Exam 2 - Cardiovascular Lab 2
Ventricular volume remains constant (HINT: "iso") during which phase(s) of the cardiac cycle?
2nd: Isovolumetric Contraction (Systole) 4th: Isovolumetric Relaxation (Diastole)
The _____________ transports oxygenated blood from the left ventricle to the body. When this vessel leaves the heart, it turns inferiorly, forming an arch from which 3 large vessels branch off.
aorta
The right and left coronary arteries are the first branches from the ___________ and their terminal branches carry the most freshly oxygenated blood to the walls of the heart.
aorta
During ventricular ejection, pressure in the ventricle exceeds pressure in the ___________, forcing the semilunar valve open.
aorta (pulmonary trunk would also be correct...)
Defects in the intrinsic conduction system can cause irregular heart rhythms, known as _____________.
arrhythmias
The anatomy and conduction properties of the heart ensure that the ___________ contract before the ___________.
atria; ventricles
Which of the two main nodes in the intrinsic conducting system has a slow impulse?
atrioventricular (AV) node
What part of the intrinsic conducting system conducts electrical impulses through the interventricular septum?
bundle branches
The majority of muscle cells (99%) in the heart are the ____________ cells; these are the cells of the myocardium layer that contract to push the blood forward in the cardiovascular system.
contractile
systole
contraction of the heart
____________ is accomplished by electrically shocking the heart, which interrupts its chaotic twitching by depolarizing the entire myocardium. The hope is that "with the slate wiped clean" the SA node will begin to function normally and sinus rhythm will be reestablished.
Defibrillation
What two structures serve as guy-wires that anchor the AV valve flaps in their closed position and prevent them from being forced backward into the atria?
chordae tendinae and papillary muscles
endocardium
innermost layer of the heart wall; contains endothelium
Each of the ___________ valves is fashioned from three pocket-like cusps, each of which are shaped like a crescent moon.
semilunar
The lungs and the heart are enclosed within their own respective double layered __________________ sacs.
serous membrane
During isovolumetric relaxation, pressure in the ____________ drops below the pressure of the aorta, closing the semilunar valve.
ventricle
During isovolumetric contraction, (atrial/ventricular) pressure rises, forcing the AV valve closed.
ventricular
During which cardiac cycle stages are the pulmonary and aortic valves open?
ventricular ejection
The highest volume of blood (end-diastolic volume or EDV) is at the end of which cardiac cycle phase? The lowest volume (end-systolic volume or ESV) occurs at the end of which cardiac cycle phase?
ventricular filling; ventricular ejection
At what point in the cardiac cycle is pressure in the ventricles the highest (around 120 mm Hg in the left ventricle)?
ventricular systole
When the ventricles (contract/relax), the elastic recoil of the artery walls pushes the blood backward toward the heart, it fills the semilunar cusps which causes the valves to close, catching the blood in the semilunar cusps.
relax
diastole
relaxation of the heart
When a person is standing in anatomical position, the heart is actually tilted slightly, so that the (left/right) ventricle forms most of the anterior surface of the heart.
right
Both the superior and inferior vena cava return deoxygenated blood to which chamber of the heart?
right atrium
Blood flowing through the right semilunar valve is traveling from the __________ to the ___________.
right ventricle; pulmonary artery (to the lungs)
Although the ventricles are contracting, blood volume remains the same (end diastolic volume, EDV) during THIS phase of the cardiac cycle.
second phase: isovolumetric contraction
Deep to the fibrous pericardium; a thin, slippery, two-layer serous membrane that forms a closed sac around the heart.
serous pericardium
What part of the intrinsic conducting system initiates the heartbeat (pacemaker)?
sinoatrial (SA) node
The fibrous _______________ is a connective tissue structure that anchors all the valves to the heart wall.
skeleton
What is the dicrotic notch in the aortic pressure trace?
small peak in aortic pressure = transient increase in aortic pressure resulting from the sudden closure of the semilunar valve, which causes blood in the aorta to rebound off the closed valve; occurs during isovolumetric relaxation
skeletal muscle v. cardiac muscle
SKELETAL: long, cylindrical multinucleate cells; independent of one another both structurally and functionally; under voluntary control CARDIAC: short, fat, branched and interconnected cells; plasma membrane of cardiac muscle cells interlock with each other at junctions called intercalated disks; under involuntary control (for the most part)
The posterior interventricular artery supplies oxygenated blood to the posterior ventricular walls and forms an _____________ with the left anterior descending (LAD) (aka anterior interventricular artery) on the anterior surface of the heart.
