Cardio 2 Flashcards
What happens during “lub”?
- Ventricular contraction (depolarization)
- S1
What happens during “dub”?
- ventricular filling (repolarization)
- S2
S1 =
Tricuspid and mitral valves close
S2 =
Aortic and pulmonic valves close
What are the rhythms to worry about as a PT?
- normal sinus rhythm
- PVC
- A-fib
- V-fib
- flatline
What structures control heart action?
- cardiac action potentials
- conduction system
Cardiac action potentials =
Electrical impulses
SA node: where is it?
- in RA
- just above tricuspid valve
What does the SA node do?
Generates ~75 action potential per minute
SA node =
Sinoatrial node
AV node =
Atrioventricular node
Where is the AV node?
- in RA
- superior to tricuspid valve
- near autonomic parasympathetic ganglia
What is the function of the autonomic parasympathetic ganglia?
Slow impulse conduction through the AV node
From the AV node, where does an AP go?
- bindle of His (av bundle)
- R and L bundle branches
- Purkinje fibers
Conduction sequence:
Normal excitation originates in ______, then propagates through ______
- SA node
- both atria
Conduction sequence:
Atrial depolarization spreads to _______, and passes through _______ to the _________
- AV node
- bundle of His
- bundle branches/Purkinje fibers
The intrinsic pacemaker rate is (faster/slower) in structures further along the activation pathway
Slower
The AV nodal rate is (faster/slower) than the SA node rate
Slower
Why is the intrinsic pacemaker rate of the AV node slower than the SA node?
prevents AV node from generating a spontaneous rhythm under normal conditions
AV node rate
Refractory
Under 55 bpm
What happens if the SA node becomes inactive?
AV nodal rate determines ventricular rate
Conduction sequence (structures)
- SA node
- Atrial myocardium
- AV node
- Bundle of His
- Bundle branches
- Purkinje fibers
- Ventricular myocardium
What is resting membrane potential?
Voltage differential across the cell membrane
Depolarization =
- electrical activation of the cell
- inside the cell is less negatively charged
Drugs and depolarization
Drugs that alter ion movement can affect HR
repolarizatoin =
- electrical deactivation
- inside the cell is more negatively charged
Hyperpolarization =
- too much extracellular K+
- resting potential is more negative
Refractory period =
- no new cardiac AP can be initiated
- gives time for channels that permit Na+ and Ca2+ to re-enter the cell
What can abn refractory periods do?
Cause dysrhythmias
Due to heart dz
Electrocardiogram =
Sum of all cardiac APs
Automaticity =
generating spontaneous depolarization to threshold so that SA and AV nodes generate cardiac APs without any stimulus
Rhythmicity =
- SA sets the pace bc it’s usually the fastest (60-100 bpm)
- AV (40-60 bpm) takes over if SA damaged
What takes over for the AV node?
Conduction cells in the atria
These can also conduct potential (30-40 bpm)
Purkinje fibers
