BIOS1170 Cardiovascular System

Which of the following is the correct conduction pathway through the heart? (A) SA node; AV node; bundle of His; bundle branches; Purkinje fibers (B) SA node; Purkinje fibers; AV node; bundle of His; bundle branches (C) Bundle of His; bundle branches; Purkinje fibers; SA node; AV node (D) Purkinje fibers; bundle of His; bundle branches; SA node; AV node

(A) SA node; AV node; bundle of His; bundle branches; Purkinje fibers

Which of the following components of an ECG represents ventricular repolarization? (A) T wave (B) PQ interval (C) P wave (D) TQ segment

(A) T wave

The mean arterial pressure (MAP) is important because (A) it represents the driving pressure for blood flow (B) it reflects the difference in time that systole lasts compared to diastole (C) it is less than the average of systolic and diastolic pressure (D) it is always greater than mean venous pressure

(A) it represents the driving pressure for blood flow

Chemicals released by metabolically active cells will cause which of the following? (A) relaxation of arteriolar smooth muscle to increase blood flow (B) contraction of capillary smooth muscle to increase blood flow (C) relaxation of capillary smooth muscle to decrease blood flow (D) contraction of arteriolar smooth muscle to decrease blood flow

(A) relaxation of arteriolar smooth muscle to increase blood flow

The right marginal artery and the posterior interventricular artery are branches of the (A) right coronary artery. (B) left coronary artery. (C) coronary sinus. (D) circumflex artery.

(A) right coronary artery.

During exercise, which organs receive an increase in the proportion of cardiac output delivered to it? (A) skeletal muscle, heart, and skin (B) brain and heart (C) skeletal muscle, skin and brain (D) skeletal muscle, heart, and brain

(A) skeletal muscle, heart, and skin Blood flow to and from the brain is not affected by changes in cardiac output because cerebral blood flow is mainly affected by local metabolic activity (or neural activity in the case of the brain)

Atrial systole occurs in the interval between which two waves of the ECG?

Atrial systole (atrial contraction) occurs between the P-wave and the QRS complex

Which heart valves are open during atrial systole?

Atrioventricular valves During atrial systole, the blood is passing through from the atrium to the ventricles.

What are baroreceptors, and where are important baroreceptors located in the body?

Baroreceptors are pressure receptors. They are located in the aorta and carotid arteries.

Explain why blood flow is the slowest in capillary vascular beds.

Blood flow velocity is inversely proportional to the total cross-sectional area of the blood vessels. Consider the ascending aorta. Essentially all the blood flows through it. It's cross-sectional area is about 2cm squared (i.e. small). So if you need to get 5 litres of blood passing through the aorta every minute (i.e. the cardiac output), then the blood has to be moving very fast. In contrast the total cross-sectional area of the capillaries is huge, as about 3000 cm squared. So to get the same blood passing through them each minute, the blood will be travelling much slower. Don't forget that the same blood volume is flowing through each vessel type. So all the blood that flows through the aorta then passes through all of the arteries. Then through all the arterioles, then all the capillaries etc. So in each vessel "type" the blood flow is the cardiac output and is the same.

During exercise increase, muscle contraction increases venous return to the heart. What effect does this have on cardiac output?

Cardiac Output = Heart Rate x Stroke Volume Cardiac output increases. Venous return refers to the amount of blood that returns back to the heart. An increase in venous return leads to an increase in end diastolic ventricular volume (or how much blood is in the ventricle before ejection). An increase in end diastolic ventricular volume would mean that more force would be required to push that volume of blood up the semilunar valves, so there would be an increase in the force of ventricular contraction. Also, venous return determines stroke volume, so if the stroke volume increases, assuming heart rate remains constant, the cardiac output would increase.

What effect with the following changes have on filtration in capillaries? - Decreased capillary hydrostatic pressure - Increased plasma osmotic pressure - Increased interstitial hydrostatic pressure - Increased capillary blood pressure

Decreased capillary hydrostatic pressure - decrease filtration. Capillary hydrostatic pressure is the most important force pushing water out of the capillaries into the interstitium. Increased plasma osmotic pressure - decrease filtration. Increased interstitial hydrostatic pressure - under normal circumstances would decrease filtration. Increased capillary blood pressure - increase filtration.

