Function of Myocardial cells

5 important questions on Function of Myocardial cells

What are the types of cardiac muscle fibers?

  1. Atrial
  2. Ventricular
  3. Excitatory and conductive muscle fibers

How do the different myocardial cells act?

Atrial and ventricular are similar to skeletal
Excitatory and conductive muscle fibers have
1. Rhythmic excitability (self-excitable)
2. Rapid conduction (to atrial and ventricular muscle)

What are properties of atrial and ventricular cardiac muscle?

- Striated (actin myosin filaments) similar to skeletal muscles
- Joined by gap junctions -> intercalated discs, allowing free diffusion of ions with low resistance
- Excitation of 1 fiber leads to excitation of entire syncytium
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Why are atrial and ventricular syncytium separated?

They are separated by fibrous (valvular) tissue at the AV ring as to not conduct electricity from atrial syncytium to ventricular syncytium and allowing the atrium to contract first ALWAYS

What are the steps of excitation-contraction coupling in cardiac muscle?

1. AP travels along sarcolemma (cardiac muscle cell membrane)
2. Depolarization opens L-type Ca2+ channels
3. Ca2+ from ECF enters the cell 
4. Calcium induced calcium release from sarcoplasmic reticulum's ryanodine receptors being activated
5. Calcium causes contraction
6. Ca2+ is pumped back to SR by SERCA pump
7. Ca2+ is pumped out of the cell via Na+/Ca2+ exchanger and Ca2+ ATPase

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