Chapter 19: Heart Flashcards
What is the major function of the heart?
Pump blood throughout the body.
What is the location of the heart?
The heart lies within the mediastinum between the lungs.
What is the pericardium?
A sac that encloses the heart.
What is the structure of the pericardium?
It has 2 layers – an outer fibrous pericardium and inner serous pericardium.
What is the function of the pericardium?
It separates the heart from the lungs and allows the heart to move freely as it beats.
What is the fibrous pericardium?
It is a tough collagenous sac. It surrounds the heart but is not attached to it.
What is the serous pericardium?
It is a simple squamous epithelium overlying a thin layer of elastic tissue.
What does the serous pericardium cover?
It covers the heart surface.
What is the membrane that covers the heart surface called?
The visceral layer of the serous pericardium. Also called the epicardium.
What is the membrane that lines the inside of the fibrous pericardium called?
The parietal layer of the serous pericardium.
What is the pericardial cavity?
It’s the space between the parietal and visceral layers of the serous pericardium.
What is pericardial fluid?
A fluid discharged by the serous pericardium.
Where is the pericardial fluid found?
In the pericardial cavity.
What is the function of the pericardial fluid?
It lubricates the membranes and allows the heart to beat with minimal friction.
What is pericarditis?
Inflammation of the pericardium.
What 3 layers does the heart wall consist of?
Epicardium, myocardium, and endocardium.
What is the outermost layer of the heart?
The epicardium
The epicardium is also called ____.
Visceral layer of the serous pericardium.
Describe the epicardium.
It is thin and translucent in most areas, however, in other places it includes a thick layer of adipose tissue.
What is the function of the thick layer of adipose tissue on the heart?
It encloses the major coronary blood vessels and protects them from compression.
What is the innermost layer of the heart?
The endocardium
Describe the endocardium.
It is a simple squamous epithelium overlying a thin areolar tissue layer; however, it has no adipose tissue.
Where is the endocardium found?
It lines the interior of the heart chambers, covers the valve surfaces, and is continuous with the endothelium of the blood vessels.
What is the layer in between the epicardium and endocardium?
The myocardium
What is the function of the myocardium?
It performs the work of the heart.
What is the thickest layer of the heart wall?
The myocardium
What is myocardium composed of?
Cardiac muscle
How is the myocardium organized? What does it form?
It’s organized into bundles that spiral around the heart, forming the vortex of the heart.
Why is the myocardium the thickest layer?
Because it performs the work of the heart. Its thickness is proportional to the workload on the individual chambers.
When the ventricles contract, they exhibit a _____ that enhances the ____.
Twisting or wringing motion, ejection of blood.
What makes up the fibrous skeleton?
A framework of collagenous and elastic fibers.
How many chambers does the heart have?
4
What are the 2 superior chambers called?
The right and left atria (atria for plural, atrium for singular).
What type of chambers are the right and left atria?
They are receiving chambers for blood returning to the heart by way of the great veins.
What are the right and left auricles?
They are earlike flaps on each atrium that slightly increases its volume.
What is the structure of the atria?
They have thin flaccid walls corresponding to their light workload.
What is the function of the atria?
Pump blood into the ventricles below.
What separates the atria?
The interatrial septum.
What do the right atrium and both auricles exhibit?
Pectinate muscles
What are pectinate muscles?
Internal ridges of myocardium.
What are the 2 inferior chambers?
The left and right ventricles
What is the function of the ventricles?
They eject blood into the arteries and keep it flowing around the body.
What separates the ventricles?
A thick muscular wall called the interventricular septum.
Where does the right ventricle pump blood to?
It pumps blood only to the lungs and back to the left atrium.
What chamber bears the greatest workload of all 4 chambers?
The left ventricle
Why is the left ventricle and septum, two to four times as thick as the right ventricle?
Because it bears the greatest workload of all 4 chambers.
Where does the left ventricle pump blood to?
It pumps blood through the entire body.
Both ventricles exhibit internal ridges called ____.