anastomosis - connection between arteries
The Left Anterior Descending or LAD artery supplies blood to large portions of the anterior left ventricle and interventricular septum. This coronary artery is sometimes called "the widow maker" because if suddenly blocked, it will cause a massive heart attack that can lead to sudden death. What is another name for the LAD artery?
anterior interventricular artery
Which coronary artery branch is sometimes called "the widow maker?"
anterior interventricular artery (aka Left Anterior Descending or LAD artery)
When the left ventricle contracts, it sends blood through which valve?
aortic semilunar valve
Coronary ____________ supply freshly oxygenated blood to the wall of the heart, and coronary _____________ collect the deoxygenated blood from the heart wall and return it to the right atrium by way of the coronary ____________.
arteries; veins; sinus
The wider superior part of the heart is called its _____________, and its pointy, inferior end is called the _____________ of the heart.
base; apex
Which valve is found between the left atrium and left ventricle?
bicuspid (mitral) valve
The electrical currents generated in and transmitted through the heart can be recorded as an ____________.
electrocardiogram (ECG, aka EKG)
Which valve prevents the backflow of blood from the left ventricle into the left atrium?
mitral or bicuspid valve
When the heart chamber is relaxed, the AV valve flaps hang limply (open/close), and the blood flows passively from the atria into the ventricles. When the ventricles contract, the intraventricular pressure (falls/rises), pushing blood against the valve flaps, forcing them closed.
open; rises
epicardium
outermost layer of the heart wall; contains connective tissue
Shortly after leaving the heart, the pulmonary trunk splits into the right and left pulmonary arteries , whose branches transport (oxygen-rich/oxygen-poor) blood to the lungs.
oxygen-poor
The left ventricle contains which type of blood?
oxygenated
1% of the muscle cells in the heart are the _____________ cells of the conducting system.
pacemaker
Which cell type in the heart is autorhythmic, allowing the heart to beat on its own?
pacemaker
Attached to each AV valve flap are tiny white collagen cords called chordae tendinae, which anchor each valve cusp to a ___________ muscle which protrudes from the ventricular walls.
papillary
The ___________ layer of the serous pericardium lines the internal surface of the fibrous pericardium.
parietal
Because the gap junctions electrically couple cardiac cells, the myocardium behaves as a single coordinated unit, or functional ____________.
syncytium
After discharging its oxygen in the capillary beds of the myocardium, the deoxygenated blood is collected by the cardiac __________, whose paths roughly follow those of the coronary arteries
veins
If the SA node slows down or fails, the __________ node takes over, resulting in a much slower heat rate.
AV
Imagine the pericardial sac is like a slightly collapsed balloon, and imagine the heart as if it is your fist, which you punch into the balloon. The layer of the balloon that is against the skin of your fist (or the surface of the heart) is the _____________, and the outer layer of the balloon is the _____________.
visceral pericardium; parietal pericardium
When we talk about serous membrane sacs that surround organs in future lessons, the (parietal/visceral) layer will always be the layer that covers the surface of the organ and the (parietal/visceral) layer will always be the outer layer that lines the body cavity wall.
visceral; parietal
Describe the first phase of the cardiac cycle.
Atrial Contraction (Systole): tops off the ventricles, filling them fully with blood (end diastolic volume)
What do we call the ventricular volume during isovolumetric relaxation?
end systolic volume (ESV)
The visceral layer of serous pericardium is the outermost part of what layer of the heart wall?
epicardium
The specialized cardiac cells of the SA node are most precisely known as __________.
pacemaker cells
Explain why atrial contraction finishes before ventricular contraction begins.
Action potentials are delayed at the AV node.
Correctly order the opening and closing of the valves during the cardiac cycle (HINT: should have 4 steps).
1. AV valves close ("Lubb") - tops off blood volume in ventricles and ventricles are ready to contract 2. semilunar valves open - ventricular ejection 3. semilunar valves close ("Dubb") - pressure in ventricles falls below pressure in the aorta and pulmonary trunk 4. AV valves open - ventricular filling begins
What are the three major components of an ECG heartbeat?
1. P wave 2. QRS complex 3. T wave
List the 5 phases of the cardiac cycle.
