EX 4 LAB chemical changes in the muscle: rigor

• Different changes that occur in muscles during contraction:

  • Rupture of the sole feet with release of acetylcholine at the myoneural junction
  • Combination of acetylcholine with the receptor protein
  • Release of calcium ions from the sarco-tubular system
  • Coupling or sliding of actin filaments over the myosin filaments
  • Splitting of adenosine triphosphate
  • Liberation of energy in the form of heat, and work done
  • Syneresis or escape of water from the muscle cells
  • Lowering of pH due to liberation and subsequent accumulation of lactic acid and other acid metabolites
• • Lowering of pH due to liberation and subsequent accumulation of lactic acid and other acid metabolites
• Physico-chemical changes during muscular contraction:

  • Muscle contraction is associated with heat production
  • Rupture of the sole feet with release of acetylcholine at the myoneural junction
  • Combination of acetylcholine with the receptor protein
  • Release of calcium ions from the sarco-tubular system
  • Coupling or sliding of actin filaments over the myosin filaments
  • Splitting of adenosine triphosphate
  • Liberation of energy in the form of heat, and work done
  • Syneresis or escape of water from the muscle cells
• Rigor:

  • Place the gastrocnemius muscle of a frog in a water bath at 50° and note the effect on the muscle
  • Test the muscle with litmus paper and note the reaction
• When the legs of the frog are stimulated with faradic current, the solution in flask C becomes turbid due to the liberation of carbon dioxide from the contracting muscles. The carbon dioxide liberated combines with barium hydroxide forming a new substance which is now responsible for the turbidity of the solution
• Rigor mortis:

  • Slow shortening and hardening process that affects muscles after death
  • Muscle becomes opaque and inextensible due to a permanent coagulation of its protoplasm
  • Chemical changes show similarities to those of natural contraction but differ in that the restitution processes are in complete abeyance
• • Myotonia: persistent contraction after voluntary, mechanical, or electrical stimulation, representing an asynchronous tetanus of muscle fibers
• Abnormal states of voluntary muscular contraction:

  • Spasticity: augmented sustained contraction where the muscle resists stretching
  • Fibrillation: repeated asynchronous contractions of individual muscle fibers, leading to tremulous or shimmering wavelets
  • Fasciculation: repeated incoordinate contractions of muscles, but the fibers belonging to muscle units contract synchronously
  • Atrophy: decrease in size of muscle fibers and their contractile myofibrils due to denervation or prolonged disuse
  • Myasthenia: weakness and wasting of muscles due to disturbances of the nervous system