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Biology: The Dynamic Science (Mind...

4th Edition
Peter J. Russell + 2 others
ISBN: 9781305389892

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BuyFindarrow_forward

Biology: The Dynamic Science (Mind...

4th Edition
Peter J. Russell + 2 others
ISBN: 9781305389892
Textbook Problem

Keeping the mammalian cardiac cycle balanced is/are:

a. an AV node between the right atria atrium and right ventricle, which induces a wave of contraction.

b. pacemaker cells, which compose the AV node and signal theSA node.

c. an insulating layer that isolates the SA node from the rightatrium.

d. ion channels in pacemaker cells, which close to depolarizetheir plasma membranes.

e. neurogenic stimuli from the nervous system.

Summary Introduction

Introduction:

The contraction and relaxation of the heart muscle makes up a heartbeat. A human heart beats 72 times per minute. The alternating sequence of diastole and systole of the heart is called the cardiac cycle.

Explanation

Justification/explanation for the correct answer:

Option (a) is, an AV node between the right atria atrium and right ventricle, which induces a wave of contraction. Atrioventricular node is situated inside the heart wall between the right atrium and the right ventricle. When cells of the AV node get excited by signals and send signals to the bottom of the heart via Purkinje fibers. The cells then spread to the walls of ventricles, which induces a wave of contraction at the bottom of the heart that rises upwardsallowing blood to be release into the aorta and pulmonary arteries. It helps in keeping the mammalian cardiac cycle balanced. Hence, option (a) is correct.

Explanation for the incorrect answers:

Option (b) is, pacemaker cells, which compose the AV node and signals the SA node. The pacemaker cells of SA (Sinoatrial) node produce depolarization signal that signals the contraction of atria and fills the ventricles, which signals the AV node. Pacemaker cells compose SA node that signals the AV node...

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