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Histo 1 > Skeletal and Smooth Muscle > Flashcards

Skeletal and Smooth Muscle Flashcards

1
Q

Muscle Tissue

A

Specialized for movement

Sliding Filaments (actin/myosin)

  • 3 types
    • skeletal
    • smooth → found in blood vessels, GI Tract
    • cardiac → heart only
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2
Q

Define: Orientation

A

organization of fibers (tissues) (structures with longitudinal and lateral axes) relative to organ with longitudinal and lateral axes

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3
Q

Define: Sectioning

A

How structure with longitudinal and lateral axes was cut

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4
Q

Types of Sectioning

A

Longitudinal → cut length wise

oblique → angle cut

circular → through

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5
Q

Sectioning vs. Orientation: Smooth Muscle

A

Cells longer than they are wide

Left → longitudinal section

Right → transverse section

IC → oriented circularly

OL → oriented longitudinally

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6
Q

How was the tissue cut?

A

Longitudinal

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7
Q

Movement of muscles

A

sliding filaments of actin and myosin

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8
Q

Arrangement of fibers: Skeletal/Cardiac

A

Lined up to form striations

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9
Q

Arrangement of fibers: Smooth

A

No regular arrangement → no striations

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10
Q

Globular Actin

A

polymerizes to filamentous actin

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11
Q

Actin Filaments

A

thin cytoskeletal structures known as microfilaments

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12
Q

Bundles of Actin Filaments

A
  • form large stress fibers
    • visible on light microscopy
    • important in cells that resist shear stress
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13
Q

Actin-binding proteins (ABP)

A

Regulate microfilament function (e.g. junctions)

Include motor protein myosin

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14
Q

Define: Myosin

A

motor protein with actin and ATP binding sites

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15
Q

Myosin Filament Orientation

A

Striated

Smooth

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16
Q

Sliding Filaments

A
  • Ca2+ binds to troponin
    • moves it out of the way (shifts)
  • ATP binds to myosin
    • detaches it from actin
  • ATP cleaved to ADP
    • draws myosin head up and back
  • Myosin head drops down
  • Myosin attaches to actin
    • pulls actin filaments
  • ADP Detaches
  • ATP binds again

Energy Dependent Process

17
Q

How filaments generate force

A

actin and myosin must be connected to membrane for whole cell to contract

18
Q

Skeletal Muscle Structure

A
  • Muscle fiber is a syncytium (multicellular/multinuclear)
  • Bundles of filaments (fibrils) in the sarcoplasm (cytoplasm)
  • Mitochondria between
  • SR (Ca storgae) net to T tubules (activate Ca release in cells)
  • Z line: a-actinin → helps anchor to sarcolemma
  • I band: actin and motor proteins
  • A band: I band plus myosin
  • H band: C protein
19
Q

Syncytium Formation

A
  • Embryonic myoblasts due to form myotube
    • plasma membrane (sarcolemma)
    • surround by basal lamina and satellite cells
  • Finger-like sarcolemma processes
    • T-tubules
    • extend into sarcoplasm
    • connect with SR
  • Sarcoplasm filled with myofibrils
    • surrounded by mitochondria
    • composed of thick (myosin) and thin (actin) myofilaments
20
Q

Skeletal Muscle Syncytium Histology

21
Q

Skeletal Muscle: Myofibril Structure

22
Q

Sarcomere

A

Z-line to Z-line

23
Q

Skeletal Muscle Histology

24
Q

Skeletal Muscle Organization

A

Myofilaments → myofibril → single muscle fiber/cell → fascicle → muscle

25
Q

Skeletal Muscle: Endomysium

A

envelopes each muscle cell

26
Q

Skeletal Muscle: Perimysium

A

surrounds each fascicle

27
Q

Skeletal Muscle: Epimysium

A

surrounds the entire muscle formed by groups of fascicles

28
Q

Neuromuscular Junction

29
Q

Skeletal Muscle: Initiation of Contraction

A

ACh initiates depolarization → Ca2+ channels open and release Ca2+ → Ca2+ binds troponin C → initiates contraction → Ca2+-dependent ATPase mediates return of Ca2+ to SR

30
Q

Skeletal Muscle Histology: Orientation/Sectioning

31
Q

Muscle Spindle

A

propioceptive mechanoreceptor

contributes to reflex

32
Q

Muscle Spindle Histology

33
Q

Smooth Muscle Cells

34
Q

Fusiform Nucleus

A

Thick in the middle. thin on the ends

35
Q

Smooth Muscle Histology

36
Q

Smooth Muscle: Initiation of Contraction

A
  • Ca2+ from outside the cell
  • Responsive to nerve, hormone, or stretch stimulation
  • Phosphorylation of Myosin II light chain initiates movement
    • by MLCK
    • MLCK activated by calmodulin
    • Calmodulin only active when Ca2+ bound
37
Q

Smooth Muscle: Structural Changes

38
Q

Smooth Muscle Cell Histology: Contracted

39
Q

Skeletal v. Smooth Muscle

Histo 1 (13 decks)

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