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Cardiopulmonary Exam 2 > Smooth Muscle Physiology > Flashcards

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?

A
  • Can maintain contractions for long period of time
  • Maintain organ shape
  • Continuously generate active tension
  • Uses relatively little ATP
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3
Q

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

A
  • FIbers operate individually
  • 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

What type of neurons innervate skeletal muscle?

A

Alpha motor neurons

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8
Q

What is the innervation of smooth muscle?

A
  • Can be intrinsic or extrinsic
    • Intrinsic (IE: Enteric NS)
    • Extrinsic (IE: Stretch)
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9
Q

What is the NTX of skeletal muscle?

A

ACh

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10
Q

What is the NTX of smooth muscle?

A
  • ACh
  • NE
  • Epi
  • NO- (more of a paracrine agent)
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11
Q

What is the transmission specialization of skeletal muscle?

A

NMJ

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12
Q

What is the transmission specialization of smooth muscle?

A

Varicosities (bumps along the axon that contain ntx vesicles)

NO NMJ*

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13
Q

What is the NTX receptor on skeletal muscle?

A

nAChR

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14
Q

What is the NTX receptor on smooth muscle?

A

mAChR or adrenergic

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15
Q

Does skeletal muscle have any other NTX receptors?

A

NO

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16
Q

Are there other smooth muscle receptors?

A

Yes

  • Blood bourne (ex: hormones)
  • Paracrine (ex: NO-)
  • Intrinsic (ex: enteric NS)
17
Q

What are the steps of smooth muscle contraction?

A
  1. Ca2+ enters cytosol thru Ca2+ channels in plasma membrane (which has 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
18
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
19
Q

How can the smooth muscle cell maintain such long contractions?

A

Latch mechanism

20
Q

What is the latch mechanism?`

A
  • After 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
21
Q

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

A

Cross bridge formation is slower in smooth muscle

22
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

23
Q

What is passive tension? (very genrally speaking)

A

How individual muscle cells are able to stretch their membranes

24
Q

What is important about passive tension?

A

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

25
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
26
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)

Cardiopulmonary Exam 2 (18 decks)

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