Term
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Definition
fiber or myocyte or myofiber
multinucleated |
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Term
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Definition
| cell membrane + endomysium |
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Term
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Definition
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Term
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Definition
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Term
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Definition
long cylindrical bundles of myofilaments
-highly ordered arrangements of actin an myosin |
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Term
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Definition
1. striated (cardiac and skeletal)
2. smooth |
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Term
| Purpose of skeletal muscle |
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Definition
| voluntary muscle for locomotion |
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Term
| Connective tissue sheaths in skeletal muscle |
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Definition
1. epimysium-outermost sheath, continuous with tendon
2. perimysium-collagenous septa extending from epimysium to form fascicles
3. endomysium-network of reticular fibers, fibroblasts, and basal lamina that invests each muscle fiber within fascicle |
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Term
| Skeletal muscle development |
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Definition
-develop from mesenchymal cells
-differeniate into myoblasts
-fuse together to form myotubes--immature myofibers
-secrete external lamina to form endomysium |
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Term
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Definition
-undifferentiated cells between plasma membrane and external lamina
-potential to differentiateto myoblasts following injury to muscle
-stem cell population for increase in muscle mass |
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Term
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Definition
| dark-staining band (contains H band and M line) |
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Term
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Definition
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Term
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Definition
dark band which bisects each I band
connects to adjacent sarcomeres |
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Term
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Definition
-the basic unit of contraction
-distance fom one Z line to the next
-continuous chains form myfibrils
-change length, NOT the microfilaments
-A band stays same length
-I band shortens during contraction |
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Term
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Definition
-actin with tropomyosin and troponin
-present in I band |
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Term
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Definition
-present in A band
-composed of myosin |
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Term
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Definition
-large molecule consisting of 2 heavy chains (head and tail) and 4 light chains
-2 types of light chains, each of which are associated with head
-myosin heads have binding sites for actin and ATP
-heads have ATPase activity |
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Term
| Thin filament accessory proteins |
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Definition
In Z line,
1) alpha actin
2) nebulin
3) tropmodulin |
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Term
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Definition
| bundles thin filaments together and achors to Z line |
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Term
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Definition
-maintains geometric arrangement of thin filaments
-attaches them to Z line
-regulates # of G-actin monomers that polymerize |
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Term
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Definition
| -caps free end of thin filament |
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Term
| Thick filament accessory protein |
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Definition
1) titin
2) myomesin and C-protein |
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Term
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Definition
-very large protein that spans M line to Z disc
-maintains central position of A band by attaching thick filaments to Z line |
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Term
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Definition
| -forms lattice at Z line level that links adjacent myofibrils to each other |
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Term
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Definition
| links laminin (present in external lamina of each muscle fiber) to cytoskeleton actin filaments |
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Term
| Duchenne's muscular dystrophy |
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Definition
-absence of dystrophin
-excess Ca2+ -reactive O2
-muscle fiber death and muscle weakness |
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Term
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Definition
-muscle growth inhibitor
-drugs that inhibit effects of myostatin may be useful for treating Duchenne's dystrophy |
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Term
| Necessary molecules for muscle contraction |
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Definition
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Term
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Definition
1) calcium binds troponin, exposes myosin binding site
2) Rigor configuration--myosin head binds actin
3) Binding of ATP on myosin dettaches head from actin
4)ATP hydrolyzed to ADP and Pi, bending myosin head toward Z line
5) myosin binds actin, Pi released, resulting in tight crossbridge--> power stroke as heads return to normal position
6) myosin remains bound to actin until Ca2+ is depleted
-hundreds of cycles cause contraction |
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Term
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Definition
-specialized synaptic areas of sarcolemma
-one axon can innervate 1 or more muscle fibers
-the more motor units activated, the stronger the contraction |
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Term
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Definition
-primary synaptic cleft (where motor endplate is) has further smaller ridges called secondary synaptic clefts (junctional folds)
-acetycholine released, increase permeability of sarcolemma to Na+
-acetylcholinesterase breaks down ACH |
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Term
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Definition
-autoimmune disease
-acetylcholine receptors destroyed
-progressive muscle weakness |
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Term
| Steps in nerve impulse for muscle contraction |
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Definition
1) release of acetylcholine in synaptic cleft
2) influx of Na + causes depolarization of transverse (T ) tubules
3) depolarization conducted to terminal cisternae (sarcoplasmic reticulum)
4) junctional channel complexes sense voltage change and release Ca++ from terminal cisternae)
5) rest of SR serves as calcium sink (via calsequestrin)
6) muscle contraction
7) active uptake of calcium when muscle is at rest |
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Term
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Definition
1) nuclear bag fibers
2_ nuclear chain fibers |
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Term
| 3 types of skeletal muscle fibers |
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Definition
1) red fibers
2) white fibers
3) intermediate fibers |
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Term
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Definition
-type I, slow twitch
-lots of capillaries, red pigment (myoglobin and cytochromes)
-mitochondria with densely packed cristae
-slow sustained contraction
-predominate in limbs, back |
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Term
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Definition
-type IIb, fast twitch, fatigue prone
-few capillaries, low myoglobin
-few mitochondira
-large diameter
-rapid contraction with great force
-anaerobic glycolysis
-eye muscles and finger muscles
-more neuromuscular junctions--precise movement |
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Term
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Definition
-type IIa, fast twitch, fatigue resistant
-characteristics between red and white fibers |
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Term
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Definition
-involuntary muscle that forms bulk of heart and proximal portions of aorta and vena cava
-surrounded by endomysium only
-branching fibers with one central located nucleus
-no satellite cells but limited regenerative capacity |
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Term
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Definition
-junctional specializations that connect fibers end to end
-functional syncytium
-desmosomes and fascia adherens
-gap junctions |
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Term
| Cardiac muscle contraction |
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Definition
-similar to skeletal muscle
-BUT T tubules invaginate Z lines, not A-I junction
-no terminal cisternae or triads |
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Term
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Definition
-modified cardiac cells
-2x diameter, fewer microfibrils, lots of glycogen granules
-pale staining
-less obvious intercalated discs, with lots of gap junctions
-4x conduction velocity |
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Term
| myocardial endocrine cells |
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Definition
-resemble myocytes but have dense secretory granules
-synthesize and secrete precursor of atrial natriuretic polypeptides |
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Term
| atrial natiuretic polypeptides |
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Definition
| cause vasodilation and diuresis--lowers blood pressure and decreases blood volume |
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Term
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Definition
-involuntary muscle that slow and sustained contraction
-no sarcomeres, no striation
-fibers are fusiform, one centrally located, cigar-shaped nucleus
-found in walls of hollow organs (gut, reproductive), blood vessels, eye, skin, exocrine glands
-can regenerate |
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Term
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Definition
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Term
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Definition
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Term
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Definition
-richly innervated smooth muscle
-capable of fine contractions
-iris of eye
*most smooth muscle have poor nerve supply |
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Term
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Definition
| -axons pass near smooth muscle but do not have motor end plates |
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Term
| Initiation of contraction |
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Definition
1) autonomic nerve impulses (blood vessels)
2) hormonal stimulation (uterus)
3) stretch (GI tract) |
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Term
| Cells for contraction of smooth muscle |
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Definition
-thin filaments of F actin and tropomyosin distributed in netlike fashion
-connected t dense bodies (like Z line) and sarcolemma by alpa actinin
-myosin II is folded until regulatory light chain is phosphorylated (MLC kinase)
-thick filaments are side polar
-same sliding filament theory
-calcium necessary for contraction (but no troponin) |
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