Cardiovascular System Practice Questions

Q: Which factor most strongly influences coronary blood flow during exercise?

Metabolic demand. **Metabolic demand** - During exercise, increased **myocardial activity** leads to a higher demand for oxygen and nutrients, prompting a significant increase in coronary blood flow. - Local release of **metabolites** such as adenosine, nitric oxide, and hydrogen ions causes powerful vasodilation of coronary arteries, closely matching blood supply to demand. *Endothelin release* - **Endothelin** is a potent vasoconstrictor and plays a role in regulating vascular tone, but its primary influence is not the immediate or strongest factor dictating increased coronary flow during exercise. - While it can modulate flow, metabolic changes are the dominant driver for the rapid and substantial increases needed during exertion. *Myogenic response* - The **myogenic response** is an intrinsic property of vascular smooth muscle cells to contract when stretched (due to increased pressure) and relax when pressure decreases, helping to maintain relatively constant blood flow. - This mechanism primarily contributes to **autoregulation** and flow stability, but it does not account for the massive increase in flow required by the heart during exercise. *Neural regulation* - **Neural regulation**, primarily sympathetic stimulation, increases heart rate and contractility, which indirectly increases metabolic demand. - However, direct neural effects on coronary arteries can be complex (both vasodilation and vasoconstriction depending on receptor type), and the overriding control during exercise is typically metabolic.

Q: The PR interval in ECG denotes?

Atrial depolarization with A - V conduction. ***Atrial depolarization with A - V conduction*** * The **PR interval** reflects the time from the beginning of **atrial depolarization** (P wave) to the beginning of **ventricular depolarization** (QRS complex). * It represents the time taken for the electrical impulse to travel through the **atria** and the **AV node** to the ventricles. *Ventricular depolarization and ventricular repolarization* * **Ventricular depolarization** is represented by the **QRS complex**, and **ventricular repolarization** is represented by the **T wave**. * The PR interval occurs before the QRS complex, not during ventricular depolarization or repolarization. *Atrial depolarization with atrial repolarization* * **Atrial depolarization** is represented by the **P wave**. * **Atrial repolarization** typically occurs simultaneously with **ventricular depolarization** (QRS complex) and is often obscured by it. The PR interval includes the P wave but extends beyond it. *Atrial depolarization only* * **Atrial depolarization** is solely represented by the **P wave**. * The PR interval is a longer duration that includes the P wave and the subsequent delay in the **AV node**.

Q: PR interval in ECG shows?

Atrial depolarization and conduction delay. ***Atrial depolarization and conduction delay*** - The **PR interval** is measured from the **beginning of the P wave** to the **beginning of the QRS complex**. - It represents the **complete time** for the electrical impulse to travel from the SA node through the atria, the AV node, the Bundle of His, and bundle branches until ventricular depolarization begins. - This includes two major components: 1. **Atrial depolarization** (represented by the P wave) 2. **Conduction delay** through the AV node and His-Purkinje system (the isoelectric segment after the P wave) - **Normal PR interval**: 0.12-0.20 seconds (120-200 ms) - The **AV nodal delay** is the longest component, allowing atrial contraction to complete before ventricular contraction begins. *Conduction through AV node* - While **AV nodal conduction** is an important component of the PR interval, this option is **incomplete**. - The PR interval begins with the **P wave** (atrial depolarization), which occurs before the impulse reaches the AV node. - Stating only "conduction through AV node" ignores the atrial depolarization component that is also part of the PR interval. *Delay in ventricular depolarization* - **Ventricular depolarization** is represented by the **QRS complex**, not the PR interval. - The PR interval *ends* when ventricular depolarization begins (start of QRS). *Delay in ventricular repolarization* - **Ventricular repolarization** is represented by the **T wave** on an ECG. - This occurs much later in the cardiac cycle and is not related to the PR interval.

Q: Cardiac event at the end of isometric relaxation phase:

Atrioventricular valves open. ***Atrioventricular valves open*** - This event marks the end of isometric relaxation, where ventricular pressure has dropped below atrial pressure, allowing the **mitral and tricuspid valves** to open and ventricular filling to begin. - During **isometric relaxation**, the ventricles relax without changing volume, causing a rapid drop in intraventricular pressure until it is overcome by atrial pressure. *Corresponds to T wave in ECG* - The **T wave** on an ECG represents **ventricular repolarization**, which occurs during the early part of ventricular diastole, *before* the end of isometric relaxation when the AV valves open. - The opening of AV valves occurs a bit later, as ventricular filling phase commences. *Atrioventricular valves close* - The closing of the **atrioventricular valves** (mitral and tricuspid) occurs at the beginning of **isovolumetric contraction (systole)**, not at the end of isometric relaxation (diastole). - This event marks the start of ventricular systole and is associated with the **first heart sound (S1)**. *Corresponds to peak of C wave in JVP* - The **C wave** in the jugular venous pressure (JVP) tracing corresponds to the bulging of the **tricuspid valve** into the right atrium during early ventricular systole, immediately after the AV valves close. - This event is distinct from the end of isometric relaxation, which occurs later in diastole, *before* atrial filling.

