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COM - Cardiopulmonary > Smooth M. DSA and Lecture > Flashcards

Smooth M. DSA and Lecture Flashcards

1
Q

what helps insulate the fibers from one another?

A

collagen and glycoprotein

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2
Q

what are examples of multi-unit smooth m?

A

ciliary eye muscles, iris muscles, piloerector muscles

PIC

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3
Q

what are unitary (synctial) smooth m. joined by?

A

gap junctions

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4
Q

examples of unitary smooth m?

A

walls of viscera of the body, GI tract, bile ducts, ureters, uterus, blood vessels

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5
Q

what is the structure of smooth m? ie how is actin attached?

A

actin attached to dense bodies, bonded together by intracellular protein bridges where contraction takes place

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6
Q

the dense bodies in smooth m. serve the same role as what in skeletal m.?

A

Z discs

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7
Q

what allows a hollow organ to maintain the same amount of pressure inside the lumen despite changes in volume?

A

stress-relaxation

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8
Q

outline the steps in smooth m. contraction

A
  1. Ca enters cell
  2. Ca binds reversibly w/Calmodulin
  3. Ca-Cam complex activates MLCK
  4. Regulatory chain gets PO4’ed, head binds w/actin and m. contraction occurs
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9
Q

what is the source of Ca ions in smooth m. contraction?

A

ECF (10^-3 M)

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10
Q

what is the the time it takes for diffusion (200-300 ms) to occur called?

A

latent period

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11
Q

how is an AP propagated?

A

AP –> caveolae –> Ca released from SR tubule

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12
Q

TRUE or FALSE:

The more SR, the faster the m. contraction?

A

TRUE

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13
Q

what is required for smooth m. relaxation?

A

ATP, calcium pump that pumps Ca ions out of smooth m. fiber back into ECF

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14
Q

which lasts longer: skeletal m. contraction or smooth m.?

A

smooth m.

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15
Q

what enzyme causes detachment of the myosin head from the actin filament and relaxation of the smooth m.?

A

myosin phosphatase (splits PO4 from the regulatory light chain)

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16
Q

what do short smooth m. contractions depend on?

long?

A

SR

ECF Ca2+

17
Q

what does smooth m. of the guy, vasculature and respiratory tract do?

A 
be energy efficient
maintain shape of organ
generate active tension when stretched
use little ATP
contract periodically to mix contents of organ
18
Q

where is smooth m. found?

A 
vasculature
GI
urogenital tract
respiratory tract
eye

GRUVE

19
Q

what does intrinsic innervation of smooth m.?

A

gut, trachea, neurons

Independent of CNS + PNS

20
Q

what controls extrinsic innervation?

A

ANS

21
Q

what nts control smooth m. contraction?

what are their affects?

A

ACh excites gut sm
NorEpi/Epi inhibits gut sm, contraction of vascular sm
NO inhibits smooth m.

22
Q

can smooth m. be directly inhibited?

A

YES, has no motor end plate

23
Q

where are nts released in smooth m.?

A

varicosities

24
Q

what types of receptors does smooth m. have?

A

Muscarinic cholinergic

adrenergic (alpha + beta)

25
Q

what hormones may elicit smooth m. contraction?

A

Epi

CCK

26
Q

what paracrine molecule can activate smooth m.?

A

NO

27
Q

what is an alternate mechanism by which smooth m. may be activated?

A

stretch (ie. in vasculature)

28
Q

outline the steps in the LATCH mechanism

A
  1. dephosphorylation of light chain (MLCK)
  2. cycle proceeds VERY slowly
  3. attached crossbridges still generating tension
  4. way of INC tension and DEC ATP use
29
Q

as smooth m. is stretched, the myosin heads are free from the actin and allowed to interact with different thin filaments, what does this cause?

A
  1. Reduces passive tension by reducing the strain on points of attachment to the membrane
  2. allows smooth m. cell to continue to generate active tension over a wide range of length bc actin is always available for the myosin head
30
Q

What is multi-unit smooth m. composed of?

A

many separate smooth m. fibers

COM - Cardiopulmonary (12 decks)

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