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Arrange these elements of the intrinsic conduction system in the order that a depolarizing impulse travels during a normal heartbeat.

1.SA node 2.Internodal pathways 3.AV node 4.AV Bundle 5.Bundle branches 6.Purkinje fibers

Which of the following heart sounds is associated with final filling of the ventricles?

4th sound, S4

Which of these structures conduct(s) action potentials the slowest?

AV node

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

AV node

In the contractile cells of the heart

Addition of calcium to the cytosol is necessary for contraction

In a cardiac autorhythmic cell, which ion is responsible for the increase in membrane potential from threshold during an action potential?

Ca2+

Which cells act as the heart's pacemaker? Why are they the pacemaker cells?

Cells of the SA node are the usual pacemakers, because they are autorhythmic cells, and set the pace of the heart rate.

Bundle branches

Convey(s) the impulse down the interventricular septum

Purkinje fibers

Convey(s) the impulse throughout the ventricular walls

AV node

Delay(s) occurs here while atria contract

AV bundle

Electrical link(s) between atria and ventricles

Consider three blood vessel segments of equivalent length and diameter: vessels A, B, and C. Pressure at the beginning of each segment is as follows: A) P = 100 mmHg B) P = 80 mmHg C) P = 60 mmHg Pressure at the end of each segment is as follows: A) P = 70 mmHg B) P = 50 mmHg C) P = 30 mmHg Which vessel has the greatest blood flow through the described segment?

Flow rate is the same in all three segments, because all three vessels have the same resistance and the pressure gradient is the same in all three segments: A) ΔP = 100 - 70 = 30 mmHg; B) ΔP = 80 - 50 = 30 mmHg; C) ΔP = 60 - 30 = 30 mmHg.

Why does the pressure in the arteries and arterioles fall as the blood moves away from the heart?

Friction causes a loss of energy. Submit

What is the role of heart valves?

Heart valves ensure one-way flow of blood through the heart chambers.

A patient is given a β1 receptor agonist. What would you expect to find?

Increased heart rate and increased cardiac output

internodal pathways

Link(s) between the SA node and AV node

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

P wave

Identify the portion of the ECG that represents the electrical activity associated with atrial systole.

P wave

Which part of the intrinsic conduction system normally initiates the depolarizing impulse that causes a heartbeat?

SA node

In an ECG, which of the following is the electrical activity associated with ventricular depolarization?

QRS complex

Which of the following have the same polarity as Lead 2?

R wave T wave P wave

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

SA node

SA node

Set(s) the pace for the entire heart

Calcium ions are removed from the sarcoplasm of the cardiac cell by the action of the sarcoplasmic reticulum (SR) Ca2+-ATPase pump and which other mechanism?

Sodium-calcium exchanger on the sarcolemma

Which of the following heart murmurs would be heard during ventricular systole?

Stenotic SL valve

Which of the following pairs is(are) a correct association of electrical activity and resulting mechanical activity of the heart?

T wave : passive filling

In the conducting cells of the heart

T-type voltage gated Ca++ channels allow the pacemaker potential to reach threshold

For what are If channels responsible in cardiac autorhythmic cells?

The pacemaker potential

Through which valve must blood pass as it moves from the right atrium to the right ventricle?

Tricuspid

Blood flows through a vessel at a particular flow rate and velocity. What happens to the velocity of the blood flow through that vessel after it constricts, narrowing its diameter? You may assume that the flow rate is unchanged.

Velocity increases.

Which of the following statements is true?

Velocity of flow would be expected to decrease as the cross sectional area of a blood vessel increases

The QRS complex

is a measure of the electrical activity initiated by the AV node

What does the ECG wave tracing represent?

electrical activity in the heart

When threshold is reached at the SA node (an autorhythmic cell), what channels open causing further depolarization of the membrane?

fast calcium-unlike nerve cells or cardiac muscle cells, fast calcium channels are responsible for the depolarization phase of the autorhythmic cell action potential. When the fast calcium channels open, calcium rushes into the cell making it less negative (or more positive)

Action potentials generated by the autorhythmic cells spread to the contractile cells through what structures in the membrane?

gap junctions-action potentials generated by the autorhythmic cells spread waves of depolarization to contractile cells through gap junctions. If the depolarization causes the contractile cells to reach threshold, they will in turn generate an action potential.

One of the changes that occurs in the pacemaker potential (unstable resting membrane potential) in the SA node (an autorhythmic cell) is a decreased efflux of what ion?

potassium-if there is a decreased efflux of potassium while there is a normal influx of sodium, the inside of the cell would become less negative. Thus, threshold would be reached. The ability of these autorhythmic cells to spontaneously depolarize is what results in the pacemaker potential.

Which chamber receives blood from the superior and inferior vena cavae?

right atrium-the right atrium receives unoxygenated blood from the systemic circuit.

The electrocardiogram represents __________.

the electrical activity of all of the cardiac muscle cells

In order to cause cardiac muscle contraction, the contractile cells must also depolarize. What causes the depolarization of the contractile cells?

the flow of positive ions from the autorhythmic cells (or adjacent cells) brings the membrane to threshold initiating depolarization of the contractile cell.

Which heart chamber receives blood from the pulmonary veins?

the left atrium receives oxygenated blood from the pulmonary veins.

Which chamber pumps oxygenated blood out the aorta to the systemic circuit?

the left ventricle pumps oxygenated blood out the aorta to the entire body (systemic circuit).

Which heart chamber pumps unoxygenated blood out the pulmonary trunk?

the right ventricle pumps unoxygenated blood out the pulmonary trunk to the lungs.

The heart is actually (one, two, or three) pumps?

two pumps-the right side of the heart pumps to/from the lungs (pulmonary circuit) and the left side of the heart pumps to/from the rest of the body (the systemic circuit).

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

ventricular depolarization

Repolarization of an autorhythmic cell is due to the opening of which channels?

voltage-gated potassium channels-opening of voltage-gated potassium channels causes positive potassium ions to move out of the cell. This efflux of potassium causes the cell to become more negative inside thus, repolarizing the cell.