A&p II Exam 3 Review

The correct answer is the flow of positive ions from adjacent cells. Depolarization of the contractile cells occurs when positive ions, such as calcium and sodium, flow into the cell from adjacent cells. This influx of positive ions changes the electrical charge inside the cell, leading to the initiation of an action potential and subsequent contraction of the cardiac muscle.

Clotting factors (procoagulants) assist with the transformation of blood from a liquid to a gel during the event of hemostasis known as coagulation. This process involves a series of complex reactions that result in the formation of a fibrin clot, which helps to stop bleeding and promote wound healing.

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, allowing them to reach the point at which they can generate an action potential more rapidly. This can result in an increased heart rate and stronger contractions, leading to an overall increase in cardiac output.

Hemostasis refers to the physiological process of stopping bleeding. It involves a series of complex mechanisms that work together to prevent excessive blood loss from damaged blood vessels. These mechanisms include vasoconstriction, platelet aggregation, and blood clot formation. Therefore, the correct answer is "Stoppage of bleeding."

Sleeping in a well-ventilated room would not be a possible cause of sickling of red blood cells in someone with sickle-cell anemia because sickling occurs due to the abnormal shape of the red blood cells. In sickle-cell anemia, the red blood cells are crescent-shaped instead of the normal round shape. This abnormal shape makes it difficult for the red blood cells to flow smoothly through the blood vessels, leading to blockages and reduced oxygen delivery to tissues. Sleeping in a well-ventilated room does not have any direct effect on the shape of red blood cells and therefore would not cause sickling.

The correct order of impulse conduction in the heart is as follows: The impulse originates in the SA (sinoatrial) node, then travels to the AV (atrioventricular) node, then to the bundle of His, then to the bundle branches, and finally to the Purkinje fibers.

The statement is false because the primary source of red blood cells (RBCs) in adult humans is not the bone marrow in the shafts of the long bones. In adults, the primary source of RBCs is the bone marrow in the flat bones, such as the pelvis, sternum, and skull. The bone marrow in the shafts of long bones, such as the femur, primarily produces white blood cells and platelets.

ECG A shows a normal sinus rhythm because it has a consistent and regular pattern of P waves, QRS complexes, and T waves. The P waves precede each QRS complex, indicating normal atrial depolarization. The QRS complexes are narrow and consistent in shape, suggesting normal ventricular depolarization. The T waves are upright and follow each QRS complex, indicating normal ventricular repolarization. Overall, ECG A demonstrates a regular and coordinated electrical activity of the heart, which is characteristic of a normal sinus rhythm.

Thinning of the valve flaps is not an age-related change affecting the heart. As people age, they commonly experience atherosclerosis, which is the buildup of plaque in the arteries, leading to narrowing and hardening of the blood vessels. Fibrosis of the cardiac muscle refers to the replacement of healthy heart muscle tissue with scar tissue, which can occur with age. Additionally, there is a decline in cardiac reserve, which is the ability of the heart to respond to increased demands, as people get older. However, thinning of the valve flaps is not a typical age-related change in the heart.

If preload increases because venous return increases, it means that more blood is being returned to the heart, leading to an increase in the volume of blood in the ventricles before contraction. This increased preload results in a stronger contraction of the heart muscle, leading to an increase in stroke volume. Since cardiac output is the product of stroke volume and heart rate, an increase in stroke volume will ultimately lead to an increase in cardiac output. Therefore, the correct answer is that it will increase.

The inflammatory response is a protective mechanism of the body that is triggered in response to tissue injury or infection. It involves various processes such as increased blood flow, migration of immune cells, and release of chemical mediators. The purpose of the inflammatory response is to prevent the spread of the injurious agent to nearby tissue, set the stage for repair processes, and dispose of cellular debris and pathogens. However, replacing injured tissues with connective tissue is not a function of the inflammatory response. This process is known as fibrosis or scarring, which occurs during the later stages of tissue repair.

