Chapter 9 Cardiac Physiology

Question 1

Anatomy of the Heart

• The circulatory system is the _______ system of the body.

Answer 1

Anatomy of the Heart

• The circulatory system is the transport system of the body.

Question 2

Anatomy of the Heart

• The three basic components of the circulatory system are:
  
  1. _______
  2. _______
  3. _______

Answer 2

Anatomy of the Heart

• The three basic components of the circulatory system are:
  
  1. the heart (the pump)
  2. the blood vessels (the passageways)
  3. the blood (the transport medium).

Question 3

Anatomy of the Heart

• The heart is positioned midline in the ______ cavity at an angle with its wide base lying toward the ______ and its pointed apex toward the ______.

Answer 3

Anatomy of the Heart

• The heart is positioned midline in the thoracic cavity at an angle with its wide base lying toward the right and its pointed apex toward the left.

Question 4

Anatomy of the Heart

• The heart is a ____ pump that provides the driving pressure for blood flow through the _____________ (between the heart and lungs) and ___________ (between the heart and other body systems).

Answer 4

Anatomy of the Heart

• The heart is a dual pump that provides the driving pressure for blood flow through the pulmonary circulation (between the heart and lungs) and systemic circulation (between the heart and other body systems).

Question 5

Anatomy of the Heart

• The heart has _____ chambers: Each half of the heart consists of an ____, or venous input chamber, and a ____, or arterial output chamber.
• The ____ atrium receives O2-poor blood from the systemic circulation and the right ventricle pumps it into the ____ circulation.
• The ____ atrium receives O2-rich blood from the ____ circulation and the left ventricle pumps it into the ____ circulation.

Answer 5

Anatomy of the Heart

• The heart has four chambers: Each half of the heart consists of an atrium, or venous input chamber, and a ventricle, or arterial output chamber.
• The right atrium receives O2-poor blood from the systemic circulation and the right ventricle pumps it into the pulmonary circulation.
• The left atrium receives O2-rich blood from the pulmonary circulation and the left ventricle pumps it into the systemic circulation.

Question 6

Anatomy of the Heart

• _____ heart valves direct blood in the right direction and keep it from flowing in the other direction.
• The right and left __________ valves direct blood from the atria to the ventricles during _____ and prevent back flow of blood from the ventricles to the atria during _____.
• The aortic and pulmonary _____ valves direct blood from the ventricles to the _____ and __________, respectively, during _____ and prevent back flow of blood from these major vessels to the ventricles during _____.

Answer 6

Anatomy of the Heart

• Four heart valves direct blood in the right direction and keep it from flowing in the other direction.
• The right and left atrioventricular (AV) valves direct blood from the atria to the ventricles during diastole and prevent back flow of blood from the ventricles to the atria during systole.
  ​
• The aortic and pulmonary semilunar valves direct blood from the ventricles to the aorta and pulmonary artery, respectively, during systole and prevent back flow of blood from these major vessels to the ventricles during diastole.

Question 7

Anatomy of the Heart

• Contraction of the _______ arranged cardiac muscle fibers produces a wringing effect important for efficient _______
  .
• Also important for efficient _______ is that the muscle fibers in each chamber contract as a __________.
• The branching cardiac muscle fibers are interconnected by intercalated discs, which contain:
  
  1. _______
  2. _______

Answer 7

Anatomy of the Heart

• Contraction of the spirally arranged cardiac muscle fibers produces a wringing effect important for efficient pumping.
• Also important for efficient pumping is that the muscle fibers in each chamber contract as a coordinated unit.
• The branching cardiac muscle fibers are interconnected by intercalated discs, which contain:
  
  1. desmosomes that hold the cells together mechanically
  2. gap junctions that permit spread of electrical current between cells joined together into a functional syncytium.

Question 8

Electrical Activity of the Heart

• The self-excitable heart ______ its rhythmic contractions.
• Autorhythmic cells are ______ of the cardiac muscle cells; they do not contract but are instead specialized to__________________.
• The other _____ of cardiac cells are ______ cells that contract in response to the spread of an ______ initiated by autorhythmic cells.

Answer 8

Electrical Activity of the Heart

• The self-excitable heart initiates its rhythmic contractions.
• Autorhythmic cells are 1% of the cardiac muscle cells; they do not contract but are specialized to initiate and conduct action potentials.
• The other 99% of cardiac cells are contractile cells that contract in response to the spread of an action potential initiated by autorhythmic cells.

