Chapter 19 Study Guide Flash Cards
What is the primary function of the heart?
a) To produce oxygen for the body
b) To pump blood throughout the body
c) To regulate blood glucose levels
d) To break down nutrients
b) To pump blood throughout the body
The heart is responsible for maintaining circulation, ensuring that oxygen-rich blood reaches tissues and oxygen-poor blood is sent to the lungs for reoxygenation.
The pulmonary circuit carries oxygen-rich blood to the lungs.
False
The pulmonary circuit carries oxygen-poor blood from the right side of the heart to the lungs for oxygenation, then returns oxygen-rich blood to the left side of the heart. The systemic circuit distributes oxygen-rich blood to the rest of the body.
The innermost layer of the heart wall, which lines the heart chambers and valves, is called the __________.
Endocardium
The endocardium is a smooth, thin layer that helps reduce friction as blood flows through the heart.
Which valve prevents backflow of blood into the left atrium?
a) Pulmonary semilunar valve
b) Aortic semilunar valve
c) Mitral (bicuspid) valve
d) Tricuspid valve
c) Mitral (bicuspid) valve
The mitral valve prevents backflow from the left ventricle into the left atrium during ventricular contraction.
The superior and inferior vena cava deliver oxygen-poor blood to the right atrium.
True
Explanation: These veins return deoxygenated blood from the body to the right atrium, where it is then pumped to the lungs for oxygenation.
Oxygenated blood returns to the heart through the __________ and enters the __________.
Pulmonary veins; left atrium
Pulmonary veins are the only veins in the body that carry oxygen-rich blood, returning it from the lungs to the left atrium.
Intercalated discs in cardiac muscle cells contain which structures that help with electrical and mechanical connections?
a) Synapses and axons
b) Desmosomes and gap junctions
c) Sarcomeres and myelin
d) Ligaments and tendons
b) Desmosomes and gap junctions
Desmosomes provide mechanical strength to prevent cells from separating, while gap junctions allow electrical impulses to pass quickly between cells for synchronized contraction.
The sinoatrial (SA) node is known as the heart’s pacemaker.
True
The SA node, located in the right atrium, generates electrical impulses that set the pace for the heart’s contractions.
Which ion is primarily responsible for the plateau phase in a cardiac muscle action potential?
a) Sodium (Na⁺)
b) Potassium (K⁺)
c) Calcium (Ca²⁺)
d) Chloride (Cl⁻)
c) Calcium (Ca²⁺)
The influx of calcium ions prolongs depolarization, preventing tetanus and ensuring efficient heart contractions.
The QRS complex on an electrocardiogram represents __________.
Ventricular depolarization
Explanation: This wave corresponds to the contraction of the ventricles as electrical signals spread through them.
Defibrillators restart the heart by stopping all electrical activity momentarily.
True
Defibrillators deliver a shock to depolarize the entire heart, allowing the SA node to reestablish a normal rhythm.
During which phase of the cardiac cycle does the ventricular pressure rise and push the semilunar valves open?
a) Ventricular filling
b) Isovolumetric contraction
c) Ventricular ejection
d) Isovolumetric relaxation
c) Ventricular ejection
During this phase, the ventricles contract and force blood through the aortic and pulmonary semilunar valves.
The “lub” sound in a heartbeat is caused by the closing of the __________ valves, while the “dub” sound is caused by the closing of the __________ valves.
Atrioventricular (AV); semilunar
The first heart sound (lub) is due to the AV valves (tricuspid and mitral) closing, and the second (dub) is from the semilunar valves (aortic and pulmonary) closing.
Cardiac output is calculated by multiplying heart rate by stroke volume.
True
Explanation: Cardiac output (CO) = Heart rate (HR) × Stroke volume (SV), representing the amount of blood pumped per minute.
The parasympathetic nervous system __________ heart rate, while the sympathetic nervous system __________ it.
a) Increases; decreases
b) Decreases; increases
c) Has no effect on; increases
d) Increases; has no effect on
b) Decreases; increases
Parasympathetic stimulation (via the vagus nerve) slows heart rate, while sympathetic stimulation increases it.
Which of the following structures prevents the atrioventricular (AV) valves from inverting during ventricular contraction?
A) Trabeculae carneae
B) Chordae tendineae
C) Auricles
D) Ligamentum arteriosum
B) Chordae tendineae
Explanation: The chordae tendineae are fibrous cords that connect the papillary muscles to the AV valves, preventing them from prolapsing into the atria during systole.
