Special Circulations cerebral and coronary
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Questions and Answers

What is the primary mechanism for matching blood flow to the metabolic needs of a tissue?

  • Extrinsic control
  • Intrinsic control (correct)
  • Sympathetic control
  • Hormonal control

    • Which arteries provide the entire blood supply to the myocardium?

  • Carotid arteries
  • Aorta
  • Pulmonary arteries
  • Coronary arteries (correct)

    • What is the estimated difference in effectiveness between myocardial and skeletal muscle capillaries in exchanging small molecules?

  • 5 times
  • 15 times (correct)
  • 2 times
  • 10 times

    • What determines coronary blood flow?

    <p>A and B</p> Signup and view all the answers

    During which phase of the cardiac cycle does the majority of coronary blood flow occur?

    <p>Diastole</p> Signup and view all the answers

    What percentage of total coronary flow occurs during systole in the left ventricle?

    <p>20%</p> Signup and view all the answers

    Does intramyocardial pressure in the left ventricle exceed ventricular intracavity pressure during systole?

    <p>Yes</p> Signup and view all the answers

    Does intramyocardial pressure in the right ventricle exceed aortic pressure under normal conditions?

    <p>No</p> Signup and view all the answers

    Which organ system experiences more continuous blood flow that follows aortic pressure changes?

    <p>Right ventricle myocardium</p> Signup and view all the answers

    How does blood return to the right atrium?

    <p>Through the coronary sinus</p> Signup and view all the answers

    Why does the capillary density in the heart exceed that in skeletal muscle?

    <p>Because cardiac muscle fibers are smaller in diameter than skeletal muscle fibers</p> Signup and view all the answers

    How effective are myocardial capillaries compared to skeletal muscle capillaries in exchanging small molecules?

    <p>Myocardial capillaries are estimated to be 15 times more effective</p> Signup and view all the answers

    What percentage of the total coronary resistance to blood flow under resting conditions is accounted for by myocardial compression?

    <p>Approximately 25%</p> Signup and view all the answers

    When does blood flow to the left ventricle reduce to approximately zero?

    <p>During early ventricular systole</p> Signup and view all the answers

    When does maximal left coronary inflow occur?

    <p>Early in diastole</p> Signup and view all the answers

    What is the primary mechanism for matching blood flow to the metabolic needs of a tissue?

    <p>Local metabolic control</p> Signup and view all the answers

    Which of the following is true about changes in the duration of diastole under normal conditions?

    <p>Changes in diastole are not important in determining total coronary blood flow.</p> Signup and view all the answers

    What happens to coronary blood flow during tachycardia?

    <p>Coronary blood flow increases due to increased metabolic activity.</p> Signup and view all the answers

    What happens to coronary blood flow during bradycardia?

    <p>Coronary blood flow decreases due to reduced metabolic activity.</p> Signup and view all the answers

    Where is intramyocardial pressure greater during systole?

    <p>In the inner layers of the myocardium.</p> Signup and view all the answers

    Under normal conditions, how is the distribution of coronary blood flow across the heart wall?

    <p>The distribution is uniform.</p> Signup and view all the answers

    What may contribute to the greater frequency of sub-endocardial myocardial infarctions under pathological conditions?

    <p>Increased pressure gradient within the myocardial muscle.</p> Signup and view all the answers

    What is autoregulation of the coronary arteries?

    <p>The process by which coronary blood flow is maintained at a constant rate.</p> Signup and view all the answers

    What happens to blood flow when perfusion pressure is varied between 60 and 160 mmHg?

    <p>Blood flow varies very little.</p> Signup and view all the answers

    What happens to the autoregulatory curve when myocardial oxygen consumption increases?

    <p>The curve shifts upward.</p> Signup and view all the answers

    During which phase of the cardiac cycle is endocardial blood flow greater than epicardial blood flow?

    <p>During diastole.</p> Signup and view all the answers

    During diastole, which type of blood flow is greater in the heart?

    <p>Endocardial blood flow</p> Signup and view all the answers

    Which vessels in the heart can maintain coronary flow when arterial pressure drops?

    <p>Epicardial vessels</p> Signup and view all the answers

    What happens to average flow when myocardial oxygen consumption decreases?

    <p>Average flow decreases</p> Signup and view all the answers

    Which of the following is true about the control of coronary blood flow during exercise?

    <p>Increased metabolic activity leads to vasodilation</p> Signup and view all the answers

    What happens to the myocardium during ischemia?

    <p>Decrease in contractility</p> Signup and view all the answers

    What is a common symptom of myocardial ischemia?

    <p>Change in the ST segment of the EKG</p> Signup and view all the answers

    What is the role of collateral circulation in chronic myocardial ischemia?

    <p>Increase coronary blood flow reserve</p> Signup and view all the answers

    What happens to collateral arteries in the presence of coronary artery stenosis?

