Garman- CV2: Electrical Flashcards
What are 2 types of cell types of the heart?
Contractile cells and conductile cells
What are the contractile cells?
Bulk of atrial and ventricular tissues
-Work horses of heart
What are the conductile cells
Specialized cardiomyocytes
- sole puprose is to generate and propagate electrical activity across contractile cells
Found in:
- SA node
- Atrial internodal tracts
- AV node
- Bundle of His
- Bundle branhces (L and R)
- Purkinje Fibers
What are some characteristics of cardiomyocytes?
-sTRIATED
-50-100 uM long; diameter ~20 uM (shorter and thinner than skeletal muscle cells)
- Branched at its ends
Very small
-Mono/bi-nucleated centrally located (skeletal muscles multi-nucleated and peripherally located nuclei)
- Reduced SR system but extensive T tubule system
-Large/numerous mitochondria
What are intercalated disks?
Consist of desmosomes- mechanical coupling, gap junctions- electrical coupling
What is purpose of desmosomes?
Make sure cardiomyocytes do not tear apart at opposing plasma membranes. Keeps cells tightly bound together
What innervates cardiac muscle?
Autonomic nervous system (Brain tells heart to increase or decrease rate, or increase contractility)
What is source of Ca for cell?
SR and ECF
What causes removal of Ca in cardiomyocte?
Ca ATPase pumps (membrane and SR) AND Na/Ca exchanger (3Na/1 Ca)
When do atria contract to “top off” filling of ventricles?
End diastole
When are AV valves open and semilunar valves closed?
Passive diastole
When are all 4 valves closed?
Isovolumetric contraction and relaxation
When are semilunar valves open?
Systole
How long does propagation of signal to AV node take?
50 mseconds
What is the delay at AV node?
100 msec, total time 150 mseconds
How long does impulse take down bundle branch and purkinje fibers via moderator band?
175 msec elapsed time
How long does the impulse take to go throughout ventricular myocardium and begin contraction?
225 msec
What is normal spontaneous firing for SA node?
100 /min
What is the atrial internodal pathway?
- Specialized conducting cells ~50 msec
- Stimulus passed to contractile cells which spread it across both atria
- Stops at atria- myocardium of atria is not connected with ventricle
What makes up AV node:
- Smaller cells/ slows signal
- 100 msec to move through AV node
What is normal firing of AV node?
~40/min
What is overdrive supression?
Faster firing of SA node supresses other cells from acting as a pacemaker
What is the only electrical connection between atria and ventricle?
AV bundle or bundle of His
Which bundle branch is bigger?
Left