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anatomy > Muscle Histology > Flashcards

Muscle Histology Flashcards

1
Q

Sarcolemma

A

muscle cell membrane

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2
Q

sarcoplasm

A

cytoplasm

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3
Q

sarcoplasmic reticulum

A

similar to smooth muscle ER. Stores calcium

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4
Q

sarcosomes

A

mitochondria

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5
Q

Contractile proteins

A

actin and myosin. In all 3 muscle types

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6
Q

sarcomere

A

repetitive contractile subunit

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7
Q

Epimysium

A

surrounds entire muscle, dense irregular CT

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8
Q

Perimysium

A

surrounds muscle fasicle; dense irregular CT. Neurovascular structures course through perimysium

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9
Q

Endomysium

A

surrounds single muscle cell/fiber. Reticular fibers. Capillaries and nerve terminals course though endomysium

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10
Q

Skeletal muscle charactoristics

A

multinucleated, nuclei are peripherally located (adjacent to sarcolemma).

Long (several cm) in length

Each fiber contains many myofibrils, each myofibril contains many sarcomeres

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11
Q

M line

A

middle of sarcomere. Includes myosin binding protein that holds myosin in place

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12
Q

H zone

A

location of only myosin

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13
Q

A band

A

entire length of myosin

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14
Q

I band

A

location of only actin

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15
Q

Z disk/z line

A

each sarcomere extends from z line to z line

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16
Q

tropomyosin

A

wrapped around actin, covers binding sites for myosin (except when moved by tropinin)

17
Q

troponin

A

“tacks down’ tropomyosin to actin. Binds to calcium to cause conformational change revealing myosin binding sites

18
Q

titin

A

stabilizes myosin at z disk.

19
Q

alpha actin

A

stabilizes actin at z disk

20
Q

Steps of skeletal muscle contraction

A
  • Calcium binds to troponin, causing troponin to change conformation
  • tropomyosin is moved away from active site on actin
  • myosin binds to actin
  • ATP provides energy for power stroke
  • sarcomere shortens (actin moves towards M line)
21
Q

T tubules

A

Transverse tubules. Invaginations of sarcoplasm that allow the AP to reach deep into the muscle fiber

22
Q

Contractile mechanism (skeletal muscle)

A
  • AP travels down T tubules
  • sarcoplasmic reticulum cistern is on either side of each t tubule
  • AP triggers release of calcium from adjacent SR
23
Q

Triad

A

2 sarcoplasmic reticulum on each side of 1 t tubule.

24
Q

termination of motor signal

A
  • no ACh released from axon terminal
  • calcium transported back into SR
  • tropomyosin covers active site on actin
25
Q

Cardiac muscle characteristics

A

branches, 1 or 2 (rare) centrally located nuclei with surrounded clear area.

Mitochondria are 40% of cytoplasmic volume

Short, 50-100 micrometers

26
Q

Cytoplasmic cone

A

LM: glycogen and mitochondria.

27
Q

Intercalated disc

A

dark lines (recipricol elevations and depressions) at ends (interface) of cardiac muscle cells

28
Q

Components of intercalated disc

A

fascia aderens, desmosomes, gap junctions

29
Q

Fascia adherens

A

on end to end contacts of cells (on intercalated discs)

30
Q

desmosomes

A

on transverse (end) portions intercalated discs.

Function: prevent cardiac muscle cells from pulling apart under strain of repetitive contractions

31
Q

Gap junctions (cardiac muscle)

A

Location: lateral aspect of intercalated discs

Function: provide ionic continuity between adjacent cardiac muscle cells so cells can behave as syncytium.

32
Q

Dyads

A

term for single t-tubule adjacent to single SR

33
Q

Smooth muscle characteristics

A

spindle shaped cells, taper along axis (longer than wide). Single central nucleus. Non striated. Oblique arrangement of contractile units

34
Q

Dense bodies

A
  • along sarcolemma and within sarcoplasm.
  • contains alpha actin and serves as attachment site for actin
  • when actin and myosin interact, dense bodies move closer together (corkscrew shape)
35
Q

Dense plaques

A

AKA focal adhesions

  • dense bodies serve to mechanically attach adjacent cells, these adhesion sites include other proteins and are called dense plaques
  • allows for more efficient and forceful contraction
36
Q

Gap junction (smooth muscle)

A

electrically and chemically couple smooth muscle cells

37
Q

Caveolae

A

slight invaginations of sarcolemma

  • role in calcium signalling
  • close proximity to SR
38
Q

Smooth muscle signal transduction

A
  • Calcium channels present in region of the caveolae
  • AP passes along caveolae causing influx of calcium from ECF and release of calcium from SR
  • intracellular contractions ride, actin and myosin bind, shortening contraction occurs in the presence of ATP

anatomy (3 decks)

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