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52 Cards in this Set

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Which ventricle pumps the blood into the pulmonary circulation?
Right ventricle
Three major types of cardiac muscle
1- Atrial muscles.
2- Ventricular muscles.
3- Excitatory and conductive muscle fibers.
The difference between the contraction of skeletal muscle and atrial, ventricular muscle
the atrial and ventricular muscle have a longer contraction duration than the skeletal muscle.
the intercalated disks are
cell membranes
How does the action potential travel from the atrial syncytium to the ventricular syncytium?
Through the AV bundle.
The action potential of the ventricular muscle averages
105 millivolts
The plateau of the ventricular muscle action potential lasts for about
0.2 seconds
In the cardiac muscle, the action potential is cause by which type(s) of channels
1- Fast sodium channels.
2- Slow calcium channels.
What's the difference between the cardiac muscle and the skeletal muscle in the source of calcium driving the contractile process.
Skeletal muscle: Sarcoplasmic reticulum.
Cardian muscle: Extracellular calcium.
The plateau observed in the action potential of the heart muscle is caused by
1- The presence of the slow calcium channel.
2- The fivefold decreased permeability of the cell membrane to sodium after the onset of action potential.
What's the duration of the refractory period of the atria and the ventricles?
Atria: 0.15 second
Ventricles: 0.25-0.30 second
Why is there a need for the extracellular calcium for the contraction of the cardfiac muscle to take place?
because the sarcoplasmic reticulum is less well developed than that of the skeletal muscle
Waht's the difference between the skeletal t tubules and the cardiac t tubules?
The cardiac t tubules have a diameter 5 times as that of the skeletal t tubules, they also have a large quantity of negatively charged mucopolysaccharides to concentrate calcium ions needed for the contraction.
Why can the heart function without any atrial contraction?(percents)
80% of the blood flowing into the atria goes to the ventricles without any contraction, the 20% left is pumped to the ventricles when the atria contract.
Thwe papillary muscles attach to the cusps by the
Chordae tendinae
The incisura in the aortic pressure curve occurs due to
a short period of backflow of blood then sudden cessation of the backflow as the valve closes
The first heart sound is caused by
the closure of the A-V valves
The second heart sound is caused by
The closure of the semilunar valves
Stroke work output(definition)
the amount of energy the heart converts to work every heartbeat
Definition: Minte work output
The amount of energy the heart converts to work in 1 minute
The Frank-Sterlingh mechanism
the greater the heart muscle is stretched during contraction, the greater is the force of contraction, and the greater the quantity of the blood pumped into the aorta
Normal heart rate
70 beats/minute(60-100)
The sinus node is connected to the A-V node through the
internodal pathways
The location of the sinus node is
the superior posterolateral wall of the right atrium
The RMP of the sinus node is
-55 to -60
The channels responsible for the APs in the sinus node are
The slow calcium channels
Why don't the sodium channels contribute to the AP of the sinus node
because when the membrane potential is less negative than -55 the inactivation gate remains closed
The threshold for the SA node
-40 mv
What's the location of the A-V node?
posterior wall of the right atrium directly behind the tricuspid valve
What's the delay caused by each potion of the AV node?
1- 0.09 s A-V node.
2- 0.04 s Penetrating A-V node.
3- 0.03 s conduction delay threough the internodal pathways.
= 0.16 s of delay.
What's the cause of the slow conduction in the A-V node?
The diminished number of gap junctions between successive cells
The velocity of the transmission of the purkinje fibers is:
1.5-4.0 m/sec
What are the rhythmic rate of the following:
1- Sinus node.
2- A-V node.
3- Purkinje fibers
1- 70-80 times/minute.
2- 40-60 times/minute.
3- 15-40 times/minute.
What's an ectopic pacemaker?
A pacemakes elsewhere than the sinus node
What's stokes-adam syndrome
The delay between the blockage of the normal conduction pathway and the rhythmatical activity of the purkinge fibers
Ventricular escape
The purkinje fibers start generating their own APs after the AV and SA nodes are inhibited by the acetylcholine released from the vagi
What's the time interval between ventricular depolarization and repolarization
0.25-0.35 s
Define P-R interval
The time between the beginning of the P wave and QRS complex. It's the time between atrial excitation and ventricular excitation(0.16 s), it shows the delay shown in the A-V node.
Define Q-T interval
The interval from the beginning of the QRS complex to the end of the T wave(0.35 s), this is the duration of the ventricular contraction.
What's the configuration of the lead 1?
The negative terminal is connected to the right arm and the positive terminal is connected to the left arm
What's the configuration of lead two?
The negative terminal is connected to the right arm and the positive terminal is connected to the left leg
What's the configuration of lead III?
The negative terminal is connected to the left arm and the positive terminal is connected to the left leg
What's Einthoven's law?
If the electrical potentials of two of the leads are known at a given instant then the third one can be determined mathematically by summating the first two.
What are the precordial leads that have negative recordings, and why?
V1 and V2
Because they're near to the base of the heart which is the direction of electronegativity during most of the ventricular depolarization.
Which one of the augmented unipolar limb leads is inverted?
The aVR
The first part to be polarized in the ventricles after the impulse travels through the A-V bundle is
the left endocardial surface of the septum
What's the first area to repolarize in the atria?
The area around the sinus node
Give another name for the A-V bundle
Bundle of His
What's the normal P-R interval?
0.12 - 0.2 second
What's the normal duration of the QRS complex?
0.12 s (three squares)
What does each of the chest leads look at?
V1 & V2: Right ventricle.
V3 & V4: Ventricular Septum.
V5 & V6: anterior and lateral walls of the left ventricle.
What's the normal range of the degree of the cardiac axis?
-30 to +90