Cardiac Muscle

Question 1

Autorhythmic Cells

Answer 1

Initiate and conduct APs to the contractile cells od the heart

Question 2

Contractile Cells

Answer 2

Make up 99% of all cardiac muscle fibres

Question 3

Autorhythmic cells are located in the

Answer 3

Sinoatrial node in the right atrium

Question 4

Explain transduction for the heart muscle when contracting

Answer 4

VG Calcium channels open
Ca induces Ca release through ryanodine receptor-channels (RyR)
Ca is released from SR
The summed calcium is enough to create a Ca signal by binding to troponin

Question 5

Explain transduction for the heart muscle when relaxing

Answer 5

Ca unbinds from troponin

Ca is pumped back into the SR

Question 6

The length of an AP in the myocardial cells is over 200ms compared to skeletal muscles and neurons lasting 1-5ms. Why might this be?

Answer 6

To prevent tetanus (charlie horse - sustained muscle contraction) in the heart