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3. Cardiac
 
3. Cardiac
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==Skeletal Muscle==
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==1. Skeletal Muscle==
[[Image:Striated Muscle 1.jpg|thumb|right|150px|Striated muscle - Copyright RVC 2008]]
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[[Image:Striated Muscle 1.jpg|thumb|right|250px|Striated muscle - Copyright RVC 2008]]
[[Image:muscle.jpg|thumb|right|150px|Triad Junction - Copyright RVC 2008]]
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[[Image:muscle.jpg|thumb|right|250px|Triad Junction - Copyright RVC 2008]]
*Each muscle '''belly''' is composed of multiple '''fascicles''', each of which consists of a bundle of muscle '''fibers'''
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*Muscle "fiber" means a single cell, which is multi-nucleate, and known as '''syncitia'''
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Each muscle '''belly''' is composed of multiple '''fascicles''', each of which consists of a bundle of muscle '''fibers'''. Muscle "fiber" means a single cell, which is multi-nucleate, and known as '''syncitia'''.
**'''Parallel''' fibers: running from origin to insertion)
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***Long fibers allow for a faster contraction and a greater range of motion
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'''Parallel''' fibers: Run from origin to insertion, long fibers allow for a faster contraction and a greater range of motion.
**'''Pennate''' fibers: at an angle to line of pull of an internal tendon or aponeurosis
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***Short fibers allow for a greater force capacity
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'''Pennate''' fibers: Run at an angle to the line of pull of an internal tendon or aponeurosis. Short fibers allow for a greater force capacity.
*Within each fiber are groups of parallel, longitudinal myofibrils
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**Myofibrils are arranged as '''sarcomeres''', bound by Z-discs, which are the functional unit of muscle contraction
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Within each fiber are groups of parallel, longitudinal myofibrils. Myofibrils are arranged as '''sarcomeres''', bound by Z-discs, which are the functional unit of muscle contraction. Each sarcomere contains 2 separate groups of myofilaments:
**Each sarcomere contains 2 separate groups of myofilaments:
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***Thin filament, containing '''Actin''', located centrally
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1. Thin filament, containing '''Actin''', located centrally.
***Thick filament, containing '''Myosin''', originating from either side of each Z-disc
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*Two basic types of skeletal myofibre:
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2. Thick filament, containing '''Myosin''', originating from either side of each Z-disc.
**<u>'''Primary: Oxidative'''</u>
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***Grossly '''red'''
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There are two basic types of skeletal myofibre:
***'''High''' myoglobin level
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***'''Slow''' rate of contraction
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1. '''Primary: Oxidative'''
***High '''oxidative''' activity
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***Function - postural, sustained activity
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Grossly red, with high myoglobin level, slow rate of contraction and a high oxidative activity. The function is for postural, sustained activity.
**<u>'''Secondary: Glycolytic'''</u>
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***Grossly '''white'''
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2. '''Secondary: Glycolytic'''
***'''Low''' myoglobin level
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***'''Fast''' rate of contraction
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Grossly white, with low myoglobin level, fast rate of contraction and a high glycolytic activity. The function is for exercise and bursts of activity.
***High '''glycolytic''' activity
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***Function - exercise, bursts of activity
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===Neurogenic Contraction===
*'''Neurogenic Contraction''': Muscle activation is initiated by a nervous impulse crossing the Neuromuscular Junction  
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**Each muscle fiber is controlled by a single motor neuron
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Muscle activation is initiated by a nervous impulse crossing the Neuromuscular Junction. Each muscle fiber is controlled by a single motor neuron. The neurotransmitter, '''Acetylcholine (Ach)''', binds receptors in the muscle fiber to open Na+ channels. This causes a wave of depolarization along the sarcoplasmic membrane, further opening voltage-gated Na+ channels, which propagates the signal along the sarcolemma. Depolarization of the sarcoplasmic reticulum causes Calcium to be released, which activates muscle contraction.
**The neurotransmitter, '''Acetylcholine (Ach)''', binds receptors in the muscle fiber to open Na+ channels
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**This causes a wave of depolarization along the sarcoplasmic membrane, further opening voltage-gated Na+ channels, which propagates the signal along the sarcolemma
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Muscle contraction occurs when (thin) Actin filaments slide past (thick) Myosin filaments. The myosin heads bind actin subunits, forming cross-bridges, hydrolyzing ATP and providing energy for contraction. Myosin heads undergo power stroke, displacing Actin and releasing ADP and Pi. In the off state, tropomyosin coiled-coils block the helical grooves of the actin filament. Tropomyosin movement relieves the steric block, allowing access to myosin binding sites. Calcium regulates muscle contraction by binding troponin-C, which is attached to the thin filament. This causes inhibition of the steric block keeping Actin and Myosin from interacting. Increased Calcium causes a negative feedback inhibition of Ca release, and it is pumped back into the sarcoplasmic reticulum by the Ca/ATPase pump.
**Depolarization of the sarcoplasmic reticulum causes Calcium to be released, which activates muscle contraction
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***Muscle contraction occurs when (thin) Actin filaments slide past (thick) Myosin filaments
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Types of Muscle Contraction:
***Myosin heads bind Actin subunits, forming cross-bridges, hydrolyzing ATP and providing energy for contraction
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***Myosin heads undergo power stroke, displacing Actin and releasing ADP and Pi
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'''Concentric''': muscle shortens and bones are brought closer together.
*Control of skeletal muscle activity is regulated by the '''thin filament'''
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**In the off state, tropomyosin coiled-coils block the helical grooves of the actin filament
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'''Isometric''': muscle is active but does not change in length (force without motion).
**Tropomyosin movement relieves the steric block, allowing access to myosin binding sites
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***Calcium regulates muscle contraction by binding troponin-C, which is attached to the thin filament
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'''Eccentric''': muscle is active while lengthening.
***This causes inhibition of the steric block keeping Actin and Myosin from interacting
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*Increased Calcium causes a negative feedback inhibition of Ca release, and it is pumped back into the sarcoplasmic reticulum by the Ca/ATPase pump
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*Types of Muscle Contraction:
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**'''Concentric''': muscle shortens and bones are brought closer together  
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**'''Isometric''': muscle is active but does not change in length (force without motion)
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**'''Eccentric''': muscle is active while lengthening
      
==Smooth Muscle==
 
==Smooth Muscle==
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