Plasmin is the correct answer because it is the enzyme responsible for breaking down and removing unneeded blood clots after the healing process has taken place during fibrinolysis. Fibrin is the insoluble protein that forms the initial clot, plasminogen is the inactive precursor to plasmin, and thrombin is the enzyme responsible for converting fibrinogen into fibrin to initiate clot formation. Therefore, plasmin is the enzyme specifically involved in clot removal.

The P-R interval represents the time it takes for the electrical signal to travel from the atria to the ventricles. During this interval, the atria contract, pushing blood into the ventricles. This contraction is reflected as a small upward deflection in the ECG known as the P wave. Therefore, the correct answer is the P-R interval.

The transport of salts to maintain blood volume is not a distribution function of blood. Blood is responsible for delivering oxygen to body cells, transporting hormones to their target organs, and removing metabolic wastes from cells. However, maintaining blood volume is primarily regulated by the kidneys through the process of reabsorption and excretion, rather than by the distribution of salts through the bloodstream.

The buffy coat in a centrifuged sample of blood consists of white blood cells and platelets. When blood is spun in a centrifuge, it separates into three layers: the top layer is plasma, the middle layer is the buffy coat, and the bottom layer is composed of red blood cells. The buffy coat contains white blood cells and platelets, which are important components of the immune system and play a role in blood clotting.

The pericardial cavity is the space that separates the parietal and visceral pericardium. The parietal pericardium is the outer layer of the pericardium, while the visceral pericardium is the inner layer that covers the heart. The pericardial cavity contains a small amount of fluid that lubricates the surfaces of the parietal and visceral layers, allowing the heart to move smoothly within the pericardium.

When the threshold is reached at the SA node, fast calcium channels open. This allows calcium ions to enter the cell, causing further depolarization of the membrane. This depolarization ultimately leads to the generation of an action potential and the initiation of the cardiac cycle.

The event of hemostasis that constricts the damaged artery to reduce blood loss is vasoconstriction. Vasoconstriction is the narrowing of the blood vessels, specifically the damaged artery, which helps to decrease the flow of blood and minimize bleeding.

The QRS wave of the electrocardiogram (ECG) represents ventricular depolarization. Depolarization is the process by which the electrical charge of the heart muscle cells becomes more positive, leading to contraction of the ventricles. The QRS complex represents the spread of electrical activity through the ventricles, causing them to contract and pump blood to the rest of the body. Therefore, the correct answer is ventricular depolarization.

The Sinoatrial (SA) node is responsible for initiating electrical impulses in the heart and is often referred to as the natural pacemaker. It is located in the right atrium near the opening of the superior vena cava. The SA node sends electrical signals to the atrioventricular (AV) node, which is located in the lower part of the right atrium near the ventricles. The AV node then conducts these impulses to the atrioventricular bundle (also known as the Bundle of His), which is located in the interventricular septum. Therefore, the SA node stimulates the AV node to conduct impulses to the atrioventricular bundle.

Lymphocytes are a type of white blood cell that play a crucial role in adaptive immune responses. They are responsible for recognizing and targeting specific pathogens, such as bacteria or viruses, through the production of antibodies or by directly attacking infected cells. Lymphocytes are able to adapt and remember previous encounters with pathogens, allowing for a more efficient immune response upon subsequent exposures. Therefore, adaptive defenses heavily rely on the activities of lymphocytes to provide targeted and long-lasting protection against infectious agents.

The P wave of a normal electrocardiogram indicates atrial depolarization. Depolarization refers to the electrical activation of the heart muscle cells, causing them to contract. In this case, the P wave represents the depolarization of the atria, which is the electrical signal that spreads through the atria and causes them to contract. This is followed by the QRS complex, which represents the depolarization of the ventricles and the subsequent contraction of the ventricles. Therefore, the correct answer is atrial depolarization.

