Cardiovascular System Practice Questions

Q: All of the following favor filtration at the arteriolar end of the capillary bed, EXCEPT:

Negative net filtration pressure (NFP). ### Explanation The movement of fluid across a capillary membrane is governed by **Starling’s Forces**. The Net Filtration Pressure (NFP) determines whether fluid moves out of the capillary (filtration) or into the capillary (reabsorption). The formula for NFP is: **NFP = (Pc - Pi) - (πc - πi)** *(Where P = Hydrostatic Pressure, π = Oncotic/Osmotic Pressure, c = capillary, i = interstitial fluid)* **1. Why Option D is the Correct Answer:** A **Negative NFP** indicates that the forces favoring reabsorption (primarily capillary oncotic pressure) exceed the forces favoring filtration. This occurs at the **venular end** of the capillary, where fluid is pulled back into the vessel. Therefore, it does **not** favor filtration. **2. Analysis of Incorrect Options:** * **Option A:** An **increase in capillary hydrostatic pressure (Pc)** directly increases the outward force, pushing fluid into the interstitium, thus favoring filtration. * **Option B:** Filtration occurs when the **hydrostatic pressure gradient (Pc - Pi)** is greater than the **osmotic pressure gradient (πc - πi)**. This is the physiological state at the arteriolar end. * **Option C:** A **Positive NFP** means the sum of outward forces is greater than inward forces, which is the definition of filtration. **3. NEET-PG High-Yield Pearls:** * **Arteriolar End:** Hydrostatic pressure (~35 mmHg) > Oncotic pressure (~25 mmHg) → **Filtration.** * **Venular End:** Hydrostatic pressure (~15 mmHg) < Oncotic pressure (~25 mmHg) → **Reabsorption.** * **Edema Pathophysiology:** Edema is caused by factors favoring filtration: increased Pc (Heart Failure), decreased πc (Nephrotic syndrome/Hypoproteinemia), or increased capillary permeability (Inflammation). * **Lymphatics:** Not all filtered fluid is reabsorbed at the venular end; the excess (~2-4 L/day) is returned to circulation via the lymphatic system.

Q: In an isolated muscle piece fiber, repolarization proceeds from which layer to which layer?

Endocardium to epicardium. ### Explanation The direction of electrical activity in the heart depends on whether we are looking at an **intact heart in situ** or an **isolated muscle fiber**. **1. Why Option B is Correct:** In an **isolated muscle fiber** (or a simple strip of cardiac muscle), the sequence of repolarization follows the sequence of depolarization. The first cell to depolarize is the first to recover. Since depolarization spreads from the endocardium to the epicardium, repolarization naturally follows the same path: **Endocardium to Epicardium**. In this scenario, the action potential duration (APD) is uniform across all cells. **2. Why Other Options are Incorrect:** * **Option A (Epicardium to Endocardium):** This is the direction of repolarization in the **intact living heart**. In a whole heart, the epicardial cells have a shorter APD due to a higher density of transient outward potassium currents ($I_{to}$). Additionally, high sub-endocardial pressure during systole delays endocardial recovery. Thus, the epicardium repolarizes first. * **Options C & D:** These refer to lateral conduction across the septum or walls, which is relevant for depolarization (e.g., septal depolarization from left to right), but not the standard transmural sequence of repolarization. **3. High-Yield Clinical Pearls for NEET-PG:** * **The "Rule of Opposites":** In an isolated fiber, the T-wave would be inverted (opposite to QRS) because repolarization moves in the same direction as depolarization. * **The Normal ECG:** In a healthy intact heart, the T-wave is **upright** (concordant with QRS) because repolarization moves in the **opposite direction** (Epicardium $\rightarrow$ Endocardium) to depolarization. * **Ventricular Gradient:** The difference in APD between the endocardium and epicardium is what prevents T-wave inversion in a normal ECG.

Q: The pressure-volume curve is shifted to the left in which of the following conditions?

Aortic stenosis. **Explanation:** The **Pressure-Volume (PV) loop** represents the relationship between left ventricular (LV) pressure and volume during a single cardiac cycle. A **shift to the left** indicates a decrease in ventricular volumes (specifically End-Diastolic Volume and End-Systolic Volume). **Why Aortic Stenosis is Correct:** In **Aortic Stenosis (AS)**, the left ventricle must overcome high resistance to eject blood through a narrowed valve. This leads to **concentric LV hypertrophy**, which reduces ventricular compliance and decreases the internal chamber size. Consequently, the PV loop shifts to the left and upward (due to significantly higher systolic pressures). **Analysis of Incorrect Options:** * **Mitral Regurgitation (MR):** This causes volume overload. The LV receives blood from both the pulmonary veins and the regurgitant volume from the previous cycle, leading to eccentric hypertrophy and a **shift to the right**. * **Aortic Regurgitation (AR):** This is the classic example of extreme volume overload. The LV must accommodate the stroke volume plus the blood leaking back from the aorta, causing massive dilation (bovine heart) and a significant **shift to the right**. * **Mitral Stenosis (MS):** In MS, LV filling is impaired. While this reduces volumes, it does not typically cause the compensatory structural "shift" seen in pressure-overload states like AS. The loop simply becomes smaller. **High-Yield NEET-PG Pearls:** * **Shift to the Right:** Seen in Volume Overload (AR, MR, Dilated Cardiomyopathy). * **Shift to the Left:** Seen in Pressure Overload/Reduced Compliance (AS, Hypertension, Hypertrophic Cardiomyopathy). * **Width of the Loop:** Represents Stroke Volume (SV). SV is increased in AR and decreased in Heart Failure. * **Area of the Loop:** Represents Stroke Work. This is highest in Aortic Stenosis due to the extreme pressures required for ejection.