The ligamentum arteriosum is a remnant of fetal circulation that once connected the pulmonary trunk to the aorta.
True
Explanation: The ligamentum arteriosum is a vestigial structure from the fetal ductus arteriosus, which allowed blood to bypass the lungs in utero.
The __________ are muscular ridges found on the inner walls of the ventricles, which help reinforce the structure of the heart and prevent suction during contraction.
Trabeculae carneae
Explanation: Trabeculae carneae are irregular muscular ridges inside the ventricles that assist in contraction and help prevent over-suctioning of the ventricular walls.
Which blood vessel carries oxygen-rich blood from the lungs back to the heart?
A) Pulmonary artery
B) Pulmonary vein
C) Aorta
D) Superior vena cava
B) Pulmonary vein
Explanation: The pulmonary veins are the only veins in the body that carry oxygenated blood, delivering it from the lungs to the left atrium.
The __________ is the main artery that supplies oxygenated blood to the body, while the __________ carries deoxygenated blood from the heart to the lungs.
Aorta, Pulmonary trunk
Explanation: The aorta is the body’s largest artery, distributing oxygenated blood from the left ventricle. The pulmonary trunk carries deoxygenated blood from the right ventricle to the lungs.
Why do the atria contract before the ventricles?
A) The AV valves must be forced open before the ventricles fill
B) The SA node is located in the atria and initiates contraction there first
C) The AV node delays conduction, allowing the ventricles time to fill
D) Both B and C
D) Both B and C
Explanation: The SA node fires first, causing atrial contraction. The AV node then delays the signal for about 100 ms, ensuring the ventricles fill completely before contracting.
The action potentials of skeletal muscle, cardiac contractile cells, and cardiac nodal cells all have the same depolarization and repolarization process.
False
Explanation:
• Skeletal muscle: Rapid depolarization and short repolarization, allowing for tetanic contractions.
• Cardiac contractile cells: Have a plateau phase due to Ca²⁺ influx, preventing tetanus.
• Cardiac nodal cells: Have an unstable resting potential (pacemaker potential), leading to automatic depolarization.
Where is most of the calcium used for cardiac muscle contraction stored?
A) Sarcoplasmic reticulum
B) Extracellular fluid
C) T-tubules
D) Mitochondria
A) Sarcoplasmic reticulum
Explanation: While some Ca²⁺ enters from extracellular fluid, most is stored in the sarcoplasmic reticulum and released upon depolarization.
What would an ECG of a total AV node block likely show?
A) A missing QRS complex after some P waves
B) Widened QRS complexes
C) No P waves
D) A higher heart rate than normal
A) A missing QRS complex after some P waves
Explanation: In total heart block, atrial depolarization (P wave) still occurs, but signals do not reach the ventricles, preventing QRS complexes from forming at times.
During the __________ phase of the cardiac cycle, both the AV and semilunar valves are closed, and the ventricles are building pressure without changing volume.
Isovolumetric contraction
Explanation: In isovolumetric contraction, the ventricles are contracting but blood has not yet been ejected.
What is an average resting cardiac output (CO) in an adult?
A) 3 L/min
B) 5 L/min
C) 10 L/min
D) 15 L/min
B) 5 L/min
Explanation: Cardiac output is calculated as CO = HR × SV. At rest, this equals ~5 L/min.
The Frank-Starling Law states that increased venous return results in stronger ventricular contractions and increased stroke volume.
True
Explanation: The Frank-Starling Law describes how more blood entering the ventricles (preload) leads to a greater contraction force, improving stroke volume.
Which of the following does NOT occur during exercise?
A) Increased heart rate
B) Increased stroke volume
C) Increased venous return
D) Decreased cardiac output
D) Decreased cardiac output
Explanation: During exercise, cardiac output increases significantly to meet metabolic demands.
Which part of the autonomic nervous system decreases heart rate by acting on the SA node?
A) Sympathetic nervous system
B) Parasympathetic nervous system
C) Somatic nervous system
D) None of the above
B) Parasympathetic nervous system
Explanation: The vagus nerve (parasympathetic) releases acetylcholine, slowing SA node firing and reducing heart rate.
__________ is defined as abnormally slow heart rate (below 60 bpm), while __________ is defined as abnormally fast heart rate (above 100 bpm).
Bradycardia, Tachycardia
Explanation: Bradycardia occurs when the heart rate is too slow, while tachycardia occurs when it is too fast.