Increased vagal tone cannot trigger tachycardia because the vagus nerve, which is part of the parasympathetic nervous system, slows down the heart rate. When the vagal tone is increased, it leads to increased parasympathetic activity, resulting in a decrease in heart rate rather than an increase. Tachycardia, on the other hand, refers to an abnormally fast heart rate.

The transport of salts to maintain blood volume is not a distribution function of blood. Blood is responsible for delivering oxygen to body cells, transporting hormones to their target organs, and removing metabolic wastes from cells. However, maintaining blood volume is primarily regulated by the kidneys and their control over water and salt balance in the body.

The kidney regulates erythrocyte production. Erythrocytes, also known as red blood cells, are responsible for carrying oxygen throughout the body. The kidney produces a hormone called erythropoietin, which stimulates the production of red blood cells in the bone marrow. This hormone is released in response to low oxygen levels in the blood. Therefore, the kidney plays a crucial role in maintaining the appropriate number of red blood cells in the body.

Decreasing thyroid function (thyroxine) would cause a decrease in cardiac output (CO) because thyroxine is responsible for regulating the metabolic rate of the body. When thyroid function decreases, the metabolic rate slows down, leading to a decrease in heart rate and stroke volume, which ultimately results in a decrease in cardiac output.

During the isovolumetric contraction phase, the ventricles of the heart are completely closed chambers, meaning that the valves leading into and out of the ventricles are closed. This prevents any blood from entering or leaving the ventricles, resulting in a constant volume of blood within the chambers. At the same time, the ventricles are contracting, which increases the pressure within them. This phase occurs after the ventricles have filled with blood and before they start ejecting blood into the arteries.

The characteristic of a virus that is not mentioned in the options is "Cause infections in body fluids." Viruses can cause infections in various ways, such as respiratory droplets, contaminated surfaces, or through vectors like mosquitoes. However, the options provided do mention other characteristics of a virus, such as having an RNA or DNA core, causing cell lysis, and having a protein coating.

When B cells are initially exposed to an antigen, they respond by producing progeny cells that include plasma cells and memory cells. Plasma cells are responsible for the immediate production of antigen-specific antibodies, which help in the immune response against the antigen. Memory cells, on the other hand, are long-lived cells that "remember" the antigen and provide long-term immunity. This response allows the immune system to mount a quicker and more effective response upon subsequent exposure to the same antigen.

The primary immune response refers to the initial immune response that occurs when the body is exposed to a specific pathogen for the first time. During this response, B cells need time to recognize the pathogen, proliferate (multiply), and differentiate into plasma cells, which produce antibodies to fight against the pathogen. This process takes some time, resulting in a lag period before sufficient levels of antibodies are produced. This is why the primary immune response has a lag period while B cells proliferate and differentiate into plasma cells.

The normal heart sounds are caused by the closure of the heart valves. When the valves close, they produce a sound that can be heard with a stethoscope. This closure prevents blood from flowing back into the previous chamber, ensuring that it moves forward through the heart. The opening and closing of the heart valves, as well as the friction of blood against the chamber walls, also contribute to the overall heart sounds, but the closure of the heart valves is the primary cause. The excitation of the SA node is responsible for initiating the electrical signals that regulate the heart's rhythm, but it does not directly cause the normal heart sounds.

Vascular relaxation is not a part of hemostasis. Hemostasis refers to the process of stopping bleeding, and it involves several steps such as vascular spasm, platelet plug formation, and coagulation. Vascular spasm is the constriction of blood vessels to reduce blood flow, platelet plug formation involves the aggregation of platelets to form a temporary plug at the site of injury, and coagulation is the formation of a blood clot to seal the damaged blood vessel. Vascular relaxation, on the other hand, would counteract the vasoconstriction and promote blood flow, which is not a part of the hemostatic process.

At the circled label "5" on the graph, the occurrence is the peak systolic pressure. This refers to the highest pressure reached in the arteries during ventricular contraction. It represents the force exerted by the blood against the arterial walls when the heart pumps blood out of the ventricles.

