A&p II (Heart, Blood & Blood Vessels)

The first heart sound is heard when the AV valves close. This sound occurs during the ventricular systole phase of the cardiac cycle when the ventricles contract and the pressure inside them increases. As the ventricles contract, the AV valves, which are located between the atria and ventricles, close to prevent the backflow of blood into the atria. The closure of the AV valves produces a distinct sound, known as the first heart sound or S1, which can be heard using a stethoscope.

Increased parasympathetic stimulation is the only factor among the given options that will not increase cardiac output. Parasympathetic stimulation primarily slows down the heart rate and decreases the force of contraction, leading to a decrease in cardiac output. On the other hand, increased venous return, increased sympathetic stimulation, and increased heart rate all contribute to an increase in cardiac output by increasing the volume of blood pumped by the heart per minute.

Beta-blockers are a class of drugs that work by blocking the effects of adrenaline on the heart. By doing so, they reduce the heart's response to stress and lower the heart rate. This is beneficial for individuals with conditions such as high blood pressure or heart disease, as it helps to decrease the workload on the heart and improve overall heart function. Therefore, the correct answer is "decrease heart rate".

Plasma and interstitial fluid differ in terms of their concentration of dissolved oxygen and proteins. Plasma is the liquid component of blood that carries oxygen and nutrients to the body's tissues, while interstitial fluid is the fluid that surrounds and bathes the cells. Plasma has a higher concentration of dissolved oxygen and proteins compared to interstitial fluid. This difference in concentration allows for the exchange of oxygen and nutrients between the blood vessels and the cells, ensuring proper functioning of the body's tissues.

Red bone marrow is the correct answer because it is responsible for the production of most white blood cells. Stem cells in the red bone marrow differentiate into various types of white blood cells, such as neutrophils, lymphocytes, and monocytes, which play a crucial role in the immune system's defense against infections and diseases. The liver, thymus, spleen, and lymph tissue also have roles in the immune system, but they are not primarily responsible for the production of white blood cells.

The blood performs several important functions in the body, including the transport of nutrients and wastes, regulation of pH and electrolyte concentration of interstitial fluids, and restricting fluid loss. However, the blood does not play a direct role in the generation of body heat. Body heat is primarily generated through metabolic processes in the cells and is regulated by the hypothalamus in the brain.

Basophils are a type of white blood cell that release histamine at the site of an injury. Histamine is a chemical that causes inflammation and helps to attract other immune cells to the area. Basophils are involved in the body's immune response to allergic reactions and parasitic infections.

The pulmonary semilunar valve is responsible for guarding the entrance to the pulmonary trunk. The pulmonary trunk is a large artery that carries deoxygenated blood from the right ventricle of the heart to the lungs for oxygenation. The valve prevents the backflow of blood into the right ventricle when the ventricle relaxes, ensuring that blood flows only in one direction, from the right ventricle to the pulmonary trunk.

Platelets are formed from cells in the bone marrow called megakaryocytes. Megakaryocytes are large cells that reside in the bone marrow and are responsible for producing platelets. When megakaryocytes mature, they undergo fragmentation, releasing small fragments called platelets into the bloodstream. These platelets play a crucial role in blood clotting and the repair of damaged blood vessels.

The QRS complex represents the depolarization of the ventricles on an electrocardiogram. It is a series of waves that indicate the electrical activity of the ventricles contracting to pump blood out of the heart. The Q wave represents the initial depolarization of the interventricular septum, the R wave represents the main depolarization of the ventricles, and the S wave represents the final depolarization of the ventricles. Therefore, the QRS complex is the correct answer as it specifically represents the depolarization of the ventricles.

