Electrical Activity of the Heart

Question 1

The contraction of cardiac muscle (heart muscle) in all animals is initiated by electrical impulses known as _______. The rate at which these impulses fire controls the rate of cardiac contraction or heart rate. The cells that set the firing rate is called?

Answer 1

Action potential

Pacemaker cells

Question 2

Sinoatrial node (SA node)

Answer 2

• an area in the heart wall that causes/ initiates and conduct contraction of the heart muscle.

Question 3

How do cardiac muscle cell communicate with each other?

Answer 3

These cells are connected via intercalated disc on their cell membranes. Action potentials travels from cell to cell via gap junction along these discs.

Question 4

Atrioventricular node (AV node)

Answer 4

-Located in the right atrium. It is a part of the electrical conduction system of the heart that coordinates the top of the heart. It electrically connects the atria and ventricles

Question 5

In the heart, Impulses initiated in the SA node follows two pathways

Answer 5

1. Internodal pathway

2. Interatrial pathway

Question 6

Atrioventricular Bundle/

Bundle of His or His bundle

Answer 6

• is a collection of heart muscle cells specialized for electrical conduction
• responsible for transmitting signals from the AV node to the apex of the heart, and towards the Purkinje fibers

Question 7

Purkinje fibers

Answer 7

specialized conduction fibers composed of electrically excitable cells

These cells helps to maintain a consistent heart rhythm by synchronizing contractions of its ventricles

Question 8

The heart has two main types of cells

Answer 8

1. Autorhythmic cells: includes pacemaker cells and conduction fibers. These cells spontaneously depolarizes to levels that generate action potentials. Located primarily in the SA and AV nodes
2. contractile cells

Question 9

Why does conduction slows down at the AV node?

Answer 9

ensure the atria have ejected their blood into the ventricles first before the ventricles contract.

Question 10

How is ventricular contraction initiated?

Answer 10

-Impulses set by the SA nodes travels along the inter-nodal pathway toward the AV node. From the AV node, electrical activity moves down the bundles of His, branching into right and left fibers and to the purjunke fibers causing ventricular contraction.