Cardiovascular System Practice Questions

Q: When blood pressure falls below 40 mm Hg, which mechanism of regulation is working?

CNS ischemic reflex. ***CNS ischemic reflex*** - The **CNS ischemic reflex** is activated when blood pressure falls below 60 mmHg, with maximal activation below 40 mmHg, indicating severe ischemia in the brain's vasomotor center. - This reflex elicits an intense **sympathetic vasoconstriction** and cardiac stimulation to prioritize blood flow to the brain even at the expense of other organs. *Chemoreceptor response* - The chemoreceptor reflex is primarily activated by a decrease in **arterial pO2**, an increase in **pCO2**, or a decrease in **pH**. - While it can increase blood pressure, it is not the primary or most profound regulatory mechanism specifically triggered by extremely low blood pressure (below 40 mmHg) to prevent brain ischemia. *Baroreceptor response* - **Baroreceptors** are most sensitive to changes in blood pressure within the normal to moderately hypotensive range (e.g., 60-180 mmHg). - At very low pressures (below 40-50 mmHg), baroreceptors become **less sensitive** or "saturated," and their effectiveness in raising blood pressure significantly diminishes. *None of the options* - This option is incorrect because the **CNS ischemic reflex** specifically functions as a powerful, last-ditch mechanism to maintain cerebral blood flow during severe hypotension which is a life saving reflex during conditions like hemorrhage.

Q: By what percentage can cardiac output increase in a healthy adult during intense physical activity compared to resting levels?

300 - 400 %. ***300 - 400 %*** - In a healthy adult, **cardiac output** can increase remarkably during intense physical activity. - The heart can increase its output by **3 to 4 times** (or 300-400%) above resting levels during peak exertion. - At rest, cardiac output is approximately **5 L/min**, but during maximal exercise, it can reach **20-25 L/min** in well-conditioned individuals. - This represents the heart's **reserve capacity** to meet increased metabolic demands during exercise. *0 - 50 %* - This range represents a very **limited increase** in cardiac output and would be indicative of significant underlying cardiac impairment or **heart failure**. - A healthy individual would experience a much greater increase in cardiac output during intense activity than this small percentage. *50 - 100 %* - This range also suggests a **suboptimal cardiac response** for a healthy adult undergoing intense physical activity. - While some increase is present, it does not reflect the full capacity of a healthy cardiovascular system to adapt to extreme demands. *100 - 200 %* - While a 100-200% increase is substantial, it still **underestimates the maximal capacity** achievable in a healthy, well-conditioned individual during intense physical exertion. - The heart has a greater capacity for increasing its output to meet metabolic demands during peak exercise.

Q: Which of the following stimuli is primarily responsible for triggering the Bezold-Jarisch reflex?

Activation of cardiac C-fiber afferents. ***Activation of cardiac C-fiber afferents*** - The **Bezold-Jarisch reflex** is primarily triggered by stimulation of **cardiac mechanoreceptors and chemoreceptors** located in the ventricles, particularly the inferoposterior wall of the left ventricle. - These receptors have **unmyelinated vagal C-fiber afferents** that transmit signals to the medullary cardiovascular centers. - Activation of these afferents leads to the characteristic triad: **bradycardia, hypotension, and vasodilation** via increased parasympathetic activity and withdrawal of sympathetic tone. - Common triggers include vigorous ventricular contraction with decreased filling, certain drugs (veratridine), myocardial ischemia (especially inferior wall MI), and reperfusion. *Decreased venous return* - While **decreased venous return** creates the hemodynamic context (ventricular underfilling) that can lead to vigorous contraction of a relatively empty ventricle, it is not itself the *trigger* of the reflex. - The actual trigger is the activation of the ventricular receptors sensing this abnormal contraction pattern, which then signal via C-fiber afferents. - Decreased venous return alone, without receptor activation, would not produce the reflex. *Parasympathetic withdrawal* - **Parasympathetic withdrawal** would cause tachycardia and is opposite to the Bezold-Jarisch reflex, which involves **increased parasympathetic activity**. - This is a compensatory response seen in other reflexes like the baroreceptor reflex during hypotension. *Increased sympathetic stimulation* - **Increased sympathetic stimulation** produces tachycardia, increased contractility, and vasoconstriction—effects opposite to the Bezold-Jarisch reflex. - The reflex actually causes **sympathetic withdrawal** along with parasympathetic activation.

