11.4 Smooth Muscle Compared to Skeletal Muscle

Question 1

What are the four similarities between smooth muscle cells and skeletal muscle?

Answer 1

1. contraction is accomplished by sliding of actin and myosin filaments
2. four-step contractile cycle
3. contraction triggered by increase in cytoplasmic calcium concentration
4. cells do not branch

Question 2

Which cells are shorter and narrower: skeletal muscle cells or smooth muscle cells?

Answer 2

smooth muscle cells

Question 3

What are T-tubules not present in smooth muscle cells?

Answer 3

they are small enough that they are not required to assist in spreading of action potential in cell

Question 4

How are smooth muscle cells connected to neighboring cells?

Answer 4

gap junctions

Question 5

What causes the smooth appearance of smooth muscle cells?

Answer 5

lack of sarcomeres

Question 6

How is contraction in smooth muscle cells regulated?

Answer 6

calmodulin and myosin light chain complex

Question 7

What is the purpose of calmodulin in smooth muscle cells?

Answer 7

binds calcium and activates the myosin light chain complex

Question 8

What is the purpose of the myosin light chain complex in smooth muscle cells?

Answer 8

phosphorylates a portion of the myosin molecule activating its enzymatic/mechanical activity

Question 9

Does smooth muscle cell rely on intracellular or extracellular calcium?

Answer 9

extracellular

Question 10

What type of channels do smooth muscle cells lack and what do they rely on for action potentials?

Answer 10

lack = sodium channels
rely on = slow channel

Question 11

What are slow waves?

Answer 11

fluctuations in resting potential

Question 12

What type of neurons innervate smooth muscles?

Answer 12

autonomic motor neurons