Biology, 01.03.2020 21:24 nguyendavis17

Q1 What is the correct sequence an impulse travels through the four components of the heart’s nodal system?
(Here I have order these options in chronological sequence order)
A: bundle of HIS
B: SA node
C: AV node
D: Purkinje fibers
I ordered this as cabd and it got marked wrong
Q2: Which of the following structures depolarizes next after the AV node?
I put in purkinje fibers and it was marked wrong.
Q3: Soon after the onset of ventricular systole the:
A: AV valves open
B: Aortic pressure increases
C: First heart sound is heard
D: semilunar valves open
I put B as my answer and it was marked wrong.

Answers: 1

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Answers

1. The correct sequence in which an impulse travels through the heart’s nodal system is SA node, AV node, bundle of HIS and Purkinje fibers (B-C-A-D)

2. The structure that depolarizes next after the AV node is bundle of HIS.

3. Soon after the onset of ventricular systole the semilunar valves open.

Explanation:

1. The conduction system of the heart -nodal system- is what allows myocardial contraction, which translates into heartbeat and pumping of blood.

This conduction system begins in the sino-atrial node (SA), which is located in the upper portion of the right atrium, and is regulated by the autonomic-sympathetic and parasympathetic nervous system. The impulse generated in SA passes to the atrioventricular node (AV) that is located in the interventricular septum (IVS).From AV, impulse passes to the His-Purkinje system, formed by the bundle of His, which runs along the IVS and is divided into two branches, right and left.Purkinje fibers are born from each of the bundles of His bundle, and are distributed through the right and left ventricles.

2. As a result of the depolarization that occurs in the atrioventricular node - which undergoes a brief interruption in its path - depolarization continues in the bundle of His, which runs through the rest of the interventricular septum to divide into two branches, the right and the left.

The left branch is usually subdivided into three fascicles, the left anterior, left posterior and a central branch. Purkinje fibers are born from each of these branches and fascicles, which stimulate myocardial contraction.

3. Ventricular systole consists of contraction of the myocardium, which leads to boost blood contained in the ventricles to the lungs or general circulation. In this phase of the cardiac cycle, the semilunar valves - which allow access to the pulmonary and aortic arteries - open, which produces the second cardiac noise.

Other events that occur during systole are the increase in ventricular pressure and the closure of the atrioventricular valves (AV), to prevent ventricular blood from returning to the atria.

Learn more:

Event that occurs during systole link

Q1 What is the correct sequence an impulse travels through the four components of the heart’s nodal

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