Chapter 20: Part 5

Cardiac muscle cells and skeletal muscle cells differ in a few ways. Which of the following is not one of them? A) Cardiac muscle cells are smaller in size. B) Cardiac muscle cells have a single, centered nucleus. C) Cardiac muscle cells branch. D) Skeletal muscle cells lack intercalated discs. E) Cardiac muscle cells lack transverse tubules.

Cardiac muscle cells lack transverse tubules.

Depolarization of the atria corresponds to the EKG's A) P wave. B) QRS complex. C) QT interval. D) T wave. E) S-T segment.

P wave.

Depolarization of the ventricles is represented on an electrocardiogram by the A) P wave. B) T wave. C) S wave. D) QRS complex. E) PR complex.

QRS complex.

As a result of the long refractory period in the cardiac action potential, cardiac muscle cannot exhibit A) tonus. B) treppe. C) tetany. D) recruitment. E) fatigue.

tetany.

If the connection between the SA node and AV node becomes blocked, A) the ventricles will beat faster. B) the ventricles will beat more slowly. C) the ventricular beat will remain unchanged. D) cardiac output will increase. E) the atria will contract more forcefully.

the ventricles will beat more slowly.

Tetanic muscle contractions don't occur in a normal cardiac muscle because A) cardiac muscle tissue contracts on its own. B) neural stimulation is lacking. C) the refractory period lasts until the muscle relaxes. D) the refractory period ends before the muscle reaches peak tension. E) potassium channels outnumber sodium channels.

the refractory period lasts until the muscle relaxes.

The normal pacemaker of the heart is located in A) the Purkinje fibers. B) the sinoatrial node. C) the atrioventricular node. D) the wall of the left ventricle. E) both the left and right ventricles.

the sinoatrial node.

The T wave on an ECG tracing represents A) atrial depolarization. B) atrial repolarization. C) ventricular depolarization. D) ventricular repolarization. E) ventricular contraction.

ventricular repolarization.

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 A) 1, 4, 3, 2, 5. B) 3, 2, 4, 5, 1. C) 3, 5, 4, 2, 1. D) 4, 3, 2, 5, 1. E) 4, 2, 3, 5, 1.

4, 3, 2, 5, 1. SA node AV node AV bundle bundle branches Purkinje fibers

Pacemaker cells isolated from the SA node generate action potentials at ________ beats per minute. A) 20-40 B) 40-60 C) 80-100 D) 100-140 E) 140-180

80-100

________ is to slow heart rate as ________ is to fast heart rate. A) Tachycardia; bradycardia B) Bradycardia; cardiomyopathy C) Bradycardia; tachycardia D) Cardiac tamponade; bradycardia E) Angina; infarction

Bradycardia; tachycardia

The long plateau phase of the cardiac muscle action potential is due to A) movement of fewer sodium ions across the cell membrane. B) calcium channels remaining open. C) increased membrane permeability to potassium ion. D) decrease in the amount of calcium diffusing across the membrane. E) increased membrane permeability to sodium ions.

calcium channels remaining open.

The P wave of the electrocardiogram is a signal from A) the SA node. B) depolarization of the AV node. C) depolarization of the atria. D) repolarization of the atria. E) depolarization of the ventricles.

depolarization of the atria.

In cardiac muscle, the fast depolarization phase of the action potential is the result of A) increased membrane permeability to sodium ions. B) increased membrane permeability to potassium ions. C) decreased membrane permeability to calcium ions. D) decreased membrane permeability to sodium ions. E) increased membrane permeability to chloride ions.

increased membrane permeability to sodium ions.

Abnormally slow depolarization of the ventricles would most change the shape of the ________ in an ECG tracing. A) P wave B) T wave C) QRS complex D) P-R interval E) R-T interval

QRS complex

If there is a complete block between the SA node and the AV node, how would the ECG be affected? A) The P-R interval will be shorter. B) The QRS duration will be longer. C) There will be much bigger P waves. D) The ventricles will stop beating. E) The rate of P waves will be faster than the rate of QRS complexes.

The rate of P waves will be faster than the rate of QRS complexes.

Which of the following statements is true regarding cardiac muscle? A) Its main source of ATP production is glycogen. B) The actin and myosin myofilaments are not arranged in sarcomeres. C) Cardiac muscle preferentially metabolizes anaerobically. D) There are specialized gap junctions in cardiac muscle not found in skeletal or smooth muscles. E) Cardiac muscle goes into sustained contractions faster than skeletal muscle.

There are specialized gap junctions in cardiac muscle not found in skeletal or smooth muscles.

In cardiac muscle, A) calcium ions are not released from the sarcoplasmic reticulum. B) calcium ions do not bind to troponin molecules. C) calcium ions play no role in the process of contraction. D) about 20 percent of the calcium ion required for contraction comes from outside the cell. E) calcium ions play an important role in repolarizing the membrane after the depolarization phase.

about 20 percent of the calcium ion required for contraction comes from outside the cell.

If the pacemaker cells in the SA node become more permeable to potassium ions, the A) heart rate will increase. B) heart rate will decrease. C) cells will depolarize. D) cells will hyperpolarize. E) heart rate will decrease and cells will hyperpolarize.

heart rate will decrease and cells will hyperpolarize.

Analysis of the electrocardiogram can reveal all of the following except A) heart rate. B) stroke volume. C) the condition of the conducting system. D) the effects of drugs and poisons. E) the duration of the ventricular action potential.

stroke volume.