Explain parasympathetic Nerves System
Another system that runs parallel to the sympathetic system is termed as the parasympathetic system. This system has an effect just opposite to the sympathetic system. It relaxes the heart, decreases the heart rate (negative chronotropic), the force of contraction (negative inotropic), the conduction rate (negative dromotropic) and the excitability of tissue (negative bathmotropic). The nerves that supply the heart's atria are termed as vagi (singular vagus). As the name suggests, vagus is a vagabond, a wanderer charting an unfamiliar, vague course supplying the digestive tract, heart, the voice box etc. The heart is supplied by the right and left vagi. The peculiarity is that they do not supply the ventricles. The sympathetic system only supplies the ventricles. Overall, we have seen that the heart hangs in a balance of positive and negative forces: the sympathetic and parasympathetic system. Now you know the mechanism that may be operating when our yogis increase their heart rate or stop it! The sympathetic nerves have a chemical neurotransmitter called nor-adrenaline, whereas, the parasympathetic nerves release acetylcholine at the postganglionic nerve endings.