electrical activity of the heart Flashcards
(49 cards)
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
