Smooth Muscle Flashcards
1
Q
what kind of organ are smooth muscles a major component of
A
hollow organs
2
Q
sustained contraction is synonymous with
A
tonic contraction
3
Q
functionally what are the two ways smooth muscles can be classified
A
phasic or tonic
4
Q
what are examples of places smooth muscle would contract phasically
A
esophagus, urinary bladder
the smooth muscles contracts, for example w/ bladder, depending on volume
5
Q
what are examples of smooth muscles tonically contracted
A
sphincters
don’t want to poop yourself!
6
Q
compare energy required for smooth muscle vs. skeletal muscle
A
MUCh less energy required for smooth muscle.
1/10 - 1/300
7
Q
what do smooth muscle cells NOT possess that skeletal does
A
troponin c
t tubules
8
Q
describe the physical properties of smooth muscle cells
A
individual, long, mononucleate, they have actin, myosin, tropomyosin
9
Q
what links smooth muscle instead of z line
A
dense bodies
10
Q
are their sarcomeres in smooth msucle
A
no, not distinct
11
Q
what are contractile units made up of in smooth muscle
A
interdititating thick and thin filaments connected by dense bodies
12
Q
contraction in smooth muscle is based on
A
thick and thin filaments sliding over each other
13
Q
dense bodies serve same role as what in smooth msucle
A
z disks
14
Q
what are intermediate junctions
A
where multiple cells meet and are connected via dense bodies
15
Q
are smooth muscle cells connected via gap junctions
A
yes
16
Q
describe concentration of ATPase in smooth msucle compared to skeletal
A
smooth muscle has less, but it can contract more strongly than skeletal
17
Q
are there t tubules in smooth muscle
A
no
18
Q
describe the SR in smooth muscle
A
less developed than in skeletal
still stores and releases calcium
19
Q
what plays the majority role in calcium release to smooth msucle
A
extracellular calcium, SR has a more minor role
20
Q
what are the two different physiological classifications of smooth muscle
A
multi-unit
single unit
21
Q
describe qualities of multi-unit smooth muscle
A
no gap junctions
no spontaneous contraction
activated by extrinsic innervation or hormonal diffusion
each smooth muscle cell receives its own synaptic input
rarely have AP
local depol is what causes contraction
22
Q
what are examples of plces in body with multi-unit smooth muscle
A
iris muscle of eye
ciliary muscle of eye
vas deferens
piloerector muscles
23
Q
what are the other ways to say single-unit smooth muscle
A
unitary
visceral
syncytial
24
Q
what are characteristic of single-unit smooth muscle
A
all cells coordinate when they contract Gap junctions! spontaneously active dont need extrinsic innervation to contract they can self excite AP normally occur muscle must depol before AP RMP is more pos. than skeletal muscle
25
what are examples of places in body with single-unit smooth muscle
```
GI tract
bile ducts
bladder,
ureter
uterus
blood vessels
```
26
what are the three ways AP can occur in visceral smooth muscle
spike potential
action potentials with plateaus
slow wave potentials
27
visceral smooth muscle means
single unit smooth muscle
28
describe a spike potential
it is what is seen in skeletal muscle
duration of AP 10-50 msec
can be elicited via electrical, hormones, transmitters, stretch, spontaneous generation in muscle fiber itself
29
what can elicit a AP in spike potential
electrical, hormones, transmitters, stretch, spontaneous generation in muscle fiber itself
30
draw a spike AP
pg 10
31
describe AP with plateaus
onset timilar to spike AP
delayed repolarization
so ultimately longer AP
32
draw out AP with plateaus
pg 11
33
describe AP with slow wave potentials
this is what produces tonic muscle contraction
it is not AP but the membrane gets depol and repol slowly, but not enough to make AP.
there can be AP on top of peak
the waves will still produce weak contraction (tonic)
gap junctions
34
what is another way to say slow wave potential
basic electrical rhythm
35
What does BER stand for
basic electrical rhythm
36
frequency of slow waves vary with
location of the smooth muscle
37
what generates the slow waves
interstitial cells of cajal
38
draw out slow wave potential
pg 12
39
once interstitial cells of cajal make slow wave, how is it spread across the smooth msucle
gap junctions
40
interstitial cells of cajal are considered what
pacemaker cell in smooth muscle
41
smooth muscle is innervated extrinsically by
ANS
42
smooth musle is innervated intrinsicly by
enteric neural plexi
43
are there structurally specialized end plates in smooth muscle
no
44
action or spike potentials are generated in response to:
Neural stimulation (shown below)
Hormonal stimulation
Stretching the muscle
45
in longitudinal smooth muscle what regulates the syncytial activity
interstitial cells & myenteric plexus
46
what is the major exception b/w contraction of smooth msucle vs. skeletal
smooth muscle: much slower contractile velocity
47
why does smooth muscle have a slow contractile velocity
slow ATPase activity - so rate of activatoin
| number of crossbridge interactions
48
in smooth muscle, what does calcium bind to
calmodulin (CM)
49
what does CM stand for
calmodulin
50
what two enzymes are specific for contraction in smooth muscle
myosin light chain kinase
| myosin light chain phosphatase
51
look up video on smooth muscle contraction and draw diagram
:D
52
whatt is function of myosin light chain kinase
phosphorylates regulatory site on light chain of myosin
53
what is function of myosin light chain phosphatase
dephosphorylates regulatory site on light chain of myosin
54
describe the order of what happens in smooth muscle one calcium enters
it binds to calmodulin
myosin light chain kinase phosphorylates → phosphorylates myosin → crossbridge → catalyze ATP dependent actin and myosin sliding
to turn off: dephosphorylate via mysoin light chain phosphatase
55
what does MLCK stand for
myosin light chain kinase
56
when MLCk is actie what specifically does it do
