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MUSCLEassignaltarget
OPS
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MUSCLE CELL
STRIATED
- Skeletal
- Cardiac
SMOOTH
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For SKM and CDM the termcell isusually replaced by fiber
Note:
sarcolemma, sarcoplasm, sarcoplasmic-
reticulum (SR),sarcomere.
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SKELETAL
Axon termini, secreting Ach synapse with SKM(paracrine)*
SKM transmembrane receptor uptakes Ach
Adequate AP is required to overcome thresholdpotential of the hillock (known as: all-or-nothing law)
RMP about 95 mV. Threshold about 50 mV
*Synapse = neuromuscular-junction, =endplate
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NEURO-MUSCULAR SYNAPSE
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SKM fiber is multinucleated, cylindrical-shaped and composed of ultrastuctures.Several protein arrange in distinguished
pattern Mitochondria and nuclei located beneath the
sarcolemma
Fibres are covered with connective tissuecontaining nerves, blood vessels
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Mitosis is supressed by
myostatin factor.
Bigger muscle is
obtained by enlargement
of fibers and connective
tissues.
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One fibre has several fibrils,surrounded by SR.
Each fibril is made up of array of parallel filaments
Filament : 1. thick (myosin)2. thin (actin)
Others: Troponins (TN) (TN-C, TN-I, TN-N)
Tropomyosin (TM)Nebulin, tropomodulin, konektin.etc.
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tropomyosin actin troponin
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Sarcolemma has branches ie. transversustubuli that approach two cysternae of SR (andso the AP too !!!)
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SR in blue
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The AP depolarizes the SR cysternae (RyRc)causing a Ca-ion efflux to sarcoplasm. Itstarget is TN-C.
Increase of Ca-ion eventually contracts thefibers.
Ca ions pump back to SR fibers relaxe
AP of fibers contract-relax resembles axon
For detail see Lodish et al.,
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Energy for contraction : creatinP,glycogen, mitochondrial respiration
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CARDIAC MUSCLE
Y-shaped fiber (branching cells) usually withsingle nucleus, but mitochondria >>> SKM
Fibers are intercalated
by adherent-junction
(intercalated disc)
which have gap junction
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Gap junction enables AP passes from fiber to fiber socontraction occurs in a synchronous wave
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CDM
Gap-junction enables AP to pass from fiber to fiber socontraction occurs in a synchronous wave
Molecular mechanism of contract-relax similar to SKMBUT AP that triggers heart beat is generated within the
heart itself !! (pace-maker).
Autonomic nerves simply modulate (increasing ordecreasing the AP )
Energy : obligatory oxygen !
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SMOOTH MUSCLE
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Smooth Muscle
Cells are not striated; spindle-shaped withsingle central nucleus
Fibers smaller than those in skeletal muscle
No sarcomeres
- not arranged as symmetrically as in skeletalmuscle, not as organized striationsMore actin than myosin
Caveolae: indentations in sarcolemma;
- may act like T tubules
Dense bodies (instead of Z disk), insarcoplasm
- connect intermediate filaments, and
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JUNCTIONS in SMOTH MUSCLES
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Other proteins in smooth muscle
- desmin, vimentin, caldesmon- calponin (inhibits myosin activity)
located along actin
- calmodulin (inhibited by drug)- myosin light chain kinase (MLCK)
for contraction
- myosin light chain phosphatase
(MLCP) for relaxation
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SM i h i
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SM contraction mechanism
SM l i h i
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SM relaxation mechanism
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Stimulation does not depend on neuron (butautonomic motor neuron reach SM and canstimulate or relax depending on whichneurotransmitter. Norepinephrine? NO?
Histamin? Oxytocin ?) In brief, like CDM, SM has pace maker.
Contraction is slower than striated muscle buttakes longer time
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Nerve stimulation activates the Ca ion
receptors, so Ca influx occurs
Certain drug and hormone
can activate special receptor
so that the internal Ca ions
efflux from the SR (agonist)
The next slides show molecules
in cell signaling pathway lecture.
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C i f 3 l t
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Comparison of 3 muscle types
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Disorders of muscle tissue
Muscular dystrophy
a group of inherited muscle
destroying disease
Muscles enlarge with fat and connective tissue
Muscles degenerate
Ex./Duchenne muscular dystrophy
GIVEYOURSMILETOEVERYONEBUT
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GIVE YOUR HEART TO ONLY ONE
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THANK YOU