Bundle of His

The bundle of His is a specialized conduction pathway in the heart that carries impulses from the AV node into the ventricles. In Anatomy and Physiology II, it sits between atrial conduction and Purkinje fiber activation.

What is the bundle of His?

The bundle of His is the heart’s main electrical bridge between the atrioventricular (AV) node and the ventricles. In Anatomy and Physiology II, you learn it as part of the cardiac conduction system, where it carries the signal from the upper chambers to the lower chambers so the ventricles contract in an orderly way.

It starts where the AV node finishes its delay. That delay matters because it gives the atria time to finish pushing blood into the ventricles before the ventricles squeeze. Once the signal enters the bundle of His, it moves quickly through specialized cardiac muscle fibers rather than through ordinary contractile tissue.

From there, the bundle divides into the right bundle branch and left bundle branch. Those branches run down the interventricular septum and deliver the impulse toward the apex of the heart, where it spreads into the Purkinje fibers. This route is why ventricular contraction usually spreads in a coordinated wave instead of happening in random patches.

A useful way to picture it is as a wiring system. The SA node starts the impulse, the AV node briefly slows it, the bundle of His carries it into the ventricles, and the Purkinje fibers fan it out fast enough to trigger a strong squeeze. That sequence keeps the heart from pumping against itself.

The bundle of His is made of modified cardiac muscle cells, not nerves. That trips people up because it sounds like a nerve pathway, but it is really part of the myocardium specialized for conduction. Its job is electrical timing, not force production. The ventricles do the forceful pumping; the bundle of His just helps make sure the signal gets there in the right order.

Why the bundle of His matters in Anatomy and Physiology II

The bundle of His is the step that connects atrial timing to ventricular pumping. If the impulse could not pass through this pathway, the ventricles would not receive a clean signal, and blood would not be ejected efficiently into the pulmonary artery and the aorta.

This term also ties together two big ideas in Anatomy and Physiology II: electrical activity and circulation. You are not just memorizing a structure, you are tracing how an action potential turns into a mechanical beat that supports both pulmonary circulation and systemic circulation.

It shows up again when you study conduction problems. If the bundle or one of its branches is blocked, the electrical signal may still reach the ventricles, but not in the usual pattern. That can change the timing and appearance of the heartbeat, which is why bundle branch blocks matter in clinical discussions.

It also helps you read diagrams and ECG-related questions more accurately. If you know the bundle of His sits after the AV node and before the bundle branches, you can place each event in the sequence instead of mixing up where the signal goes next.

How the bundle of His connects across the course

Atrioventricular Node (AV Node)

The AV node comes right before the bundle of His. It slows the electrical impulse long enough for the atria to finish contracting, then passes the signal into the bundle of His so ventricular activation can begin in an organized way.

Purkinje Fibers

Purkinje fibers are the next stop after the bundle branches. The bundle of His gets the impulse into the ventricles, and the Purkinje fibers spread it quickly through the ventricular muscle so contraction happens almost at the same time across the lower chambers.

Cardiac Cycle

The bundle of His is one piece of the timing that makes the cardiac cycle work smoothly. Its conduction step happens between atrial contraction and ventricular contraction, so the sequence of filling and pumping stays coordinated instead of overlapping badly.

Action Potential

An action potential is the electrical signal moving through the conduction system. The bundle of His carries that signal through specialized cells, so this term links the cell-level electrical event to the whole-heart contraction you can trace on a diagram or ECG.

Is the bundle of His on the Anatomy and Physiology II exam?

A quiz question might ask you to identify the pathway a signal follows after the AV node or to label the bundle of His on a heart diagram. You may also need to trace what happens when the impulse reaches the right and left bundle branches, then explain why the ventricles contract after the atria. On ECG or conduction-system questions, this term helps you place the mid-level conduction pathway correctly instead of confusing it with the SA node, AV node, or Purkinje fibers. If the question mentions a bundle branch block, you should connect the problem to slowed or altered ventricular conduction rather than to atrial pacing.

The bundle of His vs Atrioventricular Node (AV Node)

The AV node and the bundle of His are neighboring parts of the conduction pathway, but they do different jobs. The AV node delays the impulse, while the bundle of His carries it into the ventricles. If you swap them, the whole timing sequence gets mixed up.

Key things to remember about the bundle of His

• The bundle of His is the heart’s conduction pathway that carries the electrical impulse from the AV node into the ventricles.

• It divides into the right bundle branch and left bundle branch, which move the signal through the interventricular septum.

• Its job is electrical coordination, not pumping force, so it helps the ventricles contract in a strong, organized sequence.

• It works between the AV node and Purkinje fibers, making it a middle step in the cardiac conduction system.

• Problems in this pathway can change ventricular timing and are often discussed as bundle branch blocks.

Frequently asked questions about the bundle of His

What is the bundle of His in Anatomy and Physiology II?

The bundle of His is a specialized conduction tract in the heart that carries impulses from the AV node into the ventricles. It is part of the cardiac conduction system and helps set up the coordinated contraction of the lower chambers.

Is the bundle of His a nerve?

No. It is made of modified cardiac muscle cells, not nervous tissue. It conducts electrical signals like wiring, but it is still part of the heart muscle system.

What comes after the bundle of His?

After the bundle of His, the impulse travels into the right bundle branch and left bundle branch, then into the Purkinje fibers. That pathway spreads the signal through the ventricles so they contract together.

How is the bundle of His different from the AV node?

The AV node slows the signal, and the bundle of His carries it onward into the ventricles. They work back to back, but they are not the same structure and they do not have the same job in the cardiac cycle.