Final answer:
The myocardial conduction system is made up of specialized myocardial muscle cells that initiate and propagate electrical impulses, leading to heart muscle contractions.
Step-by-step explanation:
The correct statement regarding the myocardial conduction system is D. The conduction system is made up of specialized myocardial muscle cells. This system comprises the sinoatrial node, atrioventricular node, atrioventricular bundle, bundle branches, and Purkinje fibers. These components work together to initiate and propagate electrical impulses through the heart, leading to coordinated contractions that pump blood throughout the body. Contrary to option A, the cells of the conduction system are not nerve cells but specialized muscle cells. Option B also does not describe the conduction system, as it is not involved in conducting blood but electrical impulses. Option C is incorrect because the conduction system does not carry impulses from the autonomic nervous system but generates its own impulses that are then modulated by the autonomic nervous system.