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SKELETAL MUSCLE NOTES. Terms. epi = upon peri = around endo = within or inner mys = muscle sarco = flesh lemma = husk fasci = bundle. Structure of skeletal muscle fiber. A sarcomere. Many packages of Twizzlers = Fascicle. Twizzler analogy. 1 package of Twizzlers = Muscle fiber - PowerPoint PPT Presentation
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SKELETAL MUSCLE NOTES
Terms
• epi = upon
• peri = around
• endo = within or inner
• mys = muscle
• sarco = flesh
• lemma = husk
• fasci = bundle
Structure of skeletal muscle fiber
A sarcomere
Twizzler analogy
Many packages of Twizzlers =
Fascicle
Twizzler analogy 2
1 package of
Twizzlers =
Muscle fiber
The packaging =
Sarcolemma
Twizzler analogy 3
1 bundle of twizzlers =
myofibril
Twizzler analogy 4
1 Twizzler strand =
Filament
Terms associated with skeletal muscles
• Tendon- Attaches muscle to bone
• Ligament- Attaches bone to bone
• Origin- The location where the muscle is attached to the relatively immovable end of the bone
Insertion- end of the muscle that is attached to the movable bone
• Prime mover- the muscle that provides most of the movement
• Synergist- muscle that assists the prime mover
• Antagonist- the muscle that opposes the action of the prime mover
Muscle Contraction
Neuromuscular Junction
Sliding Filament theory
• Boat = Myosin (thick filament)
• Oar = Myosin side arm
• Water = Actin (thin filament)
• Life ring = Calcium
Resting1. ATP is bound to myosin side arm.
2. ATP cleaves into ADP + P (high energy)
Step 1 Action potential1. A nerve action potential releases acetylcholine
into the synaptic cleft opening the Na+ channels.
2. Action potential spreads across sarcolemma releasing Ca into sarcoplasma
Step 2 Myosin-actin binding1. Ca binds to troponin2. A shape change in troponin moves
tropomyocin out of the way of actin binding site3. Actin and myosin bind using energy from
cleaved ATP.
Step 3 Power Stroke1. Side arm pivots so myosin and actin slide by
each other shortening the sarcomere.
2. ADP and P released (low energy)
Step 4 ATP binding and actin-myosin release
1. A different ATP molecule binds to active site.
2. Actin released
Step 5 ATP cleavage
1. Return to high energy state
2. Cycle will repeat if Ca still available.
A few thoughts• The boat (myosin) does not move far in one
cycle, a muscle contraction requires many cycles
• What happens if ATP is not available?• Muscle stays contracted- cramps• Why does rigor mortis occur?• ATP is not available to control Ca release
so contractions are continuous 6-8 hours after death. Body relaxes 16-24 hours as enzymes break down contractile structures
Sarcomere summary
Final animation
• animation 2
• Watch “Distonia: movie
Muscles of the Head
Anterior torso muscles
Posterior torso muscles
Anterior shoulder and arm
Anterior forearm
Anterior thigh
Lateral thigh
Posterior thigh
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