Anatomy And Physiology: The Heart Pt. 2

The cardiac output (CO) is a measure of the amount of blood that the heart pumps in one minute. It is calculated by multiplying the stroke volume (SV), which is the amount of blood pumped with each heartbeat, by the heart rate (HR), which is the number of times the heart beats per minute. During exercise, both the stroke volume and heart rate increase, leading to an increase in the cardiac output. Therefore, all of the given statements about the cardiac output are true.

Isovolumetric contraction and isovolumetric relaxation both occur during the cardiac cycle and involve the closure of valves. During isovolumetric contraction, the semilunar valves are closed to prevent blood from flowing back into the atria, while the atrioventricular valves are also closed to prevent blood from flowing back into the atria. Similarly, during isovolumetric relaxation, the semilunar valves remain closed to prevent blood from flowing back into the ventricles, and the atrioventricular valves also remain closed. Additionally, in both processes, the volume of blood in the ventricles remains the same, hence all of the above statements are true.

During ventricular ejection (systole), the semilunar valves are open, allowing blood to be pumped out of the ventricles and into the arteries. The ventricles are contracting, generating enough pressure to overcome the resistance in the arteries and push the blood forward. This phase marks the peak of the cardiac cycle where the ventricles are forcefully ejecting blood, resulting in systolic pressure.

The correct answer is "increases intracellular Ca2+". This is because increasing intracellular Ca2+ levels can help improve the force of contraction in the heart. Ca2+ is essential for the process of muscle contraction, including the contraction of cardiac muscle. By increasing intracellular Ca2+ levels, the heart muscle can generate more force during contraction, which can help improve cardiac output and overall heart function.

The T wave of an ECG represents the repolarization of the ventricles. After the contraction phase (depolarization) of the ventricles, they need to reset their electrical state to prepare for the next heartbeat. This repolarization is represented by the T wave on the ECG. It shows that the ventricles are undergoing a recovery phase and getting ready for the next cycle of contraction and relaxation.

As the ventricles begin to contract, the pressure inside the ventricles will increase. This increased pressure will cause the atrioventricular valves (also known as the mitral and tricuspid valves) to close. This closure prevents the backflow of blood from the ventricles into the atria. Therefore, the atrioventricular valves will close first before any other event mentioned in the options.

The heart changes pressure in order to produce flow by contracting to increase pressure in a chamber. When the heart contracts, it squeezes the blood, increasing the pressure inside the chamber. This increased pressure forces the blood to flow out of the chamber and into the next part of the circulatory system.

A decrease in stroke volume means that the amount of blood pumped out of the heart with each heartbeat is reduced. This would result in a decrease in cardiac output, as cardiac output is the total amount of blood pumped by the heart per minute. If there is no change in heart rate, it means that the number of heartbeats per minute remains the same. Therefore, the combination of a decrease in stroke volume and no change in heart rate would definitely cause a decrease in cardiac output.

The first sound of the heart is caused by the closing of the bicuspid valve. When the ventricles contract, the bicuspid valve, also known as the mitral valve, closes to prevent the backflow of blood into the atria. This closure creates a sound known as the first heart sound or "lub" sound. It marks the beginning of systole, the phase of the cardiac cycle where the heart is contracting and pumping blood out to the body.

The P wave on an ECG represents the depolarization, or contraction, of the atria. During this time, the electrical signals in the heart cause the atria to contract and pump blood into the ventricles. This depolarization is an important step in the overall electrical activity of the heart and is recorded as a small upward deflection on the ECG.

The correct answer is that flow will increase if the difference in pressure between two points increases. This is because flow is directly proportional to the pressure difference. When the pressure difference increases, it creates a greater force or driving pressure for the fluid to flow, resulting in an increase in flow rate.

At the end of isovolumetric relaxation, the ventricles have the smallest volume of blood. During this phase, the ventricles are in a relaxed state, and the pressure in the ventricles is low. The atrioventricular valves are closed, preventing blood from entering the ventricles. As a result, the ventricles are not filling with blood, leading to the smallest volume of blood in the ventricles at this point.

