Question

The electrical stimulus that originates in the heart's primary pacemaker is controlled by impulses from the brain that arrive by way of the:

A) parietal lobe.
B) pons and medulla.
C) somatic nervous system.
D) autonomic nervous system.

Answer 1

The electrical stimulus from the brain that controls the pacemaker cells of the heart originates in the medulla oblongata, and is conveyed through the autonomic nervous system, specifically the sympatethic and parasythepathic branches that balance heart rate.

Step-by-step explanation:

The electrical stimulus that originates in the heart's primary pacemaker is influenced by the autonomic nervous system (ANS). This system encompasses the sympathetic and parasympathetic nervous systems, and it operates independently of conscious control. The impulses from the brain that control heart rate originate in the medulla oblongata, affecting the heart's pacemaker cells through the autonomic nervous system.

These pacemaker cells are located in the sinoatrial (SA) node of the heart. During rest, the medulla oblongata provides slight stimulation to the SA node, contributing to what is known as autonomic tone, with the parasympathetic nervous system normally playing a dominant role in slowing the heart. When there is a need for an increase in heart rate, such as during physical activity, the sympathetic nervous system becomes more active, signaling the heart to beat faster.