Excitation-Contraction Coupling

Question 1

What is the function of phospholamban?

Answer 1

it modulates SERCA by decreasing its affinity for calcium

Question 2

What happens when phospholamban is phosphorylated by PKA?

Answer 2

inhibition of SERCA pump is relieved, allowing more Ca2+ to enter the SR (=relaxation)

Question 3

What happens when troponin I is phosphorylated by PKA?

Answer 3

troponin I undergoes a conformational change in which there is a decrease in affinity of the troponin complex for calcium (this allows calcium to quickly bind and unbind)

Question 4

What is contraction amplitude regulated by in cardiac muscle?

Answer 4

Ca2+ influx via slow Ca2+ current (via L-type channels) and SR Ca2+ content

Question 5

As heart rate increases the strength of contraction increases.

Answer 5

positive staircase (treppe) effect

Question 6

What is a premature beat vs. post-extrasystolic potentiation (PESP)?

Answer 6

• premature beat is a smaller than normal contraction

- PESP is a stronger than normal contraction of the beat following a premature one

Question 7

What are the 4 forces that determine cardiac output?

Answer 7

• heart rate (direct)
• myocardial contractility (direct)
• preload (direct)
• afterload (inverse)