The Heart Flashcards
A 60-year-old woman has a resting heart rate of 70 beats/min, arterial pressure is 130/85 mm Hg, and body temperature is normal. Her pressure-volume diagram of the left ventricle is shown above.
- What is her cardiac output in milliliters per minute?
A)2000
B)3000
C)4000
D)6000
E)7000
When does the second heart sound occur in the ventricular pressure–volume relationship?
A) At point D
B)Between point A and point B
C)Between point B and point C
D)Between point C and point D
E)Between point D and point A
When does the third heart sound occur in the ventricular pressure–volume relationship?
A)At point D
B)Between point A and point B
C)Between point B and point C
D)Between point C and point D
E)Between point D and point A
What is her ventricular ejection fraction?
A)33%
B)50%
C)60%
D)67%
E)80%
In which phase of the ventricular muscle action potential is the potassium permeability the highest?
A)0
B)1
C)2
D)3
E)4
In a resting adult, the typical ventricular ejection fraction has what value?
A)20%
B)30%
C)40%
D)60%
E)80%
A 30-year-old man has an ejection fraction of 0.25 and an end systolic volume of 150 ml. What is his end diastolic volume?
A)50 ml
B)100 ml
C)125 ml
D)200 ml
E)250 m
Which of the following statements about cardiac muscle is most accurate?
A)The T-tubules of cardiac muscle can store much less calcium than T-tubules in skeletal muscle
B)The strength and contraction of cardiac muscle depends on the amount of calcium surrounding cardiac myocytes
C)In cardiac muscle the initiation of the action potential causes an immediate opening of slow calcium channels
D)Cardiac muscle repolarization is caused by opening of sodium channels
E)Mucopolysaccharides inside the T-tubules bind chloride ions
A 60-year-old man’s EKG shows that he has an R-R interval of 0.55 sec. Which of the following best explains his condition?
A)He has fever
B)He has a normal heart rate
C)He has excess parasympathetic stimulation of the S-A node
D)He is a trained athlete at rest
E)He has hyperpolarization of the S-A node
A 60-year-old man’s EKG shows that he has an R-R interval of 0.55 sec. Which of the following best explains his condition?
A)He has fever
B)He has a normal heart rate
C)He has excess parasympathetic stimulation of the S-A node
D)He is a trained athlete at rest
E)He has hyperpolarization of the S-A node
Which of the following events occurs at the end of the period of ventricular ejection?
A)A-V valves close
B)Aortic valve opens
C)Aortic valve remains open
D)A-V valves open
E)Pulmonary valve closes
Which of the following phases of the cardiac cycle follows immediately after the beginning of the QRS wave?
A)Isovolumic relaxation
B)Ventricular ejection
C)Atrial systole
D)Diastasis
E)Isovolumic contraction
Which of the following conditions will result in a dilated, flaccid heart?
A)Excess calcium ions in the blood
B)Excess potassium ions in the blood
C)Excess sodium ions in the blood
D)Increased sympathetic stimulation
E)Increased norepinephrine concentration in the blood
A 25-year-old, well-conditioned athlete weighs 80 kg (176 lb). During maximal sympathetic stimulation, what is the plateau level of his cardiac output function curve?
A)3 L/min
B)5 L/min
C)10 L/min
D)13 L/min
E)25 L/min
Which of the following events is associated with the first heart sound?
A)Closing of the aortic valve
B)Inrushing of blood into the ventricles during diastole
C)Beginning of diastole
D)Opening of the A-V valves
E)Closing of the A-V valves
Which of the following conditions at the A-V node will cause a decrease in heart rate?
A)Increased sodium permeability
B)Decreased acetylcholine levels
C)Increased norepinephrine levels
D)Increased potassium permeability
E)Increased calcium permeability
Sympathetic stimulation of the heart
A)Releases acetylcholine at the sympathetic endings
B)Decreases sinus nodal discharge rate
C)Decreases excitability of the heart
D)Releases norepinephrine at the sympathetic endings
E)Decreases cardiac contractility
What is the normal total delay of the cardiac impulse in the A-V node plus bundle?
A)0.22 sec
B)0.18 sec
C)0.16 sec
D)0.13 sec
E)0.09 sec
Which of the following best explains how sympathetic stimulation affects the heart?
A)Permeability of the S-A node to sodium decreases
B)Permeability of the A-V node to sodium decreases
C)Permeability of the S-A node to potassium increases
D)There is an increased rate of upward drift of the resting membrane potential of the S-A node
E)Permeability of the cardiac muscle to calcium decreases
Which of the following structures will have the slowest rate of conduction of the cardiac action potential?
A)Atrial muscle
B)Anterior internodal pathway
C)A-V bundle fibers
D)Purkinje fibers
E)Ventricular muscle
f the S-A node discharges at 0.00 seconds, when will the action potential normally arrive at the epicardial surface at the base of the left ventricle?
A)0.22 sec
B)0.18 sec
C)0.16 sec
D)0.12 sec
E)0.09 sec
If the S-A node discharges at 0.00 seconds, when will the action potential normally arrive at the A-V bundle (bundle of His)?
A)0.22 sec
B)0.18 sec
C)0.16 sec
D)0.12 sec
E)0.09 sec
Which of the following conditions at the S-A node will cause heart rate to decrease?
A)Increased norepinephrine levels
B)Increased sodium permeability
C)Increased calcium permeability
D)Increased potassium permeability
E)Decreased acetylcholine levels
Which of the following are caused by acetylcholine?
A)Hyperpolarization of the S-A node
B)Depolarization of the A-V node
C)Decreased permeability of the S-A node to potassium ions
D)Increased heart rate
E)Increased permeability of the cardiac muscle to calcium ions
What is the membrane potential (threshold level) at which the S-A node discharges?
A)−40 mV
B)−55 mV
C)−65 mV
D)−85 mV
E)−105 mV
Which of the following conditions at the A-V node will cause a decrease in heart rate?
A)Increased sodium permeability
B)Decreased acetylcholine levels
C)Increased norepinephrine levels
D)Increased potassium permeability
E)Increased calcium permeability
If the ventricular Purkinje fibers become the pacemaker of the heart, what is the expected heart rate?
A)30/min
B)50/min
C)65/min
D)75/min
E)85/min
What is the normal total delay of the cardiac impulse in the A-V node and the A-V bundle system?
A)0.03 sec
B)0.06 sec
C)0.09 sec
D)0.13 sec
E)0.17 sec