Questions Grade A+
Trace the path of a drop of blood as it travels from the vena cava through the heart and into the
aorta. This should include the chambers, and the valves it passes through - ANSWERSSuperior
vena cava, right atrium, tricuspid valve, right ventricle, pulmonary trunk, pulmonary artery (2) --
> lungs to be oxygenated --> pulmonary veins, left atrium, mitral valve, left ventricle, aortic
valve, out to heart
Compare and contrast the histology of cardiac muscle to skeletal muscle - ANSWERSCardiac
muscle: intercalated discs, syncytial arrangement
Both: striated with myosin and actin
Describe the function of intercalated discs in relation to electrical conduction within the heart -
ANSWERSIntercalated discs help with the connectivity in the cardiac muscle. Communication
between cells (rapid diffusion of ions)
Describe the function of the papillary muscles and chordae tendinae - ANSWERSChordate
tendinae are connected to the papillary muscles which hold the fibers from the chordate
tendinae to the walls of ventricles and the AV valve
Compare the properties to the semilunar valves and the AV valves, and relate them to their
function - ANSWERS-Semilunar valves are faster and stronger than AV valves -AV valves are thin
Semilunar valves function passively without the need of chordate tendinae
-Semilunar valves have more mechanical abrasion
Name the two general mechanisms that cause the plateau in the action potential in cardiac
muscle (but differ in skeletal muscle) - ANSWERS1. Sodium (fast) and Calcium (slow) are coming
into the cell during the depolarization phase. These are allowing the ion channels to stay open
,longer; therefore, allowing more inflow of sodium and calcium to prolong depolarization, thus
causing a plateau in AP
2. decreased outflow of potassium ions to prevent repolarization from occuring. The potassium
ions are leaving which the Ca are still coming in and that creates a plateau in the AP
Explain how slow calcium channels cause the action potential in cardiac muscle to be different
than that of skeletal muscle - ANSWERSCalcium channels are slowly flowing into the cell during
the depolarization phase in cardiac muscles which means the channels are staying open longer
and allow for more time in the depolarization phase.
Compare the relative velocity of signal conduction in cardiac muscle fibers to Purkinje fibers -
ANSWERSPurkinje fibers: sets of specialized cells that conduct the pathway for action potentials
to the apex of the heart Purkinje fibers are much faster than cardiac muscle fibers They send
conduction signals from the AP to the rest of the heart
Describe the difference between absolute and relative refractory periods in cardiac muscle, and
how they relate to cardiac contraction - ANSWERS1. Absolute refractory period is the time
between depolarization and repolarization where an action potential cannot be stimulated
2. Relative refractory period is when the AP is difficult to begin but it can be done. This is right at
the end of repolarization before the resting membrane potential is reached.
Briefly describe why extracellular calcium concentration is of greater relevance for cardiac
muscle contraction compared to skeletal muscle contraction - ANSWERSCalcium used in cardiac
muscle contraction is derived from extracellular fluid from the t-tubules. Skeletal muscle will use
the sarcoplasmic reticulum
Describe the relationship between heart rate, the duration of the action potential, duration of
cardiac cycle duration, and the relative durations of systole and diastole - ANSWERS1. HR
increases then increases the amount of AP happening
-Shorter plateau
-Decreased time in systole and diastole
, -Increased ratios between Systole and Diastole because the filling ratio is less time (more AP
that occur in the same amount of time)
2. HR decreases then decreases the amount of Aps happening
systole - ANSWERSventricular muscle stimulated by action potential and contracting
QRS complex= depolarizing
Diastole - ANSWERSventricular muscle reestablishing and ventricles are relaxing
EKG P wave - ANSWERSatrial depolarization, atria contracts
EKG QRS - ANSWERSventricular depolarization (contraction)
EKG T wave - ANSWERSventricular repolarization
ESV - ANSWERSblood left in the ventricles after contraction
EDV - ANSWERSblood in the ventricles before contraction (greatest amount of blood in the
ventricles because they are full)
Explain how ventricular volume, atrial pressure, aortic pressure, and left ventricular pressure
change over the course of the cardiac cycle, and relate this to the electrocardiogram and
phonocardiogram (Figure 9-7). - ANSWERSStarting off in diastole, the heart is relaxing and all
the blood is flowing into the Left ventricle. the atria will contract once more to allow for the last
bit of blood to enter the ventricles then the AV valve will shut to prevent backflow. Now the
blood in the LV will increase in pressure but it will not be let out until the aortic valve opens up.
This is called Isolvolumic contraction. Then the aortic valve will open and there is a period of
rapid ejection in which the blood from the LV will flow out the aortic semilunar valve to the rest
of the body. once the blood gets out of the ventricles the aortic valve will shut to prevent
backflow. This is the beginning of diastole because the ventricles are relaxing. During this time