When the pressure in the aorta is higher than the pressure in the left ventricle, it indicates that the blood has been pumped out of the left ventricle and into the aorta. This increase in pressure causes the aortic semilunar valve to close, preventing the backflow of blood from the aorta back into the left ventricle. This closure ensures that blood flows in the correct direction, from the heart to the rest of the body, maintaining the efficiency of the circulatory system.

Contractility refers to the force of contraction of the heart muscle. It is the ability of the heart to contract and pump blood effectively. An increase in contractility leads to an increase in stroke volume, which is the amount of blood pumped out of the heart with each heartbeat. Therefore, contractility directly influences stroke volume.

Cor pulmonale is a type of congestive heart failure that originates from obstruction in the pulmonary circulation. This condition occurs when the right side of the heart becomes enlarged and weakened due to increased pressure in the lungs. It is commonly caused by chronic lung diseases such as chronic obstructive pulmonary disease (COPD) or pulmonary embolism. The obstruction in the pulmonary circulation leads to increased resistance and pressure in the right side of the heart, eventually causing it to fail in pumping blood effectively.

Hypotension decreases afterload. Afterload refers to the resistance that the heart has to overcome in order to pump blood out of the left ventricle and into the systemic circulation. Hypotension, or low blood pressure, reduces the resistance against which the heart has to pump, thereby decreasing afterload. This allows the heart to pump blood more easily and efficiently. Increased venous return and hyperkalemia do not directly affect afterload.

When blood pressure in the aorta or carotid arteries suddenly increases, the baroreflex mechanism would activate to restore blood pressure. This reflex involves sensing the increased pressure and sending signals to the brain. In response, the brain would initiate a decrease in heart rate through the parasympathetic nervous system. This decrease in heart rate would help to lower blood pressure and restore it to normal levels.

The volume of blood ejected by the ventricle during one cardiac cycle is called stroke volume. It represents the amount of blood pumped out of the heart with each contraction. It is an important measure of cardiac function and is calculated by subtracting the end-diastolic volume from the end-systolic volume. Cardiac output, on the other hand, refers to the total volume of blood pumped by the heart in one minute and is calculated by multiplying the stroke volume by the heart rate.

If venous return decreases, it means that less blood is returning to the heart from the veins. This would result in a decrease in the amount of blood available to fill the ventricles during diastole, leading to a decrease in preload. Since preload is the amount of blood in the ventricles before contraction, a decrease in preload would cause the ventricles to contract with less force during systole. Therefore, the correct answer is that the ventricles would contract less forcefully.

Ventricular hypertrophy is a long-term adjustment to exercise that an athlete might expect to see. This refers to an increase in the size and strength of the heart's ventricles, which are responsible for pumping blood to the rest of the body. With regular exercise, the heart adapts by growing larger and more efficient, allowing it to pump more blood with each beat. This adaptation helps to improve athletic performance and endurance. Lower stroke volume and higher resting heart rate are not long-term adjustments to exercise, making them incorrect options.

During exercise, the body's short-term response includes various changes to adapt to the increased demand for oxygen and energy. One of these responses is the activation of proprioreceptors, which are sensory receptors located in muscles, tendons, and joints. These proprioreceptors signal the cardiac center in the brain, leading to an increase in heart rate. This increased heart rate helps to deliver more oxygen and nutrients to the working muscles. Therefore, the statement "proprioreceptors signal the cardiac center which increases heart rate" accurately describes the short-term response of the body to exercise.

When arteries are clogged, it leads to increased afterload. Afterload refers to the force that the heart needs to generate in order to pump blood out of the heart and into the arteries. When the arteries are clogged, the heart needs to work harder to overcome the increased resistance and push blood through the narrowed arteries. This increased afterload results in reduced flow of blood from the heart, as the heart is unable to pump blood effectively against the increased resistance caused by the clogged arteries.

