smooth muscle

Question 1

are there any sarcomeres in smooth muscle?

Answer 1

No

thats why there are no striations present

Question 2

what shape are smooth muscles and what length roughly?

Answer 2

spindle shaped cells, about 20-220μ X 2-20

Question 3

what micro filaments does smooth muscle contain compared with skeletal or cardiac?

Answer 3

contains actin and myosin, and tropomyosin (only 10% of actin and myosin found in striated muscle) (more actin than myosin)

Question 4

what do the actin filaments attach to instead of absent Z lines?

Answer 4

dense bodies

Question 5

what needs to happen to myosin before it can bind to actin (as there is no troponin present)

Answer 5

it needs to be phosphorylated

Question 6

how is the myosin phosphorylated?

Answer 6

by a calcium regulated enzyme - myosin light chain kinase (needs 1 ATP)

Question 7

how is the myosin light chain kinase enzyme activated?

Answer 7

calcium binds to CALMODULIN; these two form a complex with the MLCK

Question 8

what is the name of the enzyme that removes the phosphate from the myosin head causing smooth muscle relaxation?

Answer 8

MLCP (myosin light chain phosphatase)

Question 9

what is the name of the swollen regions of nerves that innervate smooth muscle that contain mitochondria and neurotransmitter?

Answer 9

varicosities

Question 10

which type of smooth muscle acts as a ‘syncytium’?

Answer 10

unitary, single unit, visceral smooth muscle (have many ago junctions and are electrically coupled)

Question 11

which type of smooth muscle is made up of discrete bundles of cells which are densely innervated and contract only in response to their own innervation?

Answer 11

multi unit smooth muscle