COMPILE LABS

• Experiment 2: Muscle Tonus

  • Muscle tonus refers to a state of slight muscular contraction maintained by synchronous impulses of low frequency, discharged by the spinal motor neurons, and is reflex in nature
  • When the spinal cord is transected, there is immediate paralysis of the muscles below the point of section, leading to a condition called spinal shock
  • Cutting the roots of the right sciatic nerve results in the right lower limb becoming limp due to the removal of connections with the spinal cord
  • Destruction of the spinal cord causes both lower limbs to hang limply, indicating that the impulses responsible for maintaining muscle tonus are located in the spinal cord, specifically the spinal motor neurons
• Spinal Shock:

  • Spinal shock is attributed to the sudden cessation or removal of impulses descending from higher cortical centers to reinforce the spinal centers
  • Recovery from spinal shock may involve denervation hypersensitivity to chemical mediators chronically released by the remaining spinal excitatory endings
• Experiment 3: The Genesis of Tetanus

  • Tetanic contraction occurs when a muscle is stimulated repeatedly at a frequency where the muscle does not relax between stimuli, resulting in a contracted state
  • Complete tetanus appears as a smooth curve in the myogram due to repetitive rapid frequent stimulation, while incomplete tetanus shows undulations at the top of the curve as relaxation has occurred to a certain degree
• Tetanic contractions in skeletal muscles:

  • Complete Tetanus: muscle stimulated repeatedly at a frequency where the interval between stimuli is less than the contraction time, causing sustained contraction without relaxation.
  • Incomplete Tetanus: occurs when the frequency of stimulation allows partial relaxation between contractions
• Experiment on tetanus in a frog:

  • Started with low-frequency muscle contractions, progressing to incomplete tetanus with partial relaxation, then complete tetanus with sustained maximal contraction without full relaxation between stimuli
• Chemical changes in muscle during contraction:

  • Rupture of sole feet releasing acetylcholine
  • Combination of acetylcholine with receptor protein
  • Release of calcium ions from sarco-tubular system
  • Coupling of actin filaments over myosin filaments
  • Splitting of adenosine triphosphate
  • Liberation of energy in the form of heat and work done
  • Syneresis or escape of water from muscle cells
  • Lowering of pH due to accumulation of lactic acid and other acid metabolites
• The table compares two preparations, A and B, concerning the chemical changes observed during muscle rigor using the gastrocnemius muscle

  
• Preparation A is submerged in Barium Hydroxide, resulting in a yellowish-brown color with muscle stiffness and basic acidity
• Preparation B is placed in hot water, leading to a red color due to denaturation of hemoglobin, muscle remaining flabby, acidic nature, and faster contraction compared to Preparation A
• The experiment aimed to explore changes in muscles during contraction and rigor mortis, observing carbon dioxide release, effects of heat on muscle function, and chemical processes like acetylcholine and calcium ions
• The primary seat of fatigue in an intact body was found to be the synapse, as demonstrated by the experiment involving stimulation of sciatic nerves and gastrocnemius muscles
• The reflex arc involves components like receptors, afferent and efferent nerve fibers, synapses in the CNS, and effector organs like muscles
• Stimulation of the left sciatic nerve led to bilateral contraction of both left and right gastrocnemius muscles, indicating connections between neurons on both sides in the CNS
• Transfer of stimulation to the right sciatic nerve resulted in unexpected contraction of both gastrocnemius muscles, eliminating CNS, nerve, muscle, and myoneural junction as the primary seat of fatigue