Coronary circulation Practice Questions
26 free Coronary circulation practice questions for the Physiology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
The primary function of coronary circulation is to:
- A Supply oxygenated blood to the lungs
- B Oxygenate and nourish the myocardium
- C Drain deoxygenated blood from the chambers
- D Regulate systemic arterial blood pressure
Correct answer: Oxygenate and nourish the myocardium
Coronary circulation supplies oxygen and nutrients to cardiac muscle. The myocardium has high metabolic demand and relies on continuous blood flow.
Coronary blood flow is highest during which phase of the cardiac cycle?
- A Atrial systole
- B Ventricular systole
- C Early diastole
- D Isovolumetric contraction phase
Correct answer: Early diastole
During ventricular systole, coronary vessels are compressed. Blood flow increases during diastole when myocardial relaxation occurs.
The left coronary artery primarily supplies blood to the:
- A Right atrium and its appendage
- B Left ventricle and septum
- C Right ventricle only
- D Pulmonary trunk
Correct answer: Left ventricle and septum
The left coronary artery supplies most of the left ventricle and interventricular septum. These regions have high oxygen demand.
Which factor is the most important regulator of coronary blood flow?
- A Autonomic neural control
- B Circulating blood viscosity
- C Local metabolic activity
- D Systemic arterial blood pressure
Correct answer: Local metabolic activity
Local metabolic factors such as oxygen demand and metabolite accumulation regulate coronary flow. This ensures matching of supply to myocardial demand.
Which metabolite causes coronary vasodilation during increased cardiac activity?
- A Carbon dioxide
- B Adenosine
- C Potassium
- D Lactic acid
Correct answer: Adenosine
Adenosine is a potent vasodilator released during myocardial hypoxia. It increases coronary blood flow.
Why is myocardial oxygen extraction already high at rest?
- A Chronically low coronary blood flow
- B High hemoglobin oxygen affinity
- C High myocardial metabolic activity
- D Poor tissue diffusion capacity
Correct answer: High myocardial metabolic activity
The myocardium has high basal metabolic activity. As a result, it extracts a large proportion of delivered oxygen even at rest.
An increase in heart rate affects coronary blood flow primarily by:
- A Increasing systolic flow
- B Reducing diastolic filling time
- C Increasing oxygen extraction only
- D Reducing arterial pressure
Correct answer: Reducing diastolic filling time
Higher heart rate shortens diastole, reducing coronary perfusion time. This can compromise myocardial oxygen supply.
Which artery is most commonly involved in myocardial infarction?
- A Right coronary artery
- B Left circumflex artery
- C Left anterior descending
- D Posterior descending artery
Correct answer: Left anterior descending
The left anterior descending artery supplies a large portion of the left ventricle. Its occlusion commonly causes myocardial infarction.
Coronary autoregulation refers to the ability to:
- A Maintain a constant systemic blood pressure
- B Adjust flow despite pressure changes
- C Increase heart rate automatically
- D Prevent coronary atherosclerosis
Correct answer: Adjust flow despite pressure changes
Coronary autoregulation maintains relatively constant blood flow over a range of pressures. It protects myocardial perfusion.
Which condition most severely reduces coronary blood flow?
- A Mild anemia
- B Tachycardia
- C Systemic hypertension
- D Increased blood volume
Correct answer: Tachycardia
Tachycardia reduces diastolic duration, limiting coronary perfusion. This is particularly harmful to myocardial oxygen supply.
The coronary sinus primarily drains blood into the:
- A Pulmonary artery
- B Left atrium
- C Right atrium
- D Superior vena cava
Correct answer: Right atrium
The coronary sinus collects venous blood from the myocardium. It empties into the right atrium.
Subendocardial regions of the heart are more vulnerable to ischemia because they:
- A Contain a sparse capillary network
- B Face higher intramural pressure
- C Receive blood flow only during systole
- D Have a lower resting oxygen demand
Correct answer: Face higher intramural pressure
High intramural pressure compresses vessels in the subendocardium. This reduces blood flow during systole.
Coronary blood flow increases during exercise mainly due to:
- A Increased parasympathetic activity
- B Local metabolic vasodilation
- C Increased blood viscosity
- D Reduced cardiac output
Correct answer: Local metabolic vasodilation
Exercise increases myocardial metabolism. Local metabolites dilate coronary vessels to meet increased oxygen demand.
Which factor decreases coronary vascular resistance?
