C) To increase blood pressure and fluid balance

Explanation: The RAAS is a hormone system that regulates blood pressure and fluid balance, primarily through the actions of angiotensin II and aldosterone.

B) Compression of vessels

Explanation: Cushing's Reflex is triggered by the compression of blood vessels, leading to a cascade of physiological responses aimed at restoring blood pressure and oxygen levels.

B) ADH

Explanation: Antidiuretic hormone (ADH) is crucial for water conservation in the kidneys, helping to retain water and concentrate urine.

B) Increases sodium reabsorption

Explanation: Aldosterone is a hormone that increases sodium reabsorption in the kidneys, which leads to increased water retention and blood volume.

B) Pain due to blockage in vessels of the heart

Explanation: Angina refers to the chest pain that occurs due to reduced blood flow to the heart muscle, often caused by blockages in coronary arteries.

B) Diad (1 L tubule & 1 T tubule)

Explanation: In cardiac physiology, E-C coupling involves a diad structure, which consists of one L tubule and one T tubule, facilitating calcium signaling necessary for muscle contraction.

C) Exchange of substances

Explanation: Capillaries are primarily designed for the exchange of gases, nutrients, and waste products between blood and tissues, making them crucial for physiological function.

B) Hepatojugular reflex

Explanation: The presence of the hepatojugular reflex is indicative of right ventricular failure (RVF) and suggests systemic congestion.

B) 0.8 seconds

Explanation: The cardiac cycle lasts for 0.8 seconds, which includes all the events that occur during one heartbeat.

B) They detect changes in blood pressure

Explanation: Baroreceptors are responsible for sensing changes in blood pressure and play a crucial role in the feedback mechanism of Cushing's Reflex, helping to regulate cardiovascular responses.

C) It decreases

Explanation: In heart failure, there is a decrease in pulmonary flow, which can lead to ventilation/perfusion (V/Q) mismatch and cyanosis.

B) S2

Explanation: The S2 heart sound is produced by the closure of the semilunar valves, occurring at the end of ventricular systole.

B) Vasoconstriction

Explanation: Angiotensin II (Ag II) is known to cause vasoconstriction, which increases blood pressure and helps regulate blood flow.

A) Force Frequency Relationship

Explanation: The Bowditch effect is commonly referred to as the Force Frequency Relationship, which describes how an increase in heart rate (HR) leads to an increase in contractility.

C) 9th nerve

Explanation: The 9th nerve, also known as the nerve of Herring, carries signals from the carotid sinus to the medulla.

A) End Systolic Volume

Explanation: ESV refers to the End Systolic Volume, which is the amount of blood left in the ventricle at the end of systole, typically ranging from 40-50 ml.

C) 120-130 ml

Explanation: The normal End Diastolic Volume (EDV) is typically between 120-130 ml, representing the amount of blood in the ventricles at the end of diastole.

C) During hemorrhage

Explanation: The alternate activation of baroreceptors and chemoreceptors is particularly noted during hemorrhage, as the body attempts to regulate blood pressure and maintain homeostasis in response to significant blood loss.

C) It decreases heart rate

Explanation: Cushing's Reflex results in a decrease in heart rate (HR) as part of the body's response to increased blood pressure and the activation of the cardiovascular control centers.

D) Tricuspid Regurgitation

Explanation: A prominent Y descent in the JVP is typically associated with tricuspid regurgitation, indicating rapid filling of the right atrium during diastole.

D) Purkinje Fibres

Explanation: Purkinje fibres are known for having the fastest conduction velocity in the heart, allowing for rapid transmission of electrical impulses to the ventricles.

B) Prevent blood backlog

Explanation: Venous valves are crucial for preventing the backflow of blood in the veins, ensuring that blood flows efficiently back to the heart.

C) AV valve closure

Explanation: The S1 heart sound is associated with the closure of the atrioventricular (AV) valves, marking the beginning of ventricular contraction.

B) 0.02-0.05 m/s (Slowest)

Explanation: The AVN conducts impulses at a speed of 0.02-0.05 m/s, making it the slowest part of the cardiac conduction system, which allows for proper filling of the ventricles.

B) Diastole

Explanation: The heart receives its blood supply during diastole, which is crucial for myocardial oxygenation and overall heart function.