1. atrial contraction 2. isovolumetric contraction 3. ventricular ejection 4. isovolumetric relaxation 5. ventricular filling
The dicrotic notch occurs during phase of the cardiac cycle?
4th: isovolumetric relaxation
The smaller cells of the (SA/AV) node have fewer gap junctions, slowing down the impulse and giving the atria time to contract.
AV
What is the electrical connection between the atria and ventricles?
AV bundle
The anatomy of the intrinsic conduction system causes contraction of the ventricles to begin at the apex and move superiorly. Why is this important?
Beginning contraction at the apex causes blood to be forced upward, through the semilunar valves, and into the aorta and pulmonary trunk. This makes ventricular ejection more efficient, much like squeezing a tube of toothpaste up from the bottom is more efficient at dispensing the toothpaste than is squeezing from the top.
True or False: An ECG tracing represents contraction of the heart.
False - Not quite! An ECG tracing represents the electrical activity of the heart due to depolarization and repolarization in various areas of the heart.
True or False: Only the SA node contains pacemaker cells.
False. Pacemaker cells exist in all structures of the intrinsic conduction system of the heart. NOTE: The various cardiac pacemaker cells have different rates of spontaneous depolarization. The SA node normally drives the heart at a rate of 75 beats per minute. Slower pacemakers such as those that exist in the AV bundle and the Purkinje fibers, will NOT set the heart rate UNLESS the faster pacemakers (SA node or AV node) stop working.
____________ (HINT: ICDs) can continually monitor heart rhythms and slow an abnormally fast heart rate or emit an electrical shock if the heart begins to fibrillate.
Implantable cardioverter defibrillators
Describe the second phase of the cardiac cycle.
Isovolumetric Contraction (Systole): pressure in ventricles increases, closing AV valves, BUT pressure is not high enough to open semilunar valves => so BOTH AV and semilunar valves are closed during this brief phase; blood volume in ventricles remains constant ("iso")
Describe the fourth phase of the cardiac cycle.
Isovolumetric Relaxation (Diastole): Blood pressure lowers, closing the semilunar valves, but pressure is not yet low enough to open the AV valves; so as seen w/ isovolumetric contraction, this is a brief phase where BOTH AV and semilunar valves are closed! volume of ventricles remains constant ("iso")
Contraction of the atria is triggered by electrical activity that is recorded on the ECG tracing as the __________.
P wave
What component of an ECG heartbeat indicates atrial depolarization?
P wave
What part of the intrinsic conducting system depolarizes the contractile cells of both ventricles?
Purkinje fibers - NOTE: depolarization of the cells = ventricular contraction
What component of an ECG heartbeat indicates ventricular depolarization?
QRS complex
What part of the ECG tracing occurs just as ventricular volume reaches 130 mL (EDV)?
QRS complex - indicates ventricular depolarization, which is the electrical event that leads to ventricular contraction.
Which node depolarizes right before the P wave (atrial depolarization)?
SA node
Which part of the intrinsic conduction system initiates the depolarizing impulse and normally sets the pace for the entire heart?
SA node
What component of an ECG heartbeat indicates ventricular repolarization?
T wave
The AV node causes a delay in the signal between the atria and the ventricles. Select the section of the ECG that occurs as the signal travels through the AV node.
The PR interval - The segment between the P wave and QRS complex represents the delay in conduction from the atria to the ventricles.
The repolarization of the atria occurs during which portion of the ECG?
The QRS complex (when the ventricles are depolarizing)
Contraction of the ventricles occurs as a result of the signal that causes which portion of the ECG?
The QRS complex - The QRS complex is caused by ventricular depolarization, which stimulates ventricular contraction.
Why is it important that the AV node delays depolarization?
The delay allows the atria to finish contracting before the ventricles begin to contract.
True or False: About 80% of the blood volume in the ventricles results from passive movement of blood from atria to ventricles.
True! The remaining 20% of blood is forced into the ventricles during atrial contraction ("topping off" the ventricles).
True or False: A graph showing blood volume change in the left ventricle during the cardiac cycle would look the same for the right ventricle.
True. Each ventricle pumps the same amount of blood even though the pressures are different on the right and left side of the heart!
Describe the third phase of the cardiac cycle.