Which heart valves are open, and which are closed when blood is being pumped from the ventricles into the arteries?

During the ejection phase of ventricular systole, semilunar valves (Aortic and Pulmonary) are open, while the atrioventricular valves are closed to prevent the backflow of blood from the ventricles into the atria.

Define the term in ejection fraction. What is a normal ejection fraction and why could ejection fraction be reduced?

Ejection fraction - the measure of the % of blood in the left ventricle that is pumped out during systole. Normal ejection fraction - around 55% - 70% Ejection fraction can be reduced when the ventricles cannot contract forcefully enough to eject the appropriate volume of blood. An ejection fraction of less than 50% could indicate heart failure.

Define the terms preload and afterload.

Preload - the amount of stretch on the ventricle at the end of ventricular filling. Measured as ventricular end-diastolic volume (how much blood is in the ventricle before ejection). Increasing preload increases stroke volume. Afterload - the pressure that the heart must work against to eject blood during systole. Measured as the diastolic aortic blood pressure. Increasing afterload decreases stroke volume.

What is the name of the fibres that rapidly transmit depolarizations across the ventricles?

Purkinje fibers

What does an anti-diuretic hormone like Vasopressin do?

Regulates and balances the amount of water in your blood

Explain how the Renin-Angiotensin-Aldosterone System works when there is a drop in arterial pressure and decreased blood volume

Renin is released from the kidney cells Renin acts on Angiotensin to produce Angiotensin I, which goes into the lung circulation, and then gets converted into Angiotensin II by an angiotensin-converting enzyme in the lungs. Angiotensin II acts on the following: - Vasoconstriction of blood vessels (because Angiotensin II is a potent vasocontrictor) - Increased reabsorption of water and sodium in the kidneys, which helps to maintain blood volume. - the adrenal cortex, which causes the release of Aldosterone, which acts on the kidneys - the brain. Signals go to the pituitary gland, which sends signals to increase the feeling of thirst (which makes you drink more water) and to produce vasopressin, which is a powerful anti-diuretic and also acts on the kidneys. All of the above actions cause an increase in arterial pressure and an increase in blood volume.

Describe the circumflex branch of the coronary circulation

The left coronary artery distributes blood to the left side of the heart, the left atrium and ventricle, and the interventricular septum. The circumflex artery branches of the left coronary artery and continues around the heart to form an anastomosis with the right coronary artery.

What part of the heart normally acts as the pacemaker?

The sinoatrial node (SA node). This is where pacemaker cells reach the threshold fastest are located.

True or false. Increasing the number of vascular beds arranged in parallel reduces total resistance.

True. R = resistance 1/R(total) = 1/R(1) + 1/R(2) + 1/R(3) +... 1/R(n). With this formula, as number of vessels increases, 1/T(total) increases. Therefore R decreases.

Is the following statement true or false? Adrenaline and noradrenaline activate adrenergic receptors in the heart to increase heart rate.

True. Adrenaline is released when the sympathetic nervous system is activated. Noradrenaline is the neurotransmitter released from sympathetic nerves. Adrenaline and noradrenaline combine with adrenergic receptors on heart cells to increase heart rate.

Is the following statement true or false? Angiotensin II increases sodium reabsorption in the kidney.

True. Angiotensin does act directly on the kidney to increase Na+ reabsorption, but its action is mostly through the secondary effect of stimulating the release of the hormone aldosterone from the adrenal gland. Aldosterone strongly increases the reabsorption of sodium in the kidneys, which in turn increases blood volume.

Is the following statement true or false? Blood returning to the heart from the veins enters the atria.

True. Blood returning to the heart from the veins enters the atria (for left via the pulmonary veins, for right via the superior and inferior vena cava)

Is the following statement true or false? The right side of the heart acts as the pump for the pulmonary circulation.