C) It increases

Explanation: The Bowditch effect indicates that an increase in heart rate (HR) results in increased contractility, demonstrating a positive inotropic effect.

C) It is the slowest conduction point to ensure ventricular filling

Explanation: The AV node has the slowest conduction velocity, which allows time for the ventricles to fill with blood before they contract.

B) It creates negative ITP

Explanation: During deep inspiration, the thoracic suction pump creates a negative intrathoracic pressure (ITP), which aids in venous return by facilitating blood flow toward the heart.

C) Sinusoidal capillaries

Explanation: Sinusoidal capillaries have gaps ranging from 300-600 nm, allowing for the passage of larger molecules and cells, found in organs like the liver and spleen.

B) In hyperdynamic conditions like pregnancy

Explanation: S3 can be heard in hyperdynamic conditions such as pregnancy and certain pathological states like anemia and congestive heart failure (CHF).

B) EF < 40-45%

Explanation: An Ejection Fraction (EF) of less than 40-45% is considered a sign of ventricular failure, indicating poor ventricular efficiency.

B) It gets phosphorylated

Explanation: During sympathetic activation, Phospholamban is phosphorylated, which prevents it from inhibiting the SERCA pump, resulting in faster relaxation of the heart.

C) Increased blood pressure

Explanation: In response to hypoxia, Cushing's Reflex leads to increased blood pressure as a compensatory mechanism to enhance blood flow and oxygen delivery to vital organs.

B) CO = SV × HR

Explanation: Cardiac output (CO) is calculated using the formula CO = Stroke Volume (SV) × Heart Rate (HR), which is essential for understanding heart function.

B) They act as a peripheral heart

Explanation: The calf muscles are referred to as the 'peripheral heart' because they help push blood toward the heart, thereby improving venous return (VR).

C) Cardiogenic Shock

Explanation: Cardiogenic and obstructive shock are conditions that lead to increased JVP due to impaired heart function or obstruction in blood flow.

B) Isovolumetric contraction

Explanation: During the early phase of systole, isovolumetric contraction occurs when the AV valve closes and the semilunar valve opens, leading to an increase in ventricular pressure.

B) Decreased blood pressure

Explanation: Cardiogenic shock is characterized by decreased stroke volume, cardiac output, and blood pressure, leading to severe complications.

B) Increased filtration leading to pulmonary edema

Explanation: An increase in PCWP indicates increased filtration pressure in the pulmonary capillaries, which can lead to pulmonary edema when it exceeds 25 mmHg.

B) A complete block of the AV node leading to no impulses in the Bundle of His

Explanation: Stroke Adam syndrome occurs when there is a complete block of the AV node, resulting in no impulses reaching the Bundle of His, leading to a pulseless stage until the Bundle of His starts generating its own impulses.

B) Decrease in venous return (VR)

Explanation: The first change after a postural adjustment is a decrease in venous return (VR), which subsequently affects other cardiovascular parameters such as end-diastolic volume (EDV) and stroke volume (SV).

B) Brain

Explanation: The brain is an organ that has maximum blood flow at rest while exhibiting minimum resistance, allowing it to maintain essential functions even when the body is at rest.

B) Presence of gap junctions

Explanation: Nodal tissue contains a number of gap junctions and pacemaker cells, which are essential for the conduction of electrical impulses in the heart.

B) The Bundle of His takes over as pacemaker

Explanation: If the SAN fails, the AV node can take over as the pacemaker, and if the AV node fails, the Bundle of His can assume this role.

B) 0-5 mmHg

Explanation: The normal pressure of Jugular Venous Pressure (JVP) is typically between 0-5 mmHg, which is important for assessing right atrial pressure.

B) It recoils, contributing to diastolic blood pressure

Explanation: During diastole, the aorta recoils after being stretched during systole, which helps maintain diastolic blood pressure (DBP) and ensures continuous blood flow.

C) Storing blood and acting as a blood reservoir

Explanation: Capacitance vessels, such as systemic veins, have high compliance and low recoil, allowing them to stretch and store blood, effectively acting as reservoirs.

A) Hamburger phenomenon

Explanation: The Hamburger phenomenon refers to the effect of capillary diameter on the concentration of red blood cells and plasma, where smaller diameters lead to less RBC and more plasma.

C) Volume remains constant while pressure increases

Explanation: Isovolumetric contraction is characterized by a constant volume in the ventricles while the pressure increases, as the heart prepares to eject blood.

