Chapter 14 concept questions Flashcards
A cardiovascular system has what three major components?
A cardiovascular system has tubes (blood vessels), fluid (blood), and a pump (heart)
What is the difference between
(a) the pulmonary and systemic circulations,
(b) an artery and a vein,
(c) an atrium and a ventricle?
(a) pulmonary circulation takes blood to and from the lungs; systemic circulation takes blood to and from the rest of the body
(b) arteries carry blood away from the heart; veins carry blood blood to the heart
(c) atrium - upper heart chamber that receives blood entering the heart. Ventricle - lower heart chamber that pumps blood out of the heart.
Which is more important for determining the flow through a tube: absolute pressure or the pressure gradient?
The pressure gradient is more important
The two identical tubes below have the pressures shown at each end. Which tube has the greater flow? Defend your choice.
The bottom tube has a greater flow because it has a larger pressure gradient (50 mm Hg versus 40 mm Hg for the top tube)
All four tubes below have the same driving pressure.
Which tube has the greatest flow?
Which has the least flow? Defend your choices.
Tube C has the highest flow because it has the largest radius of the four tubes (less resistance) and the shorter length (less resistance).
Tube B has the same radius as tube C but a longer length and therefore offers greater resistance to flow.
Tube D, with the greatest resistance due to its longer length & narrow radius, has the lowest flow.
Two canals in Amsterdam are identical in size, but the water flows faster through one than through the other. Which canal has the higher flow rate?
If the canals are identical in size and therefore in cross-sectional area A, the canal with the higher velocity of flow v has the higher flow rate Q. (Q = v x A)
What prevents electrical signals from passing through the connective tissue in the heart?
connective tissue is not excitable and is therefore unable to conduct action potentials
Trace a drop of blood from the superior vena cava to the aorta, naming all structures the drop encounters along its route
superior vena cava –> right atrium —> tricuspid (right AV) valve –> right ventricle –> pulmonary (right semilunar) valve —> pulmonary trunk —> pulmonary vein –> left atrium –> mitral (bicuspid, left AV) valve –> left ventricle –> aortic (left semilunar) valve –> aorta.
What is the function of the AV valves?
What happens to blood flow if one of these valves fails?
The AV valves prevent the backward flow of blood. If one fails, blood leaks back into the atrium.
Compare the receptors and channels involved in cardiac EC coupling to those found in skeletal muscle EC coupling
skeletal muscle L-type Ca2+ channels (DHP receptors) are mechanically linked to sarcoplasmic reticulum RyR Ca2+ release channels.
Myocardial L-type Ca2+ channels open to allow Ca2+ into the cell. In both muscles, sarcolemma Ca2+ channels are associated with RyR Ca2+ release channels on the SR.
If a myocardial contractile cell is placed in interstitial fluid and depolarized, the cell contracts. If Ca2+ is removed from the fluidsurrounding the myocardial cell and the cell is depolarized,it does not contract. If the experiment is repeated with a skeletal muscle fiber, the skeletal muscle contracts when depolarized, whether or not Ca2+ is present in the surrounding fluid. What conclusion can you draw from the results of this experiment?
It is possible to conclude that myocardial cells require extracellular Ca2+ for contraction but skeletal muscle cells do not.
A drug that blocks all Ca2+ channels in the myocardial contractile cell membrane is placed in the solution around the cell. What happens to the force of contraction in that cell?
If all Ca2+ channels in the muscle cell membrane are blocked, there will be no contraction. If only some are blocked, the force of contraction will be smaller than the force created with all channels open.
Which ions moving in what directions cause the depolarization and repolarization phases of a neuronal action potential?
Na+ influx causes neuronal depolarization, and K+ efflux causes neuronal repolarization
At the molecular level, what is happening during the refractory period in neurons and muscle fibers?
The refractory period represents the time required for the Na+ channel gates to reset (activation gate closes, inactivation gate opens)
Lidocaine is a molecule that blocks the action of voltage-gated cardiac Na+ channels. What happens to the action potential of a myocardial contractile cell if lidocaine is applied to the cell?
If cardiac Na+ channels are completely blocked with lidocaine, the cell will not depolarize and therefore will not contract. Partial blockade will decrease electrical conduction
What does increasing K+ permeability do to the membrane potential of the cell?
Increasing K+ permeability hyperpolarizes the membrane potential.
A new cardiac drug called ivabradine selectively blocks If channels in the heart. What effect would it have on heart rate and for what medical condition might it be used?
Ivabradine slows heart rate and is used to lower abnormally high heart rates.
Do you think that the Ca2+ channels in autorhythmic cells are the same as the
Ca2+ channels in contractile cells? Defend your answer.
The Ca2+ channels in autorhythmic. cells are not the same as those in contractile cells.
Autorhythmic Ca2+ channels open rapidly when the membrane potential reaches about -50mV and close when it reaches about +20mV.
What happens to the action potential of a myocardial autorhythmic cell if tetrodotoxin, which blocks voltage-gated Na+ channels, is applied to the cell?
If tetrodotoxin is applied, nothing will happen bc there are no voltage-gated Na+ channels in the cell.
In an experiment, the vagus nerve, which carries parasympathetic signals to the heart, was cut. The investigators noticed that heart rate increased. What can you conclude about the vagal neurons that innervate the heart?
cutting the vagus nerve increased heart rate, so parasympathetic fibers in the nerve must slow heart rate
Name two functions of the AV node. What is the purpose of AV node delay?
The AV node conducts action potentials from the atria to the ventricles. It also slows down the speed at which those action potentials are conducted, allowing atrial contraction to end before ventricular begins.
Where is the SA node located?
The SA is in the upper right atrium
Occasionally an ectopic pacemaker {ektopos, out of place} develops in part of the heart’s conducting system. What happens to heart rate if an ectopic atrial pacemaker depolarizes at a rate of 120 times per minute?
The fastest pacemaker sets the heart rate, so the heart rate increases to 120 beats/min
During atrial filling, is pressure in the atrium higher or lower than the pressure in the venae cavae?
The atrium has lower pressure than the venae cavae.