True. Deoxygenated blood enters the right atrium via the superior and inferior vena cava, then is pumped through the right ventricles and up the pulmonary artery, which carries the deoxygenated blood away from the heart and towards the lungs, where they get refilled with oxygen.

Is the following statement true or false? The myocardial action potential lasts for about 300 m/sec.

True. Myocardial action potential lasts longer than skeletal muscle or nerve action potential, which means that they sustain their contraction for longer than the skeletal muscles or nerves can.

Is the following statement true or false? The pulmonary circulation is a low-pressure circulation.

True. Pulmonary circulation generates low pressure. An indicator of this would be the fact that right ventricle (the pump for pulmonary circulation) is less muscular than the left ventricle (the pump for systemic circulation).

Is the following statement true or false? The sinoatrial node is the auto active area of the heart with the highest rate of discharge.

True. The cells of the SA node are pacemaker cells, which means they generate their own electrical activity. They reach threshold faster than any other cells.

What is oedema?

the buildup of fluid in the interstitial space. Can be caused by reduced concentration of plasma protein, increased capillary permeability, increased venous pressure, and blockage of lymphatic vessels.

The preload is approximately the same as the ________. (A) end-systolic pressure (B) atrial pressure (C) end-diastolic pressure (D) aortic systolic pressure

(C) end-diastolic pressure Pre-load is defined as the amount of stretch on the ventricles at the end of ventricular filling. It is measured as the amount of blood that is in the ventricles before it gets ejected up the aorta/pulmonary artery (ventricular end-diastolic volume)

During which phase of the cardiac cycle are all four heart valves open? (A) ventricular ejection (B) isovolumetric contraction (C) none (D) ventricular filling

(C) none

The primary site of exchange between blood and interstitial fluid occurs across what type of blood vessel? (A) venules (B) arteries (C) veins (D) capillaries

(D) capillaries

If a person has a resting arterial blood pressure of 160/100, they would have... (A) Heart failure (B) Third degree heart block (C) hypotension (D) hypertension

(D) hypertension

In which vascular bed is the resistance to blood flow lowest?

Pulmonary vascular bed. Pulmonary circulation is a lower pressure circulation because less force is required to push blood through the pulmonary circulation.

What is the relationship between radius and pressure in a blood vessel?

There is an inverse relationship between the radius and pressure in a blood vessel. Blood pressure = 1 divided by radius to the power of 4 (according to Pouiselle's Law, and assuming that viscosity of blood and vessel length remain constant)

Is the following statement true or false? Arteries are blood vessels that carry blood away from the heart.

True. Veins carry blood to the heart, while arteries carry blood away from the heart.

Blood supply to the heart comes from ________. (A) coronary arteries (B) blood within the atria (C) blood within the ventricles (D) aorta

(A) coronary arteries

The total cross-sectional area is greatest in which blood vessel type? (A) venules (B) arteries (C) capillaries (D) veins

(C) capillaries

Where in the vascular system is the greatest resistance to blood flow?

Arterioles

Diastole (both atrial and ventricular) occurs between which 2 waves of the ECG?

Atrial diastole occurs between the QRS complex and the subsequent P-wave. Ventricular diastole occurs between the T-wave and the subsequent QRS complex.

What are the most important factors controlling blood pressure in the short term?

Cardiac output (CO) and Total Peripheral Resistance (TPR)

During ventricular systole, pressure in the ventricle increases until it becomes greater than the pressure in the arteries. At that point blood flows from the ventricles into the arteries. During isovolumetric contraction, which heart valves are open, and which heart valves are closed?

During isovolumetric contraction, the ventricles are contracting, pushing the AV valves closed, but this pressure is not enough to push open the semilunar valves. While it is a very brief phase, all the heart valves are closed.

True or false. There are two periods during the cardiac cycle where all 4 cardiac valves are opened.

False. The point of the valves is to control the direction of flow. If all 4 valves are open at the same time, there has to be blood flowing in the wrong direction through at least one of them.

