The sinoatrial node is the normal pacemaker of the human heart because it:
1. can form action potentials that can spread throughout the rest of the heart
2. depolarizes to its threshold potential before other pacemakers in the heart
3. is located in the top of right atrial wall
4. is most likely to form an ectopic focus
The average life span of human red blood cells is:
1. | 10 days | 2. | 120 days |
3. | 21 days | 4. | three months |
A chest pain or pressure, usually due to not enough blood flow to the heart muscle, is known as:
1. hypoxia | 2. infarction |
3. angina | 4. diaphoresis |
What is the percentage of atrial blood that flows into the ventricles without atrial systole?
1. | 90 | 2. | 70 |
3. | 50 | 4. | 30 |
QRS complexes on the ECG tracings show that:
1. The atria are depolarizing.
2. The ventricles are depolarizing.
3. The ventricles are repolarizing.
4. The heart is at rest.
Pulmonary veins return the oxygenated blood from the lungs to:
1. | right atrium | 2. | left atrium |
3. | right ventricle | 4. | left ventricle |
Erythrocytes in humans are destroyed mainly in:
1. | liver and spleen | 2. | heart and lungs |
3. | bone marrow | 4. | kidney |
The most common WBC under normal physiological conditions are:
1. Neutrophils | 2. Macrophages |
3. Monocytes | 4. Lymphocytes |
The chamber with the thickest musculature in the human heart would be:
1. the right atrium | 2. the left atrium |
3. the left ventricle | 4. the right ventricle |
Sympathetic stimulation would lead to:
1. increased heart rate.
2. increased stroke volume.
3. vasoconstriction in visceral blood vessels.
4. all of the above.