Q: The Bezold-Jarisch reflex causes apnea followed by rapid breathing, hypotension, and bradycardia. Where are the receptors that produce this reflex located?

Heart. ### Explanation The **Bezold-Jarisch reflex (BJR)** is a cardio-inhibitory reflex characterized by the triad of **bradycardia, hypotension, and apnea** (followed by tachypnea). **Why the Heart is Correct:** The receptors for this reflex are primarily **chemoreceptors and mechanoreceptors (C-fibers)** located in the ventricular walls, particularly the **inferior and posterior walls of the left ventricle**. These receptors are stimulated by chemical substances (e.g., serotonin, capsaicin, veratridine alkaloids) or mechanical triggers (e.g., severe hypovolemia or myocardial ischemia). The afferent pathway is via the **vagus nerve**, leading to increased parasympathetic outflow and decreased sympathetic activity. **Why Other Options are Incorrect:** * **Lungs:** While the lungs contain J-receptors (juxtacapillary receptors) that cause the **Hering-Breuer reflex** or rapid shallow breathing, they are not the primary site for the classic Bezold-Jarisch triad. * **Pleura:** The pleura contains sensory fibers that mediate pain and the "pleural shock" reflex (bradycardia/hypotension during pleural aspiration), but this is distinct from the BJR. * **Brain:** The brain (medulla) acts as the integrating center for these reflexes, but it does not house the initiating receptors. **High-Yield Clinical Pearls for NEET-PG:** * **Clinical Significance:** The BJR is often triggered during **Inferior Wall Myocardial Infarction (IWMI)** because the receptors are concentrated in the inferior wall. This explains why IWMI patients frequently present with bradycardia. * **Spinal Anesthesia:** BJR is a common cause of sudden bradycardia and hypotension following spinal anesthesia due to decreased venous return (empty heart syndrome). * **Key Triad:** Remember the "3 H's" (though technically it's **Bradycardia, Hypotension, and Apnea**). * **Afferent/Efferent:** Both are mediated by the **Vagus nerve** (Cranial Nerve X).

Question 1

Cardiac output is not affected by which of the following factors?

Accepted Answer

Systolic blood pressure

Answer

Heart rate

Answer

Peripheral resistance

Answer

Venous return

Question 2

What physiological changes are expected when the carotid sinus is digitally compressed?

Accepted Answer

Heart rate and peripheral resistance decrease

Answer

Heart rate decreases, peripheral resistance increases

Answer

Peripheral resistance and contractility decrease

Answer

Peripheral resistance and contractility increase

Question 3

All of the following favor filtration at the arteriolar end of the capillary bed, EXCEPT:

Accepted Answer

Negative net filtration pressure (NFP)

Answer

Increase in hydrostatic pressure of capillaries

Answer

Hydrostatic pressure gradient more than osmotic pressure gradient

Answer

Positive net filtration pressure (PFP)

Question 4

A physician monitoring a newborn infant's heart sounds using a stethoscope hears the characteristic murmur of a patent ductus arteriosus. How soon after birth should this murmur normally disappear?

Accepted Answer

Immediate closure

Answer

1-2 months

Answer

1-2 weeks

Answer

1-2 days

Question 5

In an isolated muscle piece fiber, repolarization proceeds from which layer to which layer?

Accepted Answer

Endocardium to epicardium

Answer

Epicardium to endocardium

Answer

Left to right

Answer

Right to left

Question 6

The pressure-volume curve is shifted to the left in which of the following conditions?

Accepted Answer

Aortic stenosis

Answer

Mitral regurgitation

Answer

Aortic regurgitation

Answer

Mitral stenosis

Question 7

What is the reception for the Bezold-Jarisch reflex?

Accepted Answer

Terminal ends of C fibers

Answer

Stretch receptors

Answer

Mechanical receptors

Answer

All of the above

Question 8

Vagal stimulation decreases heart rate by?

Accepted Answer

Decrease in the slope of prepotential

Answer

Decrease in action potential amplitude

Answer

Increase in repolarization phase duration

Answer

Decrease in conduction velocity

Question 9

Edema is due to which of the following factors?

Accepted Answer

Decreased lymph flow

Answer

Increased capillary osmotic pressure

Answer

Decreased hydrostatic pressure in capillaries

Answer

Both increased capillary osmotic pressure and decreased lymph flow

Question 10

The Bezold-Jarisch reflex causes apnea followed by rapid breathing, hypotension, and bradycardia. Where are the receptors that produce this reflex located?

Accepted Answer

Heart

Answer

Lungs

Answer

Pleura

Answer

Brain

Cardiovascular System — MCQs

Cardiovascular System — MCQs

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