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Block 5 Material > Phys - Smooth Muscle > Flashcards

Phys - Smooth Muscle Flashcards

1
Q

What is missing in smooth muscle?

A

Sarcomeres
T-tubules or terminal cisternae

SR is poorly developed
-still functions, but extracellular Ca++ is needed

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2
Q

Caldesmon and Calponin

A

Actin binding proteins that are modulatory of ATPase

Probably not primary control proteins

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3
Q

Unlike skeletal muscle, smooth muscle does not have which troponin unit?

A

Troponin I

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4
Q

Classification of smooth muscle units

A

Single unit (visceral or unitary)

Multi unit

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5
Q

Single unit smooth muscle characteristics

A

Behaves in a syncytial manner
-All the cels of the single unit act together

Tends to have many gap junctions

Relatively sparse innervation

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6
Q

Organs with single unit smooth muscles

A 
Small intestine
Colon
Bladder
Uterus 
Ureters

Lymph vessels
Precapillary sphincters

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7
Q

Do single unit smooth muscles have fast or slow wave potentials?

A

Slow

Sometimes cause contractions, sometimes do not

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8
Q

Action potentials of single unit smooth muscles

A

Spikes

All or none
Almost always contraction
More spikes = stronger contraction

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9
Q

Slow stretch vs fast stretch of single unit smooth muscle

A

Slow = lengthening

  • ex: bladder capacity w/o pressure increase
  • plasticity or stress relaxation

Fast = contraction
-ex: smallest arterioles or precapillary sphincters

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10
Q

Organs with multi unit smooth muscle

A 
Ciliary muscle
Iris
Tracheal muscle
Bronchial muscle
GI sphincter
Vas deferens

Resistance vessels
Larger arterioles

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11
Q

Multi unit smooth muscle characteristics

A

Each cell acts independently (like skeletal muscle)

Less gap junctions

Higher innervation ratios than single unit

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12
Q

True or false: multi unit smooth muscle does not have action potentials.

A

True

Typically

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13
Q

High progesterone effect of smooth muscle

A

Reduce gap junctions in myometrial smooth muscle during pregnancy

  • causes myometrium to behave more like non-innervated multiunit smooth muscle
  • myometrial muscle remains relatively inactive/dormant/quiescent
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14
Q

Effects of rising estrogen levels on smooth muscle

A

Hypertrophy

Increase gap junctions

Myometrial behaves more like a single unit
-parturition

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15
Q

Morning sickness is caused by__

A

Reduced number of gap junctions by high levels of progesterone

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16
Q

High levels of cAMP cause __

A

Relaxation

by lowering MLCK concentration

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17
Q

In smooth muscle latch state:
Efficiency is ___
Economy is ___

A

Efficiency is low
ATP required for control and cross bridge cycling

Economy is high
Absence of shortening
Maintain tone with minimal use of ATP

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18
Q

Na+ / Ca++ exchanger

A

3 Na+ / Ca++

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19
Q

Phospholamban inhibits __

A

Ca++ ATPase

Phosphorylation of PLB relaxes

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20
Q

Testing membrane potential of smooth muscle

A

-55 mV

Due to high Na+ leak

Inward Ca++ current

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21
Q

Smooth muscle has (a lot of, or few) voltage-gated Na+ channels?

A

Few

  • fast channels
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22
Q

L-type Ca++ channels

A

Long acting
Slow

Depolarization: ⬆️ intracellular Ca++

Hyperpolarization: ⬇️ intracellular Ca++

Can be blocked by Ca++ channel blockers

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23
Q

T-type Ca++ channels

A

Fast

Not blocked by Ca++ channel blockers

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24
Q

How is smooth muscle unique in activation?

A

Neurotransmitters, hormones, and drugs can lead to contraction and relaxation

25
Q

cAMP causes PKA-dependent phosphorylation of ___ which causes __

A

Phospholamban

Increased Ca++ reuptake at the SR

RELAXATION

26
Q

NO and ANP are part of

A

cGMP-dependent relaxation

Decreased myosin light chain phosphorylation

27
Q

IP3 actions

A

Releases intracellular Ca++ stores

28
Q

PLC-dependent contraction is mediated by __

A

Gq (m1,3,5 and alpha 1 adrenergic)

29
Q

DAG activates __

A

PKC

Phosphorylates myosin light chains?
L-type Ca++ channel phosphorylation

30
Q

ATP sensitive K channels
When are the closed?
Open? Mechanism?

