The fibrous, double-layered sac that encloses the heart is the pericardium.
Missing Word
pericardium
The pericardium has an outer fibrous layer and an inner serous layer with parietal and visceral parts. It anchors and protects the heart and holds lubricating fluid.
Category: Heart Anatomy
Question 2
The thick middle layer of the heart wall, made of cardiac muscle cells that contract to pump blood, is the myocardium.
Missing Word
myocardium
The myocardium is the working muscle of the heart. Damage to it, as in a myocardial infarction, weakens the pump.
Category: Heart Anatomy
Question 3
The valve that separates the right atrium from the right ventricle is the tricuspid valve.
Missing Word
tricuspid
The tricuspid valve is the right atrioventricular valve. It opens to let blood fill the right ventricle and closes during ventricular contraction to prevent backflow.
Category: Heart Anatomy
Question 4
The aortic and pulmonary valves, named for their crescent-shaped cusps, are called semilunar valves.
Missing Word
semilunar
Semilunar means half-moon. These valves guard the exits of the ventricles and close when the ventricles relax, preventing backflow from the arteries.
Category: Heart Anatomy
Question 5
The largest artery in the body, which receives blood from the left ventricle, is the aorta.
Missing Word
aorta
The aorta carries oxygenated blood from the left ventricle to the systemic arteries. Its first branches are the coronary arteries.
Category: Blood Flow and Vessels
Question 6
The circuit in which the left ventricle pumps oxygenated blood to the tissues of the body is the systemic circulation.
Missing Word
systemic
The systemic circulation runs from the left heart to the body and back to the right heart. The pulmonary circulation runs from the right heart to the lungs and back to the left heart.
Category: Blood Flow and Vessels
Question 7
The smallest branches of arteries, which feed blood into the capillary beds, are arterioles.
Missing Word
arterioles
Arterioles control flow into capillaries and are a major site of vascular resistance, so drugs that dilate them lower blood pressure.
Category: Blood Flow and Vessels
Question 8
Small vessels that collect blood from capillary beds and drain it into veins are called venules.
Missing Word
venules
Venules are the first vessels on the return side of circulation. They merge into veins that carry blood back to the heart.
Category: Blood Flow and Vessels
Question 9
The cuff instrument used to measure blood pressure in millimeters of mercury is the sphygmomanometer.
Missing Word
sphygmomanometer
A sphygmomanometer inflates a cuff to occlude an artery, then measures pressure as flow returns. It may be manual with a stethoscope or automatic.
Category: Blood Pressure Regulation
Question 10
The arterial pressure recorded while the ventricles contract, the top number of a blood pressure reading, is the systolic pressure.
Missing Word
systolic
Systolic pressure is the highest pressure in the arteries during each cycle. The bottom number, diastolic pressure, is the pressure while the ventricles relax and fill.
Category: Blood Pressure Regulation
Question 11
Stretch receptors in the carotid sinus and aortic arch that sense changes in blood pressure are called baroreceptors.
Missing Word
baroreceptors
Baroreceptors trigger rapid reflex changes in sympathetic and parasympathetic output to keep blood pressure stable, for example when a person stands up.
Category: Blood Pressure Regulation
Question 12
A heart rate counted by listening with a stethoscope at the left fifth intercostal space in the midclavicular line is the apical pulse.
Missing Word
apical
The apical pulse is heard over the point of the heart nearest the chest wall. It is often counted for a full minute before giving drugs that slow the heart rate.
Category: Conduction System
Question 13
The fibers that carry the impulse from the bundle branches into the ventricular muscle are the Purkinje fibers.
Missing Word
Purkinje
Purkinje fibers spread the impulse rapidly through the ventricles so they contract together from the apex upward. They can act as a slow backup pacemaker.
Category: Conduction System
Question 14
The rapid upstroke of the cardiac muscle action potential is caused by influx of sodium ions.
Missing Word
sodium
Fast sodium channels open and positive sodium ions rush in, making the inside of the cell positive. Class I antidysrhythmic drugs block these channels.
Category: Cardiac Action Potential
Question 15
Repolarization of cardiac cells back to the resting membrane potential is driven by efflux of potassium ions.
Missing Word
potassium
Potassium leaving the cell restores its negative resting potential. Low blood potassium disturbs this process and is a risk factor for dysrhythmias.
Category: Cardiac Action Potential