11.3 Cardiac Muscle Compared to Skeletal Muscle

Question 1

What are the four ways cardiac muscle is similar to skeletal muscle?

Answer 1

1. striated
2. T-tubules
3. troponin-tropomyosin complex
4. length-tension relationship

Question 2

What are intercalated discs?

Answer 2

gap junctions that allow action potentials to propagate throughout the entire heart without allowing nuclei and cytoplasmic contents to be shared

Question 3

What is the difference between how calcium is obtained in skeletal muscle versus cardiac muscle?

Answer 3

cardiac = both intra- and extracellularly
skeletal = intracellularly

Question 4

What are fast and slow channels in cardiac muscle?

Answer 4

fast channels = voltage-gated sodium channels
slow channels = voltage-gated calcium channels

Question 5

What is the purpose of slow channels in cardiac muscle cells?

Answer 5

cause the distinctive plateau in the cardiac action potential

Question 6

What are the two significant points of the cardiac action potential plateau?

Answer 6

1. longer duration of contraction facilitating ventricular emptying
2. longer refractory period helping prevent disorganized transmission of impulses through heart

Question 7

Is summation and tetanus possible in cardiac muscle? Why?

Answer 7

no; longer refractory period