    <p>They enlarge greatly</p> Signup and view all the answers

    What is the primary determinant of coronary blood flow?

    <p>Metabolic activity</p> Signup and view all the answers

    What happens to coronary blood flow during tachycardia?

    <p>Increases</p> Signup and view all the answers

    What happens to coronary blood flow during bradycardia?

    <p>Decreases</p> Signup and view all the answers

    What is the effect of hypoxia on coronary blood flow?

    <p>Increases</p> Signup and view all the answers

    What happens to coronary blood flow when oxygen supply does not meet oxygen demand?

    <p>Decreases</p> Signup and view all the answers

    Which of the following is a treatment option for myocardial ischemia that aims to increase blood flow?

    <p>Increase blood flow with thrombolytic agents and balloon angioplasty</p> Signup and view all the answers

    Which organ is the least tolerant of ischemia?

    <p>Brain</p> Signup and view all the answers

    What happens if flow to the brain is interrupted for only 5 seconds?

    <p>Loss of consciousness</p> Signup and view all the answers

    What is the major function of sympathetic innervation of cerebral vessels?

    <p>Protect against increase in perfusion pressure</p> Signup and view all the answers

    What happens when intracranial pressure increases?

    <p>Increase in cerebral vascular resistance</p> Signup and view all the answers

    What is the purpose of the Cushing reaction?

    <p>Protect the brain from ischemia</p> Signup and view all the answers

    What is the role of autonomic control in the normal regulation of cerebral blood flow?

    <p>Not involved in regulation</p> Signup and view all the answers

    What happens when the arterial pressure rises above the cerebrospinal fluid pressure?

    <p>Blood flow to the brain resumes</p> Signup and view all the answers

    What is the effect of chronic exposure to high blood pressure on autoregulation of cerebral blood flow?

    <p>Impairs autoregulation</p> Signup and view all the answers

    What mediators have been thought to be involved in the regulation of cerebral blood flow?

    <p>Prostaglandins and adenosine</p> Signup and view all the answers

    What is the function of the blood-brain barrier?

    <p>Limit permeability to non-lipophilic molecules</p> Signup and view all the answers

    Which of the following is a sign or symptom of a transient ischemic attack (TIA)?

    <p>All of the above</p> Signup and view all the answers

    What is the leading cause of a cerebrovascular accident (CVA) or stroke?

    <p>Blockage of blood flow in an artery of the brain</p> Signup and view all the answers

    What percentage of strokes are hemorrhagic?

    <p>15%</p> Signup and view all the answers

    What is the duration of a transient ischemic attack (TIA)?

    <p>5-50 minutes</p> Signup and view all the answers

    What happens to collateral arteries in the presence of coronary artery stenosis?

    <p>They dilate to increase blood flow</p> Signup and view all the answers

    What is the primary cause of death in a cerebrovascular accident (CVA) or stroke?

    <p>Formation of a blood clot in the brain</p> Signup and view all the answers

    What are the signs and symptoms of a transient ischemic attack (TIA)?

    <p>Impaired vision, speech, and paralysis</p> Signup and view all the answers

    Which arteries supply the arterial blood to the brain?

    <p>Internal carotid and vertebral arteries</p> Signup and view all the answers

    What happens to cerebral blood flow when blood or cerebrospinal fluid CO2 increases?

    <p>Cerebral blood flow increases</p> Signup and view all the answers

    What happens to the autoregulatory curve in individuals with chronic exposure to high blood pressure (hypertension)?

    <p>It shifts to the right</p> Signup and view all the answers

    What happens to cerebral vascular resistance when there is reflex sympathetic stimulation resulting from systemic hypotension?

    <p>It remains unchanged</p> Signup and view all the answers

    What happens to intracranial pressure when there is an increase in volume of any of the intracranial structures?

    <p>It increases</p> Signup and view all the answers

    What happens to cerebral vascular resistance when intracranial pressure increases?

    <p>It increases</p> Signup and view all the answers

    What happens to blood pressure when cerebral spinal fluid pressure rises to equal arterial pressure?

    <p>It increases</p> Signup and view all the answers

    What is the innervation of cerebral vessels?

    <p>Both sympathetic and parasympathetic nerve fibers</p> Signup and view all the answers

    What happens to the blood supply to the brain when cerebral spinal fluid pressure rises to equal arterial pressure?

    <p>It is cut off</p> Signup and view all the answers

    Which individuals are better protected against increases in systemic pressure but are more vulnerable to reductions in blood pressure?

    <p>Individuals with chronic exposure to high blood pressure (hypertension)</p> Signup and view all the answers

    What can happen if pressure is rapidly lowered in individuals with chronic exposure to high blood pressure (hypertension)?

    <p>They may experience drastic consequences</p> Signup and view all the answers

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