Trabeculae carneae
What is the function of trabeculae carneae?
It keeps the ventricular walls from clinging to each other.
What are the boundaries of the 4 chambers marked by?
The 3 sulci (grooves).
What are the sulci made up of?
They are largely filled with fat and the coronary blood vessels.
What are the 3 different sulci?
The coronary sulcus, the anterior interventricular sulcus, and the posterior interventricular sulcus.
Where is the coronary sulcus located?
It encircles the heart near the base and separates the atria above from the ventricles below.
What are the anterior and posterior interventricular sulci located?
They extend obliquely down the heart from the coronary sulcus toward the apex.
What interventricular sulci is on the front of the heart?
The anterior interventricular sulcus
What interventricular sulci is on the back of the heart?
The posterior interventricular sulcus.
What part(s) of the heart harbors the largest of the coronary blood vessels?
The coronary sulcus and the 2 interventricular sulci.
What is needed for the heart to pump blood effectively?
The heart needs valves that ensure a one-way flow.
Where are the heart valves located?
There is a valve between each atrium and its ventricle, and another at the exit from each ventricle into its great artery.
Does the heart have valves where the great veins empty into the atria?
No
What do the heart valves consist of?
Fibrous flaps of tissue covered with endocardium.
What are the fibrous flaps of tissues of the heart valves called?
Cusps or leaflets.
What valve regulates the openings between the atrias and ventricles?
The atrioventricular valves
What is the right atrioventricular valve called? Why?
The tricuspid valve. It has 3 cusps.
How many cusps does the left atrioventricular valve have?
It has 2 cusps.
What is the left AV valve also known as?
The mitral valve.
What connects the valve cusps to the conical papillary muscles on the floor of the ventricles?
Stringy tendinous chords called chordae tendineae.
What is the function of the chordae tendineae?
They prevent the AV valves from flipping inside out or bulging into the atria when the ventricles contract.
Each papillary muscle has 2 or 3 basal attachments to what?
The trabeculae carneae of the heart wall.
What are the semilunar valves?
The pulmonary and aortic valves.
What is the function of the semilunar valves?
They regulate the flow of blood from the ventricles into the great arteries.
What is the function of the pulmonary valve specifically?
It controls the opening from the right ventricle into the pulmonary trunk.
What is the function of the aortic valve specifically?
It controls the opening from the left ventricle into the aorta.
How many cusps do the aortic and pulmonary valves have? What do they look like?
Each has 3 cusps that are shaped like shirt pockets.
What happens when blood is ejected from the ventricles?
It pushes through the semilunar valves (pulmonary and aortic) from below and presses their cusps against the arterial walls.
What happens when the ventricles relax?
o Arterial blood flows back into the ventricles, but quickly fills the cusps.
o The inflated pockets meet at the center and quickly seal the opening, so little blood flows back into the ventricles.
Why don’t the semilunar valves require or possess tendinous chords (chordae tendineae)?
Because of the way they are attached to the arterial wall. They can’t prolapse any more than a shirt pocket turns inside out if you jam your hand into it.
Do the semilunar valves open and close by any muscular effort of their own?
No
How do the semilunar valves open and close?
The cusps are simply pushed open and closed by changes in blood pressure that occur as the heart chambers contract and relax.
Where does blood enter the heart?
It enters the right atrium from the superior and inferior venae cavae.
Where does blood travel to from the right atrium?
It flows through the right AV valve into the right ventricle.
What forces the pulmonary valve open?
Contraction of the right ventricle.
Where does blood travel to from the right ventricle?
It flows through the pulmonary valve into the pulmonary trunk.
What blood vessels distribute blood to the lungs? What does the blood unload/load?
The right and left pulmonary arteries. The blood drops off carbon dioxide and picks up oxygen.
Blood returns from the lungs to the heart by what blood vessel? What part of the heart does the blood return to?
Blood returns from the lungs via the pulmonary veins to the left atrium.
Where does blood travel to from the left atrium?
It flows through the left AV valve into the left ventricle.
What forces the aortic valve open?