Increased heart rate and increased stroke volume would increase cardiac output to the greatest extent. Cardiac output is the amount of blood pumped by the heart per minute and is calculated by multiplying heart rate (number of heartbeats per minute) by stroke volume (amount of blood pumped by each heartbeat). By increasing both heart rate and stroke volume, the heart is able to pump a larger volume of blood per minute, resulting in an increased cardiac output.

At the circled label "7" on the graph, isovolumetric ventricular relaxation occurs. This refers to the phase of the cardiac cycle when the ventricles are relaxed and the pressure inside them decreases. During this phase, the ventricles are not contracting, and the atrioventricular valves are closed. The decrease in pressure allows blood to flow from the atria into the ventricles, preparing for the next phase of ventricular filling.

Platelets are best suited to the clotting process that occurs when blood vessels are ruptured. Platelets are small, disc-shaped cells that are involved in the formation of blood clots. When a blood vessel is damaged, platelets adhere to the site of injury and aggregate together to form a plug, which helps to stop bleeding. This process is essential for preventing excessive blood loss and promoting wound healing. Megakaryocytes are the precursor cells of platelets, while lymphocytes are a type of white blood cell involved in the immune response. Megakaryoblasts are immature cells that eventually differentiate into megakaryocytes.

Repolarization of an autorhythmic cell refers to the process of restoring the cell's resting membrane potential after depolarization. This is achieved by allowing positively charged potassium ions to exit the cell. Voltage-gated potassium channels play a crucial role in this process by opening in response to a change in membrane potential, allowing potassium ions to flow out of the cell. This efflux of potassium ions helps to restore the negative charge inside the cell, leading to repolarization. Therefore, the opening of voltage-gated potassium channels is responsible for the repolarization of an autorhythmic cell.

The left ventricle has the highest probability of being the site of a myocardial infarction because it is responsible for pumping oxygenated blood to the rest of the body. It receives blood from the left atrium and contracts forcefully to push the blood out through the aorta. Due to its high workload and constant contraction, the left ventricle is more prone to developing blockages in the coronary arteries, leading to a myocardial infarction.

Increasing afterload is not a factor that increases stroke volume. Afterload refers to the resistance that the heart has to overcome to pump blood out of the ventricles and into the arteries. When afterload increases, it becomes more difficult for the heart to eject blood, resulting in a decrease in stroke volume. Therefore, increasing afterload actually decreases stroke volume rather than increasing it.

An abnormal P wave could be indicative of enlarged atria. The P wave represents atrial depolarization, so any abnormality in the shape or duration of the P wave could suggest an abnormality in the atria. Enlarged atria can cause changes in the electrical conduction system, leading to abnormal P wave morphology. This can be seen in conditions such as atrial enlargement or atrial fibrillation.

The protective function of blood is the prevention of blood loss. Blood contains platelets that help in clotting and forming a plug at the site of injury, preventing excessive bleeding. This function is crucial in maintaining the integrity and stability of the circulatory system, ensuring that the body does not lose excessive amounts of blood, which could be life-threatening.

Extrasystole is a condition marked by premature ventricular contraction. It is characterized by an abnormal heartbeat that occurs earlier than expected, disrupting the normal rhythm of the heart. This can cause a sensation of skipped or extra beats and may lead to palpitations, dizziness, or fainting. Extrasystole can be caused by various factors such as stress, caffeine, nicotine, or underlying heart conditions. Treatment options may include lifestyle changes, medication, or in severe cases, medical procedures to correct the abnormal rhythm.

If the membrane permeability of pacemaker cells is artificially altered to allow for more rapid sodium influx, the threshold for depolarization would be reached more quickly. This would result in an increase in heart rate, as the pacemaker cells would fire more frequently and initiate more action potentials. The other options are not likely because they do not directly relate to the effect of altering membrane permeability on the pacemaker cells.

