ch 18 pq

pacemaker cells are located where?

SA node

What heart sound (S1) corresponds to the closing of the AV valves and marks the beginning of systole?
A) "Dub"
B) "Lub"
C) Opening of SL valves
D) End of diastole

B) "Lub"

The "Dub" sound (S2) is caused by the closure of which valves and marks the start of what phase?
A) AV valves; systole
B) SL valves; systole
C) SL valves; diastole
D) AV valves; diastole

C) SL valves; diastole

During the isovolumetric phase of the cardiac cycle:
A) Blood is rapidly filling the ventricles
B) Blood is being ejected into arteries
C) All valves are closed and no blood moves
D) Only the AV valves are open

C) All valves are closed and no blood moves

When the semilunar (SL) valves open, which phase is occurring?
A) Isovolumetric relaxation
B) Filling
C) Atrial contraction
D) Ejection

D) Ejection

During ventricular filling, which valves are open?
A) AV valves
B) SL valves
C) Both AV and SL valves
D) Neither valve type

A) AV valves

Which structure directly stimulates ventricular contraction?
A) AV node
B) Purkinje fibers
C) SA node
D) AV bundle

B) Purkinje fibers

During which part of the Wiggers diagram does ventricular pressure exceed aortic pressure, causing the aortic valve to open?
A) During ventricular filling
B) During isovolumetric contraction
C) At the end of ventricular systole
D) At the beginning of ejection

D) At the beginning of ejection

Blood is ejected from the heart during which phase of the cardiac cycle?
A) Atrial diastole
B) Isovolumetric contraction
C) Ventricular systole
D) Isovolumetric relaxation

C) Ventricular systole

Which valve prevents backflow from the right ventricle into the right atrium?
A) Pulmonary semilunar valve
B) Aortic semilunar valve
C) Tricuspid valve
D) Bicuspid valve

C) Tricuspid valve

Which chamber of the heart receives oxygenated blood from the lungs?
A) Right atrium
B) Left ventricle
C) Left atrium
D) Right ventricle

C) Left atrium

Which represents ventricular repolarization on an ECG?
A) P wave
B) QRS complex
C) T wave
D) U wave

C) T wave

Which of the following events does NOT occur when the semilunar valves open?
A) Ventricles are in diastole
B) Blood enters the pulmonary arteries and the aorta
C) AV valves are closed
D) Ventricular pressure exceeds arterial pressure

A) Ventricles are in diastole

Which of the following best describes isovolumetric contraction?
A) AV and semilunar valves are both open
B) Blood is rapidly ejected from the ventricles
C) All valves are closed; pressure increases
D) Atria are contracting

C) All valves are closed; pressure increases

Which wave on the ECG marks atrial depolarization?
A) Q wave
B) T wave
C) P wave
D) S wave

C) P wave

What causes the "dub" sound (S2) of the heart?
A) AV valves closing
B) Semilunar valves closing
C) Blood entering the ventricles
D) SA node firing

B) Semilunar valves closing

The pacemaker potential (spontaneous depolarization) of SA node cells is due to:
A) Fast Na⁺ influx
B) Slow Ca²⁺ efflux
C) Na⁺ influx through funny channels and Ca²⁺ influx
D) K⁺ influx

C) Na⁺ influx through funny channels and Ca²⁺ influx

Which pressure change causes the AV valves to close?
A) Atrial pressure drops below venous pressure
B) Ventricular pressure rises above atrial pressure
C) Aortic pressure drops below ventricular pressure
D) Pulmonary artery pressure drops below atrial pressure

B) Ventricular pressure rises above atrial pressure

The pulmonary veins carry:
A) Deoxygenated blood to the lungs
B) Deoxygenated blood to the heart
C) Oxygenated blood to the lungs
D) Oxygenated blood to the heart

D) Oxygenated blood to the heart

Which structure is considered the heart’s natural pacemaker?
A) AV node
B) AV bundle
C) SA node
D) Purkinje fibers

