C) To keep the blood flowing

Explanation: Endothelial cells form the endothelium that lines the lumen of all blood vessels, playing a crucial role in maintaining blood flow and vascular health.

B) High blood pressure

Explanation: High blood pressure is a well-established major risk factor for cardiovascular disease, as it can lead to damage of the arteries and increase the risk of heart attacks and strokes.

C) Cardiac biomarker elevation

Explanation: In angina, there is no elevation of cardiac biomarkers, which distinguishes it from myocardial infarction where such elevations are present.

C) ST segment depression

Explanation: ST segment depression is a characteristic feature of angina on an ECG, indicating the presence of myocardial ischemia.

B) Diabetes

Explanation: Diabetes is a significant risk factor for cardiovascular disease, as it can lead to damage of blood vessels and increase the risk of heart attacks and strokes.

B) ST segment depression

Explanation: In angina, the ECG typically shows ST segment depression and/or T-wave inversion, which are key indicators of myocardial ischemia.

C) Myocardial ischemia

Explanation: T-wave inversion is a sign of myocardial ischemia, which is often present in patients experiencing angina.

C) Oxygen

Explanation: The heart extracts up to 65% of the available oxygen during rest, indicating that oxygen is the primary energy source needed for its metabolism.

B) Oxygen deficiency

Explanation: The primary danger of inadequate blood flow to the heart is oxygen deficiency, rather than a shortage of nutrients, highlighting the heart's critical dependence on oxygen.

D) Ability to switch from fatty acids to glucose or lactate

Explanation: The heart can switch from fatty acids to glucose or lactate when necessary, ensuring that nutrient shortages are not a problem, even though it heavily relies on oxygen.

C) Adenosine induced vasodilatation

Explanation: Adenosine induced vasodilatation is a key mechanism that helps maintain blood supply to the heart during stress, ensuring that oxygen delivery meets the heart's high demand.

C) By dilating coronary arteries

Explanation: In response to increased oxygen demand in cardiac muscle cells, the body dilates coronary arteries to enhance blood flow and meet the heightened oxygen requirements.

B) Formation of blood clots

Explanation: Thromboembolism is primarily associated with the formation of blood clots that can travel through the bloodstream, potentially leading to serious health complications.

B) Exertional chest pain that resolves with rest

Explanation: Stable angina is characterized by exertional chest pain that occurs due to partial occlusion of the coronary arteries and typically resolves with rest.

B) Local muscle metabolism

Explanation: Local muscle metabolism is identified as the primary controller of coronary blood flow, with oxygen demand being a significant factor in its regulation.

B) They play a minor role

Explanation: Sympathetic nerves are noted to play a minor role in the control of coronary blood flow, indicating that local muscle metabolism is more significant in this regulation.

C) Epithelial cells

Explanation: Endothelial cells are a specialized type of epithelial cells that create a single layer lining the lumen of all blood vessels.

B) Large- and medium-sized muscular arteries

Explanation: Atherosclerosis is characterized as a disease affecting large- and medium-sized muscular arteries, leading to a loss of elasticity in these blood vessels.

B) To balance the constrictor effect of catecholamines

Explanation: Endothelial vasodilators play a crucial role in counteracting the constrictor effects of catecholamines, especially during stress and exercise, thereby maintaining vascular health and proper blood flow.

B) Stress and exercise

Explanation: The balance between endothelial vasodilators and catecholamines is particularly significant during stress and exercise, as these conditions require adjustments in blood flow and vascular resistance.

C) They cause vasoconstriction

Explanation: Catecholamines, such as adrenaline, primarily induce vasoconstriction, which can increase blood pressure and reduce blood flow to certain areas, necessitating the role of endothelial vasodilators to counteract this effect.

A) Cold

Explanation: Cold temperatures are one of the identified triggers for vascular spasms, along with exertion and emotional stress, which can lead to temporary narrowing of coronary vessels.

D) Causing vasoconstriction

Explanation: Endothelial vasodilators are responsible for promoting vasodilation, which reduces blood pressure and enhances blood flow, rather than causing vasoconstriction.

B) The oxygen volume consumed by the heart per minute

Explanation: Myocardial oxygen consumption specifically refers to the volume of oxygen that the heart consumes in one minute, which is crucial for understanding cardiac function.

C) Recovery with impaired function

Explanation: Recovery with impaired function is an outcome where the individual survives the heart attack but experiences some level of reduced capability or function, indicating a less than complete recovery.

