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Lab Exercise 4

Intrinsic Stimulation caused by specialized, noncontractile cells called autorhythmic cells
Intrinsic Conduction System initiates action potentials for cardiac muscle fiber contraction and provides a pathway for conducting the action potential to all cardiac muscle fibers
Extrinsic Stimulation ANS and hormones, only increase or decrease the intrinsic pace
Electrocardiograph records electrical changes in the heart
Electrocardiogram (ECG or EKG) chart recording of the electrical events before each heartbeat
P Wave atrial depolarization, just before atrial contraction
QRS Complex ventricular depolarization, before ventricles contract. Occurs during atrial repolarization
T Wave ventricular repolarization, before ventricles contract
P-Q Interval the time interval between the beginning of contraction of the atrium and the beginning of the contraction of the ventricle
Q-T Interval the time from beginning of ventricular depolarization until the end of ventricular repolarization - ventricles are contracting
S-T Segment represents the time the ventricular fibers are fully depolarized
Normal Sinus Rhythm normal heart rate of 60-100 beats/min
Tachycardia HR >100 beats/min
Bradycardia HR <60 beats/min
Fibrillation from prolonged tachycardia, rapid uncoordinated heart contractions that do not pump blood
Complete Heart Block ventricles depolarizing independently from the atria
Heart Block produced by cardiac damage to the AV node or bundle, reducing electrical conduction from atria to ventricles, P-Q interval >0.2 seconds
Right or Left Bundle Block two ventricles do not contract simulatneously and QRS is prolonged.
Myocardial Ischemia decreased blood flow, longer Q-T interval
Myocardial Damage lengthens Q-T interval
Mean Electrical Axis (MEA) average direction of depolarization as the impulses spread into the ventricles.
Hypertrophy of one ventricle shifts the MEA toward the hypertrophied ventricle, because it takes longer to depolarize, about +59 degrees
Mean Electrical Magnitude average voltage of depolarization
T/F: EKGs give info about the force of contraction of the cardiac muscle False
Aside from the ANS, what other factor causes extrinsic stimulation hormones
Cardiac Cycle time in seconds for one heartbeat
Created by: connorquinby