Cardiovascular System Practice Questions

Q: Cardiac output increases in exercise primarily by

Sympathetic stimulation. ***Sympathetic stimulation*** - With exercise, the **sympathetic nervous system** is activated, leading to increased release of **norepinephrine**, which acts on beta-1 adrenergic receptors in the heart. - This stimulation directly increases **heart rate** and **contractility**, both of which contribute to a significant rise in cardiac output. *Increase in heart rate* - While an **increase in heart rate** does contribute to increased cardiac output during exercise (CO = HR x SV), it is a *consequence* of sympathetic stimulation, not the primary mechanism itself. - Sympathetic input drives the sinus node to fire faster, thus increasing heart rate. *Increase in preload* - **Increased preload** can enhance stroke volume via the **Frank-Starling mechanism**, but it is generally *not* the sole or primary factor for the dramatic increase in cardiac output during intense exercise. - During exercise, sympathetic venoconstriction can increase venous return and thus preload, but this is also mediated by sympathetic activity. *Increase in afterload* - An **increase in afterload** (resistance against which the heart pumps) typically *decreases* stroke volume and, consequently, cardiac output. - Although the mean arterial pressure may rise during exercise, the overall systemic vascular resistance often decreases in active muscles due to vasodilation, preventing a significant increase in afterload that would impair output.

Q: A decrease in which of the following is the most likely cause of peripheral edema in a patient with long-term alcoholism and liver disease?

Plasma colloid osmotic pressure. ***Plasma colloid osmotic pressure*** - **Liver disease** leads to decreased synthesis of **albumin**, the primary protein responsible for maintaining **plasma colloid osmotic pressure** [2]. - A reduction in this pressure allows fluid to extravasate from the capillaries into the interstitial space, causing **edema** [1], [3]. *Interstitial colloid osmotic pressure* - An increase, rather than a decrease, in interstitial colloid osmotic pressure would pull more fluid into the interstitial space, contributing to edema. - However, in liver disease with reduced albumin production, the primary issue is reduced plasma, not interstitial, colloid osmotic pressure [4]. *Interstitial hydrostatic pressure* - An increase in interstitial hydrostatic pressure would tend to drive fluid back into the capillaries, thus *reducing* edema. - A decrease would allow more fluid to accumulate in the interstitium, but this is not the primary mechanism in liver disease-related edema. *Capillary hydrostatic pressure* - An increase in **capillary hydrostatic pressure** can cause edema (e.g., in heart failure) [1]. - While liver disease can lead to conditions like **portal hypertension** (an increase in pressure within the portal venous system), this primarily causes ascites and not directly peripheral edema, which is more directly linked to decreased plasma colloid osmotic pressure [4].

Q: Maximum cross sectional area is seen in which of the following vessels?

Capillaries. ***Capillaries*** - While individual capillaries are very narrow, their **vast number** and extensive branching result in the largest total cross-sectional area in the circulatory system. - This large cross-sectional area is crucial for **slow blood flow**, allowing for efficient exchange of nutrients, oxygen, and waste products with tissues. *Arteries* - Arteries have a relatively **small total cross-sectional area** compared to capillaries due to their limited number, even though individual arteries are wide. - This smaller area contributes to the **high pressure** and rapid flow of blood from the heart. *Arterioles* - Arterioles are smaller than arteries but still represent a collectively **smaller cross-sectional area** than capillaries due to their branching pattern. - They primarily function in **regulating regional blood flow** and systemic blood pressure through vasoconstriction and vasodilation. *Veins* - Veins collectively have a **larger cross-sectional area than arteries**, but it is still significantly less than the total cross-sectional area of the capillary beds. - They serve as a **blood reservoir** and return deoxygenated blood to the heart at low pressure.

Q: Hormone primarily responsible for blood pressure regulation following acute blood loss is:

ADH. ***ADH*** - **Antidiuretic hormone (ADH)**, also known as **vasopressin**, is released in response to decreased blood volume and pressure detected by **baroreceptors**. - Its primary role is to increase water reabsorption in the **renal collecting ducts** and cause **vasoconstriction**, both of which help restore blood volume and pressure. - This makes ADH the key **hormonal mechanism** for BP regulation following acute blood loss. *Aldosterone* - **Aldosterone** is crucial for long-term **blood pressure regulation** by increasing sodium and water reabsorption in the kidneys. - While important for volume restoration, its effects are **slower** (hours) and more focused on electrolyte balance rather than immediate BP stabilization after acute blood loss. *ANP* - **Atrial natriuretic peptide (ANP)** is released in response to **atrial stretch** due to increased blood volume and acts to lower blood pressure. - It promotes **vasodilation** and **sodium/water excretion**, counteracting the body's efforts to raise blood pressure after blood loss. - ANP levels are **suppressed** during hypovolemia. *Epinephrine* - **Epinephrine** increases heart rate and cardiac contractility, and causes vasoconstriction, providing an immediate increase in blood pressure. - However, it's primarily a **catecholamine** (not a classic hormone) part of the **sympathetic nervous system** response, and while it acts immediately, ADH provides the sustained hormonal BP regulation.

