Cardiac Muscle Contraction 1

Question 1

Thin filaments are composed of which of the following?

A. Actin filaments
B. Titin
C. Light chains
D. Myosin-binding proteins
E. Desmin

Answer 1

A. Actin

Question 2

Thick filaments are composed of which of the following?

A. Myosin
B. Tropomyosin
C. Connexin
D. Troponin complex
E. Nebulin

Answer 2

A. Myosin

Question 3

Cardiomyocyte ion channels include which of the following?

A. The ryanodine receptor
B. The beta adrenoceptor
C. Calcium activated channels
D. ADP-sensitive potassium channels

Answer 3

A & C.

A. The ryanodine receptor is a cardiomyocyte ion channel.
C. Calcium activated channels are cardiomyocyte ion channels.

B. Incorrect. The beta adrenoceptor is a not cardiomyocyte ion channel. Beta receptors are G protein-coupled enzymatic receptors.

D. Incorrect. Cardiomyocytes possess ATP-sensitive, i.e. not ADP-sensitive, potassium channels.

Question 4

In contrast to skeletal muscle, cardiac muscle has which of the following?

A. Greater capillary density
B. T-tubules corresponding to A-band and I-band overlap
C. Longer and thinner transverse tubules
D. More mitochondria by volume
E. Cytoplasm joined by connexons

Answer 4

A., D. & E.

In contrast to skeletal muscle, cardiac muscle has:

Greater capillary density
Cytoplasm joined by connexons
More mitochondria (up to 25% by volume, compared to 2% in skeletal muscle cells)
However, cardiac muscle does not have:

T-tubules corresponding to A-and I-band overlap
Longer and thinner transverse tubules