Chapter 19 Study Guide

Question 1

The right side of the heart furnishes blood to what circuit? Where does it carry the blood to and from? Is the blood oxygenated, deoxygenated or both? It pumps the blood into what trunk? Is the blood in that vessel oxygenated or deoxygenated? What does this trunk divide into?

Answer 1

Right side receives deoxygenated blood through the superior and inferior vena cava, then leaves via pulmonary trunk, which branches into the left and right pulmonary arteries (pulmonary circuit)

Question 2

The left side supplies blood to what circuit, and where does this circuit carry blood to? Is the blood oxygenated, deoxygenated or both? It receives blood from what vessels? It pumps blood into what vessel? Is the blood in that vessel oxygenated or deoxygenated?

Answer 2

The left side receives oxygenated blood via the pulmonary veins and leaves through the aorta (systemic circuit) and goes to the rest of the body.

Question 3

What is the pericardium? The pericardial sac has how many layers?
Which is the tough fibrous layer? Is it superficial or deep? What is the name of the thin serous layer? Is it superficial or deep? The serous membrane covering the heart is also known by what two names?

Answer 3

1) Pericardium: double-walled sac around the heart
2) Pericardial sac has 2 layers:
-Superficial fibrous layer of connective tissue (parietal pericardium)
-Deep, thin serous layer (aka visceral pericardium aka epicardium)

Question 4

Where is the pericardial cavity and what does it contain? What is the function of this fluid?

Answer 4

Pericardial cavity: a space below the pericardial sac filled with 5 to 30 mL of pericardial fluid; serous membrane makes the fluid. It lubricates the layers of the heart

Question 5

1) What isolates the heart from other thoracic organs and allows it room to expand, without overfilling?
2) What is inflammation of the membranes?

Answer 5

1) The pericardium
2) Pericarditis is painful inflammation of the membranes

Question 6

The heart wall consists of three layers, what are those three layers?

Answer 6

Epicardium,myocardium, endocardium

Question 7

The ______________ (visceral pericardium) is a serous membrane on the heart surface.

Answer 7

epicardium

Question 8

What coronary blood vessels travel through the epicardium?

Answer 8

The largest branches of coronary blood vessels travel through the epicardium.

Question 9

What lines the interior of the heart chambers?

Answer 9

The endocardium

Question 10

What is the middle layer of the heart called and what is composed of? What is this layer responsible for?

Answer 10

1) Myocardium has cardiac muscle as well as a fibrous skeleton framework of collagenous and elastic fibers
2) Responsible for the muscle that spirals around the heart (produces wringing motion)

Question 11

1) Which side of the heart’s myocardium has more muscle and why?
2) The fibrous skeleton of the myocardium has multiple functions, what are some of these functions?

Answer 11

1) The left side has more muscle because the number of layers of cardiac muscle is proportional to workload
2) Functions of the fibrous skeleton of the myocardium:
-Provides structural support and attachment for muscle and valves
-Electrical insulation between atria and ventricles (limits spread of action potentials)

Question 12

The heart has how many chambers? How would you describe them and what is their function?

Answer 12

1) The heart has 4 chambers
2)
The atria are the top two smaller thin-walled chambers, their function is to pump blood into the ventricles
The ventricles are the larger bottom two chambers, and they have thicker walls, and their function is to pump blood into blood vessels

Question 13

Why are the atria called receiving chambers? Which veins empty into each atria?

Answer 13

1) The atria are called the receiving chambers because they are the first chamber the blood enters when it gets to the heart
2) The right atrium receives blood from the superior and inferior vena cavae, and the left atrium receives blood from the pulmonary veins.

Question 14

What is the pectinate muscle? What are the auricles, where are they found, and what is their purpose?

Answer 14

1) The pectinate muscle is the internal ridges of atria and auricles
2) Auricles can be seen on the surface of the heart on the atria, and they are used to enlarge the atria.

Question 15

1) The inferior chambers, are named what?
2) What do they do? Why are they described as discharging chambers?

Answer 15

1) The left and right ventricles
2) They’re the discharging chambers of the heart, meaning that when they contract, they push blood from their chambers to the outside of the heart

Question 16

1) What are the trabeculae carneae and what is their purpose?
2) Which arteries do the ventricles empty into?

