A&p 2 The Heart

Heart rate is primarily influenced by factors such as age, gender, and body temperature. Skin color, on the other hand, does not directly impact heart rate. While certain medical conditions may cause changes in skin color, these changes do not have a direct effect on the heart rate. Therefore, skin color is not considered a factor that influences heart rate.

The left ventricular wall of the heart is thicker than the right wall in order to pump blood with greater pressure. The left ventricle is responsible for pumping oxygenated blood to the entire body, while the right ventricle pumps deoxygenated blood to the lungs. Since the left ventricle has to generate enough force to pump blood throughout the body, its wall is thicker to provide the necessary strength and contractile power. This allows the left ventricle to pump blood with greater pressure, ensuring that oxygenated blood reaches all the organs and tissues efficiently.

If cardiac muscle is deprived of its normal blood supply, damage would primarily result from decreased delivery of oxygen. The cardiac muscle requires a constant supply of oxygen to function properly and produce energy through aerobic respiration. Without sufficient oxygen, the cardiac muscle cells cannot generate enough ATP to sustain their metabolic activities, leading to cell dysfunction and damage. This can ultimately result in conditions such as myocardial infarction or heart attack.

Hepatic portal circulation is the correct answer because it refers to the circulatory route that carries blood from the digestive organs to the liver for processing and detoxification. This circulation allows the liver to regulate the levels of nutrients, hormones, and toxins in the blood before it is distributed to the rest of the body. Pulmonary circulation refers to the flow of blood between the heart and the lungs, coronary circulation refers to the blood flow within the heart muscle, and cerebral circulation refers to the blood supply to the brain.

The correct answer is papillary muscles. The papillary muscles are small muscle masses that are attached to the chordae tendineae, which are fibrous cords that connect the papillary muscles to the cusps of the atrioventricular valves (mitral and tricuspid valves). The contraction of the papillary muscles helps to prevent the valves from inverting or prolapsing during ventricular contraction, ensuring the proper flow of blood through the heart. The trabeculae carneae are irregular muscular ridges on the internal walls of the ventricles, the pectinate muscles are muscular ridges found in the atria, and the venae cavae are large veins that return deoxygenated blood to the heart.

Arteries are blood vessels that carry blood away from the heart to various parts of the body. They play a crucial role in the circulatory system by transporting oxygenated blood, nutrients, and hormones to tissues and organs. Unlike veins, arteries do not contain valves to prevent the backflow of blood. Additionally, it is important to note that all arteries, regardless of their size, are lined with endothelium, a thin layer of cells that provides a smooth surface for blood flow.

Capillaries are the smallest blood vessels in the body and play a crucial role in the exchange of nutrients and gases between the blood and tissue cells. Their thin walls and large surface area allow for efficient diffusion of substances such as oxygen, carbon dioxide, glucose, and waste products. Capillaries connect arterioles (small arteries) and venules (small veins), forming a network throughout the body. This network ensures that every cell in the body receives the necessary oxygen and nutrients while waste products are removed. Therefore, capillaries are responsible for the primary function of permitting the exchange of nutrients and gases between the blood and tissue cells.

A blood pressure reading of 170/96 in a 50-year-old man would be indicative of hypertension. Hypertension is defined as consistently elevated blood pressure levels above 130/80 mmHg. In this case, the systolic pressure (170) is significantly higher than the normal range, and the diastolic pressure (96) is also elevated. This reading suggests that the individual has high blood pressure, which can increase the risk of cardiovascular diseases such as heart attack and stroke.

Hemorrhage with a large loss of blood causes a lowering of blood pressure due to a change in cardiac output. When there is a significant loss of blood, the volume of blood in the circulatory system decreases. This leads to a decrease in the amount of blood being pumped by the heart per minute, known as cardiac output. Since blood pressure is determined by the force exerted by the blood on the walls of the blood vessels, a decrease in cardiac output results in a lowering of blood pressure.

