"The sympathetic nervous system is often referred to as the "fight or flight" response,
since it is activated during physically or mentally stressful situations. It is responsible for
HR raising due to the increase in the
SA stimulation and for increasing the
strength of contractions due to an increase in the propagation velocity of the depolarization wave that travels through the heart (slower response - about 5 seconds). The
parasympathetic nervous system is like the "rest and digest" mechanism, since it slows down the HR, decreases the Blood Pressure (BP), and increases the digestive system
activity (faster response - less than 1 second). "