cardiac muscle

Question 1

similarities of cardiac muscle to skeletal muscle

Answer 1

striated appearance
multinucleate
T tubule system

Question 2

similtaries of cardiac muscle to smooth muscle

Answer 2

gap junctions allowing functional syncytium

has its own inherent rhythmicity

Question 3

what generates the action potential

Answer 3

pacemaker cells (SAN)

Question 4

describe the cardiac muscle cell action potential

Answer 4

1. spontaneous rapid depolarisation - fast influx of Na+
2. plateau phase - Na+ channels suddenly close, Ca2+ in slow, counteracts open K+ channels
3. rapid decrease in membrane potential- Ca2+ channel closes, K+ still open and leaking out, back to -90 membrane potential

Question 5

describe the pacemaker cell action potential (not cardiac muscle)

Answer 5

1. funny channels open and Na+ flows in
2. membrane potential rises and reaches threshold
3. T type Ca2+ channels open, funny channels close
4. -40 threshold is reached and T type closes, L type opens
5. Large Ca2+ influx , mp rises to +10
6. L type closes, K+ opens and K+ leaks out lowering membrane potential

Question 6

what triggers action potential in cardiac muscle cells

Answer 6

gap junctions to neighbouring cells (functional syncytium)

Question 7

importance of long refractory period

Answer 7

prevents tetanus and new AP cannot be generated until membrane has recovered from the first