Which heart valves are closed during atrial systole?

Semilunar valves During atrial systole, the ventricle is relaxed, so the semilunar valves (aortic and pulmonary valves) are closed to prevent blood from flowing back into ventricles from the arteries.

Is the following statement true or false? Blood flows into the coronary arteries during ventricular systole when blood is flowing into the aorta.

False. During ventricular systole the aortic valve is open and its seals off the entrance into the coronary arteries. Blood flows into the coronary arteries during ventricular diastole when the aortic valve is closed.

What part of the heart is it located in and why?

It is located at the top of the right atrium close to the entry point of the superior vena cava. From there, electrical activity will spread out across the atrium, causing it to contract and push blood into the ventricle.

What does the P-wave of the ECG represent?

atrial depolarization

What happens in the condition known as complete (or 3rd degree) heart block? (A) Coronary arteries are blocked by plaques, preventing blood and oxygen from reaching the myocardial contractile cells (B) Electrical signals from the SA node never reach the ventricles, so the contraction of the atria is not coordinated with the contraction of the ventricles (C) The mitral valve leaflets calcify and close, preventing blood from being pumped efficiently by the left side of the heart (D) The fibrous skeleton of the heart breaks down, interfering with the passage of blood from the atria to the ventricles

(B) Electrical signals from the SA node never reach the ventricles, so the contraction of the atria is not coordinated with the contraction of the ventricles. Heart block - refers to a conduction problem through the AV node. In a complete heart block, the AV node is not able to propagate action potentials from the atria to the ventricles, so the ventricles must generate their own activity via pacemaker muscle cells in the ventricle itself. This results in the atria and ventricles contracting out of sync with each other.

Which of the following equations is correct? (A) resistance = (length × radius4) / viscosity (B) cardiac output = stroke volume × heart rate (C) mean arterial pressure = resistance × viscosity (D) cardiac output = mean arterial pressure × total peripheral resistance

(B) cardiac output = stroke volume × heart rate

The term autorhythmicity refers to the heart's ability to________. (A) act as a functional syncytium (B) generate its own contractile cycle (C) intrinsically modify its contractility (D) conduct action potentials along the conduction pathway

(B) generate its own contractile cycle

Blood returning to the heart from the pulmonary circuit first enters the... (A) left ventricle (B) left atrium (C) right ventricle (D) right atrium

(B) left atrium

What are the small muscle masses called that attached to the chordae tendineae (A) pectinate muscles (B) papillary muscles (C) venae cavae (D) trabeculae carneae

(B) papillary muscles

Which of the following is FALSE regarding the following statement? Edema is likely to occur when... (A) a subject sits in a stationary position for an extended period of time. (B) the capillary hydrostatic pressure decreases. (C) the concentration of protein in the blood decreases. (D) the flow rate of lymph in the lymphatic circulation decreases.

(B) the capillary hydrostatic pressure decreases.

Through which of the following regions do action potential propagate most slowly? (A) sinoatrial (SA) node (B) atrial muscle (C) atrioventricular (AV) node. (D) atrioventricular (AV) bundle

(C) atrioventricular (AV) node. Slow conduction through the AV node allows the atrial muscle to contract before the ventricular muscle.

The long plateau phase of the cardiac muscle action potential is due to... (A) movement of fewer sodium ions across the cell membrane (B) decrease in the amount of calcium diffusing across the membrane (C) calcium channels remaining open (D) increased membrane permeability to potassium ion

(C) calcium channels remaining open During the plateau phase of the cardiac muscle action potential, calcium enters the cell slowly while potassium rushes out of the cell.

