Cardiovascular System Practice Questions

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.

Q: Which of the following is the mechanism for a decrease in splanchnic blood flow during exercise?

Arteriolar vasoconstriction due to sympathetic stimulation. ***Arteriolar vasoconstriction due to sympathetic stimulation*** - During **exercise**, the **sympathetic nervous system** is activated, leading to a release of **norepinephrine** and **epinephrine**. These neurotransmitters bind to **alpha-1 adrenergic receptors** on **splanchnic arterioles**, causing **vasoconstriction**. - This **vasoconstriction** shunts blood away from the gastrointestinal tract, liver, and spleen, redirecting it towards the **skeletal muscles** and heart, which have a higher metabolic demand during exercise. *Increased splanchnic metabolic demand* - The **splanchnic organs** (gut, liver, spleen) actually experience a *decrease* in activity and metabolic demand during strenuous exercise, as their primary functions are temporarily reduced. - An increase in splanchnic metabolic demand would typically lead to **vasodilation** to meet those demands, not a decrease in blood flow. *Arteriolar vasodilation due to parasympathetic stimulation* - **Parasympathetic stimulation** generally causes **vasodilation** in the gut and is primarily active during rest and digestion. - During exercise, **parasympathetic activity** is *reduced*, and **sympathetic activity** predominates, leading to **vasoconstriction**, not vasodilation. *Decreased cardiac output to splanchnic organs* - While the *proportion* of **cardiac output** directed to splanchnic organs decreases during exercise, the overall **cardiac output** *increases* significantly. - The reduction in splanchnic blood flow is a result of **active vasoconstriction** and blood redistribution, not a direct decrease in total cardiac output itself, which is actually elevated.

Q: Cerebral perfusion pressure is

mean arterial pressure - intracranial pressure. ***mean arterial pressure - intracranial pressure*** - **Cerebral perfusion pressure (CPP)** is defined as the net pressure gradient causing blood flow to the brain, calculated by subtracting the **intracranial pressure (ICP)** from the **mean arterial pressure (MAP)**. - A healthy CPP is crucial for maintaining adequate **cerebral blood flow** and preventing **brain ischemia** or injury. *cerebral blood flow / brain surface area in m^2* - This formula represents **cerebral blood flow density** or intensity across a surface area, not the actual perfusion pressure. - While relating to brain perfusion, it does not account for the **pressure gradient** that drives blood into the brain. *cerebral blood flow * brain surface area in m^2* - This calculation yields a value that is a product of flow and area, not a measure of the effective **perfusion pressure**. - It does not incorporate the **intracranial pressure**, which is a critical opposing force to cerebral blood flow. *mean arterial pressure + intracranial pressure* - Adding **mean arterial pressure (MAP)** and **intracranial pressure (ICP)** would result in a value that does not reflect the *net driving pressure* for blood into the brain. - **ICP** acts as a resistance against arterial flow, so it must be subtracted, not added, to determine the effective perfusion pressure.

Q: In a fetus highest oxygen concentration is found in?

Umbilical vein. ***Umbilical vein*** - The **umbilical vein** carries oxygenated blood from the **placenta**, which serves as the site of gas exchange, making its oxygen concentration the highest in the fetal circulation. - This highly oxygenated blood bypasses the fetal lungs via shunts such as the **ductus venosus** and **foramen ovale** to supply vital organs. *Superior vena cava* - The **superior vena cava** carries deoxygenated blood from the upper body and head back to the heart, mixing with oxygenated blood in the right atrium. - Its blood has a relatively **low oxygen saturation** compared to the umbilical vein. *Left ventricle* - The **left ventricle** receives blood that has already mixed in the atria and passed through the foramen ovale, then the left atrium. - While relatively oxygen-rich for systemic circulation, its oxygen concentration is lower than that in the umbilical vein due to **mixing with deoxygenated blood**. *Ascending aorta* - The **ascending aorta** receives blood from the left ventricle, which has a moderate oxygen content. - The blood in the ascending aorta feeds the upper body, but its oxygen saturation is lower than that in the umbilical vein due to the **physiological shunts** and mixing of blood.

Q: Which centre first gets the input from neural control of cardiovascular system?

NTS. ***NTS (Nucleus Tractus Solitarius)*** - The **NTS** is the primary medullary relay nucleus for **baroreceptor** and **chemoreceptor afferent inputs**, making it the first center to receive information regarding cardiovascular status. - It integrates sensory information from the **glossopharyngeal (CN IX)** and **vagus (CN X)** nerves. *Raphe Nucleus* - The **raphe nuclei** are a collection of nuclei in the brainstem that primarily play a significant role in modulating **serotonin release**, affecting mood, sleep, and pain. - They are not the initial receiving centers for primary cardiovascular sensory inputs. *RVLM (Rostral Ventrolateral Medulla)* - The **RVLM** is a crucial site for generating **sympathetic vasomotor tone** and is influenced by the NTS. - While essential for cardiovascular control, it receives its primary regulatory input from the NTS and is not the *initial* input center. *Nucleus ambiguus* - The **nucleus ambiguus** contains **preganglionic parasympathetic neurons** that project to the heart (via the vagus nerve) to decrease heart rate. - It receives input from the NTS for cardiovascular regulation but is not the first structure to process afferent cardiovascular information.