Q: All are true about S1 except:

heard at the end of ventricular systole. ***heard at the end of ventricular systole*** - The **S1 sound** marks the **beginning of ventricular systole**, not the end. - It occurs immediately after the atria have emptied their blood into the ventricles and before the ventricles begin to pump blood out. *better heard with diaphragm of stethoscope* - **S1** is a **high-pitched sound** produced by the closing of the **mitral and tricuspid valves**. - High-pitched sounds are best auscultated with the **diaphragm** of the stethoscope. *caused by closure of mitral valve* - **S1** is primarily caused by the simultaneous closure of the **mitral and tricuspid valves**. - The **mitral valve closure** contributes the most to the intensity and timing of S1, as it handles higher pressures. *lower frequency than s2* - **S1** has a **lower frequency** and longer duration compared to **S2**. - This is because the closure of the **AV valves** (mitral and tricuspid) produces lower-pitched sounds than the closure of the semilunar valves.

Q: A hormone involved in regulation of blood pressure is:

Angiotensin-II. ***Angiotensin- II*** - **Angiotensin II** is a potent **vasoconstrictor** that directly increases **blood pressure** by narrowing blood vessels. - It also stimulates **aldosterone** release, leading to **sodium and water retention**, further contributing to increased blood volume and blood pressure. *Serotonin* - **Serotonin** (5-hydroxytryptamine or **5-HT**) plays a role in mood, sleep, and appetite, but its direct role in systemic **blood pressure regulation** is less prominent than **Angiotensin II**. - While it can affect vascular tone locally, it is not considered a primary hormonal regulator of overall systemic BP. *Dopamine* - **Dopamine** is a neurotransmitter involved in motor control, reward, and motivation, and at low doses can cause **renal vasodilation**. - Its direct and sustained role in systemic **blood pressure regulation** is not as central as the **renin-angiotensin-aldosterone system**. *Prostaglandin* - **Prostaglandins** are lipid compounds that act as local hormones, with some (**PGE2**, **PGI2**) causing **vasodilation** and others (**PGF2α**) causing **vasoconstriction**. - They are more involved in localized inflammatory responses, blood flow to specific organs (e.g., kidneys), and pain, rather than serving as a primary systemic regulator of ongoing **blood pressure**.

Q: As a general rule, arteries carry :

Oxygenated blood. ***Oxygenated blood*** - Arteries are generally responsible for carrying **oxygenated blood** away from the heart to the rest of the body's tissues and organs. - The only exception is the **pulmonary artery**, which carries deoxygenated blood from the heart to the lungs. *Urine* - Urine is transported by the **ureters** from the kidneys to the bladder, and then by the urethra out of the body. - This is part of the **urinary system**, separate from the circulatory system. *Deoxygenated blood* - While veins primarily carry **deoxygenated blood** back to the heart, arteries generally carry oxygenated blood. - The exception is the **pulmonary artery**, which carries deoxygenated blood to the lungs for oxygenation. *Lymph fluid* - **Lymph fluid** is carried by the lymphatic system, a network of vessels and nodes that is part of the immune system. - The lymphatic system helps maintain fluid balance and fights infection, distinct from the circulatory function of arteries.

Q: The non-invasive method to measure the blood flow is:

Laser Doppler flowmetry. ***Laser Doppler flowmetry*** - This method uses **laser light** to measure blood flow in the microvasculature by detecting the **Doppler shift** caused by moving red blood cells. - It is a **non-invasive**, real-time technique used to assess blood perfusion in tissues, particularly useful for microvascular flow assessment. - Commonly applied in research and clinical settings to evaluate **skin perfusion**, **peripheral circulation**, and **microvascular function**. *Doppler ultrasound* - While **Doppler ultrasound** is also non-invasive and measures blood flow velocity using the Doppler principle, it is typically used for **larger vessels** rather than microcirculation. - It provides information about **blood flow velocity** and direction in arteries and veins, not the detailed microvascular perfusion that Laser Doppler provides. *Plethysmography* - **Plethysmography** measures volume changes in an organ or limb, which can reflect blood flow indirectly. - It is non-invasive but provides information about **total blood volume changes** rather than direct, real-time microvascular blood flow measurement. - Types include venous occlusion plethysmography and impedance plethysmography. *Fick's principle* - **Fick's principle** is used to measure cardiac output by calculating the difference in oxygen content between arterial and venous blood. - While valuable for measuring overall blood flow (cardiac output), it requires **blood sampling** or breath analysis, making it less directly non-invasive compared to Laser Doppler flowmetry for microvascular assessment.