Continuous capillaries have a complete lining, meaning that their endothelial cells are tightly joined together, forming a continuous tube. This type of capillary allows for the exchange of small molecules and fluids between the blood and surrounding tissues. Fenestrated capillaries, on the other hand, have small pores or fenestrations in their endothelial lining, allowing for increased permeability. Sinusoidal capillaries have large gaps between their endothelial cells, allowing for the passage of larger molecules, such as proteins and blood cells. Sinusoids are similar to sinusoidal capillaries but are found in specific organs, such as the liver and spleen. Vasa vasorum refers to the small blood vessels that supply blood to the walls of larger blood vessels.

Monocytes are large phagocytic white cells that spend most of their time outside the blood as fixed and free phagocytic cells. These cells are part of the innate immune system and play a crucial role in engulfing and destroying pathogens. They are known for their ability to migrate to tissues and differentiate into macrophages or dendritic cells, depending on the specific immune response required. Monocytes are important for initiating the inflammatory response and are involved in the clearance of dead cells and debris.

During the plateau phase of the cardiac muscle action potential, the calcium channels remain open longer than the sodium channels. This leads to an influx of calcium ions into the cell, which helps to maintain the depolarization and prolong the action potential. The prolonged opening of calcium channels allows for the sustained contraction of the cardiac muscle, ensuring that the heart has enough time to pump blood effectively. This is in contrast to the initial depolarization phase, where the sodium channels are primarily responsible for the rapid influx of sodium ions that triggers the action potential.

The entrance to the ascending aorta is guarded by the semilunar valve. The semilunar valve is located between the left ventricle and the aorta, preventing the backflow of blood from the aorta into the left ventricle. This valve consists of three cusps that open and close to allow the blood to flow forward into the aorta during ventricular contraction and prevent it from flowing back into the ventricle during relaxation.

The correct answer is coronary. The coronary arteries are the first blood vessels to branch from the aorta. They supply oxygenated blood to the heart muscle itself, ensuring that the heart receives the necessary nutrients and oxygen to function properly.

The coronary sulcus is a groove that marks the border between the atria and ventricles. This groove is located on the surface of the heart and separates the atria, which receive blood from the veins, from the ventricles, which pump blood out of the heart. The coronary sulcus is also known as the atrioventricular groove and it contains important structures such as the coronary arteries and veins, as well as fat and connective tissue.

The T wave on an ECG tracing represents ventricular repolarization. This is the phase where the ventricles of the heart are relaxing and preparing for the next heartbeat. During ventricular repolarization, the electrical charge of the ventricles is restored to its resting state after the contraction phase (ventricular depolarization). The T wave is a positive deflection on the ECG waveform that indicates this repolarization process. It is important to note that the T wave is different from the P wave, which represents atrial depolarization.

Neutrophils are granular leukocytes that are phagocytic, also known as polymorphonuclear leukocytes, and active in fighting bacterial infections. However, they are not important in coagulation. Coagulation is the process of blood clotting, which involves platelets and clotting factors, but neutrophils do not play a significant role in this process.

The internal jugular vein is responsible for returning blood from the brain back to the heart. It is a major vein located in the neck that receives deoxygenated blood from the brain, face, and neck, and carries it towards the heart. This vein is an important pathway for the drainage of blood from the brain, allowing for the removal of waste products and the delivery of oxygen and nutrients to the brain.

Stroke volume refers to the volume of blood that is ejected from each ventricle during a contraction. It is the difference between the end-diastolic volume (the amount of blood in the ventricle at the end of relaxation) and the end-systolic volume (the amount of blood in the ventricle at the end of contraction). Cardiac output, on the other hand, refers to the total volume of blood pumped by the heart in one minute, and it is calculated by multiplying stroke volume by heart rate. Cardiac reserve refers to the ability of the heart to increase its output above its resting level.

After passing the first rib, the subclavian artery continues as the axillary artery. The axillary artery is located in the armpit region and supplies blood to the upper limb. It gives rise to several branches that provide blood to different structures in the arm, such as the brachial artery, which is the main artery of the arm. The radial, ulnar, and digital arteries are branches of the brachial artery, not the axillary artery. Therefore, the correct answer is axillary.

