Excitable Tissue Flashcards
Amount of neurotransmitter released from presynaptic bud is directly related to
Rise in cystolic Ca
P wave:
Atrial depolarization
ECa2+
+125 mV
PR interval:
Conduction delay in AV node
Lead 1+ and Lead aVF- =
Left axis deviation
Upstroke of AP in nodal cells mediated by
Ca current rather than Na
QRS complex:
Ventricular depolarization
Phase 0
Hypercalcemia on the heart
Increases QT interval
ENa+
+70 mV
T wave:
Ventricular repolarization
Phase 3
Mobitz type 1
Second-degree heart block
Progressive prlongation of PR until a ventricular beat is missing and then cycle begins again
Unsteady rhythm
ECl-
-76 mV
Hyperkalemia on the heart
Increases rate of repolarization
Sharp-spiked T waves and shortened QT intervals
Lead 1+ and Lead aVF+ =
Normal axis
Wolff-Parkinson-White syndrome
Bundle of kent between atria and ventricles becomes activated
Short PR
Steady rhythm and normal rate
Widened QRS
First-Degree heart block
Long PR
Slowed conduction through the AV node
Rate and Rhythm are typically normal
Phase 0 AP of cardiac creats what of EKG
QRS
Mobitz type 2
Second-degree heart block
PR is consistent
Steady or unsteady rhythm depending on block ratio
EK+
-95 mV
Hypokalemia on the heart
Decreases rate of repolarization
Resulting in U waves and prolonged QT
ST segment:
Ventricles are depolarized during this segment
Phase 2
Phase 2 AP of acridac creates what of EKG
ST segment
Hypocalcemia on the heart
Decreases QT interval
Phase 3 of AP of cardiac creates what of EKG
T wave
Relative refractory period is
period during which a greater than threshold stimulus is required to induce a second action potential
What channels are important to determining RMP of a cell
Ungated (leak) channels
What blocks fast Na channels
Extracellular Ca
Absolute refractory period is
Period during which no matter how strong the stimulus, it cannot induce a second action potential
Lead 1- and Lead aVF+ =
Right axis deviation
