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(OMS1) CPR Exam 1 > Lecture 18: Smooth Muscle Physiology > Flashcards

Lecture 18: Smooth Muscle Physiology Flashcards

1
Q

Where can smooth muscle be found?

A
  • Gut
  • Respiratory Tract
  • Vasculature
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2
Q

What are some of the features (physiologically) of smooth muscle?

More thin or thick filaments than skeletal muscle?

NMJs?

Ca2+ bind what?

A
  • Can maintain contractions for long period of time
  • Maintain organ shape
  • Continuously generate active tension
  • Uses relatively little ATP
  • More thin filaments, less thick filaments
  • No. Uses varicocities
  • Calmodulin
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3
Q

What are the key features of a multi-unit smooth muscle?

A
  • Fibers operate individually
    • allows finer control
  • Innervated by a single nerve
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4
Q

What are some examples of multi-unit smooth muscle?

A
  • Ciliary muscles or eye
  • Iris
  • Piloerector muscles
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5
Q

What are the key features of unitary smooth muscle?

A
  • Syncytial or visceral
  • Work together as a unit
  • Cell membranes adhere to one another and contain gap junctions
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6
Q

Where can you find unitary smooth muscle?

A
  • GI Tract
  • Bile Ducts
  • Uterus
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7
Q

When smooth muscle contracs, what does actin attach to?

A

Dense Bodies/Adherens Junction

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8
Q

What is the latch mechanism?`

A
  • Phosphate is removed from myosin via myosin phosphatase
  • Actin and myosin are still latched together
  • This complex has LOW affinity for ATP
  • Remaining latched: the muscle can continue to generate active tension
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9
Q

What are the steps of smooth muscle contraction?

A
  1. Ca2+ enters cytosol thorugh Ca2+ channels in plasma membrane (much bigger effect than Ca2+ released from SR)
  2. Ca2+ binds to CaM and together they form REVERSIBLE Ca2+-CaM complex
  3. Ca2+-CaM complex activates MLCK (myosin light chain kinase)
  4. MLCK phosphorylates myosin
  5. Myosin-actin cross bridges can form and contraction can occur
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10
Q

What neurotransmitters can control smooth muscle?

What do they do?

A
  • Norepinephrine/Epinephrine: Adrenergic Receptors
    • α1: vasoconstriction
    • β2: vasodilation
  • Acetylcholine: Cholinergic receptors
    • Can be excitatory or inhibitory
    • Contraction is direct effect
    • Relaxation is indirect effect
  • Angiotensin II, Vasopressin, Endothelin: Contraction
  • Adenosine: Relaxation
  • Nitric Oxide: Relaxation
  • Other: CCK, oxytocin, serotonin, histamine
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11
Q

What neurotransmitters contract smooth muscle?

What neurotransmitters relax smooth muscle?

A

Contraction:

  • Norepinephrine/Epinephrine w/ α1 receptors
  • Acteylcholine (direct)
  • Angiotensin II
  • Vasopressin
  • Endothelin

Relaxation:

  • Norepinephrine/Epinephrine: β2
  • Acetylcholine (indirect effect)
  • Adenosine
  • Nitric Oxide
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12
Q

What is the NTX of skeletal muscle?

A

Acetylcholine

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13
Q

What environmental ques can cause vasodilation ino smooth muscle?

A
  • Will cause vasodilation:
    • Hypoxia
    • Excess CO2
    • Increased H+
    • Increased K+
    • Adenosine
    • ANP
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14
Q

What type of neurons innervate skeletal muscle?

A

Alpha motor neurons

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15
Q

How is the activity of smooth muscle locally controlled? What do they maniupulate? What activates them?

A
  • Spiked potentials: slow wave oscillations - control Ca2+ influx and K+ efflux in oscillating manner (pacemaker like) to control muscle contraction. Stimulated by hormones, NTs and stretch
  • Plateaus
    • stimulated by NT and stretch

Important for fine tuning

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16
Q

How can the smooth muscle cell maintain such long contractions?

A

Latch mechanism

17
Q

What is the transmission specialization of skeletal muscle?

A

NMJ

18
Q

What is the transmission specialization of smooth muscle?

A

Varicosities (bumps along the axon that contain neurotransmiiter vesicles)

NO NMJ*

19
Q

What is the NTX receptor on skeletal muscle?

A

nAChR

20
Q

What is the NTX receptor on smooth muscle?

A

mAChR or adrenergic

21
Q

Does skeletal muscle have any other NTX receptors?

A

NO

22
Q

Are there other smooth muscle receptors?

A

Yes

  • Blood bourne (ex: hormones)
  • Paracrine (ex: NO-)
  • Intrinsic (ex: enteric NS)
23
Q

What are the steps of smooth muscle relaxation?

A
  1. Myosin phosphatase dephosphorylates myosin
  2. Ca2+-CAM complex dissociates
  3. Ca2+ transported out of the cell (via Na+/Ca2+ exchanger) or pumped back into the SR (via Ca2+/ATPase)
  4. CAM hangs out in the smooth muscle cell
24
Q

Why does smooth muscle use ATP at a slower rate than skeletal muscle?

A

Cross bridge formation is slower in smooth muscle

25
Q

What is active tension? (very general sense)

A

What the cross bridges do

There is an optimal range of active tension for both smooth and skeletal muscle

26
Q

What is passive tension? (very genrally speaking)

A

How individual muscle cells are able to stretch their membranes

27
Q

What is important about passive tension?

A

Limits the muscles ability to continue stretching despite increases in length (this helps prevent injury)

28
Q

What is unique about smooth muscle regarding passive tension?

A
  • Once actin and myosin release maximum passive tension, the smooth muscle cell can reduce its tension back to zero via rearrangement of the dense bodies and cell as a whole
  • This enables smooth muscle to maintain contractions for long periods of time
29
Q

Identify the red and blue lines on each graph.

Which type of muscle is represented by each graph?

A

Left: Skeletal muscle cell

  • Blue: active tension
  • Red: passive tension

Right: Smooth muscle cell

  • Blue: active tension
  • Red: passive tension

(OMS1) CPR Exam 1 (30 decks)

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