The membrane that lines the heart chambers and covers the valves is the endocardium.
Missing Word
endocardium
The endocardium is the innermost layer of the heart wall, a smooth endothelium continuous with the lining of the blood vessels. Its smooth surface reduces friction as blood moves through the chambers.
Category: Heart Anatomy
Question 2
Chordae tendineae attach the AV valve cusps to cone-shaped papillary muscles that contract to keep the cusps from everting into the atria.
Missing Word
papillary
Papillary muscles project from the ventricular walls and tense the chordae tendineae during ventricular contraction. This keeps the AV valve cusps from being pushed back into the atria.
Category: Heart Anatomy
Question 3
The right atrioventricular valve has three cusps and is called the tricuspid valve.
Missing Word
tricuspid
The tricuspid valve lies between the right atrium and right ventricle and is named for its three cusps. It closes during ventricular contraction to prevent backflow into the right atrium.
Category: Heart Anatomy
Question 4
The pointed inferior tip of the heart, which lies to the left of the midline, is called the apex.
Missing Word
apex
The apex is the inferior point of the heart, directed toward the left hip. The broad superior portion where the great vessels attach is the base.
Category: Heart Anatomy
Question 5
The heart sits in the mediastinum, the central region of the thoracic cavity between the two lungs.
Missing Word
mediastinum
The mediastinum is the central compartment of the thoracic cavity that houses the heart, great vessels, trachea and esophagus. The lungs lie on either side of it in their pleural cavities.
Category: Heart Anatomy
Question 6
Cardiac muscle cells contain abundant myoglobin, a red protein that binds and stores oxygen inside the cell.
Missing Word
myoglobin
Myoglobin is an oxygen-binding protein in muscle cells, related to the hemoglobin of red blood cells. Its large supply in cardiac muscle supports the continuous aerobic metabolism the heart needs.
Category: Cardiac Muscle
Question 7
The long plateau of a contractile cardiac action potential is maintained mainly by calcium ions entering through slow channels.
Missing Word
calcium
Calcium entering through slow channels balances potassium leaving, which holds the membrane near zero millivolts for a sustained period. This calcium also triggers further calcium release from the sarcoplasmic reticulum for contraction.
Category: Cardiac Muscle
Question 8
The visceral layer of the serous pericardium, which adheres directly to the outer surface of the heart, is also called the epicardium.
Missing Word
epicardium
The epicardium is the outermost layer of the heart wall and is the same tissue as the visceral layer of the serous pericardium. The coronary vessels run through it on the heart surface.
Category: Heart Anatomy
Question 9
The SA node depolarizes faster than any other region of the heart, so it sets the heart rhythm and is called the pacemaker.
Missing Word
pacemaker
The pacemaker is the region whose spontaneous depolarization sets the pace of the whole heart. The SA node holds this role because its intrinsic rate is the fastest in the conduction system.
Category: Conduction System
Question 10
The phase of the cardiac cycle in which a chamber relaxes and fills with blood is called diastole.
Missing Word
diastole
Diastole is the relaxation phase of a heart chamber, when it fills with blood. Its counterpart, systole, is the contraction phase that ejects blood.
Category: Cardiac Cycle
Question 11
The degree of stretch of the ventricular muscle cells just before they contract, set by end-diastolic volume, is called preload.
Missing Word
preload
Preload reflects how much the ventricles are stretched by filling at the end of diastole. Greater preload produces a stronger contraction and a larger stroke volume through the Frank-Starling mechanism.
Category: Cardiac Physiology
Question 12
An adult resting heart rate above 100 beats per minute is called tachycardia.
Missing Word
tachycardia
Tachycardia is an abnormally fast resting heart rate, above 100 beats per minute in an adult. Causes include fever, anemia, hypoxia, hyperthyroidism, anxiety, blood loss and some drugs.
Category: Cardiac Physiology
Question 13
Parasympathetic fibers that slow the heart rate reach the SA and AV nodes through the vagus nerve.
Missing Word
vagus
The vagus nerve, cranial nerve X, carries parasympathetic fibers from the cardioinhibitory center to the SA and AV nodes. Its acetylcholine release slows the heart rate.
Category: Cardiac Physiology
Question 14
Stretch-sensitive receptors in the aortic arch and carotid sinuses that monitor blood pressure and help adjust heart rate are called baroreceptors.
Missing Word
baroreceptors
Baroreceptors detect stretch of vessel walls caused by blood pressure. When pressure rises they increase their firing, and the cardiovascular centers respond by slowing the heart rate.
Category: Cardiac Physiology
Question 15
The heart develops from mesoderm, the middle of the three primary germ layers of the embryo.
Missing Word
mesoderm
Mesoderm is the middle embryonic germ layer that gives rise to the heart, blood vessels, muscle and connective tissues. The heart begins forming from it in the third week of development.
Category: Heart Development