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Flashcards in 10 Smooth Muscle Deck (37):
1

phasic contraction

contraction followed by relaxation

2

tonic contraction

sustained contraction

3

features of smooth muscle (5)

1/ uninuclear
2/ no striations
3/ no T-tubules
4/ lots of caveolae
5/ numerous cell-to-cell junctions

4

dense bands from adjacent cells combine to form

intermediate junctions (mechanical coupling) - for transmission of force between cells

5

a gap junction provides

electrical (ionic) coupling

6

major storage site for Ca2+ ions in smooth muscle

SR

7

2 receptors in the SR

IP3 and ryanodine

8

binding of IP3 to its receptors allows

release of intracellular Ca2+ needed for contraction

9

three types of myofilaments in smooth muscle

actin, myosin, intermediate

10

thin filaments contain

actin, tropomyosin
calponin, caldesmon
NO TROPONIN!

11

instead of troponin, smooth muscle has

calponin and caldesmon

12

thick filaments are composed of

two heavy chain subunits
two light chain subunits

13

intermediate filaments are

a cytoskeletal component

14

neurotransmitters that cause contraction

excitatory transmitters

15

neurotransmitters that cause relaxation

inhibitory transmitters

16

these are also not present in smooth muscle

NMJs

17

multi-unit smooth muscle

-neurogenic (requires nerve stimulus to initiate contraction, like striated muscle)
-walls of large blood vessels, large airways of respiratory tract, eye muscles

18

single unit (unitary) smooth muscle

-arranged in sheets; sheets act as a single unit
-sparsely innervated
-electrically coupled via gap junctions

19

pacemaker regions contain these special cells

Interstitial cells of Cajal (ICC)

20

cross-bridges (for sliding filament mechanism) project from the ___ filaments

thick filaments

21

myosin light chains must be ____

phosphorylated

22

this enzyme is responsible for myosin phosphorylation

myosin light chain kinase (MLCK)

23

myosin light chain kinase (MLCK) requires these two things for activity

calcium and calmodulin

24

this initiates smooth muscle contraction

calcium-dependent phosphorylation of myosin light chain

25

MLC dephosphorylation occurs via

myosin light chain phosphatase (MLCPase)

26

for smooth muscle contraction, increase this, decrease that

increase MLC-p
increase MLCK
decrease MLCPase

27

for smooth muscle relaxation, increase what decrease what

decrease MLCK
decrease MLC-p
increase MLCPase

28

increased cytosolic ____ activates myosin light chain kinase (MLCK)

calcium

29

electro-mechanical coupling is when

depolarization of the membrane leads to opening of voltage-gated Ca2+ channels, followed by increase in cytosolic Ca2+

30

these receptors on the SR are stimulated to release more Ca2+ via calcium-induced-calcium release

ryanodine receptors (RyR)

31

pharmaco-mechanical coupling of smooth muscle

binding of an agonist on the membrane leads to elevation in cytosolic Ca2+ without any change in membrane electrical potential

32

pharmaco-mechanical pathway involves

G-q (heterotrimeric G protein)
PLC-B1
IP3
DAG

33

in the pharmaco-mechanical pathway, IP3 binds to its receptor ____ on the SR which does this:

IP3R, to release calcium

34

smooth mm relaxation results from reduction in cytosolic ____

calcium

35

second messengers involved in smooth muscle relaxation

cAMP and cGMP

36

For smooth muscle relaxation, cAMP is stimulated by

B-adrenergic activators (adrenalin)

37

for smooth muscle relaxation, cGMP is stimulated by

NO