This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
[{'content': 'Which cells are referred as "Pacemaker cells" with relation to \'BER\'? \nSelect and explain. \nA. SA node, B. AV node, C. Interstitial cells of Cajal., D. Pyramidal cells', 'role': 'user'}, {'content': 'Answer: C \nExplanation: 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).', 'role': 'assistant'}]