E) Their origin can be complex

Explanation: The statement mentions the tricky place of origin of coronary arteries, indicating that their anatomical positioning can be complex and variable.

B) Rupture of coronary artery atherosclerotic plaque

Explanation: A myocardial infarction is primarily caused by the rupture of atherosclerotic plaque in the coronary arteries, leading to acute thrombosis and blockage of blood flow to the heart muscle.

B) Angiography followed by angioplasty

Explanation: A specific treatment for Angina involves performing angiography to assess the condition of the coronary arteries, followed by angioplasty or open heart surgery if required.

B) If angioplasty is not sufficient

Explanation: Open heart surgery may be considered if angioplasty does not adequately address the issues causing Angina, making it a secondary option based on the patient's condition.

B) To ensure adequate oxygen supply for metabolism

Explanation: The primary purpose of matching coronary blood flow to the oxygen needs of cardiac muscle cells is to ensure that these cells receive sufficient oxygen for their metabolic processes, which is crucial for maintaining heart function.

B) Thromboembolism

Explanation: Atherosclerosis may lead to thromboembolism, which is a serious condition where a blood clot forms and can travel to block blood vessels, potentially causing severe complications.

B) It remains permanently depolarized

Explanation: During a myocardial infarction, the damaged area of the heart remains permanently depolarized, which leads to the production of abnormal currents even during the ST segments of the ECG.

B) They are partially blocked by the open aortic valve

Explanation: During ejection systole, the open aortic valve partially blocks the entrance to the coronary vessels, which affects blood flow to the heart muscle.

C) Decreased contractility

Explanation: Decreased contractility would not increase myocardial oxygen consumption; rather, it would typically reduce the heart's workload and oxygen demand.

C) Regular exercise

Explanation: Regular exercise is generally considered a protective factor against thromboembolism, while prolonged immobility, smoking, obesity, and certain medical conditions are known risk factors.

C) Adenosine deaminase

Explanation: Adenosine deaminase is the primary enzyme responsible for the breakdown of adenosine, converting it into inosine, which is a key step in its metabolic fate.

B) Myocardial ischemia

Explanation: CAD can lead to myocardial ischemia, which is a condition where the heart muscle does not receive enough blood and oxygen, potentially resulting in more severe complications like acute myocardial infarction.

B) During diastole

Explanation: The heart primarily receives its blood supply during diastole, the phase when the heart muscle relaxes and allows blood to fill the chambers.

B) Hypoxia and adenosine

Explanation: Hypoxia and adenosine are the most important metabolic factors that influence local coronary blood flow, highlighting their role in responding to oxygen demand.

B) Lipid lowering drugs

Explanation: In addition to vasodilators and beta blockers, lipid lowering drugs may be prescribed if necessary to manage cholesterol levels in patients with Angina.

B) Creatinine kinase-MB and troponins

Explanation: During a myocardial infarction, cardiac biomarkers such as Creatinine kinase-MB and troponins are elevated, which are critical for diagnosis.

C) ST-segment elevation

Explanation: A myocardial infarction that involves the full thickness of the myocardial wall is characterized by ST-segment elevation on an ECG, indicating significant damage to the heart muscle.

C) High physical activity

Explanation: High physical activity is not a risk factor for atherosclerosis; rather, factors such as smoking, hypertension, dyslipidemia, diabetes, age, sex, and family history are associated with increased risk.

C) Increased risk of cardiovascular diseases

Explanation: An imbalance between endothelial vasodilators and catecholamines can lead to excessive vasoconstriction, which may increase the risk of cardiovascular diseases due to sustained high blood pressure and reduced blood flow.

C) Oxygen demand of the myocardium

Explanation: The primary factor influencing coronary blood flow is the oxygen demand of the myocardium (heart muscle), as increased demand necessitates greater blood flow to supply adequate oxygen.

C) It promotes vasodilation

Explanation: Adenosine plays a crucial role in regulating coronary blood flow by promoting vasodilation, which increases blood flow to meet the oxygen needs of cardiac muscle cells.

B) Increased afterload

Explanation: Increased afterload, which refers to higher aortic pressure, is one of the factors that increases myocardial oxygen consumption, as it requires the heart to work harder to pump blood.

B) Blockage of blood vessels

Explanation: The primary physiological consequence of thromboembolism is the blockage of blood vessels, which can disrupt blood flow and lead to serious health issues.