Ventricular Ejection: rising blood pressure finally opens the semilunar valve and blood rushes from the ventricles into the pulmonary trunk and aorta; ventricular volume decreases as blood leaves the heart
Describe the fifth phase of the cardiac cycle.
Ventricular Filling: pressure in ventricles becomes low enough that AV valves open => blood flows passively from the R and L atria into the R and L ventricles; ventricular volume increases over time
fibrillation
a condition of irregular or out-of phase contractions in which control of heart rhythm is taken away from the SA node by rapid activity in other heart regions; Fibrillating ventricles are useless as pumps; and unless the heart is defibrillated quickly, circulation stops and brain death occurs.
Blood volume (increases/decreases) during systole, and blood volume (increases/decreases) during diastole.
decreases (ventricle ejects blood); increases (ventricle relaxes and fills with blood)
The waveforms that can be seen in an ECG tracing represent periods of ____________ or _____________. A ___________ refers to the time period between two adjacent waveforms, and an ____________ is a time period that includes one or more waveforms plus or minus one or more segments.
depolarization; repolarization; segment; interval
cardiac cycle
describes the mechanical events associated with blood flow through the heart in one complete heartbeat - atrial systole and diastole followed by ventricular systole and diastole.
What do we call the ventricular volume during isovolumetric contraction?
end diastolic volume (EDV)
Blood always flows through the heart according to pressure gradients, from (high/low) to (high/low) pressure.
high; low
During atrial contraction, atrial pressure is (higher/lower) than ventricular pressure.
higher
The 1st heart sound (lub) occurs during ventricular systole (contraction), when pressure in the ventricle is (lower/higher) than in the atrium, and the AV valves close. The 2nd heart sound (dub) occurs during closure of the semilunar valves, when pressure in the aorta (or pulmonary trunk) is (lower/higher) than the pressure in the ventricle.
higher; higher
When looking at a trace of pressure changes in the heart, valve events always occur at the ____________ of pressure traces.
intersection
During ventricular filling, ventricular pressure is (higher/lower) than atrial pressure, resulting in the AV valve opening.
lower
end systolic volume (ESV)
minimum blood volume reached at the end of ventricular ejection (third phase of the cardiac cycle)
The second and third phases of the cardiac cycle represent ventricular (diastole/systole).
systole
What is the PR interval (in an ECG)?
the time between the start of atrial depolarization to the start of ventricular depolarization
What is the main function of heart valves?
to prevent backward flow of blood
What are the two types of cardiac muscle cells in the heart?
1. contractile 2. pacemaker
What are the three layers of the heart wall?
1. endocardium (innermost) 2. myocardium 3. epicardium (outermost)
List the three large blood vessels that can be identified at the base (superior edge) of the heart.
1. superior vena cava 2. pulmonary trunk 3. aorta
Electrical impulses pass through the conduction system of the heart in the following sequence: A. SA node, AV node, bundle of His, bundle branches, and Purkinje fibers B. SA node, bundle branches, bundle of His, AV node, and Purkinje fibers C. SA node, bundle of His, AV node, bundle branches, and Purkinje fibers D. SA node, bundle branches, AV node, bundle of His, and Purkinje fibers
A. SA node, AV node, bundle of His, bundle branches, and Purkinje fibers The impulses of the heart originate at the SA node (pacemaker). The impulse is then transmitted to the AV node (atrioventricular node), where the impulse slows down to allow the atria to completely contract and thereby fill the adjacent ventricles. The AV node then transmits the impulse to the bundle of His, which branches into left and right bundle branches. The bundle branches give rise to the Purkinje fibers, which transmit the impulse to the ventricle walls and stimulate ventricular contraction.
What ion provides the signal that allows for cross-bridge activation and contraction of the muscle fiber?
Ca2+
True or False: Pulmonary veins carry oxygen-poor blood.
False! Pulmonary veins are carrying blood from the lungs TO the heart, so the blood is oxygen-rich!
True or False: Unlike skeletal muscle, cardiac muscle does not follow the sliding filament mechanism of contraction.
False. Like skeletal muscle, cardiac muscle is striated and contracts by the sliding filament mechanism.
True or False: The left and right AV valves are also known as bicuspid valves.
False. Only the left AV valve is known as the bicuspid (aka mitral) valve. The right AV valve is a tricuspid valve.
True or False: The left AV valve has 3 flaps and is called the mitral valve.
False. The left AV valve has 2 flaps (bicuspid). Yes, it's called the mitral valve.
