Smooth Muscle

Question 1

What is the shape of smooth muscle cells?

Answer 1

short, fusiform

Question 1

do smooth muscle cells have a sarcomere?

Answer 1

no- smooth muscle has no striations= no sarcomeres

Question 2

how many nuclei does smooth muscle have

Answer 2

smooth muscle has one-centrally located nucleus

Question 3

does smooth muscle still have actin and myosin?

Answer 3

yes

Question 4

Why in a smooth muscle cell is the major source of calcium external?

Answer 4

because it has less sarcoplasmic reticulum

Question 5

in smooth muscle cells are the thin filaments attached to Z lines?

Answer 5

no- they are attached to dense bodies

Question 6

Is innervation apparent in smooth muscle cells?

Answer 6

yes- there are nerve fibers that are attached to bundles of smooth muscle cells

Question 7

What is different in the arrangement of myosin and actin in smooth muscle

Answer 7

the actin is longer

Question 8

Smooth muscle cells are linked together by…

Answer 8

attachement plaques (like adhering junctions)

Question 9

describe the myosin ATPase activity of smooth muscle cells

Answer 9

it is much slower

Question 10

what does the myosin light chain do?

Answer 10

it regulates the ATPase behavior of myosin head

Question 11

the longer actin and myosin filaments push in which direction?

Answer 11

antiparallel

Question 12

What is the calcium sensor in smooth muscle cells

Answer 12

calmodulin

Question 13

How many calcium channels do smooth muscles have

Answer 13

3; RyR, IP3, and calcium channels from the outside (surface L-type calcium channels)

Question 14

What does a kinase do

Answer 14

phosphorylates

Question 15

What does myosin light chain kinase do and how is it activated?

Answer 15

it is activated by Ca2+ -calmodulin; it phosphorylates the myosin light chain

Question 16

What happens when MLCK phosphorylates light chains in myosin heads?

Answer 16

increases the myosin ATPase activity

Question 17

What does a phosphatase do?

Answer 17

pulls phosphate off, relaxes muscle

Question 18

What does kinase use as its source of phosphate

Answer 18

ATP (hydrolysis)

Question 19

Where does smooth muscle rest?

Answer 19

-50

Question 20

Pharmacomechanical Coupling

Answer 20

occurs when chemical signals change muscle tension through signal transduction pathways with little to no change in membrane potential

Question 21

What is the first messenger for a metabotropic receptor?

Answer 21

Receives signal on the outside (something like a drug, hormone or a neurotransmitter)

Question 22

What is an example of a second messenger (metabotropic)

Answer 22

IP3 (small molecules that initiate and coordinate intracellular signaling pathways)

Question 23

What can modulatory pathways do (smooth muscle)

Answer 23

alter the activity of MLCK or phosphatase

Question 24

What effect does nitric oxide have on Ca2+ in the smooth muscle cells

Answer 24

pumps more calcium into the sarcoplasmic reticulum -> causing contraction

Question 25

Compare to the other muscle cells, smooth muscle cells are (describe their contraction)

Answer 25

the slowest to contract and to relax