anatomy: heart 2 homework questions

The portion of the tracing of an electrocardiogram, ECG, that represents ventricular depolarization is the __________.

QRS complex

Which part of the conduction system initiates the depolarizing impulse, which spreads throughout the heart?

SA node

The heart is innervated by ________ nerves.

both parasympathetic and sympathetic

The following are structural components of the conducting system of the heart. 1. Purkinje fibers 2. AV bundle 3. AV node 4. SA node 5. bundle branches The sequence in which excitation would move through this system is which of the following?

4, 3, 2, 5, 1

Compute Joe's stroke volume if his end-systolic volume (ESV) is 40 mL and his end-diastolic volume (EDV) is 125 mL.

85 mL

Which part of the intrinsic conduction system delays the impulse briefly before it moves on to the ventricles?

AV node

What effect would an increase in venous return have on the stroke volume? An increase in venous return would fill the ventricles with more blood, increasing sarcomere length, which would increase the stroke volume. An increase in venous return would fill the ventricles with less blood, decreasing sarcomere length, which would increase the stroke volume. An increase in venous return would fill the ventricles with less blood, decreasing sarcomere length, which would decrease the stroke volume. An increase in venous return would fill the ventricles with less blood, increasing sarcomere length, which would decrease the stroke volume. An increase in venous return would fill the ventricles with more blood, decreasing sarcomere length, which would decrease the stroke volume.

An increase in venous return would fill the ventricles with more blood, increasing sarcomere length, which would increase the stroke volume.

Define autorhythmicity

Autorhythmicity is the ability of the heart to contract without neural or hormonal stimulation.

Contraction of the atria results from which wave of depolarization on the ECG tracing?

P wave

What structure carries the electrical signal from the septum of the heart through the ventricular myocardium?

Purkinje fibers

If the cells of the SA node failed to function, how would the heart rate be affected? The heart would stop beating because the SA node was not acting as the pacemaker. The heart would beat slower because the AV node would be the pacemaker. The heart would beat faster because the AV node would be the pacemaker. The heart would beat faster because the inherent rate of myocardial depolarization is faster than the SA node pacemaker. The heart would go into an arrhythmia because the Purkinje fibers would try to be the pacemaker.

The heart would beat slower because the AV node would be the pacemaker.

Cardiac output is increased by increased stroke volume. increased end-diastolic volume. more sympathetic stimulation. All of the answers are correct. None of the answers is correct.

all of the answers are correct

What electrolyte (ion) is responsible for the plateau in the cardiac action potential?

calcium

The first heart sound ("lubb") is associated with

closing of the mitral valve

What does the ECG wave tracing represent?

electrical activity in the heart

The ________ is the volume of blood in a ventricle at the beginning of systole.

end-diastolic volume

The ________ is the amount of blood in a ventricle after it has contracted and before it begins to refill.

end-systolic volume

Pacemaker cells in the SA node generate action potentials that spread to the myocardium. have an action potential identical to contractile cardiac muscle cells. are located in the left atrium. have a well-defined resting potential. are highly contractile.

generate action potentials that spread to the myocardium.

Caffeine has effects on conducting cells and contractile cells that are similar to those of NE. What effect would drinking large amounts of caffeinated beverages have on the heart rate?

heart rate would increase

Which of the following would decrease heart rate? increased sympathetic stimulation of SA node increased parasympathetic stimulation of nodal fibers. faster depolarization of the pacemaker potential increased levels of norepinephrine and/or epinephrine decreased parasympathetic stimulation of nodal fibers

increased parasympathetic stimulation of nodal fibers.

Heart rate is controlled by neurons of the cardiovascular center located in the

medulla oblongata.

The volume of blood ejected from each ventricle during a contraction is called the

stroke volume.

The normal pacemaker of the heart is located in

the sinoatrial node

The amount of blood returning to the heart is the

venous return

What does the QRS complex represent in the ECG wave tracing?

ventricular depolarization