Question

what controls how the heart beats.

Explanation:

The heart's rhythm is mainly controlled by the sino - atrial (SA) node, a group of specialized cardiac muscle cells that act as the heart's natural pacemaker. It generates electrical impulses that spread through the heart muscle, causing it to contract and relax in a coordinated manner. The autonomic nervous system (both sympathetic and parasympathetic branches) also influences the heart rate, adjusting it according to the body's needs such as during exercise or rest. Hormones like adrenaline can also affect heart rate.

Answer:

The sino - atrial node, the autonomic nervous system, and hormones control how the heart beats.