ECG Flashcards
What is stroke volume
End diastolic volume- end systolic volume
What causes the heart beat
Depolarization via action potential
Sinoatrial node in top of right atrium
Atrioventricular node in bottom right of right atrium
Bundle of his and purkinje fibres
What causes the depolarisation causing the heart beat?
Pacemaker potential is a slow depolarization
Na- voltage gated channels called funny channels
Ca- Voltage gated calcium channels - Ltype more rapid
Then Ltype closes and K channels open to repolarise
What is the pacemaker
Sinoatrial node wave looks like a skating slope- Na in fast!, K out fast, Ca in slow so levels out, K out fast
What is excitation contraction coupling
Increase in cytosolic calcium- combines with troponin
What does abnormal K levels do
changes resting potential
decreases cardia excitability and contractility
Can cause arrhythmias
What does abnormal Ca levels do
affects membrane permeability causing rhythm abnormalities of the heart
Ca blockers decr. force of contraction
Digoxin incr. ca and contractility
What are the labels for the heart beat peaks? (letters)
P first bump- depolarisation of atria due to SAN
Q dip
R peak
S dip
T last bump- ventricular repolarisation
What do funny channels do
slowly allow Na into cells in SA node causing slow depolarisation
What is the P-R interval
Delay of AV node to allow filling of ventricles
Describe the curve of the electrical activity in the SAN pacemaker cells
usual curve however slow depolarisation from Na Funny channels
Generates action potentials
Starts on own-spontaneous
Repolarisation opens funny channels causing depolarisation again
NO RESTING POTENTIAL
Describe the curve of the electrical activity in the SAN cardiomyocytes
Steep increase, small peak then plateau for a bit then steep decrease again
Pass action onto each other by gap junctions
Depolarisation by Na channels open- K open causing small repolarisation, plateau by Ca flowing into cell, balance of Ca in and K out
K channels open floods out= repolarisation
HAS A RESTING POTENTIAL
What’s the differences between SA node pacemaker cells and cardiomyocytes
SA node pacemaker cells cause cardiac impulse
cardiomyocytes contract the heart muscle from the impulse of the pacemaker
