conduction system of the heart is densely innervated by the
autonomic nervous system. The parasympathetic portion of the
autonomic nervous system decreases sinus node automaticity and
slows AV node conduction and hence decreases the heart rate.
On the other hand the sympathetic division can increase the
heart rate by increasing the sinus node automaticity and enhancing
conduction through the AV node.
autonomic nervous system functions involuntarily to control
motor functions of the heart, lungs, other internal organs and
of the smooth muscles of the blood and lymph vessels.
divided into two parts, as follows:
1) the parasympathetic coming from the mid and hind brain and
the spinal cord and able to cause constriction of the pupils
of the eyes and slowing of the heart rate amongst other functions;
sympathetic orginating in the spinal cord and concerned with
causing the involuntary response to alarm such as by speeding
the heart rate and raising the blood pressure.