The left ventricle is known for having a thicker wall, being round in cross section, developing higher pressures when it contracts, and producing 6 to 7 times more force when it contracts. However, it does not relax more slowly compared to the right ventricle.

The contraction of the papillary muscles prevents the atrioventricular valves from reversing into the atria. When the ventricles contract, the papillary muscles also contract, pulling on the chordae tendineae. This prevents the valve flaps (cusps) from being pushed back into the atria, ensuring that blood flows in the correct direction from the atria to the ventricles. If the atrioventricular valves were to reverse into the atria, blood would flow back into the atria instead of being pumped out to the rest of the body, leading to inefficient circulation.

The circle of Willis is an anastomosis, or a network of blood vessels, that connects the internal carotid arteries and the basilar artery at the base of the brain. It is a circular arrangement of arteries that helps to ensure a constant blood supply to the brain, even if there is blockage or narrowing of one of the arteries. This network allows for collateral circulation, meaning that if one artery is compromised, blood can still flow to the brain through alternative routes. Therefore, the circle of Willis is the correct answer in this case.

The difference between the systolic and diastolic pressures is called the pulse pressure. This is because the pulse pressure represents the force generated by the contraction of the heart during systole and the relaxation of the heart during diastole. It is a measure of the strength and elasticity of the arterial walls and is often used as an indicator of cardiovascular health.

Increased venous blood flow to the right atrium can lead to several effects. Firstly, it causes cells of the SA node to depolarize faster, which results in an increased heart rate. Additionally, this increased blood flow can trigger the atrial (Bainbridge) reflex, which further increases heart rate. Therefore, all of the above options are correct.

The auricle is the correct answer because it is the expandable extension of the atrium. The auricle is a small, ear-like structure that protrudes from the atrium and allows for increased blood flow and storage capacity. It helps to regulate the filling and emptying of the atrium, allowing for efficient pumping of blood into the ventricle.

Artery is to efferent as vein is to afferent. This analogy is based on the fact that arteries carry blood away from the heart, while veins carry blood towards the heart. The terms efferent and afferent are used in physiology to describe the direction of flow or transmission of signals. Therefore, the analogy correctly relates the directional flow of blood in arteries and veins to the directional flow of signals in efferent and afferent pathways.

The presence or absence of collateral systems does not affect blood flow through the circulatory system. Collateral systems are alternative pathways that can develop when there is a blockage in a blood vessel. They help to maintain blood flow to tissues and organs. However, the question is asking for factors that directly affect blood flow, and collateral systems are not one of them. The viscosity of the blood, the amount of friction in the blood vessels, the length and diameter of the blood vessels, and pressure differences are all factors that can affect blood flow.

Polycythemia is a condition characterized by an elevated hematocrit, which is the percentage of red blood cells in the blood. In this condition, the blood volume remains normal, meaning that there is no increase or decrease in the overall volume of blood. Polycythemia can be primary, caused by an overproduction of red blood cells by the bone marrow, or secondary, caused by factors such as chronic hypoxia or certain diseases.

Erythrocytes, also known as red blood cells, are formed from stem cells called hemocytoblasts. Hemocytoblasts are multipotent cells found in the bone marrow that have the ability to differentiate into various types of blood cells. They give rise to all the different cell types in the blood, including erythrocytes. Reticulocytes, band cells, myeloid cells, and pronormoblasts are not specifically involved in the formation of erythrocytes.

Bilirubin is a waste product that is produced when heme molecules, found in red blood cells, are broken down. Heme molecules consist of a porphyrin ring structure and an iron atom at the center. When the iron is removed from the heme molecule, it becomes a waste product called bilirubin. Therefore, the correct answer is "portions of heme molecules that do not contain iron."

