Control of Heart by Sympathetic and Parasympathetic Nerves
Sympathetic Nervous System
Supplies SA node, AV node as well as ventricular musculature.
Baseline activity ⟶ keeps the heart pumping 30% above that without sympathetic activity.
Simulation
Increases heart rate by stimulating the SA node.
Increases force of contraction by stimulating ventricular muscle cells.
The net result is increased cardiac output.
Inhibition
Decreases heart rate.
Decreases force of contraction decreases.
The net result is decreased cardiac output.
Parasympathetic Nervous System
Mainly supplies SA node and atria but not much to ventricles.
Calms down the heart.
Stimulation
Mainly decreases heart rate.
not much effect on the force of contraction as ventricles do not receive significant parasympathetic innervation.
Very Strong Stimulation
Stop the heart for a few seconds
↓
Heart Escapes
↓
The heart starts beating at a lower rate of 20-40 beats per minute
Decrease strength of contraction to some extent.