B) To detect changes in blood pressure

Explanation: Low-pressure baroreceptors play a crucial role in detecting changes in blood pressure, particularly in response to variations in venous return during respiration.

C) To maintain mean blood pressure

Explanation: Baroreceptors act as a brake to blood pressure by responding to changes in blood pressure and helping to maintain mean blood pressure within a normal range.

C) It decreases

Explanation: As heart rate increases, the duration of the cardiac cycle decreases, leading to increased work done and higher oxygen demand.

C) Increased blood pressure

Explanation: Increased activity of the vascular motor center (VMC) during Cushing's Reflex leads to vasoconstriction and subsequently increases blood pressure as a compensatory response to hypoxia.

B) -40 to -60 mV

Explanation: The resting membrane potential of nodal tissue is non-stable and ranges from -40 to -60 mV, which is crucial for its auto-rhythmicity.

B) Prevent separation during contraction

Explanation: Intercalated discs contain desmosomes that prevent the separation of cardiac muscle cells during contraction, ensuring mechanical stability.

C) Distribute blood

Explanation: Resistance vessels, primarily arterioles, are responsible for the distribution of blood throughout the body, regulating blood flow and pressure.

C) Increases blood flow

Explanation: During exercise, there is recruitment of capillaries which decreases resistance and increases blood flow to meet the metabolic demands of tissues.

B) Turbulent flow

Explanation: A Reynolds number greater than 3000 indicates turbulent flow, which is less efficient compared to laminar flow (Re < 2000).

B) ↓ Ag II

Explanation: ACE inhibitors decrease the levels of angiotensin II, leading to venodilation, which subsequently reduces venous return (VR), end-diastolic volume (EDV), and preload.

A) Atrial flutter

Explanation: A cannon wave in JVP is associated with conditions such as complete AV block, atrial flutter, and ventricular extrasystole, indicating a lack of coordination between atrial and ventricular contractions.

C) Total peripheral resistance (TPR)

Explanation: Total peripheral resistance (TPR) is the primary determinant of afterload, influencing the pressure the heart must generate to eject blood.

B) Decreases HR due to increased intrathoracic pressure

Explanation: During deep expiration, intrathoracic pressure increases, leading to decreased venous return (VR), which results in decreased heart rate (HR) due to reduced baroreceptor stimulation.

B) Aortic Regurgitation (AR)

Explanation: A rightward and upward movement on the graph indicates an increase in EDV, which is characteristic of Aortic Regurgitation (AR).

C) In the adventitial layer of the artery wall

Explanation: Baroreceptors are located in the adventitial layer of the artery wall, particularly at sites such as the carotid sinus and aortic sinus.

B) Calcium release from the sarcoplasmic reticulum (SR)

Explanation: In CICR, calcium influx from the extracellular fluid (20-25% from DHPR) triggers the release of 75-80% of calcium from the ryanodine receptor (RyR2) in the sarcoplasmic reticulum, which is crucial for cardiac muscle contraction.

C) It prevents the sensing of blood pressure

Explanation: Cutting the Buffer Nerve leads to an inability to stimulate the medullary centers, which results in the body not being able to sense blood pressure, ultimately causing neurogenic hypertension.

C) Beyond physiological limits

Explanation: In chronic heart failure (CHF), the heart may operate beyond its physiological limits, which can impair the beneficial effects of the Bowditch effect.

C) 2000 ml/100 gm/min

Explanation: The maximum blood flow in tissues is noted to be 2000 ml/100 gm/min, indicating the high demand for blood supply in active tissues.

B) From endocardium to epicardium for depolarization and from epicardium to endocardium for repolarization

Explanation: The depolarization wave travels from the endocardium to the epicardium, while repolarization occurs in the reverse direction, from epicardium to endocardium.

B) Amount of blood pumped by each ventricle per beat

Explanation: Stroke Volume (SV) is defined as the amount of blood pumped by each ventricle with each heartbeat, typically around 70-80 ml.

B) Decreased vagal supply leading to ventricular escape phenomena

Explanation: Idio-ventricular rhythm occurs when there is less or no vagal supply, leading to a phenomenon where the ventricles escape from the normal pacing mechanisms.

B) S2 is loud and high frequency

Explanation: S2 is characterized by being loud and high frequency, while S1 is also loud but has less frequency compared to S2.