The correct answer is "noticing the thickness of the ventricle walls." When viewing a dissected heart, one can visually distinguish the right and left ventricles by observing the thickness of their walls. The left ventricle typically has a thicker wall compared to the right ventricle due to its role in pumping oxygenated blood to the rest of the body, while the right ventricle pumps deoxygenated blood to the lungs. By examining the thickness of the ventricle walls, one can identify and differentiate between the two ventricles.

Cardiac muscle has gap junctions that allow it to act as a functional syncytium. Gap junctions are specialized protein channels that connect adjacent cardiac muscle cells, allowing for the rapid transmission of electrical impulses. This allows the entire cardiac muscle to contract as a coordinated unit, ensuring efficient pumping of blood. Unlike skeletal muscle, cardiac muscle cells are interconnected and function as a single unit, allowing for synchronized contractions. This is essential for the proper functioning of the heart as a pump.

The correct answer is left atrium because the pulmonary veins are responsible for carrying oxygenated blood from the lungs back to the heart. Once the blood is oxygenated in the lungs, it enters the left atrium through the pulmonary veins. From there, it will be pumped into the left ventricle and then distributed to the rest of the body.

The AV valve, also known as the atrioventricular valve, is not part of the conduction system of the heart. The conduction system consists of specialized cells that generate and transmit electrical signals to coordinate the contraction of the heart muscles. The AV node, bundle of His, and SA node are all components of this conduction system, responsible for regulating the electrical activity and ensuring the proper sequence of contractions in the heart. The AV valve, on the other hand, is a mechanical valve that helps prevent the backflow of blood between the atria and ventricles during the cardiac cycle.

During ventricular systole, the ventricles contract, forcing blood out of the heart. The aorta and pulmonary trunk are the two main vessels that receive this blood. The aorta receives oxygenated blood from the left ventricle and distributes it to the rest of the body, while the pulmonary trunk receives deoxygenated blood from the right ventricle and sends it to the lungs for oxygenation. Therefore, both the aorta and pulmonary trunk receive blood during ventricular systole.

The tunica intima of an artery contains endothelium. The tunica intima is the innermost layer of the artery wall and is composed of endothelial cells. These cells form a smooth lining called the endothelium, which helps to reduce friction as blood flows through the artery. The tunica intima also contains a layer of connective tissue and a layer of elastic fibers, which provide structural support to the artery.

During vigorous exercise, the body requires increased oxygen and nutrients to the active muscles. To meet this demand, capillaries in the active muscles dilate and become engorged with blood. This allows for increased blood flow, delivering more oxygen and nutrients to the muscles, and removing waste products such as carbon dioxide. This process helps to support the increased energy demands of the muscles during exercise.

The P wave of a normal electrocardiogram indicates atrial depolarization. Depolarization refers to the contraction of the heart muscle, and in this case, it specifically refers to the contraction of the atria. The P wave represents the electrical activity that triggers the contraction of the atria, causing them to contract and pump blood into the ventricles. This is followed by the QRS complex, which represents ventricular depolarization and the contraction of the ventricles. Therefore, the correct answer is atrial depolarization.

Arterioles are the correct answer because they are the small branches of arteries that directly feed into the capillary beds. Arterioles have smooth muscle in their walls, which allows them to constrict and dilate, thereby regulating blood flow to the capillaries. Muscular arteries and elastic arteries are larger arteries that do not directly feed into the capillary beds. Venules, on the other hand, are small veins that receive blood from the capillaries.

During right ventricular systole, the right ventricle contracts and pumps blood out of the heart. The pulmonary trunk is the vessel that receives this blood and carries it to the lungs for oxygenation. The vena cavae bring deoxygenated blood from the body back to the right atrium, while the aorta carries oxygenated blood from the left ventricle to the rest of the body. The pulmonary veins, on the other hand, bring oxygenated blood from the lungs to the left atrium.

