Vagal stimulation in hea causes decrease in hea rate by ?
Ans. is 'b' i.e., Decrease in slope of prepotential Effect of autonomic nervous system The SA node develops from structures on the right side of the embryo and the AV node from structures on the left. This is why right vagus (parasympathetic) is distributed primarily to SA node and the left vagus (parasympathetic) mainly to AV node. Similarly, the sympathetic innervation on the right side is distributed primarily to the SA node and the sympathetic innervation on the left side primarily to AV node. Effects of ANS on cardiac physiology are as follow : ? A) Parasympathetic (vagal) stimulation i) Negative chronotropic (decreased hea rate) : - Vagal stimulation cause decrease in slope (flattening) of prepotential (pacemaker potential) and therefore the time taken to reach the threshold level is increased --> Hea rate is decreased. ii) Negative dromotropic (decreased conduction). iii) Increased refractory period of all type of cardiac cells. B) Sympathetic stimulation i) Positive chronotropic (Increased hea rate):- Sympathetic stimulation increases the slope of phase 4 prepotential (pacemaker potential); therefore, time taken to reach the threshold is decreased and hea rate is increased. ii) Positive ionotropic (Increased contractility). iii) Positive dromotropic (Increased conduction velocity in conductive tissue). iv) Decreased in refractory period of all type of cardiac cells. v) Positive bathmotropic (Increased automaticity).
Decrease in action potential spike
Decrease in slope of prepotential
Increase in repolarization
Decrease conduction