Circulatory Physiology - AP Biology

The chordae tendinae (tendinous chords or heart strings) are physical structures located in the heart lumen that connect the muscular wall of the heart to the tricuspid and mitral valves via papillary muscles.

The other answer options are examples of cell bundles and tissues that orchestrate the electrical conduction through the heart. Signals begin at the sinoatrial node and transition to the atrioventricular node. They then pass through the atrioventricular bundle (or bundle of His) to the purkinje fibers, which coordinate simultaneous ventricular contraction.

The sinoatrial node is responsible for initiating the contraction of the heart. Depolarization of the sinoatrial node coincides with atrial contraction. The depolarization travels very quickly to the atrioventricular node during this period. The atrioventricular node delays the spread of the impulse, preventing it from triggering ventricular contraction. This time delay allows the atria to fill the ventricles with blood before the impulse causes the ventricles to contract. Without this delay, an inadequate amount of blood would be pumped from the ventricles.

The vagus nerve is responsible for slowing down the heart rate, and is able to "override" the faster, natural pace of the sinoatrial node. When the vagus nerve is severed from the heart, the heart will pump at the pace of the SA node.

Note that innervation is not necessary for the heart to continue beating; it is self-sustaining, but can be affected by innervation from the vagus nerve.

The chordae tendinae (tendinous chords or heart strings) are physical structures located in the heart lumen that connect the muscular wall of the heart to the tricuspid and mitral valves via papillary muscles.

The other answer options are examples of cell bundles and tissues that orchestrate the electrical conduction through the heart. Signals begin at the sinoatrial node and transition to the atrioventricular node. They then pass through the atrioventricular bundle (or bundle of His) to the purkinje fibers, which coordinate simultaneous ventricular contraction.

The sinoatrial node is responsible for initiating the contraction of the heart. Depolarization of the sinoatrial node coincides with atrial contraction. The depolarization travels very quickly to the atrioventricular node during this period. The atrioventricular node delays the spread of the impulse, preventing it from triggering ventricular contraction. This time delay allows the atria to fill the ventricles with blood before the impulse causes the ventricles to contract. Without this delay, an inadequate amount of blood would be pumped from the ventricles.

The vagus nerve is responsible for slowing down the heart rate, and is able to "override" the faster, natural pace of the sinoatrial node. When the vagus nerve is severed from the heart, the heart will pump at the pace of the SA node.

Note that innervation is not necessary for the heart to continue beating; it is self-sustaining, but can be affected by innervation from the vagus nerve.

The chordae tendinae (tendinous chords or heart strings) are physical structures located in the heart lumen that connect the muscular wall of the heart to the tricuspid and mitral valves via papillary muscles.

The other answer options are examples of cell bundles and tissues that orchestrate the electrical conduction through the heart. Signals begin at the sinoatrial node and transition to the atrioventricular node. They then pass through the atrioventricular bundle (or bundle of His) to the purkinje fibers, which coordinate simultaneous ventricular contraction.

The sinoatrial node is responsible for initiating the contraction of the heart. Depolarization of the sinoatrial node coincides with atrial contraction. The depolarization travels very quickly to the atrioventricular node during this period. The atrioventricular node delays the spread of the impulse, preventing it from triggering ventricular contraction. This time delay allows the atria to fill the ventricles with blood before the impulse causes the ventricles to contract. Without this delay, an inadequate amount of blood would be pumped from the ventricles.

The vagus nerve is responsible for slowing down the heart rate, and is able to "override" the faster, natural pace of the sinoatrial node. When the vagus nerve is severed from the heart, the heart will pump at the pace of the SA node.

Note that innervation is not necessary for the heart to continue beating; it is self-sustaining, but can be affected by innervation from the vagus nerve.

The chordae tendinae (tendinous chords or heart strings) are physical structures located in the heart lumen that connect the muscular wall of the heart to the tricuspid and mitral valves via papillary muscles.

The other answer options are examples of cell bundles and tissues that orchestrate the electrical conduction through the heart. Signals begin at the sinoatrial node and transition to the atrioventricular node. They then pass through the atrioventricular bundle (or bundle of His) to the purkinje fibers, which coordinate simultaneous ventricular contraction.

The sinoatrial node is responsible for initiating the contraction of the heart. Depolarization of the sinoatrial node coincides with atrial contraction. The depolarization travels very quickly to the atrioventricular node during this period. The atrioventricular node delays the spread of the impulse, preventing it from triggering ventricular contraction. This time delay allows the atria to fill the ventricles with blood before the impulse causes the ventricles to contract. Without this delay, an inadequate amount of blood would be pumped from the ventricles.

Erythrocytes and leukocytes are both produced and mature in bone marrow, with the exception of T cells, a type of white blood cell that matures in the thymus. Unlike leukocytes, red blood cells contain no nuclei or mitochondria, which could interfere with transporting oxygen, carbon dioxide, and nutrients.

Because Jack has blood type B, he will form antibodies against blood types A and AB, as they contain a foreign antigen that his body will reject. Furthermore, he cannot accept any blood types that are Rh+, as this antigen will also seem foreign to his body. He can thus only accept from the blood types B- and O- (the universal donor type).

Arteries carry blood away from the heart, while veins transport blood towards the heart. Because the pulmonary arteries transport blood from the right ventricle towards the lungs to exchange carbon dioxide for oxygen, they contain deoxygenated blood.

The aorta, however, transports oxygenated blood from the left ventricle to the rest of the body for circulation. The pulmonary vein carries oxygenated blood from the lungs to the left ventricle and the vena cavae return deoxygenated blood to the right atrium.

Arteries have thick, muscular walls that allow for constriction and flow direction, while veins have thin walls to carry blood.

Capillaries have extremely thin walls to allow exchange of oxygen, carbon dioxide, and nutrients with tissues, resulting in both oxygenated and deoxygenated blood in these vessels. Pressure in the arteries is always higher than in veins so that blood can be continuously pushed forward, negating the need for valves to prevent backflow. Such valves are present in veins and help to counteract gravity when returning blood to the heart.

Hemoglobin will have varying affinity for oxygen depending on its environment. For example, hemoglobin will have a very high affinity for oxygen in the lungs, where most oxygen is loaded onto the hemoglobin molecules. Once hemoglobin goes to the tissues of the body, there is a much lower oxygen tension. This decreased oxygen causes hemoglobin to have a lower affinity for oxygen and release the oxygen to the tissues.

Hemoglobin is comprised of two alpha and two beta proteins and uses iron to facilitate oxygen transportation. Some variations of hemoglobin, such as fetal hemoglobin, contain gamma proteins that changes the shape of the protein. Consistent with the theme that structure determines function, fetal hemoglobin has a higher affinity for oxygen than does adult hemoglobin. This is necessary since fetuses lack lungs; they obtain all of their oxygen from the hemoglobin of their mothers.

Capillaries are the smallest blood vessels, which allow transport of oxygen and other small molecules. There are capillaries involved in gas exchange in the lungs, but it does not involve transfer of oxygen to the cells. Rather, it involves uptake of oxygen by red blood cells from the air inside the alveoli, and removal of carbon dioxide from the blood into the air in the alveoli to be exhaled. All other blood vessels have walls that are too thick to allow transport of any substances across them. The heart is the muscular pump of the circulatory system, which provides the pressure required to drive blood flow.

Erythrocytes and leukocytes are both produced and mature in bone marrow, with the exception of T cells, a type of white blood cell that matures in the thymus. Unlike leukocytes, red blood cells contain no nuclei or mitochondria, which could interfere with transporting oxygen, carbon dioxide, and nutrients.