How is heart rate controlled?
Although the heart initiates it’s own impulse to contract the actual adjustments to it’s activity (to meet the bodies demands) derive from the autonomic nervous system. Sympathetic nerves increase the heart rate and parasympathetic nerves slow the heart rate. The dual innervation of the heart is co-ordinated by the cardiac centre in the medulla oblongata in the brain. Now the SA node is normally the pacemaker of the heart due to it’s rapid firing rate of 60-100 electrical discharges per minute, however, the specialised cells at the AV node and at the bundle of His are also capable of spontaneously producing an electrical discharge and taking over control of the rhythm, but they are normally required to do so only if the SA node fails or becomes slow for some reason.
