**Core Concept**
Purkinje fibers are specialized cardiac muscle cells that play a crucial role in the conduction of electrical impulses in the heart, specifically in the atrioventricular (AV) junction and the ventricles. They are responsible for transmitting the impulse from the AV node to the ventricular muscle, thereby initiating the contraction of the ventricles.

**Why the Correct Answer is Right**
Purkinje fibers have a unique structure that allows them to rapidly conduct electrical impulses. They have a large diameter and a low resistance, which enables them to transmit the impulse quickly. Additionally, Purkinje fibers have a high concentration of gap junctions, which facilitate the exchange of ions and electrical signals between adjacent cells. This allows for a synchronized contraction of the ventricles, ensuring efficient pumping of blood throughout the body.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the role of Purkinje fibers in cardiac conduction.
**Option B:** This option is incorrect because it is not a characteristic of Purkinje fibers; rather, it describes the function of the sinoatrial (SA) node.
**Option C:** This option is incorrect because it is not a true statement regarding Purkinje fibers; the SA node is responsible for initiating the heartbeat, not the Purkinje fibers.

**Clinical Pearl / High-Yield Fact**
Purkinje fibers can be affected by various conditions, such as myocardial infarction, which can lead to ventricular fibrillation and cardiac arrest. Understanding the role of Purkinje fibers in cardiac conduction is essential for diagnosing and managing cardiac arrhythmias.

**Correct Answer: C. The SA node initiates the heartbeat and is responsible for the generation of the cardiac rhythm, not the Purkinje fibers.**