C) SA node

Which of the following would increase heart rate?
A) Parasympathetic stimulation
B) Vagus nerve activation
C) Acetylcholine release
D) Sympathetic stimulation

D) Sympathetic stimulation

What happens during ventricular systole?
A) Atria fill with blood
B) AV valves open
C) Semilunar valves open
D) Ventricles relax

C) Semilunar valves open

Which wave on an ECG represents atrial depolarization?
A) P wave
B) QRS complex
C) T wave
D) U wave

A) P wave

When are all heart valves closed?
A) During ventricular filling
B) During isovolumetric contraction and relaxation
C) During atrial systole
D) During ejection phase

B) During isovolumetric contraction and relaxation

What initiates the rapid depolarization phase in contractile cardiac muscle cells?
A) Na⁺ influx
B) Ca²⁺ influx
C) K⁺ efflux
D) Cl⁻ influx

A) Na⁺ influx

Which ion maintains the plateau phase in cardiac muscle action potentials?
A) Sodium
B) Potassium
C) Calcium
D) Chloride

C) Calcium

The amount of blood ejected from a ventricle in one beat is called:
A) Cardiac output
B) End-systolic volume
C) End-diastolic volume
D) Stroke volume

D) Stroke volume

The term “afterload” refers to:
A) The volume of blood in the ventricle at the end of diastole
B) The resistance the ventricle must overcome to eject blood
C) The heart rate x stroke volume
D) The passive filling of the ventricles

B) The resistance the ventricle must overcome to eject blood

Which of the following increases preload?
A) Increased venous return
B) Decreased ventricular filling
C) Dehydration
D) Hemorrhage

A) Increased venous return

What happens if the AV node is damaged?
A) Atrial contraction ceases
B) Ventricles beat faster than atria
C) SA node takes over
D) Ventricles contract at a slower, abnormal rate

D) Ventricles contract at a slower, abnormal rate

Which structure prevents backflow into the left ventricle?
A) Pulmonary valve
B) Tricuspid valve
C) Aortic semilunar valve
D) Mitral valve

C) Aortic semilunar valve

Which ion is primarily responsible for the depolarization phase in a neuronal action potential?
A) Ca²⁺ influx
B) K⁺ efflux
C) Na⁺ influx
D) Cl⁻ influx

C) Na⁺ influx

What ion is responsible for depolarization in pacemaker cells (SA node)?
A) Na⁺ via voltage-gated fast channels
B) Ca²⁺ via L-type calcium channels
C) K⁺ influx
D) Cl⁻ channels

B) Ca²⁺ via L-type calcium channels

The “funny” (If) channels in pacemaker cells allow:
A) K⁺ efflux
B) Na⁺ influx during repolarization
C) Na⁺ influx during spontaneous depolarization
D) Ca²⁺ influx during repolarization

C) Na⁺ influx during spontaneous depolarization

Which of the following best explains why cardiac muscle cannot be tetanized like skeletal muscle?
A) Rapid K⁺ efflux
B) Long absolute refractory period due to plateau
C) Short refractory period
D) Pacemaker cells reset quickly

B) Long absolute refractory period due to plateau

n contractile cardiac cells, what ion movement occurs during repolarization (phase 3)?
A) Na⁺ influx
B) Ca²⁺ influx
C) K⁺ efflux
D) Cl⁻ influx

C) K⁺ efflux

What ion movement brings neurons back to resting membrane potential after depolarization?
A) Na⁺ efflux
B) K⁺ efflux
C) Ca²⁺ influx
D) Cl⁻ efflux

B) K⁺ efflux

Which phase is absent in pacemaker action potentials compared to contractile cardiac cells?
A) Depolarization
B) Plateau phase
C) Repolarization
D) Resting membrane potential

B) Plateau phase

What is the resting membrane potential of most neurons?
A) +30 mV
B) 0 mV
C) –90 mV
D) –70 mV

D) –70 mV