The heart, which is in charge of sending essential
substances such as oxygen, glucose etc. via blood veins throughout the body, works in
biochemical ways, mainly with the help of the nervous system. The main nerve mechanism
that has an influence on the heart is the parasympathetic part of the nervous system that
functions involuntarily.
When,
any kind of impulse reaches the brain, the
branches of the vagus nerve (the tenth cranial nerve which supplies parasympathetic fibres
to the heart) stimulates the heart, thus causes the pumping action of the heart to be
slowed down. With this kind of impulse the effect reaches immediately, whereas with the
sympathetic system which works in the opposite direction, the influence occurs gradually,
the heart accelerates and this time, the dominant function is the parasympathetic one.
Parasympathetic system is one part of the involuntary nervous system, and generally
speaking, it makes up the functions that dominate the body of a person who is taking a
rest. The sympathetic nervous system, on the other hand, consists of the stress hormones;
namely, adrenaline and noradrenaline. The sinus knot, the starting point of the heart
circulation, is stimulated and controlled with the vagus nerve (the tenth cranial nerve).