The heart beats approximately 100,000 times each day. This is because the heart is responsible for pumping blood throughout the body, supplying oxygen and nutrients to all the organs and tissues. On average, a healthy adult's heart beats around 60-100 times per minute. Multiplying this by the number of minutes in a day (1440) gives us an estimate of around 86,400 to 144,000 beats per day. Therefore, 100,000 is a reasonable approximation for the number of times the heart beats in a day.

The marginal branch and posterior interventricular branch are both branches of the right coronary artery. The right coronary artery is responsible for supplying blood to the right side of the heart, including the right atrium and ventricle. The marginal branch supplies blood to the right ventricle, while the posterior interventricular branch supplies blood to the posterior part of the interventricular septum and the posterior walls of the ventricles. Therefore, the correct answer is the right coronary artery.

Vascular resistance refers to the impediment or opposition to blood flow within blood vessels. It is influenced by several factors, including the length and diameter of blood vessels, the nature of blood flow, and the viscosity of the blood. However, it is not directly related to the osmolarity of interstitial fluids, which refers to the concentration of solutes in the fluid surrounding the cells. Therefore, the correct answer is the osmolarity of interstitial fluids.

The great and middle cardiac veins drain blood from the heart muscle. This blood is then collected and emptied into the coronary sinus, which is a large vein located in the coronary sulcus. The coronary sinus acts as a reservoir for the deoxygenated blood before it is returned to the right atrium of the heart. The superior and inferior vena cava drain blood from the rest of the body into the right atrium, while the aorta is the main artery that carries oxygenated blood from the heart to the rest of the body.

The correct answer is popliteal because the femoral artery, which is located in the upper thigh, continues down the lower leg and becomes the popliteal artery behind the knee. The popliteal artery supplies blood to the lower leg and foot.

Blood pressure is influenced by various factors such as age, sex, time of day, and body size. Capillary density in the skin, however, does not directly affect blood pressure. Capillaries are tiny blood vessels that allow for the exchange of nutrients and waste products between the blood and surrounding tissues. While capillary density in the skin may have an impact on skin health and temperature regulation, it does not play a significant role in regulating blood pressure.

Erythropoiesis is the process of producing red blood cells. When the oxygen levels in the blood decrease, it indicates that the body is not receiving enough oxygen. In response, the body increases erythropoiesis to produce more red blood cells, which carry oxygen to the tissues. This adaptive mechanism helps to restore oxygen levels in the blood and maintain adequate oxygen supply to the body's cells.

An increase in the level of carbon dioxide at the tissue causes blood vessels to dilate, leading to an increase in blood flow to the tissue. This is known as the Bohr effect. When carbon dioxide levels rise, it causes a decrease in pH (increase in acidity), which in turn triggers vasodilation. This mechanism ensures that tissues receive adequate oxygen and nutrients while removing waste products. Therefore, an increase in carbon dioxide levels at the tissue results in an increase in blood flow.

Iron is an essential component of hemoglobin, the protein responsible for carrying oxygen in the blood. When hemoglobin degrades, the iron is released. Instead of being excreted by the kidneys, liver, or intestines, the iron is recycled back to the bone marrow. This is because the bone marrow is responsible for producing new red blood cells, which require iron for their formation. Therefore, recycling the iron back to the bone marrow ensures that it can be used again in the production of new hemoglobin and red blood cells.

The heart pumps approximately 8,000 liters of blood each day. This is because the heart is responsible for circulating blood throughout the body, supplying oxygen and nutrients to the organs and tissues. On average, the heart beats around 100,000 times a day, pumping about 70 milliliters of blood with each beat. Therefore, multiplying the volume of blood pumped per beat by the number of beats per day gives us an approximate value of 8,000 liters of blood pumped daily.

The blood osmotic pressure is primarily determined by the concentration of plasma proteins. Plasma proteins, such as albumin, exert an osmotic force that helps to maintain the balance of fluids between the blood vessels and surrounding tissues. When the concentration of plasma proteins is altered, such as in conditions like liver disease or malnutrition, it can lead to changes in blood osmotic pressure. Changes in the concentration of plasma sodium ions, glucose, waste products, or white blood cells do not have as significant of an impact on blood osmotic pressure as plasma proteins do.