Answer 16

1) The trabeculae carneae are internal ridges in both ventricles; they prevent the heart from suctioning itself together.
2) The left ventricle empties into the aorta, and the right ventricle empties into the pulmonary artery.

Question 17

1) What chambers do the atrioventricular sulcus separate?
2) What chambers do the interventricular sulcus separate?

Answer 17

1) The atrioventricular sulcus separates the atria and ventricles
2) The interventricular sulcus overlies the interventricular septum that separates the left and right ventricles

Question 18

What blood vessels are contained within the sulci of the heart?

Answer 18

Both sulci contain coronary arteries

Question 19

1) What is the interatrial septum and what does it divide?
2) What is the name of the hole in the fetal interatrial septum?

Answer 19

1) The interatrial septum is a wall that separates the left and right atria
2) Foramen ovale is the hole in the fetal interatrial septum

Question 20

What is the interventricular septum, and what does it divide?

Answer 20

The interventricular septum is the muscle that separates the left and right ventricles

Question 21

1) What do the valves of the heart ensure?
2) Valves lie between which chambers?
3) The atrioventricular (AV) valves regulate the openings between what?

Answer 21

1) The valves of the heart ensure the one-way flow of blood.
2) Valves lie between the atria and ventricles, and the heart and the exterior
3) The AV valves regulate the openings between the atria and ventricles

Question 22

1) What is the right AV valve also known as, and how many cusps does it have?
2) What is the left AV valve also known as, and how many cusps does it have?

Answer 22

1) The right AV valve is also known as the tricuspid valve; 3 cusps
2) The left AV valve is also known as the bicuspid or mitral valve; 2 cusps.

Question 23

What are the chordae tendineae and what is their function? What muscle do they connect the AV valves to? What do they prevent from happening?

Answer 23

The chordae tendineae connect the AV valves to the papillary muscles; they prevent the AV valves from flipping (eversion) or bulging into atria when ventricles contract

Question 24

1) The semilunar (SL) valves regulate the openings between what?
2) The pulmonary SL valve controls the opening from what heart chamber to what blood vessel?
3) The aortic SL valve controls the opening from what heart chamber to what blood vessel?

Answer 24

1) The semilunar valves regulate the exits of the ventricles.
2) The pulmonary SL valve controls the opening between the right ventricle and the pulmonary trunk
3) The aortic SL valve controls the opening between the left ventricle and the aorta.

Question 25

1) The semilunar valves make no muscular effort but are simply pushed open and closed by what?
2) How many cusps do SL valves have? Do they have tendinous cords?

Answer 25

1) The valves make no muscular effort but are pushed open and closed by ventricular pressure
2) The SL valves have 3 cusps and do not have chordae tendineae

Question 26

Regarding blood flow, what is happening when the ventricles contract? Include where the blood is going, what valves are open or closed and ventricular pressure?

Answer 26

When the ventricles contract, blood is being pushed out of the heart/ ventricles. When the left ventricle contracts, the bicuspid valve is closed, and due to high ventricular pressure blood goes out the aortic semilunar valve and into the aorta, then to the rest of the body. When the right ventricle contracts, the tricuspid valve is closed, and due to high ventricular pressure blood goes out the pulmonary semilunar valve, into the pulmonary trunk, and into the lungs.

Question 27

Regarding blood flow, what is happening when the ventricles relax? Include where the blood is going, what valves are open or closed and ventricular pressure

Answer 27

When the ventricles relax, the SL valves are closed, the bicuspid and tricuspid valves are open, and the ventricles are filling up with blood from the atriums due to gravity.

Question 28

Be able to trace blood flow from the right atrium all the way to the systemic circulation, i.e., through the aorta. Be sure to include heart chambers, heart valves, lungs as part of the tracing.