Contraction of the left ventricle.
Contraction of the left and right ventricles is ____.
Simultaneous
Where does blood travel to from the left ventricle?
It travels through the aortic valve into the ascending aorta.
What happens to blood in the aorta?
It is distributed to every organ in the body where it drops off oxygen and picks up carbon dioxide.
Blood is kept entirely separate on the ____ and _____ sides of the heart.
Right, left
The myocardium has its own supply of ____.
Arteries and capillaries that deliver blood to every muscle cell.
What are the 2 major divisions of the cardiovascular system?
The pulmonary circuit and the systemic circuit.
What is the function of the systemic circuit?
It supplies blood to every organ of the body, including other parts of the lungs and the wall of the heart itself.
What is the function of the pulmonary circuit?
It carries blood to the lungs for gas exchange and returns it to the heart.
The pathways of blood flow, steps 4 through 6, is the ____ circuit.
Pulmonary
The pathway of blood flow, steps 9-11, is the ____ circuit.
Systemic
What part of the heart supplies the pulmonary circuit?
The right half of the heart.
What part of the heart supplies the systemic circuit?
The left half of the heart.
What is the coronary circulation?
A system of blood vessels that serve the wall of the heart.
What are the major vessels of the coronary circulation?
The right and left coronary arteries.
What 2 branches does the left coronary artery divide into?
The anterior interventricular branch and the circumflex branch.
What 2 branches does the right coronary artery divide into?
The right marginal branch and the posterior interventricular branch.
What does the right coronary artery supply?
The right atrium and sinoatrial node (pacemaker).
Why is the energy demand of the cardiac muscle so critical?
An interruption of the blood supply to any part of the myocardium can cause necrosis within minutes.
What can cause a myocardial infarction (heart attack)?
A fatty deposit or blood clot in a coronary artery.
The points where 2 arteries come together is called ____.
Arterial anastomoses.
What is the function of arterial anastomoses?
They provide alternative routes of blood flow (collateral circulation) that can supply the heart tissue with blood if the primary route becomes obstructed.
When does arterial blood peak in organs other than the heart? When does it diminish?
o Flow usually peaks when the heart contracts and ejects blood into the systemic arteries. It diminishes when the ventricles relax and refill.
When does arterial blood peak in the coronary arteries?
Flow peaks when the heart relaxes.
When does blood flow increase in coronary blood vessels?
During ventricular relaxation.
What is veinous drainage?
The route by which blood leaves an organ.
Why is the heart described as autorhythmic?
Because it doesn’t depend on the nervous system for its rhythm.
What allows the heart to be on its own without relying on the nervous system?
It has its own built-in pacemaker and electrical system.
Cardiac muscle and skeletal muscle are both ____.
Striated
What is a cardiomyocyte?
A cardiac muscle cell.
What is the cell shape and dimensions of a cardiomyocyte.
Cardiomyocytes are short, branched and roughly rectangular.
Describe the nucleus of a cardiomyocyte.
A cardiomyocyte typically has 1 centrally located nucleus
Through the branches, each cardiomyocyte contacts several others and collectively they form ____.
A network throughout each pair of heart chambers – one in the atria and one in the ventricles.
What does the cardiomyocyte lack that skeletal muscle fibers have?
Terminal cisterns
Do cardiomyocytes have mitochondria?
Yes, due to the continuous need for contraction.
Cardiomyocytes are joined end to end by thick connections called ____.
Intercalated discs.
What is an intercalated disc?
A complex steplike structure with 3 distinctive features.
What are the 3 distinctive features of an intercalated disc?
Interdigitating folds, mechanical junctions, and electrical junctions.
What are interdigitating folds?
The plasma membrane at the end of the cell is folded somewhat like the bottom of an egg carton.
What are mechanical junctions?
The cells are tightly joined by 2 types of mechanical junctions: the fascia adherens and desmosomes.
Which of the 2 mechanical junctions if the most extensive?
The fascia adherens.
What are electrical junctions?
