Biology, Eighth Edition (Raven)

Chapter 49: The Circulatory and Respiratory Systems

Conducting System of the Heart

How are all the components of the heart able to work together without direct control from the central nervous system? For proper function of the heart it is necessary that all the muscle fibers in a region contract in unison. It is also necessary that all the different regions of the heart contract in a coordinated but NOT in unison. The non-synchronous coordination is accomplished by central control with a time delay. The sinoatrial sends out signals for contractions to the entire heart. These signals are propagated through muscle rather than nervous tissue and are conducted such that they are received by different regions after different periods of delay. This system does not require separate control of different regions of the heart and thus is probably less susceptible to malfunctions.

View the animation below, then complete the quiz to test your knowledge of the concept.


1.	In the heart, an action potential originates in the...

		A)	Purkinje fibers.
		B)	bundle branches.
		C)	atrioventricular bundle.
		D)	atrioventricular node.
		E)	sinoatrial node.

2.	The sequence of travel by an action potential through the heart is...

		A)	sinoatrial node, atrioventricular node, atrioventricular bundle, bundle branches, Purkinje fibers.
		B)	atrioventricular node, sinoatrial node, atrioventricular bundle, bundle branches, Purkinje fibers.
		C)	atrioventricular bundle, atrioventricular node, sinoatrial node, bundle branches, Purkinje fibers.
		D)	Purkinje fibers, atrioventricular bundle, atrioventricular node, sinoatrial node, bundle branches.
		E)	atrioventricular node, sinoatrial bundle, atrioventricular node, bundle branches, Purkinje fibers.

3.	Which of the following is true concerning the heart conduction system?

		A)	action potentials pass slowly through the atrioventricular node.
		B)	action potentials pass slowly through the atrioventricular bundle.
		C)	action potentials pass slowly through the Purkinje fibers.
		D)	action potentials pass slowly through the ventricle wall.
		E)	action potentials pass slowly through the bundle branches.

4.	In the ventricles, the action potential travels along the interventricular septum to the apex of the heart, where it then spreads superiorly along the ventricle walls.

		A)	True
		B)	False

5.	Action potentials are carried by the Purkinje fibers from the bundle branches to the ventricular walls.

		A)	True
		B)	False