Answer 28

1) Superior and inferior venae cavae
2) Coronary sinus
3) Right atrium
4) Tricuspid valve (right AV valve)
5) Right ventricle
6) Pulmonary semilunar valve
7) Pulmonary trunk
8) Left and right pulmonary arteries
9) Alveolar capillaries of the left and right lungs; here the blood picks up O2 and releases CO2
10) Four pulmonary veins (2 left & 2 right)
11) Left atrium
12) Bicuspid valve
13) Left ventricle
14) Aortic semilunar valve
15) Ascending aorta
16) Body’s tissues

Question 29

How much of the blood supply is pumped to the heart muscle? When does this occur, when the heart is contracting or when the heart is relaxed?

Answer 29

5% of blood pumped by the heart is pumped into the cardiac muscle
This occurs when the heart is relaxed

Question 30

Name the two major arteries that supply the heart. What blood vessel did the arteries branch off of?

Answer 30

The right & left coronary arteries supply the heart, and they branch from the ascending aorta

Question 31

1) What is angina pectoris?
2) What is a cause?
3) Why does a person feel pain?

Answer 31

1) Defined as chest pain from partial obstruction of coronary blood flow (ischemia)
2) The cause is that an obstruction partially blocks blood flow
3) The myocardium shifts to anaerobic respiration/fermentation, producing lactate and thus stimulating pain

Question 32

1) What is a myocardial infraction (MI)?
2) What is a cause?
3) Why does arterial anastomoses offer some protection?

Answer 32

1) Defined as a heart attack
2) The cause is the sudden death of a patch of myocardium resulting from long-term obstruction of coronary circulation; the obstruction is often a blood clot or fatty deposit (atheroma)
3) Some protection from MI is provided by arterial anastomoses because they provide alternative routes of blood flow (collateral circulation) within the myocardium

Question 33

What are cardiocytes (cardiomyocytes); are they striated? If cardiac muscle is damaged, repair is mostly fibrosis which means what?

Answer 33

Cardiomyocytes are cardiac muscle cells; they’re striated, short, thick, branched cells
Repair of damage of cardiac muscle is almost entirely by fibrosis, which means scarring

Question 34

What are the functions of the interdigitating folds and gap junctions?

Answer 34

1) Interdigitating folds: The plasma membrane at the end of the cardiomyocyte is folded somewhat like the bottom of an egg carton. The folds of adjoining cells interlock with each other and increase the surface area of intercellular contact
2) Gap junctions: They form channels that allow ions to flow from the cytoplasm of one cardiomyocyte directly into the next. They enable each cardiomyocyte to electrically stimulate its neighbors. Thus, the entire myocardium of the two atria behaves almost like a single cell, as does the entire myocardium of the two ventricles. This unified action is essential for the effective pumping of a heart chamber.

Question 35

What are the functions of the desmosomes and fascia adherens?

Answer 35

Desmosomes: Helps tightly join cardiomyocytes; a type of mechanical junction
Fascia adherens: Helps tightly join cardiomyocytes; a type of mechanical junction

Question 36

1) In terms of metabolism, cardiac muscle depends almost exclusively on what type of respiration to make ATP?
2) Because of that, what organelle do you expect to see in abundance?

Answer 36

Cardiac muscle depends almost exclusively on aerobic respiration to make ATP
This means they have a lot of mitochondria

Question 37

1) Cardiac muscle is adaptable to fuel source, but what is it vulnerable to?
2) Why is it important to be fatigue resistant?

Answer 37

1) Cardiac muscle may be adaptable to fuel source, but it’s vulnerable to oxygen deficiency
2) It’s important for the heart to be fatigue resistant since it literally cannot ever stop pumping until you die.

Question 38

Describe autorhythmic cells; do they contract

Answer 38

Autorhythmic cells: They’re composed of an internal pacemaker and nerve-like conduction pathways through myocardium that initiate and distribute action potentials through the heart. These action potentials lead to depolarization and contraction of the rest of myocardium. These cells do not contract.

Question 39

Which parts of the conduction system spontaneously generate an action potential?

Answer 39

The SA node typically generates the action potential, but all components of the conduction system are capable of generation an AP (ectopic focus)

Question 40

The cardiac conduction system generates rhythmic electrical signals in a particular order. What is that order?

Answer 40

SA node, AV node, AV bundle/ bundle of HIS, AV bundle branches, Purkinje fibers.