The correct answer is coronary arteries. The myocardium, which is the muscular tissue of the heart, receives its blood supply from the coronary arteries. These arteries branch off from the aorta and deliver oxygenated blood to the heart muscle. The coronary arteries ensure that the myocardium receives the necessary nutrients and oxygen for proper functioning.

An increase in the sympathetic nervous system would increase stroke volume by increasing contractility. The sympathetic nervous system releases norepinephrine, which binds to beta-1 adrenergic receptors in the heart. This leads to an increase in calcium influx into the cardiac muscle cells, resulting in stronger and more forceful contractions. As a result, the heart is able to pump out a larger volume of blood with each beat, leading to an increased stroke volume.

An increase in venous return refers to an increased amount of blood returning to the heart from the veins. This increased blood volume fills the ventricles of the heart during diastole, leading to an increased end diastolic volume. The end diastolic volume is the volume of blood in the ventricles just before they contract. When the end diastolic volume increases, it stretches the myocardial fibers, leading to an increased force of contraction. This increased force of contraction, known as increased contractility, allows for a larger volume of blood to be ejected from the ventricles during systole, resulting in an increased stroke volume.

The role of antigen-presenting cells in immunity is to activate T cells, display antigen fragments, bind antigens to glycoproteins, and process antigens. Antigen-presenting cells play a crucial role in the immune response by presenting antigens to T cells, which then recognize and respond to the antigens. They display antigen fragments on their cell surface, allowing T cells to recognize them. They also bind antigens to glycoproteins, facilitating their presentation to T cells. Additionally, antigen-presenting cells process antigens by breaking them down into smaller fragments for presentation. Therefore, all of the answers are correct.

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Increasing extracellular potassium levels would cause a decrease in the contractility of the heart. High levels of extracellular potassium can disrupt the electrical balance in cardiac muscle cells, leading to a decrease in the strength and efficiency of contractions. This can result in a decrease in the contractility of the heart, affecting its ability to pump blood effectively.

During ventricular systole, the ventricles contract, causing an increase in pressure within the blood vessels. This increase in pressure is known as systolic blood pressure. As the ventricles forcefully pump blood out of the heart and into the arteries, the blood pressure rises. This increase in blood pressure helps to propel the blood forward and ensures that it reaches all parts of the body. Therefore, the correct answer is that blood pressure increases during ventricular systole.

The correct answer is that the ventricles are not reaching systole in every cardiac cycle. This means that the ventricles are not contracting fully or effectively, leading to a reduced pumping of blood from the heart. This can result in inadequate blood flow to the body and may cause symptoms such as fatigue, shortness of breath, and fainting. It is important to diagnose and treat this condition to prevent further complications.

The abnormal swishing or whooshing sound that is heard as blood regurgitates back into an atrium from its associated ventricle is caused by blood turbulence. When there is a disruption in the normal flow of blood, such as when it regurgitates back into the atrium, it creates turbulence, resulting in the characteristic sound. This can be caused by various factors, including valve dysfunction or structural abnormalities in the heart.

The answer "There is no relationship" suggests that preload and ESV are not related to each other. Preload refers to the amount of blood in the ventricles at the end of diastole, while ESV (end-systolic volume) refers to the amount of blood remaining in the ventricles at the end of systole. The question implies that there is no direct cause-and-effect relationship between preload and ESV. Therefore, changes in preload would not have any specific effect on ESV.

The statement "Not a living cell" is not characteristic of bacteria because bacteria are living cells. Bacteria are single-celled microorganisms that can be found in various environments. They have a distinct cellular structure, including a cell wall, and contain genetic material in the form of a single chromosome. Additionally, some bacteria may have a slime coat, which helps protect them and aid in their attachment to surfaces.

During ventricular systole, the ventricles contract and pump blood out into the arteries. This contraction creates pressure in the ventricles, causing the pressure to rise to its highest point (around 120 mm Hg). This is when the blood is forcefully pushed out of the heart and into the systemic circulation.