The intercalated discs also contain gap junctions, which form channels that allow ions to flow from the cytoplasm of 1 cardiomyocyte directly to the next.
What are the contractile proteins of a cardiomyocyte?
Actin and myosin
What is the heartbeat coordinated by?
A cardiac conduction system.
What is the cardiac conduction system composed of?
It is composed of an internal pacemaker and nervelike conduction pathways through the myocardium.
How does the cardiac conduction system generate and conduct rhythmic electrical signals?
o The sinoatrial (SA) node fires.
o Excitation spreads through atrial myocardium.
o The atrioventricular (AV) node fires.
o Excitation spreads down AV bundle.
o The subendocardial branches (Purkinje fibers) distribute excitation through ventricular myocardium.
What is an arrhythmia?
A condition in which the heart beats with an irregular or abnormal rhythm.
What is ventricular fibrillation?
The ventricles quiver instead of contracting normally. This prohibits the heart from pumping blood causing collapse and cardiac arrest.
What is atrial fibrillation?
A weak crippling contraction in the atria, appearing in the ECG as chaotic, high-frequency depolarizations.
What is a heart block?
A failure of any part of the cardiac conduction system to conduct signals, usually as the result of disease and degeneration of conduction system fibers.
What is an atrial flutter?
A type of abnormal heart rhythm that occurs when the chambers beat faster than normal and not always in coordination.
What is defibrillation?
An emergency procedure in which the heart is given a strong electrical shock with a pair of paddle electrodes.
What is tachycardia?
A persistent, resting adult heart rate above 100 bpm.
What causes tachycardia?
It can be caused by stress, anxiety, stimulants, heart disease, or fever.
What is bradycardia?
A persistent resting adult hear rate below 60 bpm.
When is bradycardia common?
During sleep and in endurance-trained athletes.
What is systole?
The contraction phase when the heart pumps blood out.
What is diastole?
The relaxation phase when the heart fills with blood.
What is a sinus rhythm?
The normal heartbeat triggered by the SA node.
How are action potentials propagated in cardiac muscle?
Via branching of the cells and cell: cell communication through intercalated discs. The intercalated discs contain gap junctions which allow positively charged ions (cations) to move between cells to depolarize the next cell.
What cardiac events generates the P wave?
Atrial depolarization
What cardiac event generates the QRS complex?
Ventricular depolarization
What cardiac event generates the T wave?
Ventricular repolarization
What are the sources of ATP used by cardiac muscle?
o Cardiac muscle is very rich in myoglobin which is a short-term source for aerobic respiration.
o It is also rich in glycogen which is for stored energy.
What does cardiac muscle depend on to make ATP?
Cardiac muscle depends almost exclusively on anerobic respiration to make ATP.
When given the heart rate, how do you calculate the time of 1 completed cardiac cycle?
Take the number 60 and divide it by the heart rate. This will give you the duration of 1 cardiac cycle in seconds.
What 2 phases make up the cardiac cycle?
Diastole and systole
Listening to the sounds made by the body is called ____.
Auscultation
The first and second heart beats, symbolized S1 and S2, are often described as a ____.
“Lubb-dupp”
Between S1 and S2, which heart sound is louder and longer, and which heart sound is a little softer and sharper?
S1 is louder and longer. S2 is a little softer and sharper.
What cardiac event is responsible for the “lubb-dupp” (S1 and S2) sound?
The closing of the valves.
What cardiac event is responsible for the “lubb” S1 sound?
The closing of the tricuspid and mitral valve.
How do the tricuspid and mitral valves close?
The papillary muscles close shut the tricuspid valve and mitral valve by pulling on the chordae tendineae.
What cardiac event is responsible for the “dubb” S2 sound?
The closing of the aortic and pulmonary valves.
What causes the aortic and pulmonary valves close?
When the ventricles relax, blood flows back into the aorta and pulmonary trunk which causes the valves to close.
What is cardiac output?
The amount ejected by each ventricle in 1 minute.
What is the formula for calculating cardiac output?
Cardiac output = heart rate x stroke volume
Define cardiac reserve.