Question 41

1) Regarding the nerve supply to the heart, which increases heart rate and contraction strength; sympathetic or parasympathetic?
2) Which slows heart rate?

Answer 41

1) Sympathetic nerves increase heart rate and contraction strength
2) Parasympathetic nerves slow heart rate

Question 42

Define systole.
Define diastole.
When you use systole or diastole, are you referring to the action of the ventricles or the atria?

Answer 42

Systole: contraction
Diastole: relaxation
Usually refer to the action of the ventricles

Question 43

What is sinus rhythm? What part of the cardiac conduction triggered the sinus rhythm?

Answer 43

Sinus rhythm: normal heartbeat triggered by the SA node

Question 44

What is the normal range in resting adults in beats per minute (bpm)? How fast does the SA node actually fire? What nerve slows it down to the normal range? Is that sympathetic or parasympathetic?

Answer 44

SA node’s normal firing rate is actually about 100 bpm, but the vagus nerve slows it to ~75 bpm (vagal tone); parasympathetic

Question 45

1) Any region of spontaneous firing other than the SA node is called what?
2) What is nodal rhythm?

Answer 45

1) Any region of spontaneous firing other than the SA node is called ectopic focus.
2) Nodal rhythm: If the SA node is damaged, the AV node will set heart rate to 40 to 50 bpm.

Question 46

If the heart rate is 40 to 50 bpm, what part of the conduction system is triggering the nodal rhythm?

Answer 46

AV node

Question 47

If you produce an even slower heart rate of 20 to 40 bpm, does a heart rate that slow provide enough flow to the brain for it to survive? When do you need to use an artificial pacemaker?

Answer 47

If it’s any other type of ectopic focus other than nodal rhythm (i.e lower than 40 bpm), then the heart rate is too slow to sustain life; you need to use a pacemaker if the ectopic focus is anything other than the AV node.

Question 48

1) Do the cells of the SA node have a stable resting potential meaning the line is flat or does it drift upwards?
2) What electrolyte causes the gradual depolarization?
3) Why is this called the pacemaker potential?

Answer 48

1) The SA node does NOT have a stable resting membrane potential; the line drifts upwards
2) The influx of Sodium (Na) ions causes gradual depolarization of the SA node
3) This is called pacemaker potential because it shows a chance for depolarization

Question 49

1) When the SA node reaches threshold, what electrolyte channel opens to cause faster depolarization?
2) What channel opens to cause repolarization?

Answer 49

1) When it reaches threshold, the voltage-gated calcium ion and sodium ion channels open, which causes faster depolarization
2) The K+ channels opening and potassium leaving the cell cause repolarization

Question 50

Each depolarization of the SA node sets off one heartbeat. At rest, the SA node typically fires every ___ second or so, creating a heart rate of ____ bpm

Answer 50

0.8; 75 bpm

Question 51

1) The SA node stimulates the two atria to contract, even though the SA node is in the right atria, what cell junction allows the near simultaneous depolarization? 2) Why is there a delay as the signal goes through the AV node?

Answer 51

1) The gap junctions allow for near simultaneous depolarization
2) There’s a delay in signal through the AV node to give the atria time to finish contracting, and the ventricles time to finish filling

Question 52

1) The signal speeds up through the last three structures of the heart’s conduction system, which are what?
2) Where does ventricular systole start, from the apex or from the base?

Answer 52

1) Bundle of HIS/ AV bundle, Bundle branches, and Purkinje fibers
2) Ventricular systole starts at the apex of the heart and twists it

Question 53

1) The cells of the heart that actually contract are called what? What is their resting membrane potential?
2) What gates open to cause the cells to depolarize?

Answer 53

1) The cells that actually contract are called cardiomyocytes and they have a stable resting potential of -90mV
2) The Na+ voltage-regulated gates open, causing the cell to depolarize

Question 54

1) What is the purpose of the plateau phase? What electrolyte is responsible for the plateau phase in these contracting cells?
2) What channel closes and what channel opens for repolarization to occur?

Answer 54

1) The plateau phase is to sustain contraction for the expulsion of blood from the heart, this is because the Ca2+ channels open, allowing Ca2+ to flow in from the ECF
2) For repolarization to occur, Ca2+ channels close, and K+ channels open, causing K+ to rapidly diffuse out of the cell.

