Flashcards in Cardiac Muscle Structure & Function Deck (32):
What are the contractile proteins in the heart muscle?
- Myosin: Two heavy chains and 4 light chains.
- Actin: Similar to skeletal muscle actin; binds tropomyosin and Troponin
List the regulatory proteins
- Troponin C (TN-C)
- Troponin I (TN-I)
- Troponin T (TN-T)
how many Ca2+ binding sites in Troponin C (TN-C)?
Contains only one Ca2+-binding site (unlike skeletal which contains two)
Describe the structure of Troponin I (TN-I)
Contains a unique N-terminal extension of 32 amino acids containing 2 PKA phosphorylation sites critical for adrenergic responsiveness of the heart.
What does Troponin T (TN-T) bind?
What isoform of tropomyosin is found in the heart?
T or F: Myofibrils and mitochondria occupy about 85% of the heart cell volume
True, the rest contains sarcolemma, T-tubules, SR, intercalated disks, gap junctions
T or F: Cardiac muscles are not under direct neural control (unlike skeletal)
Contrast cardiac and skeletal muscle cells
Cardiac muscle cells are shorter, narrower & richer in mitochondria than skeletal muscle cells have only one nucleus
T or F: ATPase activity of myosin is slower in cardiac than skeletal