Threshold
Minimal amount of stimulation needed to start an AP
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| Term | Definition |
|---|---|
| Threshold | Minimal amount of stimulation needed to start an AP |
| Action potential | Signal cell uses to communicate |
| Action potential upstroke | Rapid rising phase of AP |
| #35 SLO Autorhythmic CMC's | Na+ slowly enters --> causes gradual depolarization Ca2+ enters at threshold --> causes depolarization (AP upstroke) K+ exits --> repolarize cell |
| Contractile CMC's | Rapid Na+ influx --> fast depolarization Ca2+ influx (slow channels) --> creates plateau phase K+ efflux --> repolarization (back to resting potential) |
| Plateau phase | Na+ channels close, slow Ca2+ channels open & Ca2+ enters cell Ca2+ enters cell, some K+ continues to leave Results in plateau phase -Membrane stays depolarized longer |
| ECG importance | Records all AP -Made from nodes & cells |
| What does the P wave mean? | SA node fires due to atria being full of blood -Signals spread through atriums, causing them to depolarize |
| What does QRS mean? | Firing of AV node -Represents ventricular depolarization |
| What does the Q wave mean? | Depolarization of interventricular septum |
| What does the R wave mean? | Depolarization of masses of ventricles |
| What does the S wave mean? | Last wave of ventricular depolarization |
| What does the T wave mean? | Ventricular repolarization -Immediately before ventricular relaxation/diastole |
| S-T | Plateau in myocardial AP When ventricles contract; pumping blood |