Circulatory System - 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.

When blood enters the heart from systemic circulation, it is first collected in the right atrium. It then passes through the tricuspid valve into the right ventricle. To understand where the blood travels next, we must remember that this blood is deoxygenated after its passage through the body; it must pass to the lungs for oxygenation. It does so by entering the pulmonary arteries, which carry the blood away from the heart to the lungs. The pulmonary veins later return the oxygenated blood to the left side of the heart.

Gap junctions allow the same action potential to be experienced by multiple neighboring cardiac muscle cells via electrical synapses. This simultaneous electrical stimulus allows for a more unified and powerful contraction by the heart.

Intercalated discs, a unique structure to cardiac muscle, also play a key role in synchronizing contraction.

The left ventricle is responsible for pumping blood to all body tissues. Because it needs to pump blood a farther distance than the right ventricle (which pumps blood to the lungs), it requires a thicker myocardial wall. This provides it with a more powerful contraction in order to send blood throughout the body. The left ventriclar wall is approximately three times thicker than the right ventricular wall.

The atria generally have the thinnest myocardium, as they are only responsible for receiving blood and transferring it to the ventricles.

A centrifuge will organize a solution into distinct sections, separating them based on their density. The least dense sections will rise to the top, while the most dense compounds will settle at the bottom. Plasma is the least dense section, so it will rise to the top section in the tube. It will be followed by the buffy coat, and the dense red blood cells will settle at the bottom of the tube.

Plasma is composed mostly of water and proteins. The buffy coat contains most white blood cells and platelets.

The foramen ovale is needed to shunt blood away from the lungs, which are still developing in the fetus. The ductus venosus connects the umbilical vein to the inferior vena cava, while the ductus arteriosus connects the pulmonary artery to the aorta. The pulmonic semilunar valve is used in developed circulatory systems between the right ventricle and the pulmonary artery.

The major function of heart valves between the chambers of the heart is to restrict blood flow to one direction. This unidirectional flow prevents backflow and mixing of blood between chambers. This allows blood to deliver nutrients and oxygen to the peripheral tissues, return carbon dioxide to the lungs, become reoxygenated in the lungs, and maintain the circulatory system cycle without traveling backward at any point in the process. The patterns of valve opening and closing ensure that the contraction of a chamber will only expel blood in one direction, rather than allowing it to exit from both opening in the chamber.

The amount of pumped blood, also known as cardiac output, is controlled by the strength and rate of heart contractions. Since the heart valves are not constructed from muscle, they are unable to contract and propel blood. The valves are passive structures composed of connective tissue.

The atria and ventricles of the heart are separated by two valves, one on each side of the heart. The left atrium and left ventricle is separated by the mitral valve, also known as the bicuspid valve. The right atrium and right ventricle is separated by the tricuspid valve, named for its three flaps that work together to form the valve.

The semilunar valves separate the aorta from the left ventricle and the pulmonary artery from the right ventricle. They are commonly called the "aortic valve" and "pulmonary valve."

The right atrium receives blood that is returning to the heart from the body. The vena cavae are responsible for collecting the blood from the rest of the body and depositing it in this heart chamber. The superior vena cava collects blood from the head and upper extremities, while the inferior vena cava collects blood from the lower trunk and lower extremities.

The aorta is the artery that exits the left ventricle to deliver blood back to the body's tissues. The carotid artery carries blood to the head; the left branch is derived from the aorta, while the right branch is derived from the brachiocephalic artery.