phosphorylate myosin head of thick filaments so they can interact with actin thin filaments
57
describe phasic contraction
twitch-like shortening followed by relaxation
58
describe tonic contraction
force sustained for long period
59
describe how tonic contractions work
calcium enters and initiates phosphorylation and contraction, then calcium levels fall and it just keeps sustaining that contraction
60
in smooth muscle, release of Ca from SR is function of
second messenger, IP3
61
how is calcium taken out of the cell
ATP calcium pump
| Na-Ca exchanger
62
Draw the DAG/PIP pathway and how it relates to calcium
pg 23
63
how does smooth muscle couple excitation to contraction
sarcolemma depol → voltage gated calcium channels
chemical agents → neutotransmitters and hormones bind to release calcium
stretch → stretch sensitive calcium channels opened on sarcollema
64
an increase in tension in smooth muscle will result in
depolarization
65
describe Vmax and Fmax in smooth muscle compared to skeletal
force velocity relationship
Vmax low
Fmax the same
66
list the similarities b/w smooth and skeletal muscle
Actin and myosin required for cross-bridge cycling
Myosin head contains binding site for actin
Blocked when Ca2+ levels are low
Open when Ca2+ binds to troponin or calmodulin
Binding of actin and myosin causes
ATP energy release from myosin ATPase
Cycling of the cross-bridges
67
does phasic contraction last long
no
68
tonic contractions will be contracted until
there is signal telling it to relax
69
draw graph for patterns of contraction in differnt smooth muscles
pg 4
70
in blood vessels there is always some
tone/tonic contraction
71
why do blood vessels always have some tone
to work against the pressure of blood flowing through it
72
smooth muscle cells don't use as much
ATP
73
which is more efficient smooth or skeletal muscle
smooth
74
what are all the pits in the pic of smooth muscle
caveoli - more extensive in smooth muscle
75
what are all the lines in the pic of smooth muscle
actin and myosin
76
skeletal muscle has very extensive
intracellular membrane network of SR
77
Is SR well developed in smooth muscle
no
78
dense bodies
contain α-actinin as found in Z lines in skeletal muscle, and anchor actin filaments to form diagonal lattice of contractile units
79
membrane-associated dense bodies
appear to serve as anchors for thin filaments and transmit the force of contraction to adjacent cells.
80
intermediate filaments in smooth muscle
contain desmin and hold dense bodies in place
81
visceral smooth msucle have high degree of
gap junctions
| want to act in same time frame as functional unit
82
thick filaments in smooth muscle
contain myosin
83
thin filaments in smooth muscle
contain actin and tropomyosin (no troponin complex*)
84
in multiunit there is direct
innervation of each cell
85
single unit smooth muscle has modulation of activity but it's not
innervating every one
| it has gap junctions
86
What modultes and regulates single unit smooth msucle
ANS
87
depending on size of amplitude of slow wave potential determines
how much tensino you get
88
variscosity
where transmitter is stored
| in synaptic vessicles and released b/c of AP
89
plateau in unitary smooth muscle due to
voltage gated potassium channels
90
what is BER
depolarization, repolarization, about 35 mv
91
what is the mv of the BER
about 35 mv
92
sometimes during BER it will reach thershold (hormones, stretch, etc.) and what will happen
amplitude will change and get AP on top of it
93
when smooth muscle contraction is must more forceful what is happening
AP created in BER
94
frequency of BER based on activity of
ICC (interstitial cells of cajal)
95
stomach BER
3/min
96
SI BER
11-12/min
97
colon BER
2-13/min
98
why is there high freq in SI
reuptake, moving everything along
99
ICC stands for
interstitial cells of cajal
100
in between long muscular and circular muscular layer are
ICC
101
ICC are in communication with
muscles that modulate and determine activity of the smooth muscles
102
in most regions frequency of ICC
same frequency
103
how is slow wave amplitude modified
ex: responding to Ach
104
the more Ach that comes in the more
AP
105
the more spike potentials on top of cell wave the
stronger the contraction will be
106
ex of parasympathetic stimulation
Ach
107
EC coupling in smooth muscle, what are entyr pathways
calcium
108
calcium doesn't bind to what in smooth
troponin c
109
what does calcium bind to in smooth muscle
calmodulin
110
what has to occur in order to stimulate myosin light chain kinase
calcium bind to calmodulin
111
in smooth musle what direction is it contraction
myosin heads are all different direction so you get contraction all over
112
to relax smooth muscle have
dephosphorylate
113
how many molecules of ATP for every cycle in smooth muscle contraction
2
114
what dephosphorylates myosin
myosin light chain phosphatase
115
calcium is pumped out of cell and exchanged for ____ when repolarizing
sodium
116
draw pic for the way myosin heads contract in smooth muscle
pg 20
117
you can get calcium release from SR to assist with EC coupling, but it's not
the major pathway
118
latch-bridge formation
producing force development and maintain the force for long period of time b/c have decreased number of activated crossbridges that are not using as much energy
119
if intracellular calcium down b/c of long stimulation will get
latch-bridge formation
120
if dephosphorylate all myosin get
complete repolarization
121
what are all the ways calcium can enter cell in smooth muscle
voltage gated calcium channel
leak channels
ligand gated channels
agonist or ligrand gated channels taht go through g proteins (DAG/IP3)
122
how does calcium leave cell in smooth muscle
calcium ATPase
sodium calcium exchanger
calcium ATPase in SR
123
smooth muscle has more ability to have different proload and operates in wider range meaning it can
accommodate different volumes