The difference between the maximum and resting cardiac output is called the cardiac reserve.
What are action potentials?
They are changes in resting membrane potential that travels for a long distance.
What is voltage?
A charge separation
What are the 3 voltage gated channels?
o Voltage gated sodium (Na+)
o Voltage gated calcium (Ca2+)
o Voltage gated potassium (K+)
Voltage gated sodium (Na+) channel opens and closes ____.
Fast
Voltage gated potassium (K+) channel opens and closes ____.
Slowly
What are the 3 phases of action potentials?
o Depolarization
o Repolarization
o Hyperpolarization
What is depolarization?
A decrease in polarity (less negative).
What is repolarization?
Returns to polarized/resting membrane potential.
What is hyperpolarization?
An increase in polarity (more negative).
What generates and distributes action potentials throughout the cardiac muscle?
The intrinsic conduction system.
Intrinsic means ____.
Within
Conduction means ____.
Generate and distribute
What are the 6 parts of the intrinsic conduction system (ICS)?
o Sinoatrial node (SA node)
o Internodal pathways
o Atrioventricular or AV node
o AV bundle of His
o Right and left bundle branches
o Purkinje fibers or subendocardial branches.
What do modified cardiomyocytes/cardiac muscle cells lose? What does this mean?
They lose actin and myosin. This means they cannot contract.
What are the cells that spontaneously generate action potentials and distribute them throughout the cardiac muscle called?
Autorhythmic cells
Autorhythmic cells make up what percentage of the heart?
Less than 1%
Where is the SA node located?
In the posterior wall of the right atrium. Below the SVC entrance.
What is the SA node called/referred to?
The pacemaker of the heart.
What is the normal rate of the SA node?
80-100 beats/minute.
How big is the SA node?
15mm ellipsoidal tissue.
What is the main function of the SA node?
It generates impulses for contractions of the heart.
Where do action potentials generated at the SA node travel through the atria?
By internodal pathways.
Where do the action potentials travel to after reaching the atria?
They come to the AV node.
Where is the AV node located?
On the interventricular septum, superior to the tricuspid valve.
How long do the AP’s delay at the AV node so that the atria can contract?
100 msec
Where is the AV bundle/bundle of HIS located?
On the interventricular septum.
The AV bundle/bundle of HIS branches into what? What is the location?
Branches to right and left bundle branches which travel on either side of interventricular septum, right up to the apex.
The bundle branches become bigger in diameter called what?
Purkinje fibers/subendocardial network.
Does the conduction system have a resting membrane potential? Why or why not?
No because they must constantly contract.
What are the steps of the action potentials of the conduction system?
o At the end of hyperpolarization (#4 on graph) the membrane slowly depolarizes to -40mv (which is the threshold).
o This happens because the membrane is leaky to sodium ions, so sodium enters.
o Depolarization to threshold occurs.
o Slow depolarization (#2a on graph) is called unstable resting membrane potential or prepotential or pacemaker potential.
o After the threshold (#2b on graph) voltage gated calcium channels open. Calcium enters and membrane potential is 0 or +20mv.
o Voltage gated calcium channels close.
o Voltage gated potassium channels open. Potassium rushes out and membrane is repolarized.
o As voltage gated potassium channels close slowly, potassium leaks out more causing hyperpolarization.
o At the end of hyperpolarization, it starts all over again.
What is an ECG/EKG?
An electrocardiogram
What does an ECG/EKG record?
The electrical activity of the heart.
The ECG is the sum of what?
Adding up the action potential of the cardiac muscle and the conduction system.
What is a straight line in an ECG called?
An isoelectric line.
What is a cardiac cycle?
All events in 1 single heartbeat.
A cardiac cycle is a __________ that happens after the _________.
Mechanical event, electrical event
What is the electrical event?
The action potential.
How long does 1 cardiac cycle last?
0.8 seconds
The R-R wave is 1 ____?
Cardiac cycle
How do you figure out how many cardiac cycles occur in 1 minute?