Question 9

Electrical Activity of the Heart

• Autorhythmic cells display a ________, a slow drift to threshold potential, as a result of a complex interplay of inherent changes in _____ movement across the _____.
• The first half of the pacemaker potential results from opening of unique funny channels that permit entry of ____ at the same time _____ channels slowly close so that exit of _____ slowly declines.
• Both of these actions gradually _____ the membrane toward threshold.
• The final boost to threshold results from Ca⁺² ____ on opening of_____Ca⁺² channels.
• The ____ phase of the action potential is the result of further Ca⁺² entry on opening of _____ Ca⁺² channels at threshold.
• The _____ phase results from K⁺ _____ on opening of K⁺ channels at the peak of the action potential.
• Slow closure of these K⁺ channels at the end of ________ contributes to the next pacemaker potential.

Answer 9

Electrical Activity of the Heart

• Autorhythmic cells display a pacemaker potential, a slow drift to threshold potential, as a result of a complex interplay of inherent changes in ion movement across the membrane.
• The first half of the pacemaker potential results from opening of unique funny channels that permit entry of Na⁺ at the same time K⁺ channels slowly close so that exit of K⁺ slowly declines.
• Both of these actions gradually depolarize the membrane toward threshold.
• The final boost to threshold results from Ca⁺²entry on opening of T-type Ca⁺² channels.
• The rising phase of the action potential is the result of further Ca⁺² entry on opening of L-type Ca⁺² channels at threshold.
• The falling phase results from K⁺ efflux on opening of K⁺ channels at the peak of the action potential.
• Slow closure of these K⁺ channels at the end of repolarization contributes to the next pacemaker potential.

Question 10

Electrical Activity of the Heart

• The cardiac impulse originates at the _____ node, the pacemaker of the heart, which has the fastest rate of spontaneous _____ to threshold.

Answer 10

Electrical Activity of the Heart

• The cardiac impulse originates at the SA node, the pacemaker of the heart, which has the fastest rate of spontaneous depolarization to threshold.

Question 11

Electrical Activity of the Heart

• Once initiated, the action potential spreads throughout the right and left _____, partially facilitated by_______________ but mostly by cell-to-cell spread of the impulse through __________.

Answer 11

Electrical Activity of the Heart

• Once initiated, the action potential spreads throughout the right and left atria, partially facilitated by specialized conduction pathways but mostly by cell-to-cell spread of the impulse through gap junctions.

Question 12

Electrical Activity of the Heart

• The impulse passes from the ____ into the ____ through the ____ node, the only point of electrical contact between these chambers.
• The action potential is delayed briefly at the ____ node, ensuring that ____ contraction precedes ____ contraction to allow complete ventricular ____.

Answer 12

Electrical Activity of the Heart

• The impulse passes from the atria into the ventricles through the AV node, the only point of electrical contact between these chambers.
• The action potential is delayed briefly at the AV node, ensuring that atrial contraction precedes ventricular contraction to allow complete ventricular filling.

Question 13

Electrical Activity of the Heart

• The impulse then travels rapidly down the interventricular septum via the __________ and rapidly disperses throughout the _______ by means of the __________.
• The rest of ventricular cells are activated by cell-to-cell spread of the impulse through __________.

Answer 13

Electrical Activity of the Heart

• The impulse then travels rapidly down the interventricular septum via the bundle of His and rapidly disperses throughout the myocardium by means of the purkinje fibers.
  ​
• The rest of ventricular cells are activated by cell-to-cell spread of the impulse through gap junctions.

Question 14

Electrical Activity of the Heart

• The atria contract as a ______ unit, followed after a brief delay by a synchronized ______ contraction.

Answer 14

Electrical Activity of the Heart

• The atria contract as a single unit, followed after a brief delay by a synchronized ventricular contraction.

Question 15

Electrical Activity of the Heart

• The action potentials of cardiac contractile cells exhibit a prolonged ____________ accompanied by a prolonged period of ________, which ensures adequate ejection time.
• This plateau is primarily the result of activation of _________ channels.

Answer 15

Electrical Activity of the Heart

• The action potentials of cardiac contractile cells exhibit a prolonged positive phase, or plateau, accompanied by a prolonged period of contraction, which ensures adequate ejection time.
• This plateau is primarily the result of activation of slow L-type Ca⁺² channels.

Question 16

Electrical Activity of the Heart

• Ca⁺² entry though the _____ channels in the T tubules triggers a much larger release of Ca⁺² from the ________.
• This Ca⁺² -induced Ca⁺² release leads to ___________ and ___________.

Answer 16

Electrical Activity of the Heart

• Ca⁺² entry though the L-type channels in the T tubules triggers a much larger release of Ca⁺² from the sarcoplasmic reticulum.
  ​
• This Ca⁺² -induced Ca⁺² release leads to cross-bridge cycling and contraction.