B) It shortens at high heart rates

Explanation: Diastole is longer at low heart rates, but it shortens as the heart rate increases, which can affect the heart's ability to receive adequate blood supply.

B) Vasodilators and beta blockers

Explanation: Symptomatic treatment for Angina typically includes vasodilators and beta blockers, which help alleviate the symptoms associated with this condition.

D) Adrenaline

Explanation: Adrenaline is not a paracrine released by endothelial cells; instead, Nitric Oxide, prostacyclin, and Endothelin are examples of paracrines that affect smooth muscle contraction.

B) Stimulation of new vessel growth (angiogenesis)

Explanation: Certain chemicals released by endothelial cells can trigger long-term vascular changes, including the stimulation of new vessel growth, known as angiogenesis.

B) ST-segment depression

Explanation: In subendocardial infarcts, ST-segment depression may be observed on an ECG, indicating less severe damage compared to full-thickness myocardial infarctions.

C) Ischemia and potential tissue damage

Explanation: If coronary blood flow does not meet the oxygen needs of cardiac muscle cells, it can lead to ischemia, which is a lack of oxygen that can cause tissue damage and impair heart function.

B) Early signs of coronary artery disease (CAD)

Explanation: Vascular spasms may be a warning sign of early coronary artery disease (CAD), highlighting the importance of monitoring such symptoms.

C) Regulation of blood flow

Explanation: Adenosine plays a crucial role in regulating blood flow, particularly in response to metabolic needs, by causing vasodilation and influencing coronary blood flow.

B) They squeeze the vessels

Explanation: The myocardial muscle squeezes the coronary vessels during systole, further limiting blood flow to the heart muscle at this time.

B) Physical exertion

Explanation: Stable angina is often triggered by physical exertion, as the heart requires more oxygen during activity, which can lead to chest pain due to narrowed coronary arteries.

B) Progressive, degenerative arterial disease

Explanation: Atherosclerosis is defined as a progressive, degenerative arterial disease that leads to the occlusion of affected vessels, which ultimately reduces blood flow through them.

B) Buildup of cholesterol plaques in the intima

Explanation: Atherosclerosis is specifically caused by the buildup of cholesterol plaques in the intima of arteries, which is a form of arteriosclerosis.

C) Abdominal aorta

Explanation: The abdominal aorta is noted as the most commonly affected artery in cases of atherosclerosis, followed by other arteries such as the coronary and popliteal arteries.

B) Abnormal spastic constriction that temporarily narrows the coronary vessels

Explanation: A vascular spasm is characterized as an abnormal spastic constriction that temporarily narrows the coronary vessels, affecting blood flow to the heart.

C) Immediate death

Explanation: One of the possible immediate outcomes of an Acute Myocardial Infarction (heart attack) is immediate death, highlighting the severity and urgency of this medical condition.

B) Anxiety, stress, and anger

Explanation: Emotional states such as anxiety, stress, and anger are known to be associated with vascular spasms, indicating their impact on coronary blood flow.

C) Platelet-activating factor (PAF)

Explanation: The release of platelet-activating factor (PAF) is associated with vascular spasms, contributing to the abnormal constriction of coronary vessels.

B) A stroke or pulmonary embolism

Explanation: If a thrombus dislodges, it can travel to other parts of the body, leading to serious conditions such as a stroke or pulmonary embolism, which are critical health risks associated with thromboembolism.

B) It is taken up by nearby cells

Explanation: After its release, adenosine is often taken up by nearby cells, where it can exert its physiological effects or be metabolized further.

B) Decreases heart rate

Explanation: Adenosine has a negative chronotropic effect on the heart, meaning it decreases heart rate by acting on specific receptors in the cardiac tissue.

B) Smooth muscle cells

Explanation: The lipid-rich core of atherosclerotic plaques is covered by an abnormal overgrowth of smooth muscle cells, which plays a role in the progression of the disease.

B) Smoking cigarettes

Explanation: Smoking cigarettes is a significant lifestyle risk factor for cardiovascular disease, as it contributes to the development of atherosclerosis and increases the likelihood of heart-related issues.

B) High body mass index (BMI)

Explanation: A high body mass index (BMI) is a common metabolic risk factor for cardiovascular disease, as it is associated with obesity, which can lead to other risk factors such as diabetes and hypertension.

