cardiovascular system 3 Flashcards
what is the heart
a pump with a variable rate to meet changes in metabolic demand
what does the conduction system do
assures that cardiac chambers become stimulated to contract in a coordinated manner
what is the conduction system made up of
network of specialized cardiac muscle fibres called autorhythmic cells
how does the conduction system work
repeated generated spontaneous action protentional that trigger heart contractions
describe autorhythmic cells
1 act as a pacemaker
2 form the conduction system
3 are found in specific locations
what is the healthy adult pulse
at rest roughly 75bpm range is 60-100
at sleep 40bpm
strenuous exercise 200-220bpm
what is the route taken by action potentials
sinoatrial node - atrioventricular node - atrioventricular bundle - R+L bundle branches - purkinje fibres
what 2 things can change the speed of the heart rate through the node fibres
hormones and neurotransmitters
where is the ectopic pacemaker site
out with the SA node
what triggers the ectopic pacemaker site
caffeine and nicotine
toxic reactions to drugs
what does an electrocardiogram do
records electrical changes that accompany AP propagation that can be detected at the surface of body
how many recognizable waves are within an ECG
3
name the 3 waves of an EGC
p wave, QRS complex, T wave
what does the P wave show
atrial depolarization (contraction)
what does the QRS complex show
onset of ventricular depolarisation
what does the T wave show
ventricular repolarization, just before ventricles start to relax
what does it mean if the P wave is enlarged
enlarged atrium
what does it mean if Q is enlarged in the QRS complex
MI
what does it mean if R is enlarged in the QRS complex
enlarged ventricles
what does it mean if T wave is flatter
insufficient O2
what does it mean if the P-Q interval is lengthened
there is scar tissue
what does it mean if the S-T segment is elevated
acute MI
what does it mean if the S-T segment is depressed
insufficient O2
what does it mean if the Q-T interval is lenghtened
myocardial damage or conduction abnormalities
