, fast, movements
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Define large motor unit?
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Coarser, stronger movements
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Define muscle spindle
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Specialized receptor unit in muscle. It is a ct capsule surrounding a fluid filled space.
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Define intrafusal fibers
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A few long, thick fibers and short, thin fibers and have several sensory nerve fibers that are innervated and send information
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Define Golgi tendon organs
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Collagen fibers of the tendon innvervated by sensory nerves
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How many types of skeletal muscle fibers are there and name them
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Three
1. Type I fiber 2. Type II and 3. Intermediate fibers |
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Define type 1 fibers
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Slow twitch fibers
Rich in sarcoplasm and myoglobin dark red color continuous contraction, most of energy is derived from oxidative phosphorilation of fatty acids |
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Define type 2 fibers
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fast twitch fibers
Less myoglobin light red color rapid, discontinuous contraction |
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Define intermediate fibers
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Morphologically and functionally in the middle between type 1 and type II fibers
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Describe cardiac muscle
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Come from splanchnic mesoderm cells
one or two central nuclei numerous mitochondria cells are smaller in atria than in the ventricles |
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What is the difference in the cardiac muscle and skeletal muscle?
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Cross striation is identical in both
SR and T tubules aren't arranged in as regularly in cardiac Diad: one T tubule and one SR terminal cisernae |
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Define intercalated discs
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Junctional complexes at the interface between adjacent cardomyocytes
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What two regions can be distinguished from each other at transverse portion
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1. Fasciae Adherens (anchoring sites for actin filaments
2. Desmosomes or maculae adherentes (bind cells together) |
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What on the lateral portion of the intercalated discs provides ionic continuity between adjacent cells
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Gap junctions
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Describe smooth muscle
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Elongated,non striated fusiform cells
Single central nuclei Bundles of myofilaments form a lattice network |
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How does smooth muscle and skeletal muscle differ
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Contraction differs. NO tropomyosin
Calmodulin: binds Ca2+ & activates myosin light chain kinase, phosphorylates myosin, allows it to interact with actin filaments No T tubules Rich desmin and vimentin Dense bodies: on membrane and cytoplasm Similar to z lines and function as an anchor for actin filaments |
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What type of innervation does smooth muscle
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Autonomic. both sympathetic and parasympathetic
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What is visceral smooth muscle and what are abundant in them
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A large sheet of smooth muscle cells, found in the intestines, uterus , ureter.
Abundant gap junctions, relatively poor nerve supply |
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Define multiunit smooth muscle
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rich innervation. precise and graded contractions
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Do cardiomyocytes/ skeletal fibers/smooth muscle undergo regeneration
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cardiomyocytes haveAlmost no regeneration
Skeletal fibers have limited regeneration Smooth muscles have active regeneration |
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Satelite cells defined
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inactive myoblast in the basal lamina of mature muscle fiber
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