Q: During ocular surgery, when the eye surgeon touches the medial rectus, he asked the assistant to measure heart rate because of

Oculocardiac reflex. ***Oculocardiac reflex*** - The **oculocardiac reflex** is a trigeminal-vagal reflex where pressure or traction on the **extraocular muscles** or globe can cause **bradycardia**, or other arrhythmias. - This reflex is mediated by the **trigeminal nerve (V1 ophthalmic branch)** carrying afferent signals to the **Gasserian ganglion**, then to the **main sensory nucleus of the trigeminal nerve** in the brainstem, which subsequently excites the **vagus nerve (efferent)** causing efferent parasympathetic stimulation to the heart leading to decreased heart rate. *Oculocephalic reflex* - The **oculocephalic reflex** (doll's eye maneuver) is used to assess brainstem function. - It involves turning the head and observing eye movements, which are generally conjugate in the opposite direction of head movement if the brainstem is intact. *Oculovagal reflex* - This term is essentially synonymous with the **oculocardiac reflex**, as the oculocardiac reflex involves the **vagus nerve** as its efferent pathway. - It specifically refers to the vagal (parasympathetic) response initiated by ocular stimulation leading to cardiac rate changes. *None of the options* - This option is incorrect because the oculocardiac reflex accurately describes the described phenomenon. - The surgeon is monitoring for a known physiological reflex where ocular manipulation affects cardiac rhythm.

Q: A healthy, 37-year-old woman loses her job at the auto factory. She picks up her three young children from school and is involved in a road traffic accident. Her 5-year-old son sustains a severe head injury. The woman was not hurt in the accident but is hyperventilating as she sits in the waiting room at the hospital. She complains of feeling faint and has blurred vision. Which of the following is decreased in this woman?

Cerebral blood flow. ***Cerebral blood flow*** - **Hyperventilation** leads to a decrease in arterial **pCO2**, causing **vasoconstriction** of cerebral blood vessels. - Reduced cerebral blood flow results in symptoms like **dizziness**, **lightheadedness**, and **blurred vision** due to decreased oxygen delivery to the brain. *Arterial pH* - **Hyperventilation** causes a decrease in arterial pCO2, leading to **respiratory alkalosis** (increased arterial pH). - A decreased arterial pH would be characteristic of acidosis, which is the opposite of what occurs during hyperventilation. *Arterial oxygen content* - While hyperventilation increases the amount of oxygen in the blood, the **arterial oxygen content** (total oxygen bound to hemoglobin plus dissolved oxygen) is not significantly decreased in a healthy individual. - The primary effect of hyperventilation is on CO2 levels and pH, not a reduction in overall oxygen-carrying capacity. *Arterial oxygen tension (PO2)* - **Hyperventilation** actually leads to an **increase** in arterial PO2 due to increased alveolar ventilation. - A decreased arterial PO2 would indicate hypoxemia, which is not caused by hyperventilation and is generally associated with conditions causing impaired gas exchange.

Question 1

Which factor most strongly influences coronary blood flow during exercise?

Accepted Answer

Metabolic demand

Answer

Endothelin release

Answer

Myogenic response

Answer

Neural regulation

Answer

Baroreceptor reflex

Question 2

The PR interval in ECG denotes?

Accepted Answer

Atrial depolarization with A - V conduction

Answer

Ventricular depolarization and ventricular repolarization

Answer

Atrial depolarization with atrial repolarization

Answer

Atrial depolarization only

Question 3

PR interval in ECG shows?

Accepted Answer

Atrial depolarization and conduction delay

Answer

Conduction through AV node

Answer

Delay in ventricular depolarization

Answer

Delay in ventricular repolarization

Question 4

Cardiac event at the end of isometric relaxation phase:

Accepted Answer

Atrioventricular valves open

Answer

Corresponds to T wave in ECG

Answer

Atrioventricular valves close

Answer

Corresponds to peak of C wave in JVP

Question 5

All are true about S1 except:

Accepted Answer

heard at the end of ventricular systole

Answer

better heard with diaphragm of stethoscope

Answer

caused by closure of mitral valve

Answer

lower frequency than s2

Question 6

A hormone involved in regulation of blood pressure is:

Accepted Answer

Angiotensin-II

Answer

Serotonin

Answer

Dopamine

Answer

Prostaglandin

Question 7

As a general rule, arteries carry :

Accepted Answer

Oxygenated blood

Answer

Urine

Answer

Deoxygenated blood

Answer

Lymph fluid

Question 8

The non-invasive method to measure the blood flow is:

Accepted Answer

Laser Doppler flowmetry

Answer

Doppler ultrasound

Answer

Plethysmography

Answer

Fick's principle

Question 9

During ocular surgery, when the eye surgeon touches the medial rectus, he asked the assistant to measure heart rate because of

Accepted Answer

Oculocardiac reflex

Answer

Occulocephalic reflex

Answer

Oculovagal reflex

Answer

None of the options

Question 10

A healthy, 37-year-old woman loses her job at the auto factory. She picks up her three young children from school and is involved in a road traffic accident. Her 5-year-old son sustains a severe head injury. The woman was not hurt in the accident but is hyperventilating as she sits in the waiting room at the hospital. She complains of feeling faint and has blurred vision. Which of the following is decreased in this woman?

Accepted Answer

Cerebral blood flow

Answer

Arterial pH

Answer

Arterial oxygen content

Answer

Arterial oxygen tension (PO2)

Cardiovascular System — MCQs

Cardiovascular System — MCQs

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