B) Increases HR

Explanation: Rapid infusion of saline or NaCl leads to increased venous return (VR), which stimulates the SA node directly, resulting in an increased heart rate (HR).

C) Inverse correlation

Explanation: Blood flow velocity has an inverse correlation with the cross-sectional area (CSA), meaning that as the CSA increases, the velocity of blood flow decreases.

B) To sense chemical changes in the blood

Explanation: Chemoreceptors are responsible for sensing chemical changes in the blood, such as levels of oxygen and carbon dioxide, which is vital for maintaining respiratory and cardiovascular balance.

B) Orthostatic Hypotension

Explanation: This condition, known as Postural or Orthostatic Hypotension, occurs when blood pressure fails to increase appropriately after standing, leading to significant drops in systolic and diastolic pressures.

C) 2 ml/100 gm/min

Explanation: At rest, skeletal muscle has a blood flow rate of 2 ml/100 gm/min, indicating its relatively low demand for blood flow when not in use.

C) Hypertension resulting from the inability to sense blood pressure

Explanation: Neurogenic hypertension occurs when there is a lesion that prevents the body from sensing blood pressure, leading to an increase in blood pressure.

A) Cardiac Output equals Blood Pressure divided by Total Peripheral Resistance

Explanation: The equation CO = BP/TPR illustrates the relationship between cardiac output, blood pressure, and total peripheral resistance, which is crucial for understanding cardiovascular physiology.

C) Phase 0

Explanation: Phase 0 of the cardiac action potential is marked by the sudden depolarization due to the opening of sodium channels.

B) Heart failure

Explanation: The Framingham Criteria are used to diagnose heart failure by assessing various clinical signs and symptoms.

B) Atrial fibrillation

Explanation: The absence of the 'a' wave in JVP is commonly associated with atrial fibrillation, where the normal atrial contraction is disrupted.

B) ITP decreases, leading to increased venous return

Explanation: During inspiration, the intrathoracic pressure becomes negative, which increases venous return and subsequently activates baroreceptors, leading to a decrease in blood pressure.

C) They constrict to compensate for volume loss

Explanation: During shock, capacitance vessels constrict due to sympathetic activation and alpha-1 receptor stimulation, helping to compensate for volume loss and maintain blood pressure.

B) A pattern of vasomotor activity

Explanation: Mayer’s Wave is associated with the alternate activation of baroreceptors and chemoreceptors, reflecting a pattern of vasomotor activity that can be observed during certain physiological conditions.

B) A temporary increase in Ca2+ accumulation when afterload is increased

Explanation: The Anrep effect describes the initial response of the heart to increased afterload, characterized by a temporary rise in calcium accumulation, which can enhance contractility.

B) ESV remains the same, but pressure increases

Explanation: An upward movement on the graph indicates that while End-Systolic Volume (ESV) remains constant, the pressure increases, which is associated with an increase in afterload.

C) Brain

Explanation: The brain regulates its blood flow based on aerobic metabolism, responding to changes in partial pressures of oxygen (PO2) and carbon dioxide (PCO2), leading to vasodilation under hypoxic conditions.

A) Anterior bundle

Explanation: The anterior bundle is referred to as the bundle of Bachmann’s, which plays a role in the conduction system of the heart.

C) Right atrial stretching

Explanation: The release of ANP is triggered by right atrial stretching, which occurs when blood volume increases, leading to a decrease in blood pressure.

B) Current of injury

Explanation: In myocardial infarction, the leakage of potassium from myocardial cells results in tall T waves and ST elevation on the ECG, indicating a current of injury.

B) Percentage of blood ejected by the ventricle per beat

Explanation: Ejection Fraction (EF) is the percentage of blood ejected by the ventricle with each heartbeat, calculated as EF = stroke volume/EDV × 100, and is a key indicator of ventricular efficiency.

D) Capacitance vessels

Explanation: Capacitance vessels, such as systemic veins, are designed to store blood, accommodating changes in blood volume.

B) High permeability

Explanation: Exchange vessels, primarily capillaries, are characterized by their high permeability, allowing for the exchange of nutrients and waste between blood and tissues.

C) Veins

Explanation: Veins have the maximum blood volume and compliance, allowing them to accommodate significant changes in blood volume without a large change in pressure.