The second heart sound is associated with the closing of the atrioventricular valves. This occurs when the pressure in the ventricles becomes lower than the pressure in the great arteries, causing the valves to close.

During the spread of depolarization through the AV Node, the atria are contracting. This is because the AV Node is responsible for transmitting electrical signals from the atria to the ventricles, causing them to contract. Therefore, while depolarization is occurring in the AV Node, the atria are also contracting in order to pump blood into the ventricles.

B-Blockers are drugs that block the effects of norepinephrine on B-receptors, which are found in the heart. By blocking these receptors, B-Blockers prevent sympathetic stimulation of the heart rate (HR). This is beneficial for patients with weak hearts because it helps to reduce the workload on the heart and improve its efficiency. Therefore, the statement "Patients with weak hearts are sometimes given drugs called B-Blockers which prevents sympathetic stimulation of HR" is true.

If the right ventricle had lower output than the left, it would result in systemic edema. This is because the right ventricle is responsible for pumping blood to the lungs to receive oxygen, and if it has a lower output, there would be a buildup of fluid in the systemic circulation, leading to edema. Increased afterload for the right ventricle and right ventricular hypertrophy may also occur as compensatory mechanisms, but the primary consequence would be systemic edema.

Increased afterload refers to an increase in the resistance that the heart has to overcome in order to pump blood out of the left ventricle and into the systemic circulation. This can be caused by conditions such as hypertension or aortic stenosis. When afterload increases, the heart has to work harder to overcome this resistance, which can lead to a decrease in stroke volume. Stroke volume is the amount of blood pumped out of the heart with each contraction, so if afterload increases, the heart may not be able to pump as much blood out, resulting in a decrease in stroke volume.

This answer correctly identifies unbalanced ventricular output as an example of positive feedback in the circulatory system. Positive feedback occurs when a change in a system amplifies the original change, leading to further changes in the same direction. In this case, unbalanced ventricular output causes one side of the heart to fail, which then leads to failure of the other side of the heart, resulting in a continuous cycle of worsening heart failure.

The second sound of the heart is caused by the closure of the aortic semilunar valves. When the heart contracts and pumps blood out of the left ventricle into the aorta, the aortic semilunar valves open to allow the blood flow. Once the blood is ejected, the valves quickly close to prevent backflow into the ventricle. This closure creates the second sound, known as the "dub" sound, which can be heard during a heartbeat.

Hypertension is an example of increased preload. Preload refers to the amount of blood that fills the ventricles of the heart during diastole, before it contracts. In hypertension, there is an increased resistance to blood flow, causing the heart to work harder to pump blood against this resistance. This increased workload leads to an increase in the amount of blood filling the ventricles during diastole, resulting in increased preload.

MAP stands for Mean Arterial Pressure, which refers to the average pressure in the arteries over time. The reason why the formula for calculating MAP is 2/3 Diastolic and 1/3 Systolic is because the heart spends more time in diastole (relaxation phase) than in systole (contraction phase). Since diastole lasts longer, it contributes more to the overall average pressure in the arteries. Therefore, the formula reflects this by giving diastolic pressure more weight (2/3) and systolic pressure less weight (1/3) in calculating the MAP.

When the right ventricle has a higher output than the left ventricle, it means that more blood is being pumped into the pulmonary circulation compared to the systemic circulation. This can lead to an imbalance in the pressures within the heart and lungs. As a result, fluid may start to accumulate in the pulmonary tissue, causing pulmonary congestion or edema. This can lead to symptoms such as shortness of breath, coughing, and difficulty breathing.

When the left ventricle has a higher output than the right ventricle, it means that the left side of the heart is pumping more blood into the systemic circulation than the right side is receiving from the body. This can lead to an imbalance in the circulation, causing fluid to accumulate in the systemic tissues. This fluid buildup can result in edema, causing swelling and discomfort in various parts of the body.