At "A" on the graph, the semilunar valve opens. This is indicated by the upward movement of the graph. The semilunar valve is responsible for allowing blood to flow out of the heart from the ventricles to the arteries. When the semilunar valve opens, it allows blood to be ejected from the heart into the circulation.

When the muscles contract during activity, more blood is returned to the heart. This increased blood volume, known as preload, stretches the ventricles of the heart. As a result, the ventricles contract more forcefully, leading to an increased cardiac output. Therefore, an increase in preload would cause an increase in cardiac output.

At the area labeled "B" on the graph, the semilunar valve closes. This means that the valve between the ventricles and the arteries leading away from the heart shuts, preventing the backflow of blood into the ventricles. This closure ensures that blood flows only in one direction, from the ventricles to the arteries, allowing for efficient circulation throughout the body.

Blood carries body cells to injured areas for repair. This statement does not describe blood because blood does not carry body cells to injured areas for repair. Instead, it carries oxygen, nutrients, hormones, and waste products throughout the body. The process of repairing injured areas is performed by other components of the blood, such as platelets and white blood cells.

If preload increases, it means that the amount of blood returning to the heart during diastole is increasing. This increased blood volume will lead to an increase in the end-diastolic volume (EDV), which is the amount of blood in the ventricles at the end of diastole. Therefore, an increase in preload will result in an increase in EDV.

Cardiac tamponade is a condition where there is an excessive amount of fluid in the pericardial cavity, which is the space between the heart and the pericardium. This fluid accumulation puts pressure on the heart, compressing it and preventing it from filling properly with blood. As a result, the heart is unable to pump blood effectively, leading to decreased cardiac output and potentially life-threatening consequences.

When the ventricle is in systole, it is contracting to pump blood out of the heart and into the arteries. During this phase, the tricuspid valve, which is located between the right atrium and right ventricle, closes to prevent the backflow of blood from the ventricle back into the atrium. This closure ensures that blood flows in the correct direction, from the atrium to the ventricle, and then out of the heart.

Stroke volume refers to the amount of blood pumped out of the heart with each contraction. It is typically measured in milliliters. On the graph, the volume labeled "E" represents the stroke volume, indicating the volume of blood ejected from the heart during systole (contraction) and is therefore the correct answer.

Adding a chemical that reduces Na+ transport near the sinoatrial (SA) node would decrease the rate at which the SA node depolarizes. This would lead to a slower depolarization of the SA node, resulting in a decrease in the heart rate.

The correct partial path is the Aorta to smaller systemic arteries to systemic capillaries to systemic veins to right atrium through the tricuspid valve. This pathway describes the flow of blood from the heart to the rest of the body. The aorta is the main artery that carries oxygenated blood from the left ventricle to the smaller systemic arteries. These arteries then branch out into smaller vessels called capillaries, where oxygen and nutrients are exchanged with the surrounding tissues. The deoxygenated blood then flows back to the heart through systemic veins, ultimately returning to the right atrium through the tricuspid valve.

Afterload refers to the back pressure exerted by blood in the atria on the ventricles during systole. This pressure opposes the ejection of blood from the heart and determines the workload that the heart must overcome to pump blood out of the ventricles. It is influenced by factors such as vascular resistance and arterial blood pressure. The degree of stretch of the heart muscle, cardiac reserve, and contractility of the cardiac muscle are not accurate descriptions of afterload.

The volume labeled "G" on the graph represents the end-systolic volume. End-systolic volume refers to the amount of blood remaining in the ventricle at the end of systole, or the contraction phase of the cardiac cycle. This volume is important because it indicates the amount of blood that remains in the ventricle after it has pumped out blood during systole. It can be used to calculate other important cardiac parameters such as stroke volume and ejection fraction.

A decrease in blood volume would lead to a decrease in stroke volume because there is less blood available to be pumped out with each heartbeat. However, cardiac output may not necessarily change because it can be maintained by increasing heart rate to compensate for the decrease in stroke volume. Therefore, the correct answer is that there would be a decreased stroke volume and no change in cardiac output.

