Question

37. A stretch stimulus has resulted in the opening of mechanically gated calcium channels on the surface of a smooth muscle cell. Which of the following events is occurring?

a. Ca2+ binds to the myosin head and initiates the power stroke

b. Ca2+ binds to calmodulin and activates it

c. Ca2+ binds to troponin to increase interactions between actin and myosin

38. In the smooth muscle lab, why did we see an increase in contraction in response to elevated extracellular K+?

a. The smooth muscle cells become hyperpolarized

b. Less K+ was able to leave the cell resulting in depolarization of the smooth muscle

c. The opening of additional K+ channels resulted in depolarization of the membrane

39. Which of the following is occurring during the pharyngeal phase of the swallow reflex?

a. The tongue pushes the food towards the back of the mouth

b. Peristaltic waves propel the food bolus toward the stomach

c. The lifting of the soft palate, the covering of the glottis and the opening of the upper esophageal sphincter   

Answer 1

37. Option b is the correct answer.

Smooth muscle contraction occurs due to binding of Ca+ to calmodulin while in skeletal muscle contraction Ca+ binds to troponin.

38. Option b is the correct answer.

K+ ion has an important role in the development of polarization (resting potential) of cell as it continuously leak out of the cell. In the presence of higher concentration of extracellular K+ ion the concentration gradient will be compensated and thus less K+ ion will leave the cell and thus depolarization will occur.

39. Option c is the correct answer.

During pharyngeal phase upper esophagus spinchter relaxes which pulled the hyoid bone and larynx resulting into opening of the spinchter which allows the passage of food. The covering of glottis occurs with epiglottis to prevent the food from entering to the respiratory tract.