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PHYSL 212 > SMOOTH MUSCLE > Flashcards

SMOOTH MUSCLE Flashcards

1
Q

what are smooth muscle thin filaments made of

A

actin

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2
Q

what are smooth muscle thick filaments made of

A

myosin

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3
Q

why are there no striations in smooth muscle

A

lack of organization

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4
Q

how are actin filaments oriented

A
  1. parallel to long axis

2. oblique to long axis

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5
Q

what are dense bodies

A

electron dense regions where actin filaments come together

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6
Q

how are thick and think filaments organized

A

thick filaments interspersed bw thin filaments

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7
Q

what structure in skeletal muscle are dense bodies similar to

A

Z lines

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8
Q

what are thin filaments in smooth muscle lacking

A

troponin

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9
Q

what is the function of enzyme myosin light chain phosphates in smooth muscle

A

terminate contraction

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10
Q

what are 2 types of smooth muscle

A
  1. multi unit

2. unitary

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11
Q

where does unitary smooth muscle occur

A

large sheets

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12
Q

what connects individual smooth muscle cells in unitary

A

gap junctions

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13
Q

how does unitary smooth muscle function

A

as one.

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14
Q

how does multi unit smooth muscle differ from unitary

A

individual units not connected by gap junctions

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15
Q

what does lack of gap junctions in multi unit smooth muscle result in

A

little electrical coupling

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16
Q

MULTIUNIT what innervates multiunit smooth muscle

A

ANS

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17
Q

MULTIUNIT what do axons of post ganglionic fibre contain

A

branches

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18
Q

MULTIUNIT what do branches of post ganglionic fibre contain

A

vricosities

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19
Q

MULTIUNIT what do varicosities contain

A

transmitter

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20
Q

MULTIUNIT where does transmitter get released

A

surface of smooth muscle cells

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21
Q

UNITARY what innervates unitary smooth muscle

A

ANS

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22
Q

what causes spont electrical activity in smooth muscle cells

A

pacemaker potential

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23
Q

what does spont electrical activity result in

A

slow waves / regular oscillations in mem potential

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24
Q

what happens in step one of slow waves

A
  1. voltage gated Ca channels open

2. Ca moves into cell causing depol

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25
Q

what happens in step two of slow waves

A
  1. mem potential depolarizes to threshold
  2. AP causes more Ca influx
  3. AP causes contraction of smooth muscle
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26
Q

what happens in third step of slow waves

A
  1. intracellular Ca concentration increases
27
Q

what happens in forth step of slow waves

A
  1. Ca dependent K channels open
28
Q

what happens in fifth step of slow waves

A
  1. K moves out of cell causing hyper polarization
29
Q

what is sixth step of slow waves

A
  1. Ca channels close during hyper polarization

2. intracellular Ca concentration decreases

30
Q

what happens in seventh step of slow waves

A
  1. Ca dependent K channels close

2. Cell becomes less hyper polarized (K ions not leaving)

31
Q

what initiates cross bridge cycling in smooth muscle

A

Ca dependent phosphorylation of myosin

32
Q

in smooth muscle when are myosin heads able to bind to actin filaments

A

when light chains phosphorylated

33
Q

how is cross bridge cyclin initiated in smooth muscle

A
  1. 4 Ca binds to calmodulin
  2. Ca - calmodulin activates myosin light chain kinase
    3 myosin light chain kinase phosphorylates regulatory light chain
  3. myosin undergoes conformational change
34
Q

what is the function of Ca in smooth muscle

A

induce chemical change in myosin

35
Q

wha tis the function of Ca in skeletal muscle

A

induce physical change in actin

36
Q

what is Ca binding protein in smooth muscle // what is Ca binding protein in skeletal muscle

A

calmodulin // troponin

37
Q

which type of muscle (skeletal or smooth) is cross bridge cycling initiated sooner

38
Q

what is the function of calponin and caldesmon

A

tonically inhibit interaction bw actin and myosin

39
Q

how can relaxation be induced in smooth muscle

A
  1. de phosphorylating regulatory myosin light chains

2. decreasing Ca levels in cyto

40
Q

what is responsible for myosin light chain de phosphorylation

A

myosin light chain phosphotase

41
Q

what are sources of Ca in smooth muscle

A
  1. Ca can enter cyto through voltage dependent channels (in response to depol)
  2. Ca can enter cyto through voltage -independent channels
  3. Ca can enter cyto from SR
42
Q

VOLTAGE DEPENDENT what is voltage dependent Ca channel in smooth muscle

A
  1. L type Ca channel
43
Q

VOLTAGE DEPENDENT how does L type Ca channel work

A

depol causes influx of Ca

44
Q

VOLTAGE INDEPENDENT what are voltage independent channels in smooth muscle

A
  1. ligand gated channel

2. store-operated Ca channel

45
Q

VOLTAGE INDEPENDENT where are ligand gated channels located

A

mem of smooth muscle cell

46
Q

VOLTAGE INDEPENDENT how does ligand gated channel work

A

ligand binding cuases influx of Ca

47
Q

VOLTAGE INDEPENDENT when are store-operated Ca channels opened

A

Ca levels in SR depleted

48
Q

VOLTAGE INDEPENDENT where are store-operated Ca channels located

A

mem of smooth muscle cell

49
Q

VOLTAGE INDEPENDENT what happens when store-operated Ca channels open

A

influx of Ca

  • increases intracellular Ca levels
  • replenishes SR Ca levels
50
Q

CA RELEASE FROM SR what is Ca release channel of SR in smooth muscle

51
Q

what is lacking in smooth muscle

A

t tubule system

52
Q

what in smooth muscle is similar to t tubules

53
Q

what channel is located in calveoli

A

volrage gated Ca channels

54
Q

CA RELEASE FROM SR what are 2 methods of Ca release

A
  1. calcium induced calcium release (ryanodine receptors)

2. IP3 activation (ligand gated channels in mem of SR)

55
Q

CA RELEASE FROM SR how does calcium induced calcium release work

A
  1. Ca enters cell through voltage gated Ca channels

2. Ca acts on ryanodine receptors to cause release of more Ca

56
Q

CA RELEASE FROM SR how does OP3 activation work

A
  1. ligand binds G protein coupled receptor
  2. IP3 activates
  3. IP3 acts on ligand gated channels in mem of SR
57
Q

what are mechanisms of reducing Ca levels in cyto

A
  1. NCX
  2. PMCA
  3. SERCA
  4. calceriticulin
58
Q

LATCH BRIDGE MECHANISM what is latch bridge mech

A

myosin heads remain attached to actin even after Ca conc falls (i.e. during relaxation)

59
Q

LATCH BRIDGE MECHANISM what does decreased rate of detachment allow

A
  1. lower rate of cross bridge cycling

2. lower rate of ATP hydrolysis

60
Q

LATCH BRIDGE MECHANISM what is result of cross bridge cycling

A

sustained contraction without expenditure of en

61
Q

what is mech of excitation in skeletal muscle

A

neuromuscular transmutation

62
Q

what is mech of excitation in cardiac muscle

A
  1. pace maker

2. gap junctions

63
Q

what is mech of excitation in smooth muscle

A
  1. synaptic transmission
  2. hormone receptors
  3. gap junctions

PHYSL 212 (22 decks)

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