True or False: The right AV valve has 2 flaps and is called the tricuspid valve.
False. The right AV valve has 3 flaps (hence, "tri-").
True or False: The ECG is a record of individual action potentials of the pacemaker and contractile cells in the heart.
False: The ECG is a record of the electrical activity of the heart activity and represents a composite of ALL the action potentials generated by nodal and contractile cells at a given time.
Why are gap junctions a vital part of the intercellular connection of cardiac muscles?
Gap junctions are a form of electrical synapse that allow action potentials to spread to connected cells. This property allows the signal to spread efficiently through the heart.
How does the presence of pacemaker cells affect the electrical activity of the cardiac contractile cells?
The pacemaker cells are able to stimulate action potentials in the cardiac contractile cells. Without the pacemaker cells there would not be a stimulus for generating action potentials in the contractile cells, and the heart would not contract.
Which valve is located between the right atrium and the right ventricle?
The tricuspid valve is located between the right atrium and right ventricle. The tricuspid valve gets its name because it has 3 valve cusps or leaflets. The tricuspid valve is also known as the right atrioventricular (or right AV) valve.
True or False: Most of the blood flow from the atria into the ventricles occurs passively due to pressure differences.
True! The atrium does contract at the end of ventricular filling to "top off" the blood flow into the ventricle.
Explain what makes "lub" and "dub" in the lub-dub sounds of a healthy heartbeat.
When the heart valves close, the turbulence of blood pushing against the closing valves causes the heart sounds. The "lub" (S1) sound is produced by turbulence as the AV valves close, and the "dub" (S2) is caused by turbulence as the semilunar valves close and blood pushes against them.
Attached to each AV valve flap are tiny white collagen cords called _____________, which anchor each valve cusp to a papillary muscle which protrudes from the ventricular walls.
chordae tendinae
The AV valves are made up of cusps that are attached to what string-like structures? Remember, the right atrioventricular valve has __________ cusps and the left AV valve has __________ cusps.
chordae tendinae; 3 (tricuspid); 2 (bicuspid aka mitral)
You can identify the difference between the 2 semilunar valves because the ____________ are the first branches that leave the aorta and can be seen in the cross-section of the aortic valve.
coronary arteries
The veins join to form an enlarged vessel called the ____________, which is located in the coronary sulcus on the posterior surface of the heart and dumps its deoxygenated blood into the right atrium.
coronary sinus - recall that the R atrium ultimately sends blood out to the pulmonary trunk and lungs, so the blood can unload CO2 and upload O2!
The _____________ is the circular groove that runs between the atria and the ventricles and it contains coronary vessels as well.
coronary sulcus
The right coronary artery travels through the ______________ (a groove that encircles the heart between the atria and ventricles) and courses toward the right side of the heart where it gives rise to two main branches.
coronary sulcus
Recall that during excitation-contraction coupling of muscle cells, action potentials travel down t-tubules, causing a wave of (repolarization/depolarization) that causes the sarcoplasmic reticulum to release what ion into the cytoplasm.
depolarization; Ca2+
In the intercalated discs in cardiac muscle cells, the ____________ prevent adjacent cells from separating during contraction while the ____________ allow ions to pass from cell to cell, transmitting current across the entire heart.
desmosomes; gap junctions
The intercalated discs in cardiac muscle cells contain anchoring __________ and __________.
desmosomes; gap junctions
The heart sits tilted in the mediastinum so that the lateral surface of the right ventricle rests on the ________________.
diaphragm
This tough, dense connective tissue layer protects the heart, anchors it to surrounding structures, and prevents overfilling of the heart with blood.
fibrous pericardium
The loosely fitting superficial part of the pericardial sac is the ___________. This tough, dense connective tissue layer protects the heart, anchors it to surrounding structures, and prevents overfilling of the heart with blood. Deep to the fibrous pericardium is the ____________, a thin, slippery, two-layer serous membrane that forms a closed sac around the heart.
fibrous pericardium; serous pericardium
Complete blockage of coronary arteries and their branches leads to lack of oxygen, ischemia, tissue death and _____________.
heart attack
A ________________ is caused by abnormal swishing or whooshing sound that is heard as blood regurgitates back through a valve after it has closed, and usually indicates faulty valve function.
heart murmur
What causes the "lub - dub" sounds when listening to the heart with a stethoscope (generally speaking)?