A

Closed when [ATP]i is normal

Opens in ischemia (⬇️ ATP)

  • K+ influx = hyperpolarization
  • voltage sensitive Ca++ channels close
  • intracellular Ca++ decreases
  • smooth muscle relaxes
31
Q

Ligand operated G protein coupled K channels - mechanism

A

Agonists :
ACh, m2
Adenosine, A1

Activates G alpha 1 type G protein

G alpha 1 binds IK(ACh) channel
K+ channels open
K+ efflux
Hyperpolarization
L-type Ca++ channels close
Relaxation occurs
32
Q

Intermediate filaments of smooth muscle

2 protein components

A

Desmin

Vimentin

33
Q

Dense bodies contain ___
These are functionally analogous to ___
They anchor __

A

Actinin
Z lines
Actin

34
Q

____ allow communication between adjacent smooth muscle cells

A

Gap junctions and

Mechanical junctions

35
Q

Smooth muscle contains no __

A

T tubules
Terminal cisternae
Sarcomeres
Troponin

36
Q

Actin/myosin ratio in skeletal vs smooth muscle

A

Skeletal 2:1

Smooth 10:1

37
Q

Actin binding proteins whose phosphorylation can affect ATPase and modulate smooth muscle contraction

A

Caldesmon

Calponin

38
Q

Light chains serve and essential regulatory function in ___ muscle but not ___ muscle

A

Smooth

Skeletal

39
Q

Smooth muscle myosin is thought to be organized in a ___ arrangement whereas skeletal is ___

A

Side-polar
Bipolar

*contributes to smooth muscles lack of well defined sarcomeres

40
Q

What type of smooth muscle is

Small intestine

A

Single unit/Visceral

41
Q

What type of smooth muscle is

Uterus

A

Single unit:Visceral

42
Q

What type of smooth muscle is
Ciliary muscle
Iris muscle

A

Multi unit

43
Q

What type of smooth muscle is

  1. Large blood vessels
  2. Small blood vessels
  3. Lymph vessels
A
  1. Multi unit

2-3. Single unit/Visceral

44
Q

What type of smooth muscle is

Colon

A

Single unit/visceral

45
Q

What type of smooth muscle is
Urinary bladder
Ureters

A

Single unit/visceral

46
Q

What type of smooth muscle is
Bronchial muscle
Trachial muscle

A

Multi unit

47
Q

What type of smooth muscle is

GI sphincters

A

Multi unit

48
Q

What type of smooth muscle tends to have many gap junctions and sparse innervation?

A

Single unit/visceral

49
Q

True or false:

Multi unit smooth muscles do not typically display APs when stimulated to contract

A

True

50
Q

Explain “stress relaxation”

A

Slow stretch of single unit

Bladder stretches and holds urine without increasing pressure

51
Q

Regulation of smooth muscle contraction occurs on ___

*skeletal?

A

Thick filaments
Myosin
*thin filament

52
Q

Ca binds ___ and this complex binds ___, and this complex does what?

A

Calmodulin
MLCK
-phosphorylates a serine residue on 2 of the light chains

53
Q

If MLCK is high___

A

Myosin is largely phosphorylated and has high ATPase activity
High Ca levels

54
Q

Constant and stable low level of contraction.

Seen in what organs?

A

Tone
GI sphincters
blood vessels

55
Q

True or false:

Smooth muscles shorten during the latch state.

A

False

56
Q

Efficiency is ___ in smooth muscle

Economy is ___

A

Low

High

57
Q

Low levels of ___ cause relaxation in smooth muscle

A

Phosphorylated myosin light chains

58
Q

Ca is removed from the cell by ___

A

Sarcolemma 3 Na/Ca exchanger

Ca ATPase

59
Q

Resting membrane potential of smooth muscle is

A

-55

Block 5 Material (17 decks)

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