Anatomy And Physiology Advanced - Qp6

The heart usually beats between 65 and 75 times per minute but may be much lower in people who are trained athletes.

The pulmonary veins carry oxygenated blood from the lungs back to the heart. This oxygen-rich blood then flows into the left atrium of the heart. From the left atrium, the blood is pumped into the left ventricle and then to the rest of the body. Therefore, the statement that the blood in the pulmonary veins flows into the left atrium of the heart is true.

The sino-atrial node is known as the heart's own pacemaker because it is responsible for initiating the electrical signals that regulate the heart's rhythm and coordinate its contractions. Located in the right atrium, the sino-atrial node generates an electrical impulse that spreads throughout the atria, causing them to contract. This impulse then travels to the atrio-ventricular node, which further relays the signal to the ventricles, resulting in their contraction. The sino-atrial node plays a crucial role in maintaining the heart's regular rhythm and ensuring efficient blood circulation.

The statement is true because there are indeed many circumstances in which we are conscious of an increased heart rate. Vigorous exercise, powerful emotions, and sexual arousal are all examples of situations that can cause our heart rate to increase. These activities can stimulate the sympathetic nervous system, leading to an elevated heart rate as the body prepares for increased physical exertion or heightened emotional states.

Blood flow is not the force exerted by the blood against the walls of the blood vessels. Blood flow refers to the movement of blood through the circulatory system, which is driven by the pumping action of the heart. The force exerted by the blood against the walls of the blood vessels is known as blood pressure.

The pericardium is a double-layered sac that surrounds and protects the heart. It consists of an outer fibrous layer and an inner serous layer. The fibrous layer is tough and inelastic, while the serous layer is thin and smooth. The purpose of the pericardium is to anchor the heart in place and prevent it from overfilling with blood. It does not allow the heart to move freely inside the inner protective layer. Therefore, the statement is false.

The sympathetic nervous system is responsible for the "fight or flight" response in the body, which speeds up various processes such as heart rate, breathing rate, and blood flow to muscles. On the other hand, the parasympathetic nervous system is responsible for the "rest and digest" response, which slows down processes such as heart rate and digestion. Therefore, it is true that the sympathetic nervous system speeds up most processes, while the parasympathetic nervous system slows them down.