B) Load on the ventricle acting on the heart when contraction has begun

Explanation: Afterload is defined as the load or pressure that the ventricle must overcome to eject blood during contraction.

E) Increases due to increased venous return

Explanation: During deep inspiration, intrathoracic pressure decreases, leading to increased venous return (VR), which stimulates baroreceptors and results in an increased heart rate (HR).

A) Pressure Energy + Kinetic Energy = Constant

Explanation: Bernoulli's principle indicates that the sum of pressure energy and kinetic energy in a fluid system remains constant, which is fundamental to understanding blood flow dynamics.

C) It increases

Explanation: A dilated heart requires more tension to maintain its function, which leads to increased work and higher oxygen consumption.

B) Hypoperfusion of tissues

Explanation: Chemoreceptors are activated by hypoperfusion of tissues, which leads to changes in chemical levels such as decreased PO2 and increased PCO2.

C) Simple squamous epithelium

Explanation: Capillaries are lined with simple squamous epithelium, which allows for efficient exchange due to its thin structure.

D) 40-50 ml

Explanation: The normal range for End Systolic Volume (ESV) is 40-50 ml, indicating the volume of blood remaining in the ventricle after contraction.

C) Elastic recoil due to elastin protein

Explanation: Wind Kessel vessels, such as the aorta and large arteries, are characterized by their ability to stretch and recoil due to the presence of elastin protein, which helps maintain blood pressure during the cardiac cycle.

A) Organs control their own blood flow by changing their resistance

Explanation: Autoregulation refers to the ability of organs to regulate their own blood flow by adjusting their vascular resistance, ensuring adequate perfusion according to their metabolic needs.

C) At the end of the P wave

Explanation: The S4 heart sound is typically heard at the end of the P wave, indicating late ventricular filling.

A) Stages of cardiac cycle events

Explanation: The mnemonic 'MAAM COCO' helps remember the stages of the cardiac cycle, including mitral valve closure, aortic valve opening, ejection, and mitral valve opening, which are crucial for understanding the pressure-volume relationship.

B) It decreases venous return

Explanation: During expiration, the intrathoracic pressure becomes positive, which decreases venous return and activates baroreceptors, leading to an increase in blood pressure.

C) They stimulate the medulla to increase sympathetic activity

Explanation: Low-pressure baroreceptors stimulate the medulla, leading to increased sympathetic activity and decreased parasympathetic activity, which ultimately increases heart rate.

D) Capillaries

Explanation: Capillaries have the maximum cross-sectional area, which results in the minimum velocity of blood flow compared to other blood vessels.

B) Vasoconstriction

Explanation: In response to hypoxia, the primary response in the lungs is vasoconstriction, which is a unique mechanism that helps redirect blood flow to better-ventilated areas of the lungs.

B) Acute Aortic Stenosis (AS)

Explanation: An upward movement on the graph alone indicates an increase in afterload, which is characteristic of acute Aortic Stenosis (AS).

C) Fick’s principle

Explanation: Fick’s principle is noted as the best method for measuring Cardiac Output in low CO states, as it accurately assesses oxygen consumption.

C) 20-40 times

Explanation: During exercise, blood flow to skeletal muscle can increase by 20 to 40 times, reflecting the heightened demand for oxygen and nutrients during physical activity.

A) Jugular Venous Pressure

Explanation: JVP refers to Jugular Venous Pressure, which is equivalent to Central Venous Pressure (CVP) and Right Atrial Pressure (RAP), indicating the pressure in the right atrium.

B) Increase in sinus pressure and decrease in blood pressure

Explanation: Clamping the carotid artery distal to the carotid sinus increases sinus pressure, which leads to a decrease in blood pressure and heart rate.

B) Homometric Regulation

Explanation: Homometric regulation refers to the regulation of contractility that occurs without changing the muscle length, which is a key aspect of the Bowditch effect.

C) Calcium channels open

Explanation: During phase 2, also known as the plateau phase, both K+ and Ca2+ channels open, contributing to the prolonged depolarization.

B) Long absolute refractory period in phase 2

Explanation: The longest absolute refractory period occurs in phase 2, preventing tetanus and allowing the heart to fill with blood between beats.

B) Sympathetic

Explanation: The sympathetic part of the autonomic nervous system is responsible for increasing heart rate, while the parasympathetic system decreases it.

