Mechanical Activity of Cardiac Cells

Question 1

Cardiac Muscle Operation Length

Answer 1

Generally shorter lengths, not max overlap

Question 2

Calcium Cycle

Answer 2

AP -> opens Ca channels on T-Tubule -> Ryanodine R -> release Ca from SR -> Binds troponin C and shit -> SERCA pumps back into SR

Question 3

Lusitropic Effect

Answer 3

NE activates PKA -> activates phospholambin (PL) -> increases SERCA pumping Ca back into SR restoring cell for more rapid contraction

Question 4

Isometric Contractions in terms of Increasing Length

Answer 4

Difference b/w total tension and passive tension (active tension) increases w/ length, until a certain length when it drops off

Question 5

Basis for Starling’s Law

Answer 5

If L2 > L1 (length), then SL2 (shortening length upon afterload, the isotonic contraction after isometric contraction) > SL1
L1 and L2 referred to as preload, isometric contraction

Question 6

Velocity of Shortening vs. Force Relationship

Answer 6

Inverse relationship. Increased contractility like from NE shifts the curve to the right, increasing both

Question 7

Cardiac Cycle

Answer 7

Diastole expands muscle, then get systole -> isovolumetric contraction first w/ valves closed -> valves open to ejection phase where you get afterload contraction and stroke volume out. Then isovolumetric relaxation to reset