SKELETAL MUSCLE NOTES

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SKELETAL MUSCLE NOTES
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Terms

• epi upon
• peri around
• endo within or inner
• mys muscle
• sarco flesh
• lemma husk
• fasci bundle

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(No Transcript)
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Structure of skeletal muscle fiber
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A sarcomere
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Twizzler analogy

• Many packages of Twizzlers
• Fascicle

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Twizzler analogy 2

• 1 package of Twizzlers
• Muscle fiber
• The packaging
• Sarcolemma

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Twizzler analogy 3

• 1 bundle of twizzlers
• myofibril

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Twizzler analogy 4

• 1 Twizzler strand
• Filament

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Terms associated with skeletal muscles

• Tendon- Attaches muscle to bone

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• Ligament- Attaches bone to bone

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• Origin- The location where the muscle is attached
  to the relatively immovable end of the bone

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• Insertion- end of the muscle that is attached to
  the movable bone

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• Prime mover- the muscle that provides most of the
  movement

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• Synergist- muscle that assists the prime mover

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• Antagonist- the muscle that opposes the action of
  the prime mover

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Muscle Contraction
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Neuromuscular Junction
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Neuromuscular junction animation

• animation

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Sliding Filament theory

• Boat Myosin (thick filament)
• Oar Myosin side arm
• Water Actin (thin filament)
• Life ring Calcium

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Resting

1. ATP is bound to myosin side arm.
2. ATP cleaves into ADP P (high energy)

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Step 1 Action potential

1. A nerve action potential releases acetylcholine
   into the synaptic cleft opening the Na channels.
2. Action potential spreads across sarcolemma
   releasing Ca into sarcoplasma

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Step 2 Myosin-actin binding

1. Ca binds to troponin
2. A shape change in troponin moves tropomyocin out
   of the way of actin binding site
3. Actin and myosin bind using energy from cleaved
   ATP.

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Step 3 Power Stroke

1. Side arm pivots so myosin and actin slide by each
   other shortening the sarcomere.
2. ADP and P released (low energy)

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Step 4 ATP binding and actin-myosin release

1. A different ATP molecule binds to active site.
2. Actin released

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Step 5 ATP cleavage

1. Return to high energy state
2. Cycle will repeat if Ca still available.

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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

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Sarcomere summary
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Final animation

• animation 2
• Watch Distonia movie

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Muscles of the Head
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Anterior torso muscles
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Posterior torso muscles
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Anterior shoulder and arm
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Anterior forearm
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Anterior thigh
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Lateral thigh
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Posterior thigh