Rate of impulse generation is maximum in –
Correct Answer: SA node
Description: Ans. is 'a' i.e., SA node Automaticityo Cells of the conductive system also possess automaticity, i.e., the capability of spontaneous excitation,o However, the rate at which different parts of conductive system discharge impulses is not the same,o The SA node discharges impulses at fastest rateQ, hence the rate at which SA node fires determines the heart rate, therefore, SA node is normal pacemaker of the heartQ, i.e., it determines the pace of the heart,o The AV node has the next highest automaticity after SA node; therefore, if the SA node stops discharging, the AV node takes over the role of cardiac pacemaker.o The automaticity' of the SA node, being the highest, paces the excitatory' drive to all other cardiac fibers, suppressing their intrinsic automaticity. This phenomenon of suspension of pacemaker activity in cells other than those of the SA node is called overide suppression. Overide suppression occurs because an impulse originating in the SA node spreads throughout the heart by means of the conduction system and results in sequential contraction of different cardiac chambers. Before an impulse from AV node or other parts of conduction system can initiate impuse, the next impulse from the SA node is discharged because its rate of discharge is highest, i.e., before other parts of conducting system can generate their own impulse, they are overwhelmed by the wave of impulse generated and coming from the SA node.TissueRate o f impulse generationSA nodeAV nodeBundle of HisPurkinje system70-80/minute (Highest)40-60/minute40/minute24/minite
Category:
Physiology
Get More
Subject Mock Tests
Practice with over 200,000 questions from various medical subjects and improve your knowledge.
Attempt a mock test nowMock Exam
Take an exam with 100 random questions selected from all subjects to test your knowledge.
Coming SoonGet More
Subject Mock Tests
Try practicing mock tests with over 200,000 questions from various medical subjects.
Attempt a mock test now