Q: Baroreceptor is which type of feedback?

Negative feedback. ***Negative feedback*** - The **baroreceptor reflex** detects changes in blood pressure and initiates responses that **counteract** the change, bringing blood pressure back to its set point - For example, if blood pressure increases, baroreceptors signal the brainstem to **decrease heart rate** and **dilate blood vessels**, thus lowering blood pressure - This is the **primary mechanism** for maintaining cardiovascular homeostasis *Feed forward control* - This type of control **anticipates** future disturbances and makes adjustments **before** the disturbance can significantly affect the system - The baroreceptor reflex specifically responds to **current** pressure changes detected by the receptors, not predicted future changes *Positive feedback* - Positive feedback mechanisms **amplify** the initial stimulus, moving the system further **away** from the set point - Examples include blood clotting cascade and uterine contractions during childbirth - Blood pressure regulation via baroreceptors aims for **stability**, not amplification *Both negative and positive* - While some physiological systems can exhibit both types of feedback under different circumstances, the baroreceptor reflex operates **exclusively** through negative feedback - The primary function is to maintain **homeostasis** by opposing deviations from normal blood pressure

Q: ECG shows a mean axis of 90 degrees. In which of the following would be present the maximum voltage of R wave?

aVF. aVF - A mean axis of **90 degrees** means the electrical activity of the heart is primarily oriented vertically downwards. [2] - The **aVF lead** is oriented vertically downwards (inferiorly) at **+90 degrees**, so it will best "see" this electrical activity, resulting in the largest R wave. [1] *aVL* - The **aVL lead** is oriented at **-30 degrees**, looking at the lateral wall of the heart. - A 90-degree axis is nearly perpendicular to aVL, meaning the electrical activity would be mostly moving away from or across it, yielding a small or negative deflection. [1] *I* - **Lead I** is oriented horizontally at **0 degrees**, looking at the lateral wall of the heart. - A 90-degree axis is perpendicular to Lead I, so its R wave would be minimal or nonexistent, or an equiphasic complex would be observed. [2] *III* - **Lead III** is oriented at **+120 degrees**, looking at the inferior wall of the heart. - While Lead III is also an inferior lead, a 90-degree axis is not perfectly aligned with it, so the R wave amplitude would be smaller compared to aVF.

Question 1

Most potent cerebral vasodilator is

Accepted Answer

Hypercarbia

Answer

Nitroprusside

Answer

Nitro-glycerine

Answer

Beta blocker

Question 2

Which of the following is a FALSE statement regarding hemodynamic changes occurring during exercise?

Accepted Answer

Venoconstriction in exercising muscles as well as increased cardiac output leads to marked increase in systemic blood pressure.

Answer

Venous return is augmented by the pumping action of skeletal muscles.

Answer

End-diastolic volume increases in the failing heart during exercise.

Answer

The increased adrenergic nerve impulses to the heart as well as an increased concentration of circulating catecholamines help to augment the contractile state of the myocardium.

Question 3

Which of the following is the mechanism for a decrease in splanchnic blood flow during exercise?

Accepted Answer

Arteriolar vasoconstriction due to sympathetic stimulation

Answer

Increased splanchnic metabolic demand

Answer

Arteriolar vasodilation due to parasympathetic stimulation

Answer

Decreased cardiac output to splanchnic organs

Question 4

The major pressures that determine filtration and absorption of fluid by capillaries are the:

Accepted Answer

Capillary hydrostatic pressure and plasma colloid osmotic pressure

Answer

Plasma colloid osmotic pressure and interstitial hydrostatic pressure

Answer

Capillary hydrostatic pressure and tissue colloid osmotic pressure

Answer

Interstitial hydrostatic pressure and tissue colloid osmotic pressure

Question 5

Cerebral perfusion pressure is

Accepted Answer

mean arterial pressure - intracranial pressure

Answer

cerebral blood flow / brain surface area in m^2

Answer

cerebral blood flow * brain surface area in m^2

Answer

mean arterial pressure + intracranial pressure

Question 6

In a fetus highest oxygen concentration is found in?

Accepted Answer

Umbilical vein

Answer

Superior vena cava

Answer

Left ventricle

Answer

Ascending aorta

Question 7

Which one of the following is a function of PGI2?

Accepted Answer

Causes blood vessel relaxation and prevents platelet clumping

Answer

Causes blood vessel constriction and prevents platelet clumping

Answer

Causes blood vessel constriction and promotes platelet clumping

Answer

Causes blood vessel relaxation and promotes platelet clumping

Question 8

Which centre first gets the input from neural control of cardiovascular system?

Accepted Answer

NTS

Answer

Raphe Nucleus

Answer

RVLM

Answer

Nucleus ambiguus

Question 9

Baroreceptor is which type of feedback?

Accepted Answer

Negative feedback

Answer

Feed forward control

Answer

Positive feedback

Answer

Both negative and positive

Question 10

ECG shows a mean axis of 90 degrees. In which of the following would be present the maximum voltage of R wave?

Accepted Answer

aVF

Answer

aVL

Answer

I

Answer

III

Cardiovascular System — MCQs

Cardiovascular System — MCQs

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