Question 17

Electrical Activity of the Heart

• Because a long __________ occurs in conjunction with the prolonged plateau phase, __________ and __________ of cardiac muscle are impossible, ensuring the alternate periods of __________ and __________ essential for pumping of blood.

Answer 17

Electrical Activity of the Heart

• Because a long refractory period occurs in conjunction with the prolonged plateau phase, summation and tetanus of cardiac muscle are impossible, ensuring the alternate periods of contraction and relaxation essential for pumping of blood.

Question 18

Electrical Activity of the Heart

• The spread of electrical activity throughout the heart can be recorded from the ______.
• In this electrocardiogram (ECG), the P wave represents ______ depolarization; the QRS complex, ______ depolarization; and the T wave, ______ repolarization.
• ______ repolarization is masked by the QRS complex.

Answer 18

Electrical Activity of the Heart

• The spread of electrical activity throughout the heart can be recorded from the body surface.
  ​
• In this electrocardiogram (ECG), the P wave represents atrial depolarization; the QRS complex, ventricular depolarization; and the T wave, ventricular repolarization.
• Atrial repolarization is masked by the QRS complex.

Question 19

Mechanical Events of the Cardiac Cycle

• The cardiac cycle consists of three important events
  
  1. The generation of __________ as the heart autorhythmically depolarizes and repolarizes.
  2. _____ activity consisting of alternate periods of _____ (contraction and emptying) and _____ (relaxation and filling), which are initiated by the _______ cycle.
  3. Directional flow of blood through the heart chambers, guided by _______________ induced by _____ changes that are generated by _____ activity.

Answer 19

Mechanical Events of the Cardiac Cycle

​

• The cardiac cycle consists of three important events
  
  1. The generation of electrical activity as the heart autorhythmically depolarizes and repolarizes.
  2. Mechanical activity consisting of alternate periods of systole (contraction and emptying) and diastole (relaxation and filling), which are initiated by the rhythmic electrical cycle.
  3. Directional flow of blood through the heart chambers, guided by valve opening and closing induced by pressure changes that are generated by mechanical activity.

Question 20

Mechanical Events of the Cardiac Cycle

• The _____ pressure curve remains low throughout the entire cardiac cycle, with only minor fluctuations (normally varying between 0 and 8 mm Hg).
• The _____ pressure curve remains high the entire time, with moderate fluctuations (normally varying between a _____ pressure of 120 mm Hg and a _____ pressure of 80 mm Hg).
• The _____ ventricular pressure curve fluctuates dramatically because ventricular pressure must be below the low _____ pressure to allow the _____ valve to open during the ventricular filling phase, and, to force the _____ valve open to allow emptying, it must be above the high _____ pressure during the ejection phase.
• Therefore, _____ pressure normally varies from 0 mm Hg during _____ to slightly more than 120 mm Hg during _____.
• During the periods of isovolumetric ventricular contraction and relaxation, _____ pressure is above the low _____ pressure and below the _____ aortic pressure, so all valves are _____ and _____ enters or leaves the ventricles.

Answer 20

Mechanical Events of the Cardiac Cycle

• The atrial pressure curve remains low throughout the entire cardiac cycle, with only minor fluctuations (normally varying between 0 and 8 mm Hg).
• The aortic pressure curve remains high the entire time, with moderate fluctuations (normally varying between a systolic pressure of 120 mm Hg and a diastolic pressure of 80 mm Hg).
• The left ventricular pressure curve fluctuates dramatically because ventricular pressure must be below the low atrial pressure to allow the AV valve to open during the ventricular filling phase, and, to force the aortic valve open to allow emptying, it must be above the high aortic pressure during the ejection phase.
• Therefore, ventricular pressure normally varies from 0 mm Hg during diastole to slightly more than 120 mm Hg during systole.
• During the periods of isovolumetric ventricular contraction and relaxation, ventricular pressure is above the low atrial pressure and below the high aortic pressure, so all valves are closed and no blood enters or leaves the ventricles.

Question 21

Mechanical Events of the Cardiac Cycle

• The end-diastolic volume (EDV) is the volume of blood in the _______ when filling is complete at the end of diastole.
• The end- systolic volume (ESV) is the volume of blood _______ in the ventricle when _______ is complete at the end of systole.
• The stroke volume (SV) is the volume of blood _______ by each _______ each _______.

Answer 21

Mechanical Events of the Cardiac Cycle

• The end-diastolic volume (EDV) is the volume of blood in the ventricle when filling is complete at the end of diastole.
• The end- systolic volume (ESV) is the volume of blood remaining in the ventricle when ejection is complete at the end of systole.
• The stroke volume (SV) is the volume of blood pumped out by each ventricle each beat.