Q: During heavy exercise the cardiac output (CO) increases up to five fold while pulmonary arterial pressure rises very little. This physiological ability of the pulmonary circulation is best explained by

Increase in the number of open capillaries. ***Increase in the number of open capillaries*** - During heavy exercise, the significant increase in cardiac output is accommodated by the **recruitment of previously closed pulmonary capillaries**. - This recruitment, along with **distension of existing capillaries**, reduces overall pulmonary vascular resistance, allowing blood flow to increase without a substantial rise in pulmonary arterial pressure. *Large amount of smooth muscle in pulmonary arterioles* - While pulmonary arterioles do contain smooth muscle, their primary role is in **regulating regional blood flow** and response to hypoxia, not facilitating large increases in overall blood flow during exercise. - The pulmonary circulation is characterized by **low resistance** and high capacitance compared to the systemic circulation, meaning it has less smooth muscle tone at baseline. *Sympathetically mediated greater distensibility of pulmonary vessels* - The pulmonary vasculature has **limited sympathetic innervation** compared to systemic vessels, and sympathetic activity plays a minor role in its distensibility during exercise. - Changes in pulmonary vascular resistance during exercise are primarily due to **mechanical factors** (recruitment and distension) rather than neurogenic control. *Smaller surface area of pulmonary circulation* - The pulmonary circulation actually has a **vast capillary surface area** crucial for efficient gas exchange. - A smaller surface area would lead to **higher resistance** and a greater pressure increase for a given flow, which contradicts the observation during exercise.

Q: Which causes raised angiotensin in blood?

Decreased blood pressure. ***Decreased blood pressure*** - A decrease in blood pressure is the **primary physiological trigger** that signals the kidneys to release **renin**, initiating the **renin-angiotensin-aldosterone system (RAAS)**. - Renal baroreceptors in the juxtaglomerular apparatus sense decreased renal perfusion pressure and stimulate renin release. - Renin converts **angiotensinogen** to **angiotensin I**, which is then converted to **angiotensin II** (the active form) by **angiotensin-converting enzyme (ACE)**. - This represents the most direct and important mechanism for raising angiotensin levels in response to hemodynamic changes. *Raised cardiac output* - **Increased cardiac output** generally leads to **increased blood pressure**, which would suppress renin release and reduce angiotensin levels. - The body's homeostatic mechanisms aim to lower blood pressure in response to increased cardiac output, not raise angiotensin. - This has the opposite effect on the RAAS system. *Increased sympathetic tone* - While **increased sympathetic tone does stimulate renin release** via β1-adrenergic receptors on juxtaglomerular cells, it is typically a **secondary mechanism** that occurs in response to decreased blood pressure. - Sympathetic stimulation is one of three major stimuli for renin release, but in physiological terms, it usually acts as part of the compensatory response to hypotension rather than as an independent primary cause. - The question asks for the cause of raised angiotensin, and decreased blood pressure is the more direct and primary trigger. *Increased blood volume* - **Increased blood volume** results in **elevated blood pressure**, which would suppress renin release and consequently lower angiotensin levels. - Atrial natriuretic peptide (ANP) is released in response to increased blood volume, which inhibits renin secretion. - This has the opposite effect on angiotensin levels.

Q: The main cause of increased blood flow to exercising muscles is :

Vasodilatation due to local metabolites. ***Vasodilatation due to local metabolites*** - During exercise, muscles produce various **metabolites** such as **adenosine**, **lactate**, **potassium ions**, and **carbon dioxide**, which directly cause local vasodilatation. - This **metabolite-induced vasodilation** is the primary mechanism for increased blood flow to active muscles, ensuring adequate oxygen and nutrient supply. *Increased sympathetic discharge to peripheral vessels* - **Sympathetic stimulation** generally causes **vasoconstriction** in many peripheral vascular beds to redirect blood flow away from non-essential organs. - While sympathetic activity increases during exercise, its direct effect on skeletal muscle arterioles via beta-2 adrenergic receptors is vasodilatory, but this is overridden and localized by **metabolic autoregulation**. *Raised blood pressure* - While **blood pressure** does increase during exercise, it is a consequence of increased cardiac output and does not directly cause the specific **vasodilatation** within the exercising muscles. - A higher systemic blood pressure helps maintain perfusion against the dilated vascular beds, but the localized increase in flow is primarily due to local factors. *Increased heart rate* - An **increased heart rate** contributes to a higher **cardiac output**, ensuring more blood is available for distribution throughout the body, including to exercising muscles. - However, an elevated heart rate alone does not explain the selective increase in blood flow to active muscle beds; that specificity is due to **local vasodilatory mechanisms**.

