Final answer:
The P wave refers to when the electrical impulse starts in the SA node and causes the atria to contract. The P wave on an ECG is the term that refers to when the electrical impulse starts in the SA node and causes the atria to contract, which is followed by atrial contraction.
Step-by-step explanation:
The term that refers to when the electrical impulse starts in the SA node and causes the atria to contract is the P wave. The P wave represents the depolarization of the atria and is followed by atrial contraction. The atria begin contracting approximately 25 ms after the start of the P wave.
The P wave on an ECG is the term that refers to when the electrical impulse starts in the SA node and causes the atria to contract, which is followed by atrial contraction.
The term that refers to when the electrical impulse starts in the SA node and causes the atria to contract is the P wave. The P wave represents the depolarization of the atria, which precedes atrial contraction. Once the P wave occurs, the atria begin contracting approximately 25 milliseconds later. In contrast, the QRS complex represents the depolarization of the ventricles, which is followed by their contraction. The T wave, on the other hand, signifies the repolarization of the ventricles.
The term that specifically refers to the electrical impulse originating in the SA (sinoatrial) node, leading to the contraction of the atria in the heart's electrical conduction system, is represented by the P wave. The P wave is a characteristic feature on an electrocardiogram (ECG or EKG) that signifies the depolarization of the atria. As the SA node initiates the electrical impulse, it spreads across the atria, causing them to contract and push blood into the ventricles. The P wave represents the atrial depolarization phase, showcasing the electrical activity associated with atrial contraction.
The other options—QRS complex, T wave, and PR interval—correspond to different phases of the cardiac cycle. The QRS complex represents the depolarization of the ventricles, the T wave signifies ventricular repolarization, and the PR interval reflects the time it takes for the electrical impulse to travel from the atria to the ventricles. While these components are crucial for understanding the complete cardiac cycle on an ECG, the P wave specifically captures the initiation of the heartbeat as the electrical impulse originates in the SA node, triggering atrial contraction.