Question 22

Mechanical Events of the Cardiac Cycle

• Valve closing gives rise to ____ normal heart sounds.
• The first heart sound is caused by ____ of the ____ valves and signals the onset of ventricular ____.
• The second heart sound is the result of ____ of the ____ and ____ valves at the onset of ____.

Answer 22

Mechanical Events of the Cardiac Cycle

• Valve closing gives rise to two normal heart sounds.
• The first heart sound is caused by closing of the AV valves and signals the onset of ventricular systole.
  ​
• The second heart sound is the result of closing of the aortic and pulmonary valves at the onset of diastole.

Question 23

Mechanical Events of the Cardiac Cycle

• Defective valve function produces _____ blood flow, which is audible as a __________.
• Abnormal valves may be either _____ and not open completely or _____ (leaky) and not close completely.

Answer 23

Mechanical Events of the Cardiac Cycle

• Defective valve function produces turbulent blood flow, which is audible as a heart murmur.
  ​
• Abnormal valves may be either stenotic and not open completely or insufficient (leaky) and not close completely.

Question 24

Cardiac Output and Its Control

• Cardiac output (CO), the volume of blood ejected by each _____ each minute, is determined by _____ times _____.

Answer 24

Cardiac Output and Its Control

• Cardiac output (CO), the volume of blood ejected by each ventricle each minute, is determined by heart rate times stroke volume.

Question 25

Cardiac Output and Its Control

• Heart rate (HR), the number of beats per minute, varies by altering the balance of _______ and _______ influence on the ______.
• _______ stimulation slows HR, and _______ stimulation speeds it up.

Answer 25

Cardiac Output and Its Control

• Heart rate (HR), the number of beats per minute, varies by altering the balance of parasympathetic and sympathetic influence on the SA node.
  ​
• Parasympathetic stimulation slows HR, and sympathetic stimulation speeds it up.

Question 26

Cardiac Output and Its Control

• Stroke volume depends on
  
  1. the extent of ________, with an increased EDV resulting in a larger ____ by means of the length–tension relationship (Frank–Starling law of the heart, a form of ____ control)
  2. the extent of ____ stimulation, with increased ____ stimulation resulting in increased contractility of the heart, that is, increased ____ of contraction and increased ____ at a given EDV (________ control).

Answer 26

Cardiac Output and Its Control

• Stroke volume depends on
  
  1. the extent of ventricular filling, with an increased EDV resulting in a larger SV by means of the length–tension relationship (Frank–Starling law of the heart, a form of intrinsic control)
  2. the extent of sympathetic stimulation, with increased sympathetic stimulation resulting in increased contractility of the heart, that is, increased strength of contraction and increased SV at a given EDV (extrinsic control).

Question 27

Cardiac Output and Its Control

• The _____ of the heart (the workload imposed on the heart before contraction begins) is the extent of filling.
• The _____ of the heart (the workload imposed on the heart after contraction has begun) is the _____ blood pressure.

Answer 27

Cardiac Output and Its Control

• The preload of the heart (the workload imposed on the heart before contraction begins) is the extent of filling.
• The afterload of the heart (the workload imposed on the heart after contraction has begun) is the arterial blood pressure.

Question 28

Nourishing the Heart Muscle

• Cardiac muscle is supplied with O2 and nutrients by blood delivered to it by the ______ circulation, not by__________________.

Answer 28

Nourishing the Heart Muscle

• Cardiac muscle is supplied with O2 and nutrients by blood delivered to it by the coronary circulation, not by blood within the heart chambers.

Question 29

Nourishing the Heart Muscle

• Most coronary blood flow occurs during ______ because during ______ the contracting heart muscle ______ the coronary vessels.

Answer 29

Nourishing the Heart Muscle

• Most coronary blood flow occurs during diastole because during systole the contracting heart muscle compresses the coronary vessels.

Question 30

Nourishing the Heart Muscle

• Coronary blood flow is normally _____ to keep pace with cardiac _____ needs.

Answer 30

Nourishing the Heart Muscle

• Coronary blood flow is normally varied to keep pace with cardiac oxygen needs.

Question 31

Nourishing the Heart Muscle

• Coronary blood flow may be compromised by development of ________, which can lead to ________ heart disease ranging in severity from mild chest pain on exertion to fatal heart attacks.

Answer 31

Nourishing the Heart Muscle

• Coronary blood flow may be compromised by development of atherosclerotic plaques, which can lead to ischemic heart disease ranging in severity from mild chest pain on exertion to fatal heart attacks.