Cardio Flashcards
Normal refractory period of atria.
0.15 sec
P, QRS, T wave:
> represents the stage of depolarization of ventricles when ventricular muscle fibs begin to relax.
T wave. It occurs slightly before the end of ventricular contraction.
This muscle of the heart pulls the vanes of the valves inward toward the ventricles to prevent them bulging too far backward during ventricular contraction.
Papillary muscles and chordal tendineae
When the left ventricular pressure rises slightly above this pressure value, the ventricular pressures push the semilunar valves open during the period of ejection.
80mm Hg (and the R ventricular pressure slightly above 8 mm Hg
When at rest, how many liters of blood is pumped by the heart each minute?
4-6 L
Velocity of conduction of atrial and ventricular muscle
0.3 - 0.5 m/s
Specialized excitatory and conductive system of the heart that conducts impulse from atria to ventricle
AV bundle
The cause of slow conduction in AV bundle fibers
The slow conduction in the transitional, nodal, and penetrating A-V bundle fibers is caused mainly by diminished numbers of gap junc between successive cells in the conducting pathways, so that there is great resistance to conduction of excitatory ions from one conducting fiber to the next.
Effect of sympathetic stimulation to cardiac rhythm and conduction
1) increase sinus nodal discharge
2) increase level of excitability in all portions of the heart
3) increase force of conduction
What is/are the repolarization wave/s?
T wave
The rate of heartbeat can be determined easily from an ECG because the HR is the reciprocal of the time interval between 2 successive heartbeats. What is the normal interval bw 2 successive QRS complexes in the adult pErson?
About 0.83 second. This is a heart rate of 60/0.83 times per minute, or 72 beats per minute.
bipolar limb leads:
This illustrates the the two arms and the left leg form apices of a triangle surrounding the heart.
Einthoven’s triangle.
The two apices at the upper part of the triangle represent the points at which the two arms connect electrically with the fluids around the heart, and the lower apex is the point at which the left leg connects with the fluids.
Function of atria as primer pumps.
Normally, blood flows continually from the great veins into the atria.
80% of the blood flows directly thru the atria into the ventricles even without atrial contraction.
Atrial contraction causes additional 20% filling of the ventricles.
Therefore atria acts as primer pumps that increases the ventricular pumping effectiveness as much as 20%.
True or false. The semilunar valves are the valves which has chordae tendineae.
False. Semilunar valves are not supported by chordae tendineae. Only the AV valves are supported by this.
Te value of the End diastolic volume.
110-120 ml.
When large amt of blood flow into the ventricles during diastole, this becomes as great as 150-180 ml.
The amt of blood pumped by the heart each minute is determined almost entirely by the rate of blood flow into the heart from the veins, which is called ..
Venous return
Excess calcium ions causes the heart to go toward (spastic, flaccid) contraction.
Spastic. This is caused by a direct effect of calcium ions to initiate the cardiac contractile process.
Conversely, deficiency causes cardiac flaccidity.
Specialized excitatory and conductive system of the heart that conducts impulse to all parts of the ventricles
Left and right bundle branches of purkinje fibers
Cause of rapid transmission in ventricular purkinje system
The rapid transmission of action potentials by Purkinje fibers is believed to be caused by a very high level of permeability of the gap junctions at the intercalated discs between the successive cells that make up the Purkinje fibers.
Discharge rate of the ff
1) SA node
2) AV node
3) Purkinje fibers
SA node: 70-80 times per sec
AV node: 40-60 times per sec
Purkinje fibers: 15-40 times per sec
True or false: no potential is recorded in the ECG when the ventricular muscle is either completely polarized or completely depolarized.
True. Only when the muscle is partly polarized and partly depolarized does current flow from one part of the ventricles to another part, and therefore current also flows to the surface of the body to produce the ECG.
Note: Before stimulation, all the exteriors of the muscle cells had been positive and the interiors negative.
Note: in normal heart ventricles, current flows from negative to positive primarily in the direction from the base of the heart toward the apex during almost the entire cycle of depolarization
This law states that if the electrical potentials of any 2 of the 3 bipolar limb ECGic leads are known at any given instant, the third one can be determined mathematically by simply summing the first two.
Einthoven’s law.
At any given instant, the sum of the potentials in Leads I and III equals the potential in Lead II.
In what stage of nerve action potential where the membrane suddenly becomes very permeable to Nà ions, allowing tremendous numbers of (+) charged Nà ions to diffuse to the interior of the axon.
Depolarization stage