Cardiac Muscle and Electrical Activity

Definition

Cardiac muscle is the specialized type of striated muscle found in the heart that is responsible for the rhythmic contractions that pump blood throughout the body. The electrical activity that coordinates these contractions is a critical component of cardiac function and overall cardiovascular health.

5 Must Know Facts For Your Next Test

1. Cardiac muscle is striated, meaning it has a banded appearance, and is involuntary, contracting without conscious control.
2. Cardiomyocytes, the muscle cells of the heart, have a high concentration of mitochondria to support the constant need for energy to power the heart's contractions.
3. The cardiac conduction system, including the SA node, AV node, and Purkinje fibers, coordinates the electrical activity that triggers the rhythmic contractions of the heart.
4. The action potentials generated by the SA node spread through the atria, causing them to contract, then travel through the AV node and into the ventricles, causing them to contract.
5. Disruptions in the cardiac conduction system can lead to abnormal heart rhythms, or arrhythmias, which can impair the heart's ability to effectively pump blood.

Review Questions

• Describe the structure and function of cardiac muscle tissue and how it differs from skeletal muscle.
  • Cardiac muscle is a specialized type of striated muscle found exclusively in the heart. Unlike skeletal muscle, which is under voluntary control, cardiac muscle is involuntary, contracting rhythmically without conscious effort. Cardiac muscle cells, called cardiomyocytes, are tightly packed and connected by intercalated discs, allowing for the rapid and coordinated contraction of the heart. Cardiomyocytes also have a high concentration of mitochondria to support the constant need for energy to power the heart's contractions.
• Explain the role of the cardiac conduction system in coordinating the electrical activity of the heart.
  • The cardiac conduction system is responsible for generating and transmitting the electrical impulses that stimulate the rhythmic contractions of the heart. The sinoatrial (SA) node, located in the right atrium, acts as the heart's natural pacemaker, generating the initial electrical impulses. These impulses then spread through the atria, causing them to contract. The impulses then travel to the atrioventricular (AV) node, which delays the transmission of the signal, allowing the atria to fully contract before the ventricles. The impulses then travel through the ventricles via the Purkinje fibers, causing the ventricles to contract and pump blood throughout the body.
• Discuss the potential consequences of disruptions in the cardiac conduction system and how they can lead to abnormal heart rhythms or arrhythmias.
  • Disruptions in the cardiac conduction system can lead to various types of arrhythmias, or abnormal heart rhythms. For example, if the SA node malfunctions and fails to generate the proper electrical impulses, it can result in a slow heart rate (bradycardia). Alternatively, if the AV node is damaged and does not properly delay the transmission of electrical signals, it can lead to a rapid, irregular heart rate (tachycardia). These arrhythmias can impair the heart's ability to effectively pump blood, potentially leading to symptoms such as dizziness, chest pain, or even sudden cardiac arrest. Understanding the role of the cardiac conduction system and the consequences of its disruption is crucial for diagnosing and managing cardiovascular disorders.

Related terms

Myocardium:

The middle and thickest layer of the heart wall, composed of cardiac muscle cells called cardiomyocytes.

Sinoatrial (SA) Node:

The natural pacemaker of the heart, located in the right atrium, that generates the electrical impulses that stimulate the heart to contract.

Atrioventricular (AV) Node:

A group of specialized cardiac muscle fibers located between the atria and ventricles that delay the transmission of electrical impulses, allowing the atria to fully contract before the ventricles.