The opening and closing of the atrioventricular and semilunar valves is driven by ________. (A) contraction and relaxation of the valve (B) contraction of the ventricle and atria that pull the valves into place (C) differences in pressure across the valve (D) contraction of muscles attached to the valves

(C) differences in pressure across the valve

Which statement best describes arteries? (A) Only large arteries are lined with endothelium (B) All arteries have high blood pressure (C) All arteries carry oxygenated blood (D) All arteries have blood flow away from the heart

(D) All arteries have blood flow away from the heart

In the circulatory system, the largest pressure drop occurs across which blood vessels? (A) venules (B) capillaries (C) veins (D) arterioles

(D) arterioles

When viewing a dissected heart, it is easy to visually discern the right and left ventricles by ________ (A) locating the apex (B) finding the papillary muscles (C) tracing out where the auricles connect (D) noticing the thickness of the ventricle walls

(D) noticing the thickness of the ventricle walls. The left ventricular wall is thicker than the right ventricular wall.

What blood vessel carries deoxygenated blood to the lungs? (A) pulmonary vein (B) inferior vena cava (C) superior vena cava (D) pulmonary artery

(D) pulmonary artery

What causes the rapid depolarization phase of a contractile cell action potential? (A) sodium movement out of the cell (B) calcium movement into the cell (C) potassium movement into the cell (D) sodium movement into the cell

(D) sodium movement into the cell For a contractile cell, the rapid depolarization phase is when sodium rushes into the cell, causing the inside of the cell to become less negative. For a pacemaker cell, the rapid depolarization phase is when calcium rushes into the cell.

The first heart sound is heard (A) when the aortic and pulmonary valves shut. (B) when the atrioventricular valves open. (C) just after the ST interval on the ECG. (D) when the ventricles contract.

(D) when the ventricles contract The first heart sound is heard when the ventricles contract and eject blood up the aorta/pulmonary artery

What effect would a decrease in the rate of baroreceptors firing have on activity in the sympathetic nervous system?

A decrease in blood pressure would cause the baroreceptor firing rate to decrease. In such a case, the baroreceptors would send a signal to the CV centers in the brainstem to increase sympathetic cardiac and vasomotor activities. Increased sympathetic cardiac activity would cause cardiac contractility to increase, and heart rate to increase as well (parasympathetic activity to the heart also decreases at the same time), while increased sympathetic vasomotor activity (increased sympathetic activity to the blood vessels, particularly the arterioles) would cause the TPR to increase. As changes cardiac contractility and heart rate contribute to changes in cardiac output, that increase in CO and TPR would then cause the blood pressure to start increasing again.

Is the following statement true or false? An anastomosis is a connection between 2 blood vessels.

An anastomosis is formed by the left and right coronary arteries, which means that there is a ring of blood supply to the entire heart. So technically true in this case.

Is the following statement true or false? Activation of sympathetic cardiac nerves decreases the slope of the pacemaker potential.

False. It increases the slope of the pacemaker potential because sympathetic nerve activation increases heart rate. If you increase the slope of the pacemaker potential, the pacemaker cells reach threshold more quickly, so contractions of the heart are close together. In other words, the heart rate increases.

Is the following statement true or false? The mass of muscle in the left ventricle is less than the mass of muscle in the right ventricle.

False. The left ventricle has a more muscular wall because it has to produce a higher pressure to pump the oxygenated blood up the aorta and to the rest of the body. It is also the pressure pump for the systemic circulation, which is a higher pressure circulation.

Is the following statement true or false? The heart can extract the oxygen it needs to function from the blood in the chambers (the chambers are the atria and the ventricles).

False. The myocardium needs to receive blood from the systemic circulation via the coronary arteries, which originate at the base of aorta and distribute oxygenated blood across the heart.

Is the following statement true or false? The systemic circulation pumps blood through the lungs.

False. The pulmonary circulation pumps blood through the lungs. The systemic circulation pumps oxygenated blood through the tissues of the body to deliver oxygen.

Is the following statement true or false? Arteries are blood vessels that carry blood that is loaded with oxygen.

False. While arteries of the systemic circulation carry oxygenated blood, arteries of the pulmonary circulation carry deoxygenated blood.

Describe how vasopressin gets released.

