| depolarization is | charged particles move into the cell causing contraction |
| repolarization does? | allows the heart to rest |
| atrial repolarization | not ekg detectable |
| atrial depolarization | detectable on ekg |
| working cells of the heart | myocardial cells |
| cells what generate and conduct electrical impulses | pacemaker cells |
| describe automaticity | ability of the pacemaker cells to initiate an electrical impulse without being stimulated from another source |
| describe excitability | ability of the cardiac muscle cells to respond to an outside stimulus |
| describe conductivity | ability of a cardiac cell to receive an electrical stimulus and conduct that stimulus to an adjacent cardiac cell |
| describe contractility | ability of the cardiac cells to shorten, causing cardiac muscle contraction in response to an electrical stimulus |
| describe refractoriness | the period of recovery that cells need after being discharged before they are able to respond to a stimulus |
| where on the ekg is the refractory period? | T wave |
| absolute refractory period | cells can not respond to any electrical impulse |
| relative refractory period | cells can depolarize if impulse is strong enough |
| what is the primary pacemaker | sinoatrial node |
| what stimulates the left atrium | Bachman's bundle |
| how does the impulse get to the AV node from the SA node? | internodal pathways |
| what does the av node do? | delays the impulse so the ventricles have time to fill with blood |
| what ventricle are the purkinjie fibers at? | left ventricle |
| what is between the av node and the bundle branches | bundle of HIS |
| if the bundle of his has to pace the heart what is the rate and sections below it is pacing? | 40-60bpm for the left and right bundle branches |
| list 3 sections of the left bundle brach | anterior fascicle, posterior fascicle, septal fascicle |
| if the purkinjie fibers have to pace what is the rate? | 20-40bpm |
| dysrhythmias | result from impulse formation or impulse conduction disorders |
| partial conduction block | slow but all impulses are conducted |
| complete conduction blocks | no impulses are conducted |
| what does reentry do? | creates a loop that stimulates tissue that was already depolarized |
| how is the PR segment measured? | end of p to start of qrs |
| how is st segment measured | end of s to end of t |
| how long is a QRS | .11 seconds or less |
| what is the T wave | the repolarization of ventricles |
| how is the pr interval measured | start of p to start of qrs |
| how long should a pr interval be? | .12-.2 |
| what are the numbers to label for the sequence method | 300 150 100 75 60 50 |
| what do you divide by for small box method | 1500 |