- A Hypoxia
- B Sympathetic alpha stimulation
- C Increased intraventricular pressure
- D Cold exposure
Correct answer: Hypoxia
Hypoxia leads to release of vasodilators such as adenosine. This lowers coronary resistance.
The right coronary artery often supplies blood to the:
- A Left atrium
- B Sinoatrial node
- C Pulmonary veins
- D Mitral valve
Correct answer: Sinoatrial node
The right coronary artery frequently supplies the sinoatrial node. This influences heart rhythm regulation.
Coronary flow reserve refers to:
- A Total coronary blood volume at rest
- B Gap from resting to maximal flow
- C Blood stored within the coronary veins
- D Minimum coronary perfusion pressure
Correct answer: Gap from resting to maximal flow
Coronary flow reserve is the capacity to increase flow above resting levels. It reflects the ability to meet increased metabolic demand.
Which condition impairs coronary autoregulation?
- A Atherosclerosis
- B Mild exercise
- C Increased hemoglobin
- D Bradycardia
Correct answer: Atherosclerosis
Atherosclerosis reduces vessel compliance and lumen diameter. This limits the ability to adjust blood flow.
Which mechanism predominantly accounts for the rise in coronary blood flow during sympathetic stimulation, despite alpha-mediated vasoconstriction?
- A Withdrawal of vagal tone from coronary arteries
- B Increased heart rate acting on its own
- C Metabolic vasodilation overriding constriction
- D Reduced myocardial oxygen extraction at rest
Correct answer: Metabolic vasodilation overriding constriction
Sympathetic drive raises heart rate and contractility, so myocardial oxygen consumption climbs sharply. The resulting local metabolites — adenosine above all, with falling oxygen tension and rising carbon dioxide — dilate the coronary resistance vessels strongly enough to override alpha-mediated constriction, a phenomenon called functional sympatholysis. Note that the myocardium already extracts close to 70% of delivered oxygen at rest, so it cannot meet extra demand by extracting more; flow has to rise.
Which parameter best reflects myocardial oxygen consumption?
- A Resting heart rate
- B Systolic blood pressure
- C Rate-pressure product
- D Stroke volume
Correct answer: Rate-pressure product
Rate-pressure product correlates with myocardial oxygen demand. It reflects both heart rate and systolic pressure.
During severe coronary artery obstruction, collateral circulation:
- A Is entirely absent in adult hearts
- B Develops within minutes of onset
- C May partly compensate for lost flow
- D Fully prevents any myocardial ischemia
Correct answer: May partly compensate for lost flow
Collateral vessels can develop gradually in chronic obstruction. They may partially supply ischemic myocardium.
Which metabolite is a major cause of coronary vasodilation during increased cardiac activity?
- A Oxygen
- B Adenosine
- C Histamine
- D Calcium
Correct answer: Adenosine
Adenosine is produced during increased myocardial metabolism and acts as a potent vasodilator, increasing coronary blood flow.
Which coronary artery is most commonly involved in myocardial infarction?
- A Right coronary artery
- B Left circumflex artery
- C Posterior descending artery
- D Left anterior descending artery
Correct answer: Left anterior descending artery
The left anterior descending artery is most frequently affected in myocardial infarction due to its large supply territory.
Why is myocardial oxygen extraction high at rest?
- A Low oxygen demand
- B Low blood flow
- C High venous oxygen content
- D High metabolic activity
Correct answer: High metabolic activity
The myocardium has high metabolic activity and extracts a large proportion of oxygen from blood even at rest.
Sympathetic stimulation increases coronary blood flow primarily because it:
- A Causes vasoconstriction only
- B Reduces heart rate
- C Increases metabolic demand
- D Decreases oxygen consumption
Correct answer: Increases metabolic demand
Although sympathetic activity can cause vasoconstriction, the increased metabolic demand leads to net vasodilation.
The right coronary artery commonly supplies blood to the:
- A Right atrium and right ventricle
- B The left ventricle only
- C The interventricular septum only
- D The pulmonary veins only
Correct answer: Right atrium and right ventricle
The right coronary artery typically supplies the right atrium, right ventricle, and parts of the conduction system.
Subendocardial regions are more prone to ischemia because they:
- A Undergo greater systolic compression
- B Have higher oxygen supply
- C Have lower metabolic demand
- D Receive direct blood flow from veins
Correct answer: Undergo greater systolic compression
Subendocardial regions are compressed during systole, reducing blood flow and making them more vulnerable to ischemia.