<prompt> Which cells are referred as Pacemaker cells with relation to BER?SA nodeAV nodeInterstitial cells of Cajal.Pyramidal cells  <response>: Interstitial cells of Cajal Basic Electrical Rhythm BER: Smooth muscle cells of the gastrointestinal tract have spontaneous rhythmic fluctuations in membrane potential between about -65 and -45 mV. BER initiated by Pacemaker cells called Interstitial cells of Cajal. Pacemaker cells - Interstitial cells of Cajal. Stellate mesenchymal cells with smooth muscle-like features. Location: Are absent in esophagus proximal stomach. In distal stomach small intestine - Located in outer circular muscle layer near myenteric plexus. In colon - Located at the submucosal border of circular muscle layer. Frequency: In Stomach small intestine - Pacemaker frequency is in descending gradient. Pacemaker with the highest frequency usually dominates Eg., In Hea. 