Cardiovascular System Practice Questions

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: All of the following increase blood pressure except:

Atrial natriuretic peptide. ***Atrial natriuretic peptide*** - **Atrial natriuretic peptide (ANP)** is released by atrial cells in response to increased atrial stretch (due to higher blood volume/pressure). - Its primary function is to **decrease blood pressure** by promoting natriuresis (sodium excretion) and diuresis (water excretion), leading to reduced blood volume and vasodilation. *Angiotensin II* - **Angiotensin II** is a potent **vasoconstrictor**, directly increasing systemic vascular resistance and thereby blood pressure. - It also stimulates the release of **aldosterone**, which leads to increased sodium and water reabsorption, further elevating blood volume and blood pressure. *Sympathetic activation* - **Sympathetic activation** releases catecholamines (norepinephrine and epinephrine), which bind to alpha-1 adrenergic receptors on vascular smooth muscle, causing **vasoconstriction**. - It also increases **heart rate** and myocardial contractility, leading to an increased cardiac output, all contributing to elevated blood pressure. *Aldosterone* - **Aldosterone** is a mineralocorticoid hormone that promotes the reabsorption of **sodium and water** in the renal tubules. - This increases the **extracellular fluid volume** and subsequently the blood volume, which directly contributes to an increase in blood pressure.

Q: Which part of the action potential in cardiac pacemaker cells is primarily affected by calcium channel blockers?

Phase 0. ***Phase 0*** - In cardiac pacemaker cells (SA and AV nodes), **Phase 0 (rapid depolarization)** is mediated by **L-type calcium channels**, NOT the fast sodium channels seen in ventricular myocytes. - Calcium channel blockers primarily inhibit these **L-type calcium channels**, leading to a **slower rate of depolarization** and **reduced conduction velocity** through the AV node. - This is the **primary mechanism** by which these drugs slow heart rate and cause AV nodal blockade. *Phase 1* - Phase 1 (initial rapid repolarization) is **absent in pacemaker cells** because they lack the fast sodium channels and transient outward potassium currents characteristic of ventricular myocytes. - This phase is not relevant to pacemaker cell action potentials. *Phase 2* - Phase 2 (plateau phase) is also **absent or minimal in pacemaker cells**. - Pacemaker action potentials lack the prolonged plateau seen in ventricular myocytes. - This phase is not the primary target of calcium channel blockers in pacemaker tissue. *Phase 3* - Phase 3 (repolarization) occurs in pacemaker cells and is mediated by **potassium efflux**. - Calcium channel blockers do **not directly affect** this phase, as it is driven by potassium channels, not calcium channels. - Their effect on Phase 3 is minimal compared to their direct action on Phase 0.

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

Cardiac muscle has a short refractory period.. ***Cardiac muscle has a short refractory period.*** - This statement is **incorrect** because cardiac muscle has a **long refractory period** (~250 ms), which prevents summation and tetanus by ensuring that the muscle relaxes completely before another action potential can be initiated. - The long refractory period is crucial for maintaining the heart's **pumping efficiency** and preventing arrhythmias. *Cardiac muscle obeys the all or none law.* - This statement is **correct**. Individual **cardiac muscle cells** obey the **all-or-none law**; when a stimulus reaches threshold, the cell contracts fully. - The heart as a whole organ can grade its contraction force through recruitment of more fibers and the Frank-Starling mechanism, but at the cellular level, the all-or-none principle applies. *Cardiac muscle exhibits the Frank-Starling mechanism* - This statement is **correct**. The **Frank-Starling mechanism** describes the heart's ability to increase its force of contraction and stroke volume in response to an increase in **venous return** or end-diastolic volume. - This intrinsic regulatory mechanism allows the heart to match its output to the venous return, optimizing cardiac efficiency. *Cardiac muscle has automaticity and rhythmicity* - This statement is **correct**. **Automaticity** refers to the ability of specialized cardiac cells (e.g., in the sinoatrial node) to spontaneously generate action potentials without external nervous stimulation. - **Rhythmicity** is the regular, cyclical discharge of these action potentials, which drives the rhythmic beating of the heart.

Question 1

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 2

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 3

In a fetus highest oxygen concentration is found in?

Accepted Answer

Umbilical vein

Answer

Superior vena cava

Answer

Left ventricle

Answer

Ascending aorta

Question 4

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 5

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

Accepted Answer

NTS

Answer

Raphe Nucleus

Answer

RVLM

Answer

Nucleus ambiguus

Question 6

True about Postural Hypotension:

Accepted Answer

Decreases in systolic blood pressure 20 mmHg within 3 minutes.

Answer

Decreases in systolic blood pressure 20 mmHg within 6 minutes.

Answer

Decreases in diastolic blood pressure 20 mmHg within 6 minutes.

Answer

Decreases in diastolic blood pressure 20 mmHg within 3 minutes.

Question 7

Baroreceptor is which type of feedback?

Accepted Answer

Negative feedback

Answer

Feed forward control

Answer

Positive feedback

Answer

Both negative and positive

Question 8

All of the following increase blood pressure except:

Accepted Answer

Atrial natriuretic peptide

Answer

Angiotensin II

Answer

Sympathetic activation

Answer

Aldosterone

Question 9

Which part of the action potential in cardiac pacemaker cells is primarily affected by calcium channel blockers?

Accepted Answer

Phase 0

Answer

Phase 1

Answer

Phase 2

Answer

Phase 3

Question 10

Which of the following statements about cardiac muscle is incorrect?

Accepted Answer

Cardiac muscle has a short refractory period.

Answer

Cardiac muscle obeys the all or none law.

Answer

Cardiac muscle exhibits the Frank-Starling mechanism

Answer

Cardiac muscle has automaticity and rhythmicity

Cardiovascular System — MCQs

Cardiovascular System — MCQs

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