Ch 17 - Part B Flashcards
defects in intrinsic conduction system may cause:
arrhythmias, fibrillation
Arrhythmias
irregular heart rhythms; uncoordinated atrial and ventricular contractions
Fibrillation
rapid, irregular contractions; heart becomes useless for pumping blood, causing circulation to cease
ectopic focus
an abnormal pacemaker that takes over pacing; caused by defective SA node
Extrasystole (premature contraction)
ectopic focus of small region of heart that triggers impulse before SA node can, causing delay in next impulse; can be from excessive caffeine or nicotine
heart block
caused y defective AV node; few impulses or no impulses reach ventricles which is too slow to maintain adequate circulation
heart block treatment
artificial pacemaker, which recouples atria and ventricles
Heartbeat is modified via…
cardiac centers in medulla oblongata
cardioacceleratory center
sends signals thorugh sympathetic trunk to increase both rate and force
cardioinhibitory center
parasympathetic signals via vagus nerve to decrese rate
contractile muscle fibers
make up bulk of heart muscle are are responsible for pumping action
How are contractile muscle fibers different from skeletal muscle?
in skeletal muscle contraction, cardiac muscle action potentials have plateau
electrocardiograph
can detect electrical current generated by heart
electrocardiogarm (ECG or EKG)
a graphic reccording of electrical activity; composite of all action potential at a given time, not a tracing of a single one
P wave
depolarization of SA node and atria
QRS complex
ventricular depolarization and atrial repolarization
T wave
ventricular repolarization
P-R interval
beginning of atrial excitation to beginning of ventricular excitation
S-T segment
entire ventricular myocardium depolarized
Q-T interval
beginning of ventricular depolarization through ventricular repolarization
systole
period of heart contraction
diastole
period of heart relaxation
cardiac cycle
blood flow through heart during one complete heartbeat
One Cardiac cycle
atrial systole and diastole are followed by ventricular systole and diastole