B) SV decreases

Explanation: An increase in afterload leads to a decrease in stroke volume (SV) because the heart must work harder to eject blood against the higher resistance.

B) IV irritants such as alkaloids

Explanation: The Bezold-Jarisch reflex is triggered by IV irritants like veratridin, capsaicin, and serotonin, leading to decreased heart rate (HR) and blood pressure (BP), as well as apnea.

C) Adenosine

Explanation: Adenosine is the primary substance responsible for vasodilation in the heart, helping to increase blood flow during periods of increased metabolic demand.

C) Lungs

Explanation: Autoregulation is absent in the lungs, which is a unique characteristic compared to other organs where blood flow is tightly regulated based on metabolic needs.

E) Velocity encoded phase contrast MRI

Explanation: The text states that the Velocity encoded phase contrast MRI is the most accurate method for measuring Cardiac Output, highlighting its precision in assessment.

B) Inotropic drugs

Explanation: Inotropic drugs are often prescribed for the treatment of chronic heart failure (CHF) to improve contractility and overall cardiac function.

B) Relaxation of the heart

Explanation: The Lusiotropic Effect refers to the relaxation of the heart, specifically through the process of sending Ca²⁺ back to the sarcoplasmic reticulum via the Ca²⁺ ATPase (SERCA pump).

B) Right ventricular hypertrophy

Explanation: A prominent 'a' wave in JVP is indicative of right ventricular hypertrophy, as it suggests resistance to filling, along with conditions like pulmonary or tricuspid stenosis.

B) Increased venous return

Explanation: A prominent 'V' wave in JVP is indicative of increased venous return and is also prominent in conditions like constrictive pericarditis.

B) The last line of control for blood pressure regulation

Explanation: The 'Last Ditch Response' refers to the final mechanism the body employs to maintain blood pressure during critical situations, such as ischemia, highlighting its importance in cardiovascular physiology.

C) In the atria and pulmonary artery

Explanation: Low-pressure baroreceptors are primarily located in the atria and the pulmonary artery, with the maximum concentration found at the right atrium, particularly at the junction of the vena cava and atria.

B) Increase in EDV

Explanation: A rightward movement on the graph signifies an increase in End-Diastolic Volume (EDV), indicating that more blood is filling the ventricles before contraction.

B) Increases stroke volume

Explanation: The Frank-Starling law states that an increase in the initial length of muscle fibers leads to an increase in stroke volume (SV) up to a physiological limit.

C) Increases SBP and decreases DBP

Explanation: Calcification of the aorta decreases compliance, which leads to an increase in Systolic Blood Pressure (SBP) and a decrease in Diastolic Blood Pressure (DBP), resulting in an increased pulse pressure.

D) 5 L/min

Explanation: The cardiac output (CO) at rest is approximately 5 L/min, which is essential for maintaining adequate blood flow to meet the metabolic demands of the body.

A) Pink frothy sputum

Explanation: Pink frothy sputum is a classic symptom of pulmonary congestion, often seen in patients with heart failure.

B) Decrease in sinus pressure and increase in blood pressure

Explanation: Clamping the carotid artery proximal to the carotid sinus decreases sinus pressure, which results in an increase in blood pressure and heart rate.

B) Very permeable

Explanation: Exchange vessels are characterized by their high permeability, allowing for the efficient exchange of gases, nutrients, and waste products between blood and tissues.

B) ↓ TPR

Explanation: Arteriolar dilation decreases total peripheral resistance (TPR), which in turn reduces afterload and increases stroke volume (SV).

B) CO = SV x HR

Explanation: Cardiac output (CO) is calculated using the formula CO = Stroke Volume (SV) x Heart Rate (HR), which is fundamental in understanding cardiac function.

B) Heart rate

Explanation: The Bainbridge reflex is a mechanism that helps regulate heart rate in response to changes in venous return, thereby influencing cardiac output.

B) 5.4 L/min

Explanation: The text states that the normal Cardiac Output (CO) is 5.4 L/min, which is a standard measure for assessing heart function.

D) It is not reliable in case of shunt, fistula, bypass

Explanation: The Thermodilution Method is limited in its reliability when there are shunts, fistulas, or bypasses, which can affect the accuracy of the measurements.