Question 55

Where does the “plateau phase” occur?

Answer 55

In cardiomyocytes

Question 56

The absolute refractory period in cardiomyocytes is 250 ms, compared to ~2 ms in skeletal muscle, why the difference in absolute refractory period?

Answer 56

To prevent wave summation and tetanus which would stop the pumping action of the heart

Question 57

Can you identify key differences between skeletal muscle and the heart conduction system regarding the following: resting membrane potential, whether a neurotransmitter is required, slow depolarization to threshold, and where does the action potential lead to?

Answer 57

1) Skeletal muscle: Stable resting membrane potential of -90mv; requires motor neuron to release Ach, depolarization of motor end plate, action potential leads to sarcolemma across muscle cell
2) Heart conduction system: SA node membrane potential very unstable, starts at -60mv; have slow depolarization before threshold and fast after, action potential leads to rest of conduction system and and muscle cell connected by gap junctions.

Question 58

1) Can you identify commonalities between skeletal muscle and myocardium regarding depolarization, repolarization?
2) Can you identify differences between skeletal muscle and myocardium regarding plateau, length of action potential, and length of contraction?

Answer 58

1) Similarities: Na+ rushes in during both their depolarization phases, K+ rushes out during both repolarization phases, both need Na+ and K+
2) Differences: In myocardium there’s a plateau caused by Ca2+ flowing in; myocardium has much longer action potential (200-250ms vs 1-2ms); myocardium has a longer contraction (200ms vs 15-100ms).

Question 59

1) An ECG is a composite recording of all action potentials produced by what cells?
2) A typical ECG shows what?

Answer 59

1) A composite of all action potentials produced by nodal and myocardial cells
2) Typically shows a P wave, QRS complex, ST segment, and T wave

Question 60

Can you describe what is going on during each of the following: P wave, QRS complex, ST segment and T wave?

Answer 60

P wave: atrial depolarization and systole
QRS complex: atrial repolarization (hidden) and ventricular depolarization
ST segment: ventricular systole
T wave: ventricular repolarization and diastole

Question 61

1) What could ECG/ECK deviations indicate?
2) What is ventricular fibrillation? Why is this serious?

Answer 61

1) ECG deviations could indicate: Myocardial infarction (MI), abnormalities in conduction pathways, heart enlargement, or electrolyte and hormone imbalances
2) Ventricular fibrillation: Serious arrhythmia caused by electrical signals traveling randomly. This means that the heart cannot pump blood; no coronary perfusion. It’s a hallmark of heart attack (MI) and kills quickly if not stopped

Question 62

What is a defibrillation and what is it designed to do to the heart?

Answer 62

Defibrillation is a strong electrical shock designed to depolarize the entire heart at once

Question 63

1) A cardiac cycle consists what?
2) What does a sphygmomanometer measure?

Answer 63

1) Cardiac cycle: one complete contraction and relaxation of all four chambers of the heart
2) A sphygmomanometer measures blood pressure

Question 64

1) What are the two main variables that govern fluid movement?
2) Do you have to have a pressure gradient? In what direction does fluid flow, from low to high or from high to low?

Answer 64

1) The two main variables the govern fluid movement are that pressure causes flow and resistance opposes it.
2) Fluid will only flow if there is a pressure gradient (pressure difference; flows high to low)

Question 65

If you increase the volume, what happens to pressure? If you decrease the volume, what happens to pressure?

Answer 65

Increasing volume decreases pressure; decreasing volume increases pressure.

Question 66

What happens to the pressure in the ventricles if the ventricles relax and expand? Which of the heart valves are open? Which of the heart valves are closed? What chambers are blood flowing into?

Answer 66

When the ventricles are relaxed, the AV valves are open and the semilunar valves are closed, and blood is flowing into the ventricles.

Question 67

What happens to the pressure in the ventricles if the ventricles contract and internal pressure rises? Which of the heart valves are open? Which of the heart valves are closed? What vessels are the blood flowing into?

