Cardiovascular System Practice Questions

Q: All are true about baroreceptors, except?

Stimulated when BP decreases. ***Stimulated when BP decreases*** - Baroreceptors are **stretch receptors** located in the walls of the carotid sinus and aortic arch. - They are stimulated by an **increase in blood pressure (BP)**, which causes stretching of the arterial walls, not by a decrease. *Afferents are through sino-aortic nerves* - This statement is **true**. Afferent impulses from the carotid sinus baroreceptors travel via the **glossopharyngeal nerve (IX)**, and those from the aortic arch baroreceptors travel via the **vagus nerve (X)**. - These nerves collectively form the **sino-aortic nerves** that relay information to the brainstem. *Stimulation causes increased vagal discharge* - This statement is **true**. When baroreceptors are stimulated by **increased BP**, they send signals to the cardiovascular center in the medulla. - This leads to increased **parasympathetic (vagal) outflow** to the heart, causing a decrease in heart rate and contractility, and inhibition of sympathetic outflow. *Stimulate nucleus ambiguus* - This statement is **true**. The **nucleus ambiguus** is a brainstem nucleus that contains the cell bodies of preganglionic parasympathetic neurons that contribute to the vagus nerve. - Baroreceptor stimulation leads to activation of the nucleus ambiguus, thereby increasing **vagal output** to the heart.

Q: What is the role of gap junctions in cardiac muscle function?

Facilitate impulse transmission between cardiac myocytes. ***Facilitate impulse transmission between cardiac myocytes*** - **Gap junctions** are specialized channels between adjacent cells that allow for direct communication and rapid movement of **ions** and small molecules. - In cardiac muscle, they form an essential part of **intercalated discs**, enabling the heart to function as a **syncytium** by allowing electrical impulses to spread quickly from one myocyte to another. *Are not found in cardiac muscles* - This statement is incorrect; **gap junctions** are a defining feature of **cardiac muscle** and are crucial for its coordinated contraction. - They are located within the **intercalated discs** that connect individual cardiac muscle cells. *Are not found in smooth muscles* - This statement is incorrect; **gap junctions** are indeed found in **smooth muscle**, particularly in single-unit smooth muscle, where they contribute to synchronized contractions, such as in the **gastrointestinal tract**. - They allow for the rapid propagation of electrical signals, leading to coordinated muscle activity. *Have no significant role in cardiac muscle function* - This statement is incorrect; **gap junctions** play a critically significant role in cardiac muscle function by ensuring the **rapid and synchronized spread of electrical impulses**. - Without functional gap junctions, the heart would not be able to contract efficiently or effectively as a pump.

Q: What is the blood supply of the liver in ml/min/100g?

50-60 ml/min/100g. ***50-60 ml/min/100g*** - The liver receives a substantial blood supply, but when expressed per 100 grams of tissue, the value is around **50-60 mL/min/100g**. This demonstrates the organ's high metabolic demand. - This value represents the total blood flow from both the **hepatic artery** and the **portal vein** per unit weight of liver tissue. *1500-2000 ml/min/100g* - This value is extremely high and does not accurately represent the **blood flow per 100g of liver tissue**. Such a high flow rate would imply an unrealistic perfusion. - While the total blood flow to the liver is large, it's not at this magnitude when normalized to tissue weight. *1000-1500 ml/min/100g* - This range is closer to the **total blood flow to the entire liver** (1000-1800 ml/min), not the blood flow per 100 grams of tissue. - It's crucial to differentiate between total organ flow and flow density (per 100g). *250-300 ml/min/100g* - This value is significantly higher than the actual blood supply per 100g of liver tissue, suggesting an overestimation of the **perfusion density**. - While the liver is highly perfused, this rate is not physiologically accurate when normalized to the tissue weight.

Q: What physiological mechanism leads to an increase in cardiac output?

Increased myocardial contractility. ***Increased myocardial contractility*** - **Increased myocardial contractility** directly leads to a greater **stroke volume** (the amount of blood pumped with each beat), thus increasing cardiac output (Cardiac Output = Stroke Volume × Heart Rate). - This can be stimulated by factors such as **sympathetic nervous system activation** or positive inotropic agents. *Inhalation* - While inhalation can temporarily affect venous return and intrathoracic pressure, it does not directly or consistently lead to a sustained increase in **cardiac output**. - Its primary effect is on **respiration**, not cardiac performance. *Increased parasympathetic activity* - Increased parasympathetic activity, primarily via the **vagus nerve**, acts to **decrease heart rate** and myocardial contractility. - This effect would typically **reduce cardiac output**, not increase it. *Transitioning from a supine to a standing position* - Transitioning to a standing position usually causes a **temporary decrease in venous return** and a brief drop in cardiac output as blood pools in the lower extremities. - The body then compensates by increasing heart rate and peripheral vascular resistance to maintain blood pressure, but the initial effect on cardiac output is generally a transient decrease.

