The heart and ECG Flashcards
What is systemic circulation?
blood from heart via the body to provide 02 & nutrients
What do valves allow?
unidirectionality and maintain pressure
what is the circulation system in the body?
1) de02 blood enter right atria via Superior/ inferior Vena cava
2) blood enter right ventr. via tricuspid valve
3) blood exit right ventr. into pulmonary artery via Semi Lunar valve
4) blood to lungs
5) blood from lungs to left atria via pulmonary vein
6) blood from left atria to ventr. via Bicuspid Mitral valve
7) blood from left ventr. to aorta via semi lunar aortic valve for systemic circulation
What does myogenic mean?
signals itself and autorhythmic
What are pacemaker cells?
- create Action potentials
- located SA node in right atrium and AV node near tricuspid valve
What speed do Purkinje fibres conduct potential?
4m/s
What is systole?
when heart contracts and pumps blood into arteries
What is Diastole?
when heart relaxes and allows chambers to fill with blood
What is action potential transmission?
pacemakers> conduction fibres> contractile cells
how is passage to cardiac cells enabled?
cardiac muscle cells connected by gap junction channels
What are gap junction channels in cardiac cell?
Desmosomes ( protein fibres)
What do desmosomes allow?
myocardium can resist stretching
How is impulse initiated in heart?
1) SA node initiate impulse to AV node via conduction fibres
2) Small delay as AV node transmits less rapid
3) AV node > bundle of his in interventricular system
4) signal split into right and left branch
5) signal travel via Purkinje fibres which spread via Ventricles
Is there a steady resting potential?
NO
What happens with Action potential?
slow depolarisation
threshold reach= rapid action potential
Repolarization until -70mV
What causes Action potential?
increase in Ca2+ ions across membrane so depolarizes
What do Cardiac contractile cells need to generate Action potential?
Na ion
What is action potential initiation in Contractile cells?
1) depolarization - Na into cell via Na/K channel
2) Repolarization-
3) Plateau
4) repolarization
5) resting potential
What happens in depolarization in contractile cells?
Na into cell via Na/K channel
What happens in repolarization in contractile cells?
Na channels inactivate so pNA falls
Na/K pump so more Na+ pumped out
Ca channels open
What happens in plateau in contractile cells?
K channel shut
Ca channels stay open
What is 2nd repolarization after plateau ?
channels open - K pumped out cell
Membrane potential more negative
Ca channels open so AP finishes
What is resting membrane potential of contractile cell?
-90mV
How does electrical activity spread via body?
Body fluids act as conductors
What is Einthovens triangle?
Right arm
Left arm
Left leg
What is P wave?
Atrial depolarisation
What is QRS complex?
Ventricular depolarization
QRS hides atrial repolarization
What is T wave?
Ventricular repolarization
What is P-Q interval?
AV node conduction time
What is Q-T interval?
Ventricular systole
What is T-Q interval ?
Ventricular diastole
What is tachycardia?
Faster heart rate
What is bradychardia?
slow heart rates
What are problems with conduction via AV node?
1) 3rd degree heart block
2) premature atrial/ventr. contraction
3) ventr/ atrial fibrillations