Answer 67

Pressure rises in the ventricles if the ventricles contract and get smaller. When the ventricles are contracted, the AV valves are closed and the semilunar valves are opened, and blood is flowing out if the ventricles into the blood vessels (aorta from left side and pulmonary trunk from right side)

Question 68

1) When the ventricles are in (mid) diastole, are the AV valves open or closed?
2) When the ventricles are in systole, are the AV valves open or closed?
3) When the ventricles are in (mid) systole, are the semilunar valves open or closed?
4) When the ventricles are in diastole, are the semilunar valves open or closed?

Answer 68

1) When the ventricles are in mid diastole, the ventricles are filling and the AV valves are opened
2) When the ventricles are in early systole, the AV valves are closed
3) When the ventricles are in mid systole, the semilunar valves are open.
4) When the ventricles are in early diastole, the semilunar valves are closed.

Question 69

What is a valvular stenosis disorder? What is a likely cause?

Answer 69

Valvular stenosis: When the valvular cusps are stiffened and opening is constricted by scar tissue (such as from rheumatic fever); unable to prevent the backflow of blood (valvular insufficiency disorder)

Question 70

1) What is a mitral valve prolapse?
2) Define heart murmur.

Answer 70

1) Mitral valve prolapse: an insufficiency in which one or both mitral valve cusps bulge into the atrium during ventricular contraction; unable to prevent the backflow of blood (valvular insufficiency disorder)
2) Heart murmur: abnormal heart sound

Question 71

1) What is auscultation?
2) What are these two main sounds and what valves are closing to produce the sound?

Answer 71

1) Auscultation: Listening to sounds made by the body
2)
-First heart sound (𝐒𝟏), louder and longer “lubb,” occurs with closure of AV valves
-Second heart sound (𝑺𝟐), softer and sharper “dupp,” occurs with closure of semilunar valves

Question 72

The first heart sound occurs with the closure of the __________ valves, whereas the second heart sound occurs with the closure of the _________ valves

Answer 72

AV; semilunar

Question 73

The cardiac cycle can be described as having four phases, all of which are completed in less than 1 second. As the ventricles relax and expand during diastole, what valves are open and what valves are closed?

Answer 73

During early diastole, as the valves relax and expand, there are no valves open; this is called isovolumetric filling. Then, the AV valves open.

Question 74

During Isovolumetric contraction, what valves are open and what valves are closed? What is blood doing in this phase?

Answer 74

No valves are open, and blood is in the ventricles.

Question 75

During Isovolumetric relaxation, what valves are open and what valves are closed? What is blood doing in this phase? What phase occurs next?

Answer 75

No valves are open and blood is in the atria. The next phase is ventricular relaxation.

Question 76

1) What is the end-systolic volume? Are the chambers completely empty?
2) What is stroke volume?
3) Do both ventricles eject the same amount of blood?

Answer 76

1) End-systolic volume: The blood left behind in the ventricles after ventricular ejection; typically 60ml. The chambers are not completely empty
2) Stroke volume: The amount of blood ejected from the ventricles per contraction, typically 70ml
3) Both ventricles need to eject the same amount of blood.

Question 77

What is congestive heart failure?
What are possible causes?

Answer 77

1) Congestive heart failure (CHF) results from the failure of either ventricle to eject blood effectively
2) Usually due to a heart weakened by myocardial infarction, chronic hypertension, valvular insufficiency, or congenital defects in heart structure

Question 78

1) If the right ventricle pumped more blood, the blood would accumulate in the lungs causing what? Which ventricle failed?
2) If the left ventricle pumped out more blood, blood would accumulate in the systemic circuit and cause what? Which ventricle failed? If uncorrected this leads to what?

Answer 78

1) If the right ventricle pumped more blood, the blood would accumulate in the lungs causing a pulmonary edema; this would mean the left ventricle failed.
2) If the left ventricle pumped out more blood, blood would accumulate in the systemic circuit and cause a systemic edema; this would mean the right ventricle failed. Eventually leads to total heart failure if left uncorrected.

Question 79

Define stroke volume and cardiac output.
What is cardiac reserve?

