A Level Biology Practice Exam

What is the bundle of His primarily composed of?

1. Cardiac muscle tissue

2. Purkinje fibers conducting electrical signals

3. Epithelial cells for heart protection

4. Connective tissue for structural support

The correct answer is: Purkinje fibers conducting electrical signals

The bundle of His, also known as the atrioventricular bundle, is primarily composed of specialized cardiac muscle tissue. It plays a crucial role in the conduction system of the heart, facilitating the transmission of electrical impulses from the atria to the ventricles, which is essential for coordinating heartbeats. While Purkinje fibers are involved in the conduction of electrical signals within the heart, they are found in the ventricular walls and are not the primary component of the bundle of His itself. The bundle of His consists of a unique type of cardiac muscle tissue that has properties allowing it to conduct electrical signals efficiently. The other components listed, like connective tissue and epithelial cells, do not accurately represent the primary composition of the bundle of His. Connective tissue does provide support but is not the main structural component of the bundle itself, and epithelial cells do not play a role in the function of the conduction system. The focus on specialized cardiac muscle tissue highlights the unique function of the bundle of His in the heart's conduction pathway.