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My CP 2 > Phys 5 > Flashcards

Phys 5 Flashcards

1
Q

What are the characteristics of multi-unit smooth muscle?

A
  • the fibers operate individually (one nerve for multiple cells)
  • examples: ciliary muscles of the eye, iris…
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2
Q

What are the characteristics of unitary smooth muscle?

A
  • visceral smooth muscle or syncytial
  • work together as a unit
  • cell membranes there and contain gap junctions
  • the type we mainly see in CP
  • examples: GI tract, bile ducts, uterus…
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3
Q

Where does actin attach in smooth muscle?

A

dense bodies

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4
Q

What is unique about the myosin heads in smooth muscle?

A

they are bidirectional

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5
Q

Which has more actin: smooth or skeletal? myosin?

A
  1. smooth

2. skeletal

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6
Q

What is unique about the timing of smooth m. events?

A
  1. the myosin cross bridge cycling is slower
  2. the time myosin and actin are attached is longer (allows for greater contraction)

*this means that ATP demand is low (latch mechanism)

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7
Q

What replaces troponin in smooth m.?

A

calmodulin (CaM)

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8
Q

What can lead to increased Ca2+ in the cytosol?

A
  1. Nerves
  2. Hormones
  3. Environmental factors
  4. Stretch
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9
Q

How does calcium enter the cell?

A

Ca2+ L type channels

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10
Q

Calcium Entry Mxns

A
  1. Sarcolemmal
    a. L type voltage gated Ca2+ channels
    b. Receptor activated Ca2+ channels (ligand gated)
  2. SR
    a. InsP3 receptors
    b. RYRs
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11
Q

Calcium Exit Mxns

A
  1. SERCA
  2. 3 Na/Ca antiporter
  3. Sarcolemmal Ca2+ ATPase
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12
Q

How does Calcium bind to CaM?

A

reversibly (it has 4 binding sites, and once Ca2+ binds it changes conformation and binds to actin/tropomysoin)

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13
Q

What does CaM activate?

A

-Myosin light chain kinase, which phosphorylates light chain of myosin, and this leads to the heavy chain being more active

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14
Q

What is contraction strength generally proportional to?

A

Ca2+ levels

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15
Q

What two mxns allow for smooth m. relaxation?

A
  1. Ca2+ pumps (remove the Ca2+)

2. Myosin light chain phosphatase (remove phosphate group from light chain)

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16
Q

What is the difference between depolarization and hormones/NTs in Ca2+ entry? Similarity?

A
  1. Depolarization uses voltage gated and H/NTs use ligand gated
  2. They both induce Ca2+ release from the SR
17
Q

What two ways can hormones/NTs release Ca2+?

A
  1. Ligand gated channels

2. IP3

18
Q

What are varicosities?

A

bulges on nerves that they serve as NT release sites (can release ACh and more)

19
Q

Control of Smooth M:

  1. NE and Epi
  2. ACh
  3. Angiotensin II/vasopressin/endothelin I
  4. Adenosine
  5. NO
  6. CCK/Oxytocin/Serotonin/Histamine
A
  1. excitatory or inhibitory depending on receptors at target organ
  2. excitatory or inhibitory depending on organ (contraction is direct effect; relaxation can be indirect)
  3. contraction
  4. relaxation
  5. relaxation
  6. just listed
20
Q

Environmental Controls of Smooth muscle

A

Hypoxia, excess CO2, increased H+, adenosine, LA, increased K+…—-> common vasodilators (common release is exercise)

21
Q

What is the sequence of events on a G protein coupled pathway?

A

GPCR–>PLCy1–>PIP3–>IP3–>release of Ca2+ from SR

22
Q

What is the RPM of smooth m?

A

-50 to -60 mV

23
Q

What type of smooth m. can have APs?

A

unitary

24
Q

What is a spiked potential?

A
  • the spikes on top o the waves

- stimulated by hormones, NTs, stretch, spontaneous…

25
Q

What are slow waves stimulated by? Plateaus?

A
  1. Oscillating Ca2+ influx (L type VGCCs) and K+ efflux (Ca2+ activated K+ channels)
  2. Stimulated by NTs and stretch
26
Q

When do Ca2+ dependent K+ channels open?

A

with accumulation of Ca2+ (goal is to prepare for repolarization)

27
Q

What ion is most important in smooth m. APs?

A

Ca2+ (way bigger of a player than Na+)

28
Q

Latch mxn

A
  • a way to increase tension while decreasing ATP usage
  • dephosphorylation of the light chain
  • attached cross bridges are still generating tension because they are still attached and have low affinity for ATP
29
Q

What thin filaments are in skeletal m? smooth?

A
  1. Actin Tropomyosin, troponin

2. Actin, Tropomyosin

30
Q

What’s the innervation of skeletal m? smooth?

A
  1. alpha motor neuron

2. Multiple (intrinsic, extrinsic (ANS))

31
Q

What’s the difference between NMJ in skeletal vs. smooth?

A

skeletal has one, and smooth does not (varicosities)

32
Q

NT receptors in skeletal? smooth?

A
  1. Nicotinic cholinergic

2. Muscarinic cholinergic, adrenergic…

33
Q

Are APs required for both skeletal and smooth m?

A

nope, only for skeletal

*smooth can used pacemaker activity, IP3, hormonal

34
Q

Why do we want smooth muscle?

A
  1. to maintain contraction
  2. contract periodically
  3. maintain organ shape
  4. continue to generate active tensility
  5. use relatively little ATP
35
Q

Other forms of activation for skeletal? smooth?

A
  1. None

2. Paracrine, blood born, intrinsic

36
Q

Steps of Smooth m. Contraction

A
  1. Ca2+ enters cytosol through PM Ca2+ channels (a little from SR)
  2. Ca2+ binds reversibly to CaM
  3. CaM-Ca2+ complex activates myosin light chain kinase (MLCK)
  4. Phosphorylated MLCK allows myosin and actin binding
  5. Relaxation
37
Q

What is the key regulator for smooth m. relaxation?

A

myosin phosphatase because it removes phosphate from myosin (inactivates it)

38
Q

What’s the difference between active and passive tension?

A
  1. what the cross bridges do

2. stretching of the muscle cell membrane

39
Q

What is another name for Dense bodies?

A

adheren junctions

My CP 2 (20 decks)

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