Cardiac/ECG Flashcards
What causes the first heart sound? (S1)(lub)
Closing of the atrioventricular valves at the beginning of ventricular systole (contraction)
What causes the second heart sound? (s2)(dub)
The closing of the semilunar valves at the end of beginning of ventricular diastole (relaxation)
What are the two main types of heart cells?
-Specialized/pacemaker cells-working myocardial cells
Where are 5 examples of specialized pacemaker cells?
SA nodeAV nodeBundle of HISBundle branches (left and right)Purkinje fibers
What is the normal order of conduction though the heart?
SA node, atria, AV node, His bundle, bundleBranches, purkinje fibers, ventricles
What is the SA nodes main function?
Act as a pacemaker
What is the AV nodes main function?
Create a slight delay between atrial and ventricular contraction
What are the 5 phases of cardiac action potential (AP)?
-Phase 0: upstroke, rapid depolarization-Phase 1: rapid repolarization-Phase 2: depolarization plateau-phase 3: rapid repolarization after plateau-Phase 4: resting potential
What affect does an action potential have on the intracellular Ca++ concentration?
Increases it 1000 fold by opening L-type channels in the sarcolemma
How do you calculate cardiac output? (CO)
Cardiac output=stroke volume x heart rate
How do you determine stroke volume?
End diastolic volume-end systolic volume
How is blood pressure calculated?
Cardiac output x total peripheral resistance= blood pressure
What does the baroreceptor reflex do?
Corrects for changes in arterial pressure by increasing or decreasing heart rate
What does the bainbridge reflex do?
Responds to changes in blood volume by increasing heart rate
What is considered a normal sinus rhythm?
When the SA node is acting as the pacemaker
What range is normal for heart rate?
60-100 bpm
When are you tachycardic?
HR above 100
When are you bradycardic?
HR less than 60
What is happening at the p wave?
Atrial depolarization
What happens at the QRS wave?
Ventricular depolarization (Atrial repolarization happens here as well)
What happens during the T wave?
Ventricular repolarization
What interval reflects conduction from atria to ventricle?
PR
What interval reflects average AP duration in ventricles?
QT
An elevation or depression in which interval indicates myocardial infarction?
ST segment
What is the R-R interval used for? What is the formula?
Determining HRHR in BPM= 60/R-R interval
How many large boxes equal 1 second on an ECG?
5
What is the equation for Einthovens law?
Lead 1 + Lead 3= Lead 2 (mean electrical axis)
What cell junction is key in propagating an action potential through cardiac muscle?
Gap junctions
What is a primary AV block?
Wide PR interval
What is a second AV block type 1?
Cyclic lengthening, dropping QRS complex
What is a second AV block type 2?
Skips QRS complex
What is a third degree AV block?
Regular P but ventricle and atria are not in sync
What four things with you see in ECG for a heart attack?
1-ST elevation
2-T wave inversion
3-exaggerated Q wave
4-ST depression