You divide 60 seconds (1 minute) by 0.8 seconds (R-R wave). 60/0.8 = 75 beats/min.
Why does the heart contract?
To pump blood.
What is the heart never completely empty of?
Blood
Why does the heart relax?
To fill with blood.
What are the discharging chambers?
The ventricles
What measures the systole?
The QT interval
What is the QT interval?
Beginning of Q to the end of T on an ECG.
What measures the diastole?
End of T to the next R.
What are the 5 stages of a cardiac cycle?
o 1a. Isovolumetric relaxation
o 1b. Ventricular filling
o 1c. Atrial contraction
o 2a. Isovolumetric contraction
o 2b. Ventricular ejection
What happens in ventricular filling of the cardiac cycle?
o There is minimal amount of blood in the ventricles.
o The aortic and pulmonary valves are closed.
o ¾ of the ventricles are filled with blood due to gravity/pressure gradient.
o P wave occurs.
What happens in atrial contraction of the cardiac cycle?
o After the P wave occurs, the atrial contraction begins.
o It pushes the remaining ¼ of the blood into the ventricles.
o QRS wave occurs; depolarization of the ventricles happens.
What is end diastolic volume (EDV)?
The volume of blood in the ventricles at the end of diastole.
What is the measurement of EDV?
130mL of blood
What happens in isovolumetric contraction of the cardiac cycle?
o After the QRS wave, the ventricles start to contract from the apex of heart.
o The papillary muscles close shut the tricuspid and mitral valves by pulling on the chordae tendineae.
o This creates the S1 “lubb” sound.
What does isovolumetric mean?
Iso means same, volumetric has to do with volume. So, it means no change in the volume of blood.
What happens in ventricular ejection of the cardiac cycle?
o As the ventricles contract, they generate pressure to open the aortic and pulmonary semilunar valves and eject blood into the aorta and pulmonary trunk.
o T wave occurs; ventricular repolarization happens.
What blood vessel is used to measure the blood pressure of the aorta?
The brachial artery.
What is the blood pressure of the aorta at the height of systole?
120 mm of Hg
What is the systolic blood pressure of the pulmonary trunk?
25 mm of Hg
What is end systolic volume (ESV)?
The volume of blood in the ventricles at the end of systole.
What is the measurement of ESV?
60mL of blood.
What is stroke volume?
The amount of blood pumped by the ventricles per stroke/beat.
How do you calculate stroke volume?
EDV – ESV
What happens in isovolumetric relaxation of the cardiac cycle?
o After the T wave, the ventricles start to relax.
o Blood flows backwards into the aorta and pulmonary trunk.
o This causes the aortic and pulmonary valves to close and makes the “dubb” S2 sound.
What is the diastolic blood pressure of the aorta?
80 mm of Hg
What is the diastolic blood pressure of the pulmonary trunk?
8 mm of Hg
What does mm of Hg mean?
Millimeters of mercury.
What is a dicrotic notch?
A brief (small) increase in aortic pressure. In an aortic pressure graph, it is shown as a double peak.
Why is there a brief increase in aortic pressure?
Because of the backflow of blood into the aorta and pulmonary trunk.
Physiologically, what does the dicrotic notch symbolize?
It signifies the end of ventricular contraction.
What are the 4 heart structures that you listen to using a stethoscope?
Mitral valve, tricuspid valve, aortic valve, and pulmonary valve.
Where is the location of the mitral valve heart sound?
Left 5th intercostal space.
Where is the location of the tricuspid valve heart sound?
Right 5th intercostal space.
Where is the location of the aortic valve heart sound?
Left 2nd intercostal space.
Where is the location of the pulmonary valve heart sound?
Right 2nd intercostal space.
What are capillaries?
Microscopic vessels that connect the smallest arteries to the smallest veins.
What part of the body does the superior vena cava drain blood?
The upper body
What part of the body does the inferior vena cava drain blood?
Everything below the diaphragm.
What are the great vessels?
The major arteries and veins entering and leaving the heart. Called great veins, great arteries.