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At the area labeled "D" on the graph, the AV valve opens and diastolic filling begins. This means that the atrioventricular (AV) valve, which separates the atria and ventricles, opens to allow blood to flow from the atria into the ventricles. At the same time, diastolic filling begins, which refers to the phase of the cardiac cycle when the ventricles relax and fill with blood. This is an important step in the overall process of the heart pumping blood throughout the body.

An incompetent tricuspid valve is a condition where the valve does not close properly, causing blood to leak back into the right atrium instead of flowing forward into the right ventricle. This would result in reduced efficiency in the delivery of blood to the lungs because the blood that is supposed to be pumped to the lungs for oxygenation would be partially leaking back into the heart.

Cytotoxic T cells are the cells directly responsible for cellular immunity. These cells play a crucial role in the immune response by recognizing and destroying infected or abnormal cells. They do this by releasing toxic substances that induce cell death in their target cells. Cytotoxic T cells are a type of T lymphocyte and are essential for eliminating pathogens and cancer cells from the body. They are an important component of the adaptive immune system and contribute to the overall defense against infections and diseases.

B cells are the cells responsible for humoral immunity. They are a type of white blood cell that produce and secrete antibodies, which are proteins that can recognize and neutralize pathogens. B cells play a crucial role in the immune response by recognizing antigens and initiating the production of antibodies to eliminate the invaders. Helper T cells, NK cells, Suppressor T cells, and Cytotoxic T cells are all involved in different aspects of the immune response, but they are not specifically responsible for humoral immunity like B cells are.

The human immunodeficiency virus (HIV) specifically targets and infects Helper T cells, also known as CD4+ T cells. These cells play a crucial role in the immune response by coordinating and activating other immune cells. By infecting and destroying Helper T cells, HIV weakens the immune system, making the individual more susceptible to infections and diseases.

Fibrinolysis is the process of breaking down fibrin, the protein that forms blood clots, in order to prevent excessive clotting. It is not a phase of hemostasis, which refers to the body's natural process of stopping bleeding. The other options - coagulation, vascular spasm, and platelet plug formation - are all phases of hemostasis that work together to form a clot and stop bleeding. Fibrinolysis occurs after the clot has served its purpose and needs to be dissolved.

When the semilunar valves are open, blood is able to flow from the ventricles into the pulmonary arteries and the aorta. This occurs during ventricular systole, which is the contraction phase of the ventricles. During ventricular diastole, the ventricles relax and fill with blood. Therefore, the event that does not occur when the semilunar valves are open is "Ventricles are diastole."

At the circled label "4" on the graph, isovolumetric ventricular contraction occurs. This refers to the phase of the cardiac cycle when the ventricles contract without any change in volume. During this phase, the ventricles are closed and the pressure within them rises rapidly, causing the semilunar valves to remain closed. This contraction allows the ventricles to build up pressure before the next phase of ventricular ejection, where blood is pumped out of the ventricles.

Calcium channel blockers work by inhibiting the entry of calcium ions into the cytoplasm of cardiac cells. This leads to a decrease in the force of myocardial contractility, meaning that the heart beats with less force. As a result, the oxygen demand of the heart is reduced, which helps to prevent angina (chest pain) caused by a lack of oxygen supply to the heart muscle.

The question states that if preload increases, the effect on cardiac output is not known. Preload refers to the amount of blood that fills the heart before it contracts. While an increase in preload can potentially increase cardiac output, it is not always the case. Other factors such as contractility and afterload also play a role in determining cardiac output. Without information on these factors, it is not possible to determine the exact effect of an increase in preload on cardiac output.

The amino acids of globin in the hemoglobin molecule bind carbon dioxide for transport. Hemoglobin is composed of four protein chains called globins, each containing a heme group with an iron atom at its center. While the iron atom in heme binds oxygen, it does not directly bind carbon dioxide. Instead, carbon dioxide binds to specific amino acids in the globin chains, allowing for its transport in the bloodstream.