Skeletal Muscle Cell Contraction

Dr. Jack Rosenbluth

Goals

1. To understand the general structural organization that is the basis for skeletal muscle contraction.
2. To relate the mechanisms of contraction to force generation and muscle fiber movement.

Outline

1. History of the understanding of skeletal muscle contraction
• Albert Szent-Gyorgi - "Actomyosin"
• Hugh E. Huxley - X-ray diffraction studies
2. Review of the sarcomere as the muscle functional unit
• Thick Filaments
• Myosin and its subunits (HMM, LMM, S1, S2)
• Assembly of myosin molecules to thick filaments
• Thin Filaments
• Assembly of G-Actin to F-Actin
• Bipolarity of filaments: arrowhead
• Titin
3. Review of the functional structure of skeletal muscle
• Myofibrils
• Myofibers - band patterns
• Lattice Structure
4. Biophysics of the contractile system
• The sliding filament model
• Single fiber length-tension relationship
• Forces acting in series and in parallel
5. Regulation of muscle contraction
• History: A.V. Hill and A.F. Huxley
• Sarcoplasmic reticulum and T-tubular system
• Triadic junction and transmembrane signalling
• Calcium cycling
• Troponin and tropomyosin
• Excitation-contraction coupling
6. Biophysics of muscle contraction
• Crossbridge cycling
• Force-velocity relationship
• Load matching
• Isometric and isotonic contraction
7. Comparative aspects of muscle cell contraction
• Ultra-fast muscles: lobster remotor
• Ultra-slow: smooth muscle
• Insect flight muscle

For Review

Define or Explain

• myofibril
• sarcomere
• A band, I band, H band
• M line and Z disc
• thin filaments and thick filaments
• actin
• myosin
• crossbridge cycling
• lattice structure
• isotonic contraction
• isometric contraction
• tropomyosin
• troponin
• sarcolemma
• triadic junction
• sarcoplasmic reticulum
• T-tubules
• rigor mortis

Briefly Answer

• Compare the maximum active tension developed in two hypothetical sarcomeres, one with a resting length of x and the other with a resting length of 2x.
• Relate the single fiber length tension curve to myofilament structure.
• Describe the steps in excitation-contraction coupling from teh arrival of a signal at a motor-end-plate to the development of a twitch followed by a return to the resting state.

Return to the Slide List