The correct answer is that the common carotid forms an internal and an external branch. This means that the common carotid artery splits into two branches, one going internally and one going externally. This is an important anatomical feature of the carotid sinus, which is a dilation in the wall of the internal carotid artery. The internal branch supplies blood to the brain, while the external branch supplies blood to the face and neck.

The branches of the thoracic aorta include the superior phrenic, esophageal, bronchial, and intercostal arteries. However, the gastric arteries are not branches of the thoracic aorta. The gastric arteries are actually branches of the celiac trunk, which is a branch of the abdominal aorta. Therefore, the correct answer is gastric.

The external iliac artery, a major branch of the common iliac artery, gives rise to the femoral and deep femoral arteries. The femoral artery is a large vessel that supplies blood to the lower extremities, while the deep femoral artery, also known as the profunda femoris artery, provides additional blood supply to the thigh muscles.

During increased exercise, vasoconstriction occurs at the active skeletal muscles. This constriction helps to redirect blood flow to the working muscles, allowing them to receive more oxygen and nutrients. As a result of this vasoconstriction, the resistance to blood flow in the muscles increases, causing an increase in venous return. Venous return refers to the amount of blood returning to the heart from the veins. This increased venous return leads to an increase in cardiac output, which is the amount of blood pumped by the heart per minute. Therefore, the correct answer is that venous return increases.

As blood travels from the aorta toward the capillaries, the resistance increases. This is because the capillaries are smaller in diameter compared to the aorta, leading to increased friction between the blood and the vessel walls. As a result, the blood encounters more resistance, making it harder for it to flow through the capillaries.

Starling's "law of the heart" states that the cardiac output is directly related to the venous return. Venous return refers to the amount of blood returning to the heart from the veins. As the venous return increases, the heart receives more blood, leading to an increase in cardiac output. This is because a higher volume of blood in the heart stretches the cardiac muscle fibers, causing them to contract more forcefully and eject a larger volume of blood with each heartbeat. Therefore, an increase in venous return results in an increase in cardiac output.

The goal of cardiovascular regulation is to ensure that blood flow changes occur at the appropriate time, in the appropriate area, and without drastically altering blood pressure or blood flow to vital organs. However, the regulation of blood cell concentrations is not directly related to cardiovascular regulation. While blood cells are important for various physiological functions, their concentrations are not specifically regulated by the cardiovascular system to meet emergency situations.

During the compensated stage of circulatory shock, homeostatic mechanisms are able to compensate for the shock. This means that the body is able to maintain adequate blood flow to vital organs and tissues, despite the shock. The compensatory mechanisms work to increase heart rate, constrict blood vessels, and redistribute blood flow to ensure that enough oxygen and nutrients reach the organs. However, if the shock progresses to the irreversible stage, these compensatory mechanisms fail and the damage becomes permanent.

The vertebral artery is an important artery that supplies blood to the brain. It runs through the vertebrae in the neck and joins with the other vertebral artery to form the basilar artery. The basilar artery then provides blood to the brainstem and the back part of the brain. The other options listed are not specifically associated with supplying blood to the brain.

The condition of the pulmonary trunk cannot be determined by analyzing the electrocardiogram. An electrocardiogram (ECG) is a test that records the electrical activity of the heart. It provides information about the heart's rhythm, any abnormalities in the electrical conduction system, and the size and function of the chambers of the heart. However, it does not directly provide information about the condition of the pulmonary trunk, which is a blood vessel that carries blood from the right ventricle of the heart to the lungs.

