Gastro-Intestinal Tract Musculature


  • circular and longitudinal smooth muscle coats

  • small, spindle, shaped cells connected to each other forming bundles with cross connections to neighbouring bundles

  • the bundle rather than the individual muscle cell forms the basic unit for propagation of action potentials

  • GIT muscle usually shows rhythmic changes in membrane potential with a frequency of 3-15 cycles/min (slow wave

  • The presence of slow waves causes the bundles to be partly scontracted generating the muscle tone

  • Once threshold potential is reached, there is initiation of action potential resulting in complete muscle contraction

  • If the muscle bundles are hyperpolarised, slow waves disappear and tone diminishes leading to paralysis

  • Each bundle has its own slow-wave frequency, but as adjacent bundles are connected, the rhythm of the fastest bundle takes over - pacemaker.