C) Atherosclerosis

Explanation: Atherosclerosis is a condition that leads to endothelial damage and dysfunction, affecting the normal functioning of blood vessels.

B) Regular physical activity

Explanation: Regular physical activity is not a risk factor for cardiovascular disease; rather, it is a protective factor that helps reduce the risk of developing heart-related issues.

D) Full functional recovery

Explanation: Full functional recovery is a possible outcome of an Acute Myocardial Infarction, where the individual returns to normal health and functionality after treatment.

B) By diffusion from cells

Explanation: Adenosine is primarily released by diffusion from cells, especially during conditions of cellular stress or metabolic activity, allowing it to act on nearby tissues.

B) It correlates weakly with cardiac output

Explanation: Myocardial oxygen consumption correlates weakly with cardiac output, indicating that factors like aortic pressure have a more significant impact on oxygen consumption than the volume of blood pumped.

B) Coronary Artery Disease

Explanation: CAD refers to Coronary Artery Disease, which involves pathological changes in the coronary artery walls that reduce blood flow through the vessels.

D) Delayed death from complications

Explanation: A potential delayed outcome of an Acute Myocardial Infarction is death from complications that may arise after the initial event, indicating the long-term risks associated with heart attacks.

C) They balance blood flow during stress

Explanation: Endothelial vasodilators play a balancing role in maintaining blood flow to the heart during stress, working alongside adenosine to ensure adequate oxygen delivery.

C) ST segment elevation

Explanation: If the full thickness of the myocardial wall is involved during a myocardial infarction, it leads to ST segment elevation on the ECG, indicating significant damage to the heart muscle.

B) Current of injury

Explanation: The abnormal current that arises from the permanently depolarized area of the heart during a myocardial infarction is referred to as the current of injury, which contributes to the changes observed on the ECG.

B) During diastole

Explanation: Heart nourishment primarily occurs during diastole, as the coronary vessels are more open and receive blood flow when the heart muscle is relaxed.

B) Ischemic myocardium due to coronary artery narrowing or spasm

Explanation: Angina pectoris is primarily caused by ischemic myocardium, which occurs due to narrowing or spasm of the coronary arteries, leading to chest pain.

B) Anticoagulant medications

Explanation: Anticoagulant medications are commonly used to treat thromboembolism by preventing the formation of new clots and stopping existing clots from growing larger.

B) Myocardial infarction

Explanation: Unstable angina can lead to myocardial infarction (heart attack) due to thrombosis and incomplete coronary artery occlusion, making it a critical condition that requires immediate medical attention.

B) Lipid-rich core with smooth muscle cells and connective tissue cap

Explanation: Atherosclerotic plaque consists of a lipid-rich core that is covered by an abnormal overgrowth of smooth muscle cells and a collagen-rich connective tissue cap, which contributes to the narrowing of arteries.

C) Aortic pressure is more costly than volume work

Explanation: Aortic pressure is considered more costly in terms of oxygen consumption compared to volume work (cardiac output), indicating that higher pressures require more energy and oxygen from the heart.

D) Increased heart rate

Explanation: Increased heart rate is not a mechanism that leads to myocardial ischemia in the context of CAD. The mechanisms include vascular spasm, formation of atherosclerotic plaques, and thromboembolism.

C) Increased frequency or intensity of chest pain, or any chest pain at rest

Explanation: Unstable angina is defined by an increase in the frequency or intensity of chest pain, or the occurrence of chest pain at rest, indicating a more severe condition.

B) A blockage caused by a blood clot that travels through the bloodstream

Explanation: Thromboembolism refers to a blockage that occurs when a blood clot (thrombus) travels through the bloodstream and lodges in a coronary artery, which can contribute to myocardial ischemia and acute myocardial infarction in CAD.

B) To provide structural support

Explanation: The collagen-rich connective tissue cap in atherosclerotic plaques provides structural support, helping to stabilize the plaque and affecting the overall integrity of the arterial wall.

B) The formation of plaques in the coronary arteries

Explanation: Atherosclerosis refers to the formation of atherosclerotic plaques within the coronary arteries, which is one of the mechanisms that can lead to reduced blood flow and myocardial ischemia in CAD.

C) It reduces blood flow through affected vessels

Explanation: Atherosclerosis leads to the occlusion of affected vessels, which significantly reduces blood flow through them, impacting overall cardiovascular health.