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+ CAPS 301: Muscle, Bodily Fluid, Cardio > Smooth Muscle > Flashcards

Smooth Muscle Flashcards

1
Q

Where is smooth muscle located?

A

lines viscera GI tract, respiratory tract, blood vessels, reproductive system

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2
Q

Describe the structure of smooth muscle?

A
  • non-striated fibers
  • spindle-shaped
  • tapered
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3
Q

Do smooth muscle have T-tubules?

A

no

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4
Q

Is smooth muscle contraction voluntary or involuntary?

A

involuntary (spontaneous)

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5
Q

What is smooth muscle contraction regulated by?

A

ANS (both sympathetic and parasympathetic systems)

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6
Q

What is the function of smooth muscle in arteries and veins?

A

control vessel diameter (vasoconstriction/vasodilation) to regulate blood pressure

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7
Q

What is the function of smooth muscle in intestine?

A

longitudinal and circular layers work together to participate in peristalsis

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8
Q

What is peristalsis?

A

progressive and rhythmic contractions of smooth muscle that propel food through digestive tract

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9
Q

What are the 2 layers of smooth muscle in intestine?

A
  • longitudinal

- circular

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10
Q

What does the longitudinal layer of intestine smooth muscle do?

A

constricts to allow food to go down GI tract

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11
Q

What does the circular layer of intestine smooth muscle do?

A

constricts to prevent food from going up GI tract

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12
Q

What is the function of smooth muscle in stomach?

A

longitudinal, circular, and oblique layers work together to mix food when it arrives in stomach, and propel it down to intestines

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13
Q

What is the organization of smooth muscle in arteries and veins?

A

tunica media

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14
Q

What is the tunica media made of?

A

made of smooth muscle cells and elastic tissue

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15
Q

What does the tunica media surround?

A

artery and vein walls

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16
Q

Where is the tunica media thicker?

A

thicker in arteries compared to veins – arteries have to sustain higher blood circulation, therefore thicker layer protects from damage

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17
Q

What is the organization of smooth muscle in intestine?

A

two main layers of smooth muscle

  • longitudinal layer
  • circular layer
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18
Q

What is the longitudinal layer of smooth muscle in intestine?

A

outer layer of muscle fibers that run parallel to long axis of organ

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19
Q

What is the circular layer of smooth muscle in intestine?

A

inner layer of muscle fibers that run around circumference of organ

20
Q

What is the organization of smooth muscle in stomach?

A

3 layers of smooth muscle

  • longitudinal layer (upper part of stomach)
  • circular layer (middle part of stomach)
  • oblique layer (lower part of stomach)
21
Q

Describe the innervation of smooth muscle by ANS

A

axon of postganglionic autonomic neuron branches once it hits smooth muscle

  • innervates smooth muscle, but there’s no synaptic contact with smooth muscle
22
Q

What are varicosities?

A

swellings along axonal branches filled with neurotransmitters that are released on top of plasma membrane of smooth muscle fibers, and bind to their appropriate receptors

23
Q

What is a single-unit muscle?

A

one group of smooth muscle, with a single axon over the group of muscle fibers

24
Q

How are cells connected in single-unit muscle?

A

by gap junctions

  • there are more gap junctions than in multi-unit muscle
25
Q

How do single-unit muscle contract as a unit?

A

excitation in one cell is rapidly transmitted to ‘connected’ cells – allows entire unit to contract synergistically at the same time

26
Q

Where are single-unit muscles found?

A
  • walls of viscera: digestive, urinary, and reproductive tracts
  • walls of small blood vessels
27
Q

What are multi-unit muscle?

A

groups of smooth muscles separated by each other by branches of ANS neurons

28
Q

How do multi-unit muscle contract as a unit?

A

one unit can contract independently of the neighbouring units

29
Q

Where are multi-unit muscles found?

A
  • walls of large blood vessels
  • small airways of lungs
  • muscle of eye (lens)
  • iris of eye
  • base of hair follicles
30
Q

What is a myosin molecule composed of?

A
  • 2 myosin heads
  • 2 essential myosin light chains
  • 2 accessory myosin light chains
31
Q

Which myosin light chains get phosphorylated?

A

accessory myosin light chains

32
Q

What are the 2 sites on each of the myosin heads?

A
  • site that binds to actin

- site that hydrolyzes ATP into ADP and Pi

33
Q

What are caveolae?

A

plasma membrane invaginations

34
Q

What do caveolae contain?

A

dihydropyridine receptors, through which influx of Ca2+ from ECF passes to enter sarcoplasm

35
Q

What do gap junctions allow?

A

direct electrical communication between adjacent smooth muscle fibers

36
Q

Where is gap junction?

A

membranes of two adjacent muscle fibres are very close to one another

37
Q

How are thin filaments arranged?

A

obliquely in cell

38
Q

What are thin filaments attached to?

A
  • some attach to dense bodies in cytoplasm

- some attach to dense plaque of plasma membrane

39
Q

What do contractile units of smooth muscle consist of?

A

myosin and actin filaments attached to dense bodies in sarcoplasm or plasma membrane plaques

40
Q

Where are contractile units of smooth muscle?

A

stretch across cell, between plasma membrane plaques

41
Q

What happens when contractile apparatus is close to plasma membrane?

A

it binds to membrane via dense plaque on one end, and dense body (in cytoplasm) on other end

42
Q

What happens to inside contents of the cell when smooth muscle fiber is contracted?

A

everything gets wrinkled and shrinks

all organelles in cell get caught into mesh of cytoskeletal proteins (including intermediate filaments)

43
Q

What is the contractile apparatus in skeletal and cardiac muscle?

A

sarcomere

  • organized
  • parallel to each other
44
Q

Pharmacomechanical Coupling Process

A
  1. receptors bind to hormones/neurotransmitters
  2. production of IP3 within cytoplasm
  3. IP3 binds to IP3R
    - induces release of Ca2+ in SR into sarcoplasm

**no need for membrane depolarization – pressure signalling causes depolarization

45
Q

Smooth Muscle Contraction Process

A

–

+ CAPS 301: Muscle, Bodily Fluid, Cardio (13 decks)

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