Q: Slowest blood flow is seen in?

Capillaries. ***Capillaries*** - Blood flow is slowest in capillaries due to their **large total cross-sectional area**, allowing sufficient time for efficient **exchange of nutrients, gases, and waste products** between blood and tissues. - Despite their individual small diameter, the combined area of millions of capillaries significantly reduces the overall velocity of blood flow. *Arteriole* - **Arterioles** are designed to **regulate blood flow** into capillary beds by constricting and dilating, but blood velocity is still relatively high compared to capillaries. - While smaller than arteries, the **cross-sectional area** of individual arterioles does not collectively exceed that of the major arteries enough to cause the slowest flow rate in the circulatory system. *Veins* - Blood flow in **veins** is generally faster than in capillaries, and is aided by muscle pumps and valves, as they collect blood from the capillary beds. - Although veins have a larger total capacity than arteries, the **velocity of blood flow increases** as blood returns to the heart through progressively larger vessels. *Venules* - **Venules** collect blood from capillaries and begin the return journey to the heart, with blood flow velocity starting to increase as they merge into larger veins. - While slightly faster than in capillaries, the flow in venules is still relatively slow compared to larger veins and arteries, but not the slowest in the system due to their **collecting function and relatively small combined cross-sectional area compared to the entire capillary network**.

Q: What is the critical closing pressure in the context of capillary physiology?

Pressure below which capillaries close. ***Pressure below which capillaries close*** - The **critical closing pressure** is the lowest pressure at which blood can flow through a capillary. - When the luminal pressure falls below this threshold, the capillary collapses due to **extrinsic tissue pressure** and intrinsic vascular tone. *Arterial pressure minus venous pressure* - This calculation represents the **arteriovenous pressure gradient**, which drives blood flow through a vascular bed. - It does not directly define the point at which capillaries collapse. *Capillary pressure minus venous pressure* - This difference primarily influences filtration and reabsorption of fluids across the capillary wall. - It is not directly related to the **critical closing pressure** of the capillaries. *None of the options* - This is incorrect as one of the provided options accurately defines the **critical closing pressure**.

Q: Deoxygenated blood is not seen in which of the following?

Pulmonary vein. ***Pulmonary vein*** - The pulmonary veins carry **oxygenated blood** from the lungs back to the left atrium of the heart. - Their primary function is to transport blood that has undergone **gas exchange** in the lungs, making it rich in oxygen. *Pulmonary artery* - The pulmonary artery carries **deoxygenated blood** from the right ventricle of the heart to the lungs. - This is an exception to the general rule that arteries carry oxygenated blood, as its purpose is to deliver blood for **oxygenation**. *Right atrium* - The right atrium receives **deoxygenated blood** from the systemic circulation via the superior and inferior vena cava. - It acts as a collecting chamber for blood that has supplied oxygen to the body's tissues before it is pumped to the lungs. *Umbilical artery* - The umbilical arteries carry **deoxygenated blood** and waste products from the fetus to the placenta. - In fetal circulation, these arteries are responsible for removing metabolic wastes and carbon dioxide from the fetal circulation.

Q: P wave is due to:

Atrial depolarization. **Atrial depolarization** - The **P wave** on an electrocardiogram (ECG) represents the electrical activity associated with the **depolarization of the atria**. - This depolarization leads to **atrial contraction**, pushing blood into the ventricles. *Atrial repolarization* - **Atrial repolarization** also occurs but is usually hidden within the **QRS complex** and thus not separately visible as a distinct wave on a standard ECG. - While it's an electrical event, it does not produce the P wave. *Ventricular depolarization* - **Ventricular depolarization** is represented by the **QRS complex** on an ECG. - This electrical activity leads to **ventricular contraction**, pumping blood out of the heart. *Ventricular repolarization* - **Ventricular repolarization** is represented by the **T wave** on an ECG. - This process allows the ventricles to relax and refill with blood.

Q: What is the normal mean velocity of blood flow in the aorta?