In a situation such as when arterial pressure and blood volume decrease significantly (like when someone is losing a lot of blood), the arterial baroreceptors and atrial receptors get activated and send signals to the brainstem, particularly the hypothalamus and the pituitary gland. The pituitary gland releases vasopressin, which is a vasoconstrictor and an anti-diuretic hormone, so not only does it cause vasoconstriction of the blood vessels, but it also increases reabsorption of water and sodium into the kidneys. The former process results in an increase in TPR, while the latter process decreases urine volume and increases blood volume, so as to conserve water to make up for water volume lost in initial blood loss. Both of these processes result in arterial pressure and blood volume increasing back towards the set point.

What are the most important factors controlling blood pressure in the long term?

In the long-term, BP is controlled by changing blood volume, primarily through the actions of vasopressin and angiotensin II. This is regulated by renal function and urine production. When BP increases, urine output increases, leading to a decrease in blood volume. Conversely, when BP decreases, urine output decreases, leading to an increase in blood volume.

List four factors that would cause vasodilation in arterioles in skeletal muscle.

Increased concentration of metabolites in the interstitial fluid Decreased concentration of oxygen in interstitial fluid Decreased sympathetic stimulation Release of histamine

How does increased activity in the sympathetic nervous system affect heart function?

Increased sympathetic activity directly affects the heart by increasing the heart rate and by increasing the force with which the heart contracts (cardiac contractility)

Where is the great cardiac vein located?

It is located in the anterior interventricular groove next to the anterior interventricular artery.

What is the equation relating mean arterial pressure, cardiac output and total peripheral resistance?

MAP = CO x TPR

What is the myocardium?

Muscular tissue that's only found in the heart. Myo - refers to muscle; cardium - refers to the heart.

Is the following statement true or false? Atrial receptors measure blood pressure.

Somewhat true. Atrial receptors are located on the right side of the heart so they measure pressure at the right atrium (but not arterial pressure). Effectively, they measure the volume of blood returning to the heart.

True or false. There are two periods during the cardiac cycle where all 4 cardiac valves are closed.

True. The two phases where all 4 cardiac valves are closed are the isovolumetric contraction phase, and the isovolumetric relaxation phase. During the isovolumetric contraction phase, the AV valves are closed to prevent backdrip of blood from the ventricles to the atria, and the semilunar valves are closed because the ventricular pressure has not increased to the point where it exceeds pressure in the arteries. During the isovolumetric relaxation phase, pressure in the ventricles drops. Blood flows back against the cusps of the semilunar valves, causing them to shut. At the same time, while blood is flowing into the relaxed atria, the AV valves have not opened yet. This brief period is referred to as the isovolumetric relaxation phase.

What does the QRS complex of the ECG represent?

Ventricular depolarization. Atrial repolarization also occurs but it's not shown on the ECG because the atrium has relatively smaller muscle mass compared to the ventricle and therefore has little impact on the ECG reading.

What does the T wave of the ECG represent?

Ventricular repolarization

Ventricular systole occurs in the interval between which two waves of the ECG?

Ventricular systole (ventricular contraction) occurs between the QRS complex and the T-wave.

Explain the compensatory response towards a decrease in blood volume during an acute haemorrhage.

When your blood volume and pressure go down due to an acute haemorrhage, there is a decrease in cardiac filling (or a decrease in venous return), which leads to decreased cardiac output and decreased atrial receptor activity. The decrease in CO leads to a decrease in MAP, which causes a decrease in atrial baroreceptor activity. This decrease in MAP has a flow through effect onto the capillaries. In this case, this means that the capillary hydrostatic pressure drops, causing increased fluid reabsorption in the capillaries and therefore increasing blood volume. The decrease in atrial baroreceptor activity and atrial receptor activity causes an increase in the sympathetic nerve activity. The sympathetic nervous system sends signals to the veins, the arterioles, and to the heart. The veins start to constrict more, which increases the peripheral venous pressure, thus increasing venous return and contributing to the eventual increase in CO (according to Frank-Starling Law). The arterioles start to constrict more as well, causing TPR to increase, which contributes to MAP increasing. The sympathetic nerve activity to the heart increases HR and cardiac contractility, which contribute to the eventual increase in CO.