Q: What primarily causes vasoconstriction in skin?

Sympathetic. ***Sympathetic*** - The **sympathetic nervous system** primarily controls vasoconstriction in the skin via **adrenergic receptors** on vascular smooth muscle. - Activation of these nerves releases **norepinephrine**, leading to the contraction of smooth muscle and thus narrowing of blood vessels. *Warm climate* - A warm climate typically causes **vasodilation** in the skin, allowing for increased blood flow to the surface to facilitate heat loss. - This is a physiological response to prevent **overheating**, not to vasoconstrict. *Wheal and flare* - A **wheal and flare reaction** is a localized immune response, often to allergens, characterized by histamine release causing **vasodilation** (flare) and edema (wheal). - This reaction involves localized vasodilation, not systemic or primary vasoconstriction. *Parasympathetic* - The **parasympathetic nervous system** generally has minimal direct control over cutaneous vascular tone, especially regarding vasoconstriction. - Its primary role in the skin is related to **glandular secretions**, such as sweat production.

Q: Most potent cerebral vasodilator is

Hypercarbia. ***Hypercarbia*** - **Hypercapnia** (increased arterial carbon dioxide tension, PaCO2) is the most potent physiological cerebral vasodilator. - An increase in PaCO2 directly causes cerebral arterioles to dilate, leading to a significant increase in **cerebral blood flow (CBF)** to help clear excess CO2. *Nitroprusside* - **Sodium nitroprusside** is a powerful systemic vasodilator that also affects cerebral vessels, but its primary action is not selectively cerebral. - Its effects on CBF are complex and can be inconsistent in comparison to CO2, and it carries risks like **cyanide toxicity**. *Nitroglycerin* - **Nitroglycerin** primarily causes venodilation and has some arterial vasodilating effects, mainly in vascular beds like the coronary arteries. - While it can cause some cerebral vasodilation, it is not as potent or direct in modulating CBF as CO2. *Beta blocker* - **Beta-blockers** (e.g., propranolol, metoprolol) are primarily used to reduce heart rate, blood pressure, and myocardial contractility. - They generally have **minimal or no direct vasodilatory effect** on cerebral blood vessels; some may even cause vasoconstriction.

Question 1

Cardiac output increases in exercise primarily by

Accepted Answer

Sympathetic stimulation

Answer

Increase in heart rate

Answer

Increase in preload

Answer

Increase in afterload

Question 2

Which of the following is the PRIMARY location for arterial baroreceptors involved in blood pressure regulation?

Accepted Answer

Carotid sinus

Answer

Aortic arch

Answer

Left auricle

Answer

Crista terminalis

Question 3

A decrease in which of the following is the most likely cause of peripheral edema in a patient with long-term alcoholism and liver disease?

Accepted Answer

Plasma colloid osmotic pressure

Answer

Interstitial colloid osmotic pressure

Answer

Interstitial hydrostatic pressure

Answer

Capillary hydrostatic pressure

Question 4

Maximum cross sectional area is seen in which of the following vessels?

Accepted Answer

Capillaries

Answer

Arteries

Answer

Arterioles

Answer

Veins

Question 5

Hormone primarily responsible for blood pressure regulation following acute blood loss is:

Accepted Answer

ADH

Answer

Aldosterone

Answer

ANP

Answer

Epinephrine

Question 6

During heavy exercise the cardiac output (CO) increases up to five fold while pulmonary arterial pressure rises very little. This physiological ability of the pulmonary circulation is best explained by

Accepted Answer

Increase in the number of open capillaries

Answer

Large amount of smooth muscle in pulmonary arterioles

Answer

Sympathetically mediated greater distensibility of pulmonary vessels

Answer

Smaller surface area of pulmonary circulation

Question 7

Which causes raised angiotensin in blood?

Accepted Answer

Decreased blood pressure

Answer

Raised cardiac output

Answer

Increased sympathetic tone

Answer

Increased blood volume

Question 8

The main cause of increased blood flow to exercising muscles is :

Accepted Answer

Vasodilatation due to local metabolites

Answer

Increased sympathetic discharge to peripheral vessels

Answer

Raised blood pressure

Answer

Increased heart rate

Question 9

What primarily causes vasoconstriction in skin?

Accepted Answer

Sympathetic

Answer

Warm climate

Answer

Wheal and flare

Answer

Parasympathetic

Question 10

Most potent cerebral vasodilator is

Accepted Answer

Hypercarbia

Answer

Nitroprusside

Answer

Nitro-glycerine

Answer

Beta blocker

Cardiovascular System — MCQs

Cardiovascular System — MCQs

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