Heart sounds are produced by the opening and closing of the heart valves. When the valves close, they create a sound that can be heard with a stethoscope. This closure is an important event in the cardiac cycle as it ensures that blood flows in the correct direction and prevents any backflow. The closure of the heart valves is associated with the second heart sound, known as the "dub" sound. Therefore, the correct answer is closure of the heart valves.

The coronary arteries are responsible for supplying oxygenated blood to the capillaries in the myocardium. These arteries branch off from the aorta and directly deliver oxygen and nutrients to the heart muscle. The coronary arteries ensure that the myocardium receives a constant supply of blood to support its high metabolic demands.

The left ventricle of the heart is thicker than the right ventricle because it pumps blood against a greater resistance. The left ventricle is responsible for pumping oxygenated blood to the rest of the body, which requires more force compared to the right ventricle that pumps blood to the lungs for oxygenation. The thicker muscle in the left ventricle allows it to generate more pressure and overcome the higher resistance in the systemic circulation.

During the period of ventricular filling, the pressure in the heart is at its peak. This high pressure causes the blood to flow passively through the atria and the open AV valves into the ventricles. The atria, on the other hand, remain in diastole during this period. The P wave on the ECG represents the electrical activity of the atria, which is also consistent with the blood flowing through the atria and into the ventricles.

Essential hypertension, characterized by persistently elevated blood pressure, can lead to various changes in the cardiovascular system. Increased work of the left ventricle is expected as the heart has to pump against higher resistance. Hypertension also increases the risk of developing coronary artery disease due to the strain on the blood vessels. The elevated blood pressure can cause damage to the endothelium, leading to endothelial dysfunction. However, decreased size of the heart muscle is not a typical change associated with essential hypertension. In fact, chronic hypertension can lead to left ventricular hypertrophy, where the heart muscle thickens and enlarges.

Urinary output does not aid venous return. Venous return refers to the blood flow back to the heart from the veins. Factors that aid venous return include the activity of skeletal muscles, pressure changes in the thorax, and the presence of venous valves. However, urinary output does not directly affect venous return as it is related to the excretion of waste products by the kidneys.

The correct answer is that the myocardium is the layer of the heart that actually contracts. The myocardium is the middle layer of the heart wall and is composed of cardiac muscle tissue. It is responsible for the contraction and relaxation of the heart, which allows it to pump blood throughout the body. The fibrous skeleton, on the other hand, is a dense connective tissue structure that provides structural support and separates the atria from the ventricles. The endomysium is a layer of connective tissue that surrounds individual cardiac muscle fibers. While connective tissue in the heart wall aids in the conduction of the action potential, it is not the primary layer responsible for contraction.

The dural sinus reflex is not involved in regulating blood pressure. The other mechanisms mentioned, such as nervous control via reflex arcs involving baroreceptors, chemoreceptors, and higher brain centers, renal regulation via the renin-angiotensin system, and chemical controls like atrial natriuretic peptide, all play a role in regulating blood pressure. However, the dural sinus reflex does not have any direct effect on blood pressure regulation.

The AV valves, also known as the atrioventricular valves, are supported by chordae tendineae to prevent the backflow of blood into the atria during ventricular contraction. These valves, including the mitral and tricuspid valves, separate the atria from the ventricles and ensure that blood flows in one direction through the heart. The aortic and pulmonary valves, on the other hand, control the flow of blood out of the heart.

The correct answer is right ventricle, pulmonary artery, and left atrium. In pulmonary circulation, deoxygenated blood from the body enters the right atrium through the superior and inferior vena cava. It then flows into the right ventricle, which pumps the blood into the pulmonary artery. The pulmonary artery carries the deoxygenated blood to the lungs, where it picks up oxygen and gets rid of carbon dioxide. The oxygenated blood then returns to the heart through the pulmonary veins, entering the left atrium. From the left atrium, the blood is pumped into the left ventricle, which then pumps it out to the rest of the body through the aorta.

