estion 3
The intrinsic ability of cardiac muscle to generate action potentials (APs) rhythmically is achieved
by the normal pace maker, the sino-atrial node (S-A node). The S-A node is part of the special
excitatory and conductive system of cardiac muscle. With thehelp of a diagram, describe this
conductive system how the AP spreads throughout the muscle.
The cardiac conduction system consists of specialized cells that create and conduct electrical signals, allowing for the coordinated contraction of the heart muscle. The main components of this system are the sinoatrial (SA) node, atrioventricular (AV) node, bundle of His, bundle branches, and Purkinje fibers.
Here is a diagram illustrating the cardiac conduction system and how the action potential (AP) spreads throughout the muscle:
```
SA Node
↓
AV Node
↓
Bundle of His
↓
Bundle Branches
↓
Purkinje Fibers
↓
Working Cells of Ventricles
```
1. The Sinoatrial (SA) Node: This is the natural pacemaker of the heart located in the right atrium. It generates spontaneous action potentials, initiating each heartbeat. The APs spread through the atria, causing their contraction.
2. Atrioventricular (AV) Node: Located near the interatrial septum, the AV node acts as a relay station, delaying the transmission of electrical impulses from the atria to the ventricles. This delay allows for atrial contraction to complete before ventricular contraction begins.
3. Bundle of His: After passing through the AV node, the electrical signal enters the bundle of His, which is a collection of specialized cells located in the upper part of the interventricular septum.
4. Bundle Branches: The bundle of His divides into two branches— the left bundle branch and the right bundle branch— that extend into the ventricles. These branches transmit the APs down the septum toward the apex of the heart.
5. Purkinje Fibers: The bundle branches further divide into smaller fibers known as Purkinje fibers. These fibers spread out through the ventricular walls, rapidly conducting the APs to all areas of the ventricles.
6. Working Cells of Ventricles: Finally, the APs reach the working cells of the ventricles, which are the muscle cells responsible for the contractile force of the heart. The coordinated depolarization of these cells ensures a synchronized contraction and effective pumping of blood.
Overall, the cardiac conduction system allows for the efficient spread of electrical signals throughout the heart, ensuring a rhythmic and coordinated contraction that enables proper heart function.