This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: G.I.T., Subject name: Physiology
Cajal cells are involved in- 
Select and explain. 
A. Mesangial cell contraction in Kidney, B. Pacemaker activity in Heart, C. Pacemaker activity in GIT, D. Respiratory rhythm generation
C: Pacemaker activity in GIT
Answer: C: Pacemaker activity in GIT 
Explanation: Ans. is 'c' i.e., Pacemaker activity in GIT * Pacemaker cells are called interstitial cells ofCajal.* Pacemaker cells (interstitial cells of Cajal) are stellate mesenchymal cells with smooth muscle like features. Pacemaker cells are absent in the esophagus and proximal stomach. In the distal stomach and small intestine they are located in outer circular muscle layer near myentric plexus. In the colon they are at the submucosal border of circular muscle layer. In stomach and small intestine, pacemaker frequency is in descending gradient and the pacemaker with highest frequency usually dominates (like heart).