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Anatomy Module I > Lecture 3 - Muscle Histology > Flashcards

Lecture 3 - Muscle Histology Flashcards

1
Q

Three types of muscle tissue

A

Skeletal
Cardiac
Smooth

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2
Q

Sarcolemma

A

muscle cell membrane

Other cell types= plasmalemma (plasma membrane)

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3
Q

Sarcoplasm

A

Cytoplasm of the muscle Cell

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4
Q

Sarcoplasmic reticulum

A

similar to smooth endoplasmic reticulum, storage site for calcium

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5
Q

Sarcosomes

A

Term of mitochondria within a muscle cell

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6
Q

Contractile Proteins

A

actin(thin) and myosin (thick)

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7
Q

Examples of Movement of actin and myosin for each type of muscle

A

skeletal- ex. movement of limbs
cardiac- ex. movement of blood
smooth- ex. movement of bolus (involuntary)

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8
Q

Connective tissue organization

A

Epimysium
Perimysium
Endomysium
(outer to inner)

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9
Q

Epimysium (type of CT)

A

Surrounds an ENTIRE muscle; dense irregular CT

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10
Q

Perimysium (type of CT)

A

Surrounds a muscle FASCICLE; dense irregular CT, Neurovascular structures course through the perimysium

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11
Q

Endomysium (Composition)

A

surrounds a SINGLE muscle or fiber/cell; mainly comprised of reticular fibers; capillaries and nerves terminals course through endomysium

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12
Q

Muscle unit and CT

A

CT investments are continuous with the tendon

form a strong muscolotendinous unit that allows muscle contraction forces to be transmitted

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13
Q

Contraction force path

A

Muscle->tendon->bone -> movement of bone segments

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14
Q

Skeletal muscle general features

A

Each muscle fiber contains many nuclei (MULTINUCLEATED)

located peripherally, adjacent to sarcolemma

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15
Q

Myofibrils and Sarcomeres

A

each muscle fiber/cell contains many myofibrils

each myofibril contains many sarcomeres

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16
Q

Sarcomere

A

repetitive subunit of skeletal ms

Actin and myosin are two major proteins that contribute to each sarcomere

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17
Q

Sarcomere composition

A

Several proteins

  • actin (thin)
  • myosin (thick)
  • tropomyosin
  • tropo
  • titin
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18
Q

tropomyosin

A

wraps around actin

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19
Q

titin

A

stabilizes myosin at Z disc

20
Q

M-line

A

middle of sarcomere; includes myosin binding protein that holds myosin in place

21
Q

H-zone

A

corresponds to location of myosin (only)

22
Q

A-band

A

corresponds to entire length of myosin

23
Q

I band

A

corresponds to location of actin (only)

24
Q

z disc

A

each sarcomere extends from Z disc to Z disc

25
Q

alpha actin

A

stabilizes actin at the z disc

26
Q

Contractile mechanism

A

involves actin, myosin, tropomyosin, troponin

27
Q

tropomyosin in relaxtion

A

it wraps around actin

blocks binding site on actin for myosin head

28
Q

troponin in relaxation

A

holds tropomyosin in place

29
Q

during contraction

A

Ca2+ binds to troponin

  • troponin changes conformation
  • tropomyosin moves away from the active site on actin
  • myosin binds to actin
  • ATP provides energy for power stroke
  • SHORTENS sarcomere
30
Q

Neuromuscular Junction AP path

A
  1. AP travels down axon to terminal
  2. Opens Voltage Gated Ca2+ channels
  3. Ca2+ triggers release of ACh
  4. ACh traverses synaptic cleft, binds to ACh receptors on the sarcolemme (Motor end plate)
  5. Na+ ion channels open, enters Na+
  6. Depolarizing potential
  7. action potential initiated in muscle cell
  8. AP propagated along muscle cell plasma membrane
31
Q

How does AP reach myofibrils deep in the sarcomere?

A

T-tubules: invaginations of the sarcoplasm

  • permit AP to reach deep into muscle fiber
  • Surrounded on both sides by the Sarcoplasmic reticulum cistern
  • AP triggers release of Ca2+ from SR
32
Q

Triad

A

Located in Skeletal Muscle

2 sarcoplasmic reticulum cisterns surrounding 1 T tubule

33
Q

Contraction vs relaxation and Ca2+

A

Ca release = contraction

Ca sequestered in SR = relaxation

34
Q

Contractile mechanism summary

A

Action potential in motor axon -> action potential in sarcolemma
travels down T-tubule and
triggers Ca+2 release from SR -> Ca+2 binds to troponin ->
conformational change in
troponin which moves tropomyosin
and uncovers the myosin binding
site (on actin) ->myosin head binds to actin ->
via energy release from ATP->
muscle contraction (power stroke

35
Q

Relaxation summary

A

no more signal of ACh on terminal -> Ca2+ transported back into SR -> tropomyosin recovers active site on actin

36
Q

Cardiac muscle vs Skeletal

A

Both Striated,
Cardiac not a regular structure,
Cardiac has 1 or 2 central nuclei,
Cardiac has cytoplasmic cone - location of glycogen/mitochondria
cardiac is small in length
intercalated disc at interface of cardiac muscle cells

37
Q

Intercalated Disc (what is it describe structure)

A

seen as dark lines between “ends” of cardiac muscle cells (unique to cardiac), has elevations and depression (looks like waves at the end)

38
Q

intercalated disc components (with location)

A

fascia adherens - located at the end
desmosomes - located at the end
gap junctions - laterally located, and provide continuity for quick potentials

39
Q

Dyads

A

T- Tubules that dont have flanking cisterns. There is one T tuble and one SR.
This is located in Cardiac Muscle only

40
Q

Smooth Muscle Location and Structure

A

No striations
Seen many places, blood vessels, urinary, eye, lung
spindle shaped cells taper on long axis
one signel nucleus

41
Q

Contraction of smooth muscle Shape

A

Contracted called corkscrew shape

42
Q

Fiber Orientations in Smooth Muscle

A

Inner Circular Layer - go around muscle - so they look like long cells in cross setion
Longitudinal - Organized in parllel to muscle - so look like cell circles going in to the page in a cross section

43
Q

Dense Bodies

A

Located along the sarcolemma and in sarcoplasm. Similar to Z discs and bind actin

44
Q

Dense Plaques

A

Aka Focal Adhesions
Junctions between cells.
They are dense bodies with an additional proteins connecting to adjacent cells
allows for communication of neighbor cells of contraction

45
Q

Caveolae

A

Slight invaginations in the smooth muscle
location of calcium channels
are close to the sarcoplasmic reticulum
influx of calcium results in more calcium from sarcoplasmic reticulum

46
Q

Gap Junctions in Smooth Muscle

A

Electrically and chemically couple the smooth muscle

for paristalsis

Anatomy Module I (9 decks)

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