B) It inhibits the SERCA pump

Explanation: Phospholamban inhibits the SERCA pump, which is crucial for controlling the relaxation of the heart. When phosphorylated by the sympathetic system, it no longer inhibits the pump, leading to faster relaxation.

C) Capillaries

Explanation: Capillaries and venules lack elastic tissue and smooth muscle, which differentiates them from other blood vessels and allows for efficient exchange processes.

C) 2/3rd

Explanation: During early diastole, approximately 2/3rd of the ventricular filling occurs, indicating a significant phase of the cardiac cycle where the heart prepares for the next contraction.

C) They activate to decrease blood pressure

Explanation: When venous return increases during inspiration, baroreceptors are activated, leading to a decrease in blood pressure as part of the body's reflexive response to maintain homeostasis.

B) Requires less tension to balance the pressure

Explanation: Laplace's law states that a smaller radius requires less tension to balance the distending pressure on the wall of the vessel.

B) CO = SV × HR

Explanation: Cardiac Output (CO) is calculated using the formula CO = Stroke Volume (SV) × Heart Rate (HR), which quantifies the amount of blood pumped by each ventricle per minute.

B) CI = CO / BSA

Explanation: The Cardiac Index (CI) is calculated using the formula CI = CO / Body Surface Area (BSA), providing a measure of cardiac output relative to body size.

B) 0.04 sec

Explanation: The proto diastolic phase occurs just before starting S2 and lasts for 0.04 seconds, marking a brief period in the cardiac cycle.

B) 5.4 L

Explanation: The total blood volume in the human body is approximately 5.4 liters, with 16% located in central circulation and 80% in peripheral circulation.

B) They detect changes in blood pressure

Explanation: Baroreceptors are specialized sensors that detect changes in blood pressure, playing a crucial role in the regulation of cardiovascular function and homeostasis.

C) Radius of the vessel

Explanation: The Poiseuille-Hagen Law indicates that the radius of the vessel is the most important factor affecting blood flow, with changes in radius having a significant impact on flow rate.

B) Ventricular contraction

Explanation: Systolic Blood Pressure (SBP) is primarily caused by the contraction of the ventricles during the cardiac cycle.

C) 1/3 SBP + 2/3 DBP

Explanation: Mean Blood Pressure (MBP) is calculated using the formula MBP = 1/3 SBP + 2/3 DBP, which provides an average pressure in the arteries during one cardiac cycle.

B) Kinetic Energy becomes zero

Explanation: When the BP cuff occludes the vessel, it leads to a temporary stoppage of blood flow, resulting in kinetic energy (K.E.) being zero.

B) Due to variable resistance

Explanation: Different organs experience variable blood flow because of differences in resistance, which can change based on the physiological needs of the organ.

B) Short-term regulation

Explanation: The baroreceptor reflex is a mechanism for short-term regulation of blood pressure, responding quickly to changes in blood pressure to maintain homeostasis.

C) Caffeine

Explanation: Caffeine is one of the substances that can increase the force of contraction (FOC) of the heart, while conditions like hypoxia and acidosis decrease it.

B) Mitral Regurgitation (MR)

Explanation: A rightward and slight leftward movement on the graph indicates Mitral Regurgitation (MR), where there is an increase in EDV with a slight decrease in ESV.

B) Decrease in Diastolic Volume

Explanation: A leftward shift in the graph indicates a decrease in Diastolic Volume, which is associated with conditions like Mitral Stenosis (MS).

E) Fluid shifts from capillaries to interstitial space

Explanation: When blood pressure increases, it leads to vasodilation and increased permeability, causing fluid to shift from the capillaries to the interstitial space, which helps to decrease blood pressure.

C) Radius of the vessel

Explanation: The radius of the vessel is the most important factor in determining vascular resistance, as resistance is proportional to the fourth power of the radius, meaning small changes in radius can lead to significant changes in resistance.

C) Aortic recoil

Explanation: Diastolic Blood Pressure (DBP) is influenced by the recoil of the aorta after ventricular contraction, which helps maintain pressure in the arteries.

B) 400 ml/100 gm/min

Explanation: The maximum blood flow for the kidneys is approximately 400 ml/100 gm/min, indicating their high metabolic activity and demand for blood supply.

A) 50 ml/100 gm/min

Explanation: At rest, the brain receives approximately 50 ml/100 gm/min of blood flow, reflecting its metabolic needs even during periods of low activity.