electrical activity of the heart Flashcards
what are cardiac conduction pathways
detailed pathways that aid in fast /coordinated depolarization of the heart
why are conduction pathways important
allow for different parts of the heart to contract at different times
how does conduction travel through the heart
SA node»_space; bachman bundle in left atrium» AV node»_space; interventicular septum ( bundle of his)» right and left bundle branches» purkinjee fibers
why do the venticles have more conduction pathways
have the greatest amount of muscle
how does conduction velocty compare in different parts of the heart
it is different in deiiferent parts of the heart
what is the function of the AV node in terms of conduction velocity
- the AV nodes slows contraction in which it allows for the ventricles to fill before the contract again
- in other words has a very slow conduction velocity comapred to other parts of the heart
how to the AV nodes slow contraction
- they have fewer gap junctions which increases resistance and thus slows conduction velocity
- AV has less tissue around it so there are less pathways in which impulses can travel
what is the sequence of cardiac muscle depol
1) Atrial depol
> internodal pathways
> bachmans bundle
2) septal depol
> bundle of his
3) anteroseptal depol
> Bundle of his
> intial activation of
purkinjee fibers
4) depol bulk of ventricular myocardium from endocardium to pericardium
5) depol of posterior portion of bsae of left ventricle
6) ventricles are depolarized
EKG
- what are the 3 waves and what occurs in each
- first wave: P wave- atrial depol
- second wave: QRS wave- ventriculare depol and atrial repol
- thrid wave: T wave- ventriculr repol
what do ECGs represent
multiple action potentials in heart within a period of time
how does the time in which the atria contract compare to when the ventricles contract
- the ventricals contract once the atria have completely repolarized
what type of inforamation do ECGs tell us in a medical POV
- HR and rythm
- conduction velocity
- condition of the heart tissue
what is the difference between a wave and a segemnt on a ECG
- a wave us an upwaward or downward defelction from the isoelectric line
- a segement is a section on the isolectric like only (no wave included)
what does the PR segment and and ST segment represent
- PR segment - goes from the end of the P wave from the beging of the QRS compex
- ST - from the end of the QRS compex to the beginning of the T wave
what do elevated segemnts represent
there is a distabance in electrical conduction
what are intervals in an ECG
represent waves and segemtns
what is the PR interval and what does it represent
- goes from the beinig of the P wave to the beginning of the QRS complex and represent the time it takes or APs to travel from the SA to the AV node
what is the QRS interval and what does it represent
- goes from the begining to the end of the QRS comple and represents the time it takes for ventricular depolarization
what is the QT interval and what does it represent
goes from the beiginning of the QRS complex to the end of the T wave and repesents the time btwn the intitiation of the QRS complex and the end of the t wave
what is a 12 lead ECG recording
- when 10 leads are placed on the body ( limbs and chest)
- 12 electrical vectors are recorded
> 9 direct measuremnts
> 3 augmented measurements
what are the 2 kinds of limb leads
bipolar leads and augmneted uniopolar leads
where are the bipolar leads placed
Lead NE PE
lead I: right arm and left arm
lead 2: right arm and left leg
lead 3: left arm and left leg
NONE GO ON THE RIGHT LEG
where are the augmented unipolar leads placed
aVR: right arm
aVL: left arm
aVF: left leg
what are the ECG precordial chest leads? are they positve or negative electrode
V1-V6 postive elctrode
MAKE A CARD FOR SLIDE 38
make a card for slide 39
KNOW how to calculate hR slide 40
what is an arthymia
an abnormality in the origin and or the conduction of the cardiac impulse
normotopic arrhythmias
when the electrical impulse originates at the SA node but is eitier too fast too slow or irrgular
ectopic arrhythmias
orginate from an area other than the SA node
Re-entrant arrhythmias
when the electrical impulse moves in a continous pattern determined by changes in anatomical arrangement
conduction blocks
when electrical activity origniates at the SA node and follows the usual conduction pathways but has enexpected blocks or delays
pre excitation syndromes
when electrical activity moved through an accesory pathway that by passes the normal ones providing an electrical short cut
what are the 3 types of normotopic arrhythmias
- Sinus bradycardia
- Sinus tachycardia
- Sinus arrhythmia
what type of sinus rythm is this
normal sinus rythm
what type of sinus rythm is and what is it charecterized by
bradycardia - an abnormally low sinus rate
what type of sinus rythm is this and what is it characterized by
sinus tachycardia- an abnormally high sinus rate
what tyoe of sinus rythm is this and what is it charecterized by
Sinus arrhythmia- an irregular sinus rate
what is a first degree heart block and what is the result
all action potential are conducted through the AV junction but the speed of conduction is slower resulting in a longer PR interval
what is a second degree heart block and what is the result
not all action potentials are conducted through the AV junction and thus only some action potential reach the ventricles and some dont.
- this results in some P waves being followed by a QRS comlex but some do not
what is a third degree heart block and what is the result?
- what happens at the atria
- what is the result on a ECG
- action potentials are completely blocked at the AV junction and the latent ventricular pacemaker fires to maintain ventricular function
- the atria are activated by the SA node and ventricles are activated by purkinjee fibers at a slow rate ressulting in know connection btwn the P wave and QRS complex
what is fibrillation
instead of excitiation starting at the SA node it is the chaotic activation of the muscle with multiple foci being activted at once
can you live with fibrilation?
what happens during stress
yes because filling of the ventricles is 80% passive ?
- during stress atria cant contribute to the last 20% of blood to maintain metabolic need and canleed to pulmonary hypertenstion
what does an ECG of atrial fibrilation look like?
no recognizable P waves
what is ventricular fibrillation
- what does it look like on an ECG
- is it compatoble with life
- chaotic activation of the ventricular muscle
- no QRS complex
- cot compatible with life
what are you doin when you shock someone with an AED
when you apply a strong voltage to tissue you try to synchronize the heart by fully depolarizing all the cells in the heart ao the SA node can start again and resume normal rythm
what is myocardial infarcation
can occur when there is a reduction in blood flow (ischemia) to the cardiac muscle which causes damage
what are the carrying levels of myocadial infarcation
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