smooth muscle

Question 1

is smooth muscle voluntary or involuntary control?

Answer 1

involuntary

Question 2

smooth muscle contractions produce __________

Answer 2

constriction

Question 3

smooth muscle is organized in _______________

Answer 3

multidirectional contractile units

Question 4

how many nuclei do smooth muscle have?

Answer 4

one

Question 5

how is smooth muscle classified?

Answer 5

1 - by location
2 - by contraction pattern
3 - by their communication with neighboring cells

Question 6

what are the 2 contraction patterns of smooth muscles?

Answer 6

1 - phasic (ex. peristalsis)
2 - tonic (ex. sphincters)

Question 7

what are the 2 classifications of communication between neighboring cells

Answer 7

1 - single-unit/unitary/visceral smooth muscle
2 - multiunit smooth muscel

Question 8

__________ smooth muscle cells are connected by gap junctions, and the cells contract as a single unit

Answer 8

single-unit

Question 9

_______ smooth muscle cells are not linked, and each cell must be stimulated independently

Answer 9

multi-unit

Question 10

what is an example of a phasic smooth muscle that is usually relaxed?

Answer 10

esophagus

Question 11

what is an example of a phasic smooth muscle that cycles between contraction and relaxation?

Answer 11

intestine

Question 12

what is an example of a tonic smooth muscle that is usually contracted?

Answer 12

sphincter

Question 13

what is an example of a tonic smooth muscle whose contraction is varied as necessary

Answer 13

vascular smooth muscle

Question 14

smooth muscles are the _______ to contract and relax

Answer 14

slowest
(skeletal is the fastest and cardiac is in the middle)

Question 15

T or F: smooth muscle has no sarcomeres

Answer 15

T

Question 16

T or F: actin is more plentiful in smooth muscle

Answer 16

T

Question 17

T or F: smooth muscle lacks troponin

Answer 17

T, but actin is still associated with tropomyosin in smooth muscle

Question 18

T or F: myosin filaments are longer in smooth muscle and the entire surface of the filament is covered with myosin heads

Answer 18

T

Question 19

T or F: smooth muscle has an extensive cytoskeleton consisting of intermediate filaments and dense bodies

Answer 19

T

Question 20

T or F: in smooth muscle the amount of SR varies and is less organized

Answer 20

T

Question 21

T or F: smooth muscle has t-tubules and caveolae

Answer 21

F, smooth muscle only has caveolae

Question 22

_______ initiates smooth muscle contraction

Answer 22

calcium

Question 23

increased _____________ is the signal for smooth muscle contraction

Answer 23

cytosolic calcium

Question 24

describe the events for smooth muscle contraction

Answer 24

1 - intracellular Ca+ concentration increases
2 - Ca binds to calmodulin
3 - Ca-calmodulin activates myosin light chain kinase
4 - MLCK phosphorylates light chains
5 - active myosin crossbridges slide along actin (crossbridge cycling)

Question 25

____________ is the first step in smooth muscle relaxation

Answer 25

removal of Ca+ from the cytosol

Question 26

describe the steps of smooth muscle relaxation

Answer 26

1 - free Ca in cytosol decreases 2 - Ca unbinds from calmodulin 3 - myosin phosphatase removes phosphate from myosin light chains 4 - less myosin ATPase activity

Question 27

contraction caused by chemical signaling is ________________ coupling

Answer 27

pharmacomechanical

Question 28

what are the 3 different types of cell membrane ca entry in smooth muscle

Answer 28

1 - voltage gated 2 - ligand gated or receptor- operated ca channels (ROCC) 3 - stretch-activated

Question 29

some smooth muscles have unstable membrane potentials including ________ and __________ potentials

Answer 29

slow-wave and pacemaker

Question 30

membrane potentials _______ in smooth muscles

Answer 30

vary

Question 31

_____________________: chemical signals change muscle tension through signal transduction pathways with little or no change in membrane potential

Answer 31

pharmacomechanical coupling

Question 32

what are some ways chemical signals influence smooth muscle activity

Answer 32

- autonomic neurotransmitters and hormones - paracrine signals

Question 33

antagonistic control

Answer 33

both sympathetic and parasympathetic neurons influence smooth muscle

Question 34

tonic control

Answer 34

only a single autonomic branch controls smooth muscle

Question 35

chemical signal

Answer 35

different effects in different tissues with different receptors (hormonal control)

Question 36

most neurotransmitters and hormones act through:

Answer 36

G protein-linked receptors

Question 37

what are two examples of paracrine signals that influence smooth muscel

Answer 37

histamine constricts airways. nitric oxide dilates

Question 38

sympathetic + epinephrine + alpha receptor =

Answer 38

constriction of blood vessels, dilates etes, GI/bladder sphincters

Question 39

sympathetic + epinephrine + beta 2 receptors =

Answer 39

relaxes airways, wall of stomach, small intestine, and bladder, some blood vessels

Question 40

parasympathetic + acetylcholine + M receptors =

Answer 40

contracts airways relaxes GI/bladder sphincters relaxes via NO or CIP some blood vessels

Question 41

__________ must operate over a range of lengths

Answer 41

smooth muscle

Question 42

T or F: within an organ, the layers may run in several directions

Answer 42

T, like the stomach

Question 43

smooth muscles contract and relax more ________ than skeletal muscle

Answer 43

slowly

Question 44

smooth muscle uses ________ energy to generate and maintain a given force than skeletal muscle

Answer 44

less

Question 45

T or F: smooth muscle can sustain contractions for extended periods without fatiguing

Answer 45

T

Question 46

T or FL smooth muscles have small, spindle-shaped cells with multiple nuceli

Answer 46

F - single nucleus

Question 47

T or F: smooth muscle contractile fibers are arranged in sarcomeres

Answer 47

F

Question 48

Contraction in smooth muscle may be initiated by:

Answer 48

electrical or chemical signals or both

Question 49

T or F: smooth muscle is controlled by the somatic nervous system

Answer 49

F: autonomic

Question 50

T or F: smooth muscle lacks specialized receptor regions

Answer 50

T

Question 51

T or F: the Ca+ for contraction comes from the extracellular fluid as well as from the SR

Answer 51

T

Question 52

T or F: the Ca+ signal initiates a cascade that ends with phosphorylation of myosin light chain and activation of myosin ATPase

Answer 52

T