Chapter 34, Problem 3A

Summary Introduction

To determine:

The name of the term which stimulates the heart to contract.

Introduction:

The atria and ventricles function together, alternately contracting and relaxing to make the heart beat and pump blood. The electrical system of our heart is the main power origin that makes this possible. Our heartbeat is triggered via way of means of electric impulses that transfer down a special pathway through our heart.

Explanation of Solution

SA node (sinoatrial node) is referred to as the heart’s natural pacemaker. The impulse starts in a small set of specialized cells found in the right atrium, known as the SA node. The electrical activity spreads through the walls of the atria and causes them to contract. That forces blood into the ventricles. The SA node sets the rate and rhythm of our heartbeat. When heart rate drops down the set rate, the pacemaker produces (fires) an impulse that passes through the lead to the heart muscle. This reason makes the heart muscle to contract, generating a heartbeat.

Conclusion

Thus, it can be concluded that electrical impulses from the heart muscle cause our heart to beat (contract). This electrical signal initiates in the sinoatrial (SA) node, present at the top of the heart's upper-right chamber (the right atrium) which is also known as pacemaker.