Question

Question 21

An andrenergic ligand bonds to Beta 2 receptors on smooth muscle of bronchioles. Through the action of the intracellular second messenger cAMP protein kinase is activated which phosphorylates and inactivates MLCK. How does this impact bronchiole diameter?

P-MLCK can't phosphorylate myosin light chains in myosin heads, causing bronchodilation

P-MLCK will activate myosin heads to form crossbridges, resulting in bronchdilation

P-MLCK activates ATPase on myosin heads causing bronchoconstriction

Question 22

Which myofilament in smooth muscle makes up the Dark Bands in skeletal muscle?

Only actin

Myosin and overlapping actin

Only myosin

Question 23

About _________ percentage of energy (ATP) consumed by skeletal muscle is used by myosin ATPase on myosin heads for contraction.

30

50

99.9

70

Answer 1

21. The smooth muscle contraction of the bronchial muscle wall leads to decrease in the bronchiole diameter and bronchoconstriction. This process will take place when the myosin heads undergo  Phosphorylation and cross bridging.

If myosin heads undergo phosphorylation, cross bringing occur that leads to smooth muscle contraction and decreases the bronchiole diameter.

Adrenergic receptors causes bronchodilation. The Myosin light chain kinases phosphatase remove the phosphate group from the myosin head which prevent them from cross bridging and leads to bronchodilation.

Answer is P-MLCK cannot phosphorylate myosin light chains in myosin head, causing bronchodilation.

22. Myofibrils are contractile structures of a skeletal muscle fiber. There are filaments present inside the myofilaments, thick ans thin filaments. Actin is the contractile protein present in the thin filament and myosin is the contractile protein in the thick filament. There are dark bands seen in the middle of the sarcomere of a myofilament is known as A band which is formed by the Overlapping of the actin over myosin. This dark A band is also known as zone of Overlapping.

the answer is Myosin and overlapping actin.

23. Skeletal muscle have the highest number of mitochondria seen compared to other cells in the body because they are the most energy using parts of the human body as they need to work continuously for long period of time. The myosin ATPase in the sarcomeres uses 70 % of the consumed energy for contraction.

The answer is 70 %