Exam 3 A&P 2
Trace the pathway of stimulation through the heart. Which of these pathways shows stimulation in the correct order?
AV node, AV bundle, interventricular septum, subendocardial conducting network
Which statement regarding cardiac muscle structure is accurate?
Myofibrils of cardiac muscle tissue vary in diameter and branch extensively.
Adding a chemical that reduces Na+ transport near the sinoatrial (SA) node would have what effect on the heart's intrinsic conducting system?
The SA node would depolarize less quickly, reducing the heart rate.
Which description is INCORRECT for the layers of the heart and its serous membranes?
The epicardium is also considered the parietal pericardium.
When released in large quantities, thyroxine, a thyroid gland hormone, causes a sustained increase in heart rate.
True
Suppose a patient develops a myocardial infarction that disables the sinoatrial node. Would the heart still pump blood to the aorta and the pulmonary trunk?
Yes, because the atrioventricular node will still stimulate ventricular systole.
Which of the following is NOT part of the intrinsic conduction system of the heart?
atrioventricular (AV) valve
Which of the following receive(s) blood during ventricular systole?
both the aorta and pulmonary trunk
The source of blood carried to capillaries in the myocardium would be the ________.
coronary arteries
Which of the following INCREASES stroke volume?
exercise
What is the period during the cardiac cycle when the valves leading to and from the ventricles are completely closed and blood volume in the ventricles remains constant as the walls contract?
isovolumetric contraction phase
Which chambers of the heart contain oxygenated blood?
left atrium and ventricle
Which layer of the heart wall contracts and is composed primarily of cardiac muscle tissue?
myocardium
The left ventricular wall of the heart is thicker than the right wall in order to ________.
pump blood with greater pressure
Into which chamber of the heart do the superior vena cava, inferior vena cava, and coronary sinus return deoxygenated blood?
right atrium
Specifically, what part of the intrinsic conduction system generates the original stimulus that reaches the atrioventricular (AV) node, allowing it to conduct impulses to the atrioventricular bundle?
sinoatrial (SA) node
The anatomy of the intrinsic conduction system causes contraction of the ventricles to begin at the apex and move superiorly. Why is this important?
so blood is forced upward, toward the semilunar valves
If the length of the absolute refractory period in cardiac muscle cells was the same as it is for skeletal muscle cells, ________.
tetanic contractions might occur, which would stop the heart's pumping action
During exercise, which of the following would occur on an electrocardiogram (ECG) compared to an individual at rest?
the time from one R to the R of the next heartbeat would decrease
If we were able to artificially alter the membrane permeability of pacemaker cells so that sodium influx is more rapid, ________.
threshold is reached more quickly and heart rate would increase
At what point in the cardiac cycle is pressure in the ventricles the highest (around 120 mm Hg in the left ventricle)?
ventricular systole
Match the words in the left column to the appropriate blanks in the sentences on the right. Make certain each sentence is complete before submitting your answer. Words can be used more than once.
1. Aortic semilunar valve: Prevents backflow into the left ventricle. 2. Tricuspid valve: Prevents backflow into the right atrium. 3. Mitral (bicuspid) valve: Prevents backflow into the left atrium. 4. Pulmonary semilunar valve: Prevents backflow into the right ventricle. 5. Mitral (bicuspid) valve: Atrioventricular (AV) valve with two flaps. 6. Tricuspid valve: Atrioventricular (AV) valve with three flaps.