40-50 cm/sec. ***40-50 cm/sec*** - This range represents the **normal mean velocity** of blood flow in the **aorta**, reflecting efficient cardiac output and systemic circulation. - Blood flow velocity can vary slightly based on factors like age, cardiac health, and physical activity, but this range is a common physiological benchmark. *100-150 cm/sec* - This velocity is significantly **higher** than normal for mean aortic flow and would typically indicate a state of **hyperdynamic circulation** or specific pathological conditions. - Such elevated velocities might be seen in conditions like severe **aortic stenosis**, where the heart works harder to push blood through a narrowed valve. *200-250 cm/sec* - This range is **pathologically high** for mean aortic blood flow and is not compatible with normal physiological function. - Velocities in this range would strongly suggest a severe **cardiovascular abnormality**, such as critical **aortic stenosis** or a significant **arteriovenous shunt**. *250-300 cm/sec* - This velocity is **extremely high** and far exceeds any normal or even most pathological mean aortic flow rates found in humans. - Such high velocities would likely be associated with a highly turbulent and severely compromised cardiovascular system, potentially leading to **acute circulatory failure**.

Q: In a healthy person, arterial baroreceptor activity is seen at what stage of the cardiac cycle?

Both. ***Both*** - Baroreceptors respond to changes in **arterial pressure**, which fluctuates throughout both systole and diastole. - The baroreflex mechanism is continuously active, monitoring and adjusting blood pressure through changes in **heart rate**, **contractility**, and **vascular resistance** during both phases of the cardiac cycle. *Systole* - While baroreceptors are active during systole due to the **rise in arterial pressure**, they are not exclusively active during this phase. - Their primary role is to detect and respond to the **peak pressure** changes that occur during **ejection**, but their activity extends beyond this. *Diastole* - Baroreceptors continue to fire during diastole, albeit at a lower rate, as blood pressure falls; however, their activity is not limited to this phase alone. - They monitor the **decline in pressure** to help regulate the overall mean arterial pressure, not just the trough. *None of the options* - This option is incorrect because arterial baroreceptors are indeed active and crucial for blood pressure regulation throughout the entire cardiac cycle, encompassing both systole and diastole. - Their continuous monitoring is essential for maintaining **hemodynamic stability**.

Question 1

All are true about baroreceptors, except?

Accepted Answer

Stimulated when BP decreases

Answer

Stimulation causes increased vagal discharge

Answer

Stimulate nucleus ambiguus

Answer

Afferents are through sino-aortic nerves

Question 2

What is the role of gap junctions in cardiac muscle function?

Accepted Answer

Facilitate impulse transmission between cardiac myocytes

Answer

Are not found in cardiac muscles

Answer

Are not found in smooth muscles

Answer

Have no significant role in cardiac muscle function

Question 3

What is the blood supply of the liver in ml/min/100g?

Accepted Answer

50-60 ml/min/100g

Answer

1500-2000 ml/min/100g

Answer

1000-1500 ml/min/100g

Answer

250-300 ml/min/100g

Question 4

What physiological mechanism leads to an increase in cardiac output?

Accepted Answer

Increased myocardial contractility

Answer

Inhalation

Answer

Increased parasympathetic activity

Answer

Transitioning from a supine to a standing position

Question 5

Slowest blood flow is seen in?

Accepted Answer

Capillaries

Answer

Arteriole

Answer

Veins

Answer

Venules

Question 6

What is the critical closing pressure in the context of capillary physiology?

Accepted Answer

Pressure below which capillaries close

Answer

Arterial pressure minus venous pressure

Answer

Capillary pressure minus venous pressure

Answer

None of the options

Question 7

Deoxygenated blood is not seen in which of the following?

Accepted Answer

Pulmonary vein

Answer

Pulmonary artery

Answer

Umbilical artery

Answer

Right atrium

Question 8

P wave is due to:

Accepted Answer

Atrial depolarization

Answer

Atrial repolarization

Answer

Ventricular depolarization

Answer

Ventricular repolarization

Question 9

What is the normal mean velocity of blood flow in the aorta?

Accepted Answer

40-50 cm/sec

Answer

100-150 cm/sec

Answer

200-250 cm/sec

Answer

250-300 cm/sec

Question 10

In a healthy person, arterial baroreceptor activity is seen at what stage of the cardiac cycle?

Accepted Answer

Both

Answer

None of the options

Answer

Diastole

Answer

Systole

Cardiovascular System — MCQs

Cardiovascular System — MCQs

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