Q: Which of the following statements about cardiac muscle is true?

Cardiac muscle cells have centrally located nuclei.. ***Cardiac muscle cells have centrally located nuclei.*** - Unlike **skeletal muscle** cells which have multiple, peripherally located nuclei, cardiac muscle cells typically have one or two **centrally located nuclei**. - This is a key distinguishing histological feature when observing cardiac muscle tissue under a microscope. *Cardiac muscle fibers are arranged in sheets.* - While cardiac muscle forms the walls of the heart, its individual fibers (cells) are **branched** and interconnected, not typically described as being arranged in discrete sheets. - The arrangement allows for a **syncytium-like functionality**, enabling coordinated contraction. *Cardiac muscle fibers are spindle-shaped.* - **Spindle-shaped cells** with a single central nucleus are characteristic of **smooth muscle**, not cardiac muscle. - Cardiac muscle cells are branched and generally cylindrical with blunt ends. *Cardiac muscle lacks gap junctions.* - Cardiac muscle cells are abundant in **gap junctions**, which are critical for electrical coupling and synchronous contraction. - These gap junctions are located within **intercalated discs** and allow for rapid propagation of action potentials between cells.

Q: In pregnancy, plasma volume increase is maximum at what gestational age?

30 wks. ***30 wks*** - **Plasma volume** typically reaches its maximum expansion around **30-34 weeks of gestation**, increasing by approximately 40-50% compared to pre-pregnancy levels. - This increase is crucial for supporting the **fetoplacental unit**, enhancing nutrient delivery, and protecting against supine hypotension. *10 wks* - At **10 weeks**, the increase in plasma volume is still modest, with significant expansion primarily occurring in the **second trimester**. - Most of the rapid expansion begins after the **first trimester**, around the 12-week mark. *20 wks* - While plasma volume is significantly increasing by **20 weeks**, it has not yet reached its peak. - The continuous expansion continues through the **third trimester** before stabilizing. *25 wks* - At **25 weeks**, plasma volume is substantially elevated, but the maximum expansion is usually observed a few weeks later. - The peak is generally in the **early third trimester**, around 30-34 weeks.

Q: What is the duration of the second heart sound (S2)?

0.08 sec. ***0.08 sec*** - The second heart sound (S2) is composed of two components: A2 (aortic valve closure) and P2 (pulmonic valve closure). The normal duration of S2, encompassing both components, is approximately **0.08 seconds**. - This short duration reflects the rapid closure of the aortic and pulmonic valves at the beginning of **diastole**. *0.15sec* - A duration of **0.15 seconds** for S2 is significantly longer than normal, which could indicate abnormal valve function or conditions causing delayed valve closure. - Such prolonged duration might be observed in conditions like **severe pulmonic stenosis** or **pulmonic hypertension**, which are not the typical duration of a healthy S2. *0.12 sec* - A duration of **0.12 seconds** is also longer than the typical normal range for S2. - While still shorter than 0.15 seconds, it could suggest subtle delays in valve closure or splitting that exceeds the usual physiological splitting. *0.1 sec* - A duration of **0.1 seconds** is slightly prolonged but generally falls within a range that might be considered borderline or indicative of minimal physiological variations. - However, in typical healthy individuals, the S2 duration is closer to 0.08 seconds, making 0.1 seconds less precise for the most common duration.

Q: What is the primary neural mechanism responsible for vasoconstriction in the skin?

