Heart Flashcards
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.
C) the refractory period lasts until the muscle relaxes.
When the semilunar valves close, the AV valves then A) close. B) open. C) make the third heart sound. D) contract. E) prolapse.
B) open.
The pulmonary semilunar valve prevents backward flow into the A) aorta. B) pulmonary trunk. C) pulmonary veins. D) right ventricle. E) left atrium.
D) right ventricle.
The \_\_\_\_\_\_\_\_ valve prevents backward flow into the left atrium. A) semicaval B) semilunar C) bicuspid D) tricuspid E) pulmonic
C) bicuspid
Compared to the right ventricle, the left ventricle has all the following characteristics, except that it
A) has a thicker wall.
B) is round in cross section.
C) pumps a greater volume.
D) works harder.
E) produces about four to six times more pressure when it contracts.
C) pumps a greater volume.
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.
A) increased membrane permeability to sodium ions.
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.
B) calcium channels remaining open.
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.
B) the sinoatrial node.
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
C) 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.
C) tetany.
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.
E) heart rate will decrease and cells will hyperpolarize.
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.
B) the ventricles will beat more slowly.
The following are structural components of the conducting system of the heart.
- Purkinje fibers
- AV bundle
- AV node
- SA node
- 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.
D) 4, 3, 2, 5, 1.
The P wave of the electrocardiogram is a signal from A) depolarization of the SA node. B) depolarization of the AV node. C) depolarization of the atria. D) repolarization of the atria. E) depolarization of the ventricles.
C) depolarization of the atria.
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.
E) The rate of P waves will be faster than the rate of QRS complexes.
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.
D) QRS complex.