Norepinephrine acts on the heart by causing the threshold to be reached more quickly. This means that it increases the excitability of the heart cells, making them more likely to generate an action potential. This can lead to an increase in heart rate and contractility, resulting in a stronger and faster heartbeat.

The three main factors influencing blood pressure are cardiac output, peripheral resistance, and blood volume. Emotional state is not one of these factors. While emotions can temporarily affect blood pressure, they are not considered a main factor because they do not have a long-term impact on blood pressure regulation. Factors like cardiac output, peripheral resistance, and blood volume play more significant roles in determining blood pressure levels.

Nitric acid is not involved in the regulation of blood pressure. ADH (antidiuretic hormone) helps regulate blood pressure by increasing water reabsorption in the kidneys. Atrial natriuretic peptide helps lower blood pressure by promoting the excretion of sodium and water in the kidneys. Angiotensin II is a hormone that constricts blood vessels and raises blood pressure. Nitric acid, on the other hand, is a corrosive chemical and not involved in the physiological regulation of blood pressure.

The correct answer is hydrostatic and osmotic pressure. Hydrostatic pressure refers to the force exerted by the fluid against the capillary walls, while osmotic pressure is the pressure exerted by the solutes in the fluid. These two pressures work together to determine the direction and amount of fluid that flows across the capillary walls. If the hydrostatic pressure is greater than the osmotic pressure, fluid will move out of the capillaries. Conversely, if the osmotic pressure is greater than the hydrostatic pressure, fluid will move into the capillaries. Therefore, the balance or imbalance between these two pressures determines the direction and amount of fluid flow.

Blood clotting does not involve tissue perfusion because it is a mechanism that prevents excessive bleeding by forming a clot at the site of injury. It is a process that occurs in the blood vessels and does not directly involve the delivery of oxygen and nutrients to tissue cells or the removal of wastes from them. Instead, blood clotting is a crucial part of hemostasis, which is the body's response to injury and involves the formation of a clot to stop bleeding.

Angina pectoris is the correct answer because it refers to the pain that occurs when the heart muscle doesn't receive enough blood due to the temporary narrowing or spasm of the coronary arteries. This can be caused by various factors, including physical exertion, emotional stress, or cold temperatures. It is important to note that angina is not a heart attack (myocardial infarction), but it is a warning sign that there may be an underlying heart condition.

The foramen ovale is a small opening between the two atria in the fetal heart. During fetal development, this opening allows blood to bypass the non-functioning lungs and flow directly from the right atrium to the left atrium. This is important because the lungs are not yet fully developed and cannot perform their normal function of oxygenating the blood. After birth, the foramen ovale typically closes as the lungs begin functioning and the pressure in the heart changes.

Aldosterone is a hormone produced by the adrenal glands that plays a crucial role in regulating blood pressure. It acts on the kidneys to increase the reabsorption of sodium and water, leading to an increase in blood volume. This increase in blood volume subsequently raises blood pressure. Therefore, the correct answer is that aldosterone will promote an increase in blood pressure.

Pulse pressure is defined as the difference between the systolic pressure (the highest pressure in the arteries during a cardiac cycle) and the diastolic pressure (the lowest pressure in the arteries during a cardiac cycle). Therefore, the correct answer is "systolic pressure minus diastolic pressure". This calculation provides a measure of the force exerted by the heart with each heartbeat and can be used as an indicator of cardiovascular health.

The tunica media is the correct answer because it is the middle layer of an artery and contains smooth muscle fibers. These smooth muscles can contract and relax, allowing the artery to constrict or dilate. This ability to change the diameter of the artery is crucial for maintaining blood pressure and regulating blood flow throughout the body. The tunica intima is the innermost layer of the artery and primarily functions to provide a smooth surface for blood flow. The tunica externa is the outermost layer and provides structural support. The basement membrane is not a layer of the artery and is not directly involved in maintaining blood pressure or circulation.

