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Terms in this set (50)
Ability to produce electrical activity w/o stimulation from the CNS
Ability to respond to electrical stimuli
Ability to pass the electrical stimuli from cell to cell
Ability to create a mechanical response to electrical stimulus
Ability to recreate stimuli
Locations of automatistic stimulation
Myocyte responding to stimulation and becoming positively charged. results in muscular contraction.
myocytes returning to resting state and becoming negatively charged once again. results in muscular relaxation
The muscle response to depolarization resulting in ejection of blood from ventricles
What occurs during repolarization resulting in muscle relaxation
What records the electrical activity of the heart from the body surface?
T/F ECG works by evaluating pathology based on electrical reaction to the pathology (such as ischemia or structural or electrical pathology)
No stimulus can depolarize the cell no matter how strong
absolute refractory period
a large enough stimulus will be able to depolarize the cell
relative refractory period
What is the dominant pacemaker in the heart?
The sinoatrial node
Where is the SA node located?
In the right atrial wall near the SVC junction
What is the intrinsic pacing rate of the SA node?
T/F norepinephrine decreases HR
F. norepinephrine increases HR, where as acetylcholine decreases HR
T/F The AV node slows electrical potential to allow for atrial/ventricular contraction timing
T/F The AV node is located between the tricuspid and the mitral valve
What is the intrinsic pacing rate of the AV node?
T/F The AV node is located in the RA and intraventricular septum
F. The above describes where the bundle of HIS is located. The bundle of HIS is also distal to the AV node
T/F The bundle of HIS and bundle branches have the same intrinsic pacing rate of ____-____
T, 40-45 BPM
T/F The purkinje fibers have ability to produce own action potential and has an intrinsic pacing rate of ___-____
T/F The purkinje fibers are just the terminal projections that innervate the ventricles
F. The purkinje fibers actually make up the bundle of HIS and the R and L bundle branches
What hormones of the SNS increases SA rate, AV conduction, excitability, and force of contraction?
Norepinephrine and epinephrine
What hormones of the PNS decreases rate of SA node, AV conduction, and excitability?
What two receptors does NE act upon?
Beta 1 and beta 2
What receptor does acetylcholine act upon?
1 small box on ECG is _____ sec and ____ mm.
1 big box on ECG is ____ sec.
5 big boxes is _____ sec.
1 small box = 0.04 sec and 1 mm.
1 big box = 0.2 sec.
5 big boxes is 1 sec.
T/F V1-V6 leads are also known as the frontal leads
F. These are the precordial leads. I, II, III, aVR, aVL, and aVF are frontal leads.
T/F, the limb leads look at the heart in a horizontal plane.
F. It looks at the heart in a vertical plane.
What leads look at the inferior part of the heart? What artery is this?
II, III, aVF; RCA
What leads look at the anterior part of the heart? What artery is this?
V3, V4; distal part of LAD (left anterior descending)
what leads look at septal part of the heart? What artery is this?
V1, V2; LAD (Left ant descending artery)
What leads look at the lateral part of the heart? What artery is this?
I, aVL, V5, V6; circumflex
What leads look at the posterior part of the heart? What artery is this?
V7, V8, V9; RCA
What does the PR interval represent and what is the normal duration?
It represents the beginning of atrial depolarization to the beginning of ventricular depolarization.
Normal duration is 0.12-0.2s (3-5 small boxes)
What does the QRS complex represent and what is the normal interval?
It represents depolarization of both ventricles. Normal duration is 0.04-0.12 s (1-3 small boxes)
What does the ST segment represent and what is the normal interval?
Beginning of ventricular repolarization. Normal duration is 0.08-0.12s (2-3 small boxes). Normally isoelectric.
What does the T wave represent?
repolarization of both ventricles and usually is a low voltage, positive, well rounded deflection
What does the QT interval measure and what is its normal duration?
ventricular depolarization and repolarization. Normal interval is 0.34-0.45 s (around 10 boxes)
Describe one systematic approach to looking at EKGs
Rate, Rhythm, Axis, Evaluate each EKG element (ex: p wave, PR interval, QRS, T wave, QT interval, ST segment)
What is a "trick" for counting rate with a normal rhythm strip?
300, 150, 100, 75, 60, 50, 43, 38
How should you calculate rate with an irregular rhythm?
Count # of QRS in 30 big boxes then x 10.
T/F a regular rhythm has a constant RR and PR interval (among other things)
Average direction of the depolarization of the QRS complex
T/F, when identifying axis we use precordial leads
F. We use frontal leads.
What could we see on the EKG when the sum of depolarization shifts toward the right such as in RVH, loss of muscle strength to the Left ventricle, left posterior fascicular block, or in tall thin individuals?
Right axis deviation
What might you see on an EKG when you have the sum of the depolarization shifting towards the left such as in loss of muscle strength to the right ventricle, conduction block to the left side, or hyperkalemia?
Left axis deviation
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