heart valves are closing
The ______________ returns deoxygenated blood from the lower body to the right atrium.
inferior vena cava
The left anterior descending (LAD) artery travels in the anterior interventricular sulcus on the front of the heart and supplies blood to the _____________ and anterior walls of both ventricles.
interventricular septum
You can tell the division of the right and left ventricles because of the location of the anterior ________________, a groove that holds one of the important coronary arteries on the anterior surface of the heart.
interventricular sulcus
The pacemaker cells are located in special locations in the heart and form the ____________ (HINT: ICS) of the heart; they do not contract, but they initiate special action potentials that stimulate the other cells to contract.
intrinsic conducting system
What system of the heart controls the heartbeat?
intrinsic conducting system
As ventricular systole starts, the AV valves are closed and the semilunar valves are closed. Because the ventricles are contracting and both valves are closed, pressure increases rapidly leading to ejection. This describes what phase of the cardiac cycle?
isovolumetric contraction phase
anastomoses
junctions between the coronary arterial branches => provide collateral blood flow to different areas of the heart
The (right/left) coronary artery is only a few centimeters in length and immediately branches into the anterior interventricular artery and the circumflex artery.
left
The apex of the heart is made up of the (right/left) ventricle.
left
The left coronary artery splits into two main branches: the anterior interventricular artery, which is most commonly called the _____________ in clinical situations, and the _____________ artery, which circles around to the posterior side of the heart.
left anterior descending or LAD artery; circumflex
Which heart chamber pushes blood through the aortic semilunar valve?
left ventricle
Which of the heart chambers is the most muscular? (i.e has the thickest myocardium) - Why?
left ventricle - The left ventricle is responsible for pumping freshly oxygenated blood out to the body. This requires a lot of force.
Blood flowing through the left semilunar valve is traveling from the ___________ to the __________.
left ventricle; aorta (to the body)
The aorta transports oxygenated blood from which chamber of the heart to the _____________.
left ventricle; body
The circumflex artery supplies blood to the (right/left) atrium and the posterior walls of the (right/left) ventricle.
left; left
The right coronary artery splits into two main branches: the right ___________ artery, which serves the myocardium of the lateral right side of the heart, and the posterior ___________ artery, which travels in the interventricular groove on the posterior surface of the heart.
marginal; interventricular
The heart and the great blood vessels associated with the heart are located in the _______________, which is the central area of the thoracic cavity, between the lungs.
mediastinum
myocardium
middle layer of the heart wall; contains cardiac muscle
At the superior margin of the heart, the _____________ layer attaches to the large arteries exiting the heart, and then turns inferiorly and continues over the external heart surface as the visceral layer, which is also called the ______________.
parietal; epicardium
Build-up of fluid or infection within what space between the visceral pericardium and parietal pericardium of the heart can lead to serious clinical conditions, including death?
pericardial cavity
In between the two layers of the pericardium (visceral and parietal) is a potential space, called the _____________, and it contains a small amount of slippery serous fluid that allows the two layers of the sac to move against each other with minimal friction.
pericardial cavity
The heart is enclosed in a double-walled sac called the _______________.
pericardium
Each lung is surrounded by a ______________ sac, and the heart is surrounded by the pericardial sac or ________________.
pleural; pericardium
What determines whether valves are open or closed?
pressure gradients
Deoxygenated blood leaving the right ventricle must pass through the _____________________ valve.
pulmonary or pulmonic semilunar
The _____________ branches into the right and left pulmonary arteries.
pulmonary trunk
The ________________ is an artery that ultimately transports deoxygenated blood from the right ventricle of the heart to the lungs.
pulmonary trunk *Note that in this case, an artery is transporting deoxygenated blood!
When the ventricle contracts and intraventricular pressure (falls below/rises above) the pressure in the aorta and pulmonary trunk, the semilunar valves are forced open and their cusps flatten against the arterial walls as blood passes through.
rises above
The ______________ returns deoxygenated blood from the upper body to the right atrium.
superior vena cava
Which blood vessels bring deoxygenated blood from the body tissues to the right atrium?
superior vena cava and inferior vena cava
What part of the intrinsic conducting system electrically connects the atria to the ventricles?
the atrioventriular (AV) bundle
Which blood vessels bring freshly oxygenated blood to the left atrium?
the pulmonary veins