Sympathetic. ***Sympathetic nervous system*** - The **sympathetic nervous system** primarily controls blood vessel tone, including vasoconstriction in the skin, through the release of **norepinephrine**. - **Adrenergic receptors** (alpha-1) on vascular smooth muscle cells respond to norepinephrine, leading to contraction and narrowing of the blood vessels. *Parasympathetic nervous system* - The **parasympathetic nervous system** generally has very limited, if any, direct innervation to cutaneous blood vessels for vasoconstriction; its primary role in the cardiovascular system is to decrease heart rate. - While it can cause vasodilation in some tissues, it does not mediate vasoconstriction in the skin. *Somatic nervous system* - The **somatic nervous system** is responsible for voluntary muscle control and transmitting sensory information, not for regulating **autonomic functions** like skin blood flow. - It innervates **skeletal muscles** and sensory receptors directly, lacking connections to cutaneous blood vessels for vasoconstriction. *Enteric nervous system* - The **enteric nervous system** is a complex network of neurons found within the walls of the **gastrointestinal tract**, where it primarily controls digestion. - It does not play any direct role in regulating vasoconstriction in the skin.

Question 1

When blood pressure falls below 40 mm Hg, which mechanism of regulation is working?

Accepted Answer

CNS ischemic reflex

Answer

Chemoreceptor response

Answer

Baroreceptor response

Answer

None of the options

Question 2

By what percentage can cardiac output increase in a healthy adult during intense physical activity compared to resting levels?

Accepted Answer

300 - 400 %

Answer

0 - 50 %

Answer

50 - 100 %

Answer

100 - 200 %

Question 3

Which hormone is primarily responsible for regulating blood pressure in response to significant blood loss due to hemorrhage?

Accepted Answer

Epinephrine (Adrenaline)

Answer

Vasopressin (ADH)

Answer

Aldosterone

Answer

Atrial Natriuretic Peptide (ANP)

Question 4

Which of the following stimuli is primarily responsible for triggering the Bezold-Jarisch reflex?

Accepted Answer

Activation of cardiac C-fiber afferents

Answer

Parasympathetic withdrawal

Answer

Decreased venous return

Answer

Increased sympathetic stimulation

Question 5

Which of the following statements regarding fetal circulation is correct?

Accepted Answer

The heart of the fetus receives blood with higher oxygen saturation than maternal mixed venous blood.

Answer

The presence of fetal hemoglobin shifts the oxyhemoglobin dissociation curve to the right.

Answer

The foramen ovale closes before birth.

Answer

PO2 of fetal blood leaving the placenta is higher than maternal mixed venous PO2.

Question 6

Which of the following statements about cardiac muscle is true?

Accepted Answer

Cardiac muscle cells have centrally located nuclei.

Answer

Cardiac muscle fibers are arranged in sheets.

Answer

Cardiac muscle fibers are spindle-shaped.

Answer

Cardiac muscle lacks gap junctions.

Question 7

In pregnancy, plasma volume increase is maximum at what gestational age?

Accepted Answer

30 wks

Answer

10 wks

Answer

20 wks

Answer

25 wks

Question 8

What is the duration of the second heart sound (S2)?

Accepted Answer

0.08 sec

Answer

0.15 sec

Answer

0.1 sec

Answer

0.12 sec

Question 9

What is the primary neural mechanism responsible for vasoconstriction in the skin?

Accepted Answer

Sympathetic

Answer

Parasympathetic

Answer

Enteric nervous system

Answer

Somatic nervous system

Question 10

Which one of the following is the CORRECT statement regarding coronary blood flow?

Accepted Answer

Coronary blood flow is directly related to perfusion pressure and inversely related to resistance

Answer

Coronary blood flow is inversely related to perfusion pressure and directly related to resistance

Answer

Coronary blood flow is directly related to perfusion pressure and also to resistance

Answer

Coronary blood flow is inversely related to both pressure and resistance

Cardiovascular System — MCQs

Cardiovascular System — MCQs

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