ECG and Cycle Flashcards
P
Atrial excitation
QRS
ventricle excitation
T
End of ventricular excitation
Phase 4
Rectifier channels leak K out
The greater the preload and stretching of the sarcomeres
the more SV
In cardiac muscle, the fast depolarization phase of the action potential is the result of
increased membrane permeability to sodium ions.
The long plateau phase of the cardiac muscle action potential is due to
Calcium channels remaining open
The normal pacemaker of the heart is located in
the SA node
Abnormally slow depolarization of the ventricles would most change the shape of the ________ in an ECG tracing.
QRS complex
As a result of the long refractory period in the cardiac action potential, cardiac muscle CANNOT exhibit
Tetany
If the pacemaker cells in the SA node become more permeable to potassium ions, the
HR will decrease and cells with HYPERPOLARIZE
If the connection between the SA node and AV node becomes blocked, A) the ventricles will beat faster.
the ventricles beat more slowly
Components of the conducting system of the heart. (in order)
- SA node
- Atrial depolarization
- AV node
- AV bundle of His
- Bundle branches (Left and Right)
- Purkinje fibers
- Ventricular repolarization
The P wave of the electrocardiogram is a signal from
Depolarization of the atria
If there is a complete block between the SA node and the AV node, how would the ECG be affected?
Rate of P waves will be faster than the QRS complexes
Depolarization of the ventricles is represented on an electrocardiogram by the
QRS complex
The T wave on an ECG tracing represents
Ventricular Repolarization
Pacemaker cells isolated from the SA node generate action potentials at ________ beats per minute.
80-100
Depolarization of the atria corresponds to the EKG’s
P wave.
Cardiac muscles have specialized
Gap junctions in cardiac muscle not found in skeletal or smooth muscles.
The structures responsible for distributing excitation to the contractile cells are
Conducting cells
Collectively, the conducting cells that carry the impulse from the SA node to the AV node is known as the
Internodal pathway
The AV node delay is beneficial because
t allows time for the atria to contract.
The first heart sound (“lubb”) is associated with
closing of the atrioventricular valves.
Considering the left ventricle, why does isov-olumetric ventricular contraction occur during ventricular systole?
Aortic pressure is higher than ventricular pressure and the ventricle must pressurize the blood to open the aortic valve.
The phase in the cardiac cycle when the mitral valve is closed and the aortic valve is open is the
Systolic ejection phase
During ventricular systole, the
AV valves are closed
With each ventricular systole,
Blood pressure increases
In mitral valve prolapse, the cusps of the mitral valve are pushed into the
Left atrium
The ________ is the amount of blood in a ventricle after it has contracted and before it begins to refill.
End Systolic Volume
The ________ is the volume of blood in a ventricle at the beginning of systole.
End-Diastolic Volume
The amount of blood remaining in the ventricle when the semilunar valve closes is the
End Systolic volume
The heart spends most of the cardiac cycle in which phase?
Ventricular diastole
During the beginning of ventricular systole when the muscle is contracting but not enough pressure has built up to open the semilunar valves the heart is said to be in
Isovolumetric relaxation
When heart rate increases, the time spent in all phases _______ but most of it is during _____
Decreases;; Diastole
In an adult at rest, the end-diastolic volume is typically
130ml
During ventricular diastole…
The ventricles are passively filling and atria are contracting.
The volume of blood ejected from each ventricle during a contraction is called the
Stroke Volume
ECG reading Step RRCEI
Rate Rhythm Conduction Ectopic Interpretation
P wave is the
Atrial depolarization
PR INTERVAL
Time from onset of depolarization to the onset of ventricular depolarization
QRS complex
Sum of all ventricular depolarizations
ST interval
Ventricular myocardium depolarized
Qt interval
Electrical systole of the ventricles
T wave
Ventricular repolarization
Each tiny box is _____mm and ___sec
1mm ; 0.04 sec
5 tiny boxes is ____mm and ______sec
5; 0.20 sec
5 large boxes _____mm and _____sec
25mm 1 sec
PR should be less than _____ boxes
5
QRS complex should be less than
3 small boxes
Wave heights
P wave up to
3mm
Wave heights QRS at least
5 mm
Wave height T wave
Up to 5mm
Depolarization of atrial contractile fibers produces ____wave and tell us ___________
P wave ; action potential in SA node
Depolarization of ventricular contractile fibers produce
QRS complex
End of QRS complex is
Ventricular contraction
Repolarization of ventricular contractile fibers produce
T wave
Ventricular diastole
After the t wave