Answer 79

1) Stroke volume: The amount of blood ejected from a ventricle per contraction, typically 70ml
Cardiac output (CO): The amount of blood ejected by each ventricle in 1 minute (heart rate x stoke volume)
2) Cardiac reserve: the difference between a person’s maximum and resting CO; increases with fitness, decreases with disease

Question 80

1) How does the resting heart rate change over the course of a person’s life?
2) What is Tachycardia and what causes it?
3) What is Bradycardia? When or who is it common in?

Answer 80

1) Babies have high resting heart rates, then it decreases throughout childhood into young adulthood, then it steadily rises until the end of life.
2) Tachycardia: Fast heart rate (>100bpm); anxiety, caffeine, nicotine
3) Bradycardia: Slow heart rate (<60 bpm); extreme athleticism, ectopic focus

Question 81

1) Factors that raise the heart rate are called?
2) Factors that lower it are called?
3) Increasing heart rate will increase cardiac output up to a point, then cardiac out declines, why?

Answer 81

1) Positive chronotropic agents: factors that raise the heart rate
2) Negative chronotropic agents: factors that lower the heart rate
3) At a certain point in increasing heart rate, cardiac output will decline because if heart is going too fast, there is no time between contractions to fill the ventricles, so the ventricles are less efficient and cardiac output goes down.

Question 82

The sympathetic nervous system is a ______ chronotropic agent, whereas the parasympathetic nervous system is a _______ chronotropic agent

Answer 82

positive; negative

Question 83

1) In what organ is the cardiovascular center?
2) What 2 areas can influence signal with their input?

Answer 83

1) The cardiovascular center is in the Medulla of the brain
2) The cerebral cortex and limbic system can influence the cardiovascular center’s signals with their output

Question 84

1) If proprioceptors are activated, what happens to HR? Does it increase or decrease?
2) If baroreceptors are activated, what happens to HR? Does it increase or decrease?
3) If chemoreceptors are activated, what happens to HR? Does it increase or decrease?

Answer 84

1) If proprioceptors are activated, heart rate will increase
2) If baroreceptors are activated, they can either increase or decrease heart rate depending on blood pressure
3) If chemoreceptors are activated, heart rate increases to dispose of CO2 and wastes

Question 85

Which are some positive chronotropic agents?
Which are some negative chronotropic agents?

Answer 85

1) Positive chronotropic agents: Nicotine, caffeine, thyroxine, epinephrine
2) Negative chronotropic agents: Potassium, beta blockers

Question 86

1) What three variables impact stroke volume?
2) Which of the variables, if increased, increases stroke volume?
3) Which of the variables, if increased, decreases stroke volume?

Answer 86

1) Three variables affect stroke volume: Preload, contractility, and afterload
2) Stroke volume increases with increased preload or contractility
3) Stroke volume decreases with increased afterload

Question 87

What is preload? What activity can cause this to increase?

Answer 87

1) Preload: the amount of tension in ventricular myocardium immediately before it begins to contract
-Increased preload causes increased force of contraction
2) Exercise increases venous return and stretches myocardium

Question 88

Frank-Starling law of the heart states what?

Answer 88

That stroke volume is proportional to the end diastolic volume
-Ventricles eject almost as much blood as they receive
-The more they are stretched, the harder they contract

Question 89

1) Contractility refers to what?
2) Factors that increase contractility are called what? Examples?
3) Factors that decrease contractility are called what? Examples?

Answer 89

1) Contractility refers to how hard the myocardium contracts for a given preload
2) Positive inotropic agents increase contractility: Hypercalcemia, catecholamines, glucagon, and digitalis
3) Negative inotropic agents decrease contractility: Hypocalcemia, hyperkalemia, acidosis, and drugs such as calcium channel blockers

Question 90

1) What is afterload?
2) What increases afterload?
3) Why is an increased afterload damaging to the heart?

Answer 90

1) Afterload: The sum of all forces opposing ejection of blood from ventricle; mostly is the blood pressure in aorta and pulmonary trunk
-Opposes the opening of semilunar valves
-Limits stroke volume
2) Hypertension and anything that impedes arterial circulation increases afterload.
3) Increased afterload is damaging due to the fact that it can cause many complications such as ventricular failure.