Answer :
Final answer:
The heart's beating frequency is controlled by internal pacemaker cells, originating from the sinoatrial node, influenced by the autonomic nervous system and hormones.
Explanation:
The frequency of heartbeats is controlled by the heart's internal pacemaker through electrical charges. This pacemaker is the sinoatrial (SA) node, located near the wall of the right atrium. The SA node generates electrical impulses, causing the atria to contract. The signal then travels to the atrioventricular (AV) node, where it is briefly delayed, allowing the atria to relax before the ventricles contract. The electrical charges then move through the bundle of His, into the bundle branches, and finally through the Purkinje fibers, resulting in a coordinated contraction of the ventricles. Hormones and the autonomic nervous system can influence the SA node to modify the heart rate in response to various physiological demands.