Arterioles are known as resistance vessels because the contraction and relaxation of the smooth muscle in their walls can change their diameter. This ability allows arterioles to regulate blood flow and control the resistance to blood flow in different parts of the body. When the smooth muscle contracts, the arterioles constrict, increasing resistance and reducing blood flow. Conversely, when the smooth muscle relaxes, the arterioles dilate, decreasing resistance and increasing blood flow. This dynamic adjustment of arteriolar diameter helps regulate blood pressure and ensure that organs and tissues receive the appropriate amount of blood supply.

When the semilunar valves are open, blood enters the pulmonary arteries and the aorta. This occurs during ventricular systole, when the ventricles are contracting and pumping blood out of the heart. Therefore, the event that does not occur when the semilunar valves are open is that the ventricles are in diastole, which is the phase of the cardiac cycle when the ventricles are relaxed and filling with blood.

The correct answer is intrinsic autoregulatory mechanisms. Intrinsic autoregulatory mechanisms refer to the ability of the blood vessels in the brain to regulate their own diameter and blood flow in response to changes in metabolic demand. This ensures a constant supply of oxygen and nutrients to the brain, regardless of changes in systemic blood pressure or other factors. Skin temperature, ADH, and the hypothalamic "thermostat" are not directly involved in regulating cerebral blood flow.

Isovolumetric contraction refers to the short period during ventricular systole when the ventricles are completely contracted but the volume of blood in them remains constant. This occurs while the AV valves are closed and the aortic and pulmonary valves have not yet opened. It is a normal part of the cardiac cycle and is not limited to people with heart valve defects.

When the environmental temperature rises, the blood flow to the skin increases. This is because the body needs to dissipate heat and cool down. By increasing blood flow to the skin, more heat can be transferred from the body to the surrounding environment through radiation and convection. This helps to regulate body temperature and prevent overheating.

The correct answer is morning. Research has shown that the risk of heart attacks is highest in the morning hours. This is because the body's natural circadian rhythm causes an increase in blood pressure and heart rate in the morning, which can trigger a heart attack in individuals with underlying heart conditions. Additionally, morning activities such as waking up, getting out of bed, and starting daily routines can also contribute to the increased risk.

Commotio cordis is a condition where the heart goes into failure due to a relatively mild blow to the chest that happens during a specific vulnerable interval of 2 milliseconds. This vulnerable interval occurs when the heart is repolarizing, which means it is in the process of resetting itself after a heartbeat. During this vulnerable period, even a mild blow to the chest can disrupt the heart's rhythm and lead to sudden cardiac arrest. This condition is not caused by an electrical shock to the heart or body, or by loss of blood from an artery.

The correct answer is 90/55. This blood pressure reading is considered normal for a newborn baby. The first number, 90, represents the systolic pressure which is the pressure in the arteries when the heart beats and pumps blood. The second number, 55, represents the diastolic pressure which is the pressure in the arteries when the heart is at rest between beats. These values fall within the normal range for a newborn baby's blood pressure.

This answer suggests that even though the person's blood pressure is almost normal, it does not guarantee that the tissues are receiving adequate blood flow. Other factors such as the efficiency of the heart in pumping blood, the volume of blood loss, and the body's compensatory mechanisms play a role in determining if the tissues are receiving enough blood flow.

During systole, the ventricle contracts and pumps blood out of the heart to the rest of the body. The tricuspid valve is located between the right atrium and right ventricle and prevents the backflow of blood from the ventricle to the atrium during systole. Therefore, the tricuspid valve is closed when the ventricle is in systole to ensure that blood flows in the correct direction and does not flow back into the atrium.

If we were able to artificially alter the membrane permeability of pacemaker cells so that sodium influx is more rapid, the threshold for action potential generation would be reached more quickly. This would result in an increased heart rate because the pacemaker cells would fire more frequently, leading to a faster contraction of the heart muscle.