The correct answer is "QRS complex of the ECG precedes the increase in ventricular pressure." This is because the QRS complex represents the depolarization of the ventricles, which leads to the contraction of the ventricles and the subsequent increase in ventricular pressure. The increase in ventricular pressure then causes the first heart sound (S1) to occur, which is the closure of the mitral and tricuspid valves. Therefore, the QRS complex precedes the increase in ventricular pressure and the occurrence of the first heart sound.

The blood hydrostatic pressure and the blood osmotic pressure are not equal in magnitude but opposite in direction. Blood hydrostatic pressure is the force exerted by the blood against the walls of the capillaries, and it pushes fluid from the capillary to the interstitial space. On the other hand, blood osmotic pressure is the pressure exerted by the proteins in the blood, and it pulls fluid from the interstitial space to the capillary. These two pressures are not equal in magnitude, as the osmotic pressure is typically lower than the hydrostatic pressure.

In cardiac muscle, at least half of the calcium ions required for contraction come from outside the cell. This is because the calcium ions are not released from the sarcoplasmic reticulum and do not bind to troponin molecules. However, calcium ions still play an important role in the process of contraction by allowing the actin and myosin filaments to interact and generate force. Additionally, calcium ions also play a crucial role in repolarizing the membrane after the depolarization phase.

Symptoms of shock typically include hypotension (low blood pressure), rapid and weak pulse, decreased urine formation, and acidosis (excessive acidity in the body). However, profuse sweating is not typically associated with shock. While sweating can occur in response to various stimuli, it is not a common symptom of shock.

The left subclavian artery is a branch off the aortic arch. It supplies blood to the left arm and part of the brain. This artery is important for maintaining proper blood flow and oxygenation to these areas of the body.

The peroneal artery is a branch of the popliteal artery. It runs along the outer side of the leg and supplies blood to the muscles and tissues in that area. It plays a crucial role in the circulation of the lower leg and foot. The other options listed, such as the femoral artery, iliac artery, dorsalis pedis, and plantar arch, are not branches of the popliteal artery.

Blood moves forward through veins with the aid of the thoracoabdominal pump, valves in the veins that prevent the backflow of blood, and contractions of skeletal muscles. The smooth muscle in the wall of the vein does not play a significant role in pumping blood forward.

In response to hemorrhage, there is mobilization of the venous reserve. This means that the body will release stored blood from the veins to compensate for the blood loss. This helps to maintain blood volume and prevent a drop in blood pressure. Decreased vasomotor tone and peripheral vasodilation can also occur in response to hemorrhage, which helps to redistribute blood flow and increase circulation to vital organs. However, increased parasympathetic stimulation of the heart is not directly related to hemorrhage.

Stimulation of the aortic baroreceptors leads to an increased activity by the parasympathetic nervous system. The parasympathetic nervous system is responsible for promoting rest and relaxation, and it counteracts the effects of the sympathetic nervous system. When the aortic baroreceptors detect an increase in blood pressure, they send signals to the brain, which in turn activates the parasympathetic nervous system. This activation results in a decrease in heart rate and vasodilation, leading to a decrease in blood pressure and a return to homeostasis.

The correct answer is "internal thoracic" because the major branches of the subclavian artery include the internal thoracic artery, which supplies blood to the chest wall and the breasts. The other options, such as radial, brachial, and digital arteries, are not major branches of the subclavian artery.

The two vertebral arteries fuse to form a large artery called the basilar artery. The basilar artery is responsible for supplying blood to the brainstem and the cerebellum. It runs along the back of the brainstem and gives off branches that supply blood to various parts of the brain. The basilar artery is an important component of the circle of Willis, which is a network of arteries at the base of the brain that helps to ensure a constant blood supply to the brain.

The pace established by the SA node, which is responsible for initiating the electrical signals that regulate the heart rate, is influenced by various factors. These factors include the extracellular concentration of potassium ion and calcium ion, the temperature of the body, and the type and amount of neurotransmitter present. However, the frequency of sympathetic and parasympathetic action potentials, which are controlled by the autonomic nervous system, does not directly affect the pace established by the SA node.