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Histo & Embryo > Muscle > Flashcards

Muscle Flashcards

1
Q

What do skeletal muscle differentiate from

A

Mesenchymal cells

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2
Q

Skeletal muscle development

A
  • Myoblasts align and fuse to make multinucleated myotubes
  • Myotubes synthesize myofilaments; cross-straitions gradually begin to appear
  • Myotubes continue to differentiate into myofibrils
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3
Q

Endomysium

A
  • Thin Reticular fibers

- Supplies fascicles with nerves and capillaries

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4
Q

Perimysium

A

CT (collagen) layer surrounding fascicles

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5
Q

Septa

A
  • Between fascicles

- Carry nerves, blood vessels and lymphatics

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6
Q

Epimysium

A

-Dense irregular CT

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7
Q

Myotendinous Junction

A
  • Between muscle and tendon

- Tendon is dense collagen

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8
Q

Myofilaments

A

Actin and myosin

-Arraged into sarcomeres

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9
Q

A-bands

A

Ansiotropic/birefringent in polarized LM

-Myosin

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10
Q

I bands

A

Isotropic

-Actin

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11
Q

Thin filaments contain

A

F-Actin and G-actin, tropomyosin, and troponin

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12
Q

Sarcoplasmic reticulum has high amount of which organelle

A

Mitochondria

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13
Q

Muscle Contraction

A
  • Nerve impulse triggers Ach release
  • Ach binds nicotinic receptors in motor end plate
  • Impulse travels down sarcolemma and t-tubule
  • Ca release from SR
  • Ca binds troponin, moves trypomysin out the way
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14
Q

Muscle contraction at myosin head

A

-Attach, powerstroke, detatch, return

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15
Q

Myasthenia Gravis

A
  • Autoimmune disorder
  • circulating antibodies bind to Ach receptors, interfering with EPP
  • Leads to skeletal muscle weakness
  • Extraocular eye muscles are easily affected, causing diplopia (double vision) early sign
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16
Q

How does body attempt to combat myasthenia gravis

A
  • Junctional folds with affected receptors are internalized, digested by lysosomes, and replaced
  • However, this doesn’t last long, bc antibodies attack again
17
Q

Early sign of myesthenia gravis

A

Diplopia (double vision) bc extrinsic eye muscles affected

18
Q

Muscular dystrophy types and similarities

A

Duchenne muscular dystrophy and Becker muscular dystrophy

  • Both X-linked mutations of the dystrophin gene, more common in boys
  • Childhood onset: weakness begins after a delayed onset, develops after achieving motor milestones
19
Q

Dystrophin

A

-Connects the Z-line to both the sarcolemma and ECM, giving stability to myofibrils

20
Q

Duchenne Muscular Dystrophy

A
  • Weakness occurs at 3-5 y/o
  • Disease progresses rapidly
  • Loss of fxn by 12
  • May become dependent on assisted breathing
21
Q

Becker Muscular Dystrophy

A

Later onset (12 y/o)

  • Slow progression
  • Loss of fxn before 30
22
Q

LM appearance of Muscular Dystrophy

A
  • Fat replaces muscle
  • Hypertrophy and atrophy of some fibers
  • Dystrophin disruption
23
Q

Muscle spindles

A
  • Encapsulated by modified perimysium
  • Contain intrafusal fibers
  • Intrafusal fibers are modified muscle fivers
24
Q

Golgi Tendon

A
  • Provide sensation of body position and maintain muscle tone
  • Responsible for proprioception, reflexive inhibition, and activation of opposing muscles
25
Q

Cardiac muscle

A
  • Branched

- Consists of tight bundles of cells INTERWOVEN in spiraling layers

26
Q

Syncytium

A

-Myocardial fibers plus intercalated disc

27
Q

How is an MI detected in blood

A

Elevated troponin

28
Q

Smooth muscle

A
  • Under control of autonomic nervous
  • Parasym activate contraction
  • Cells are separated by ECM
  • Linked by Gap Junctions
  • No striations
29
Q

Where do thin actin filaments attach in smooth muscle

A

-Dense bodies located throughout sarcoplasm

30
Q

How does smooth muscle contract

A
  • No T-Tubules, No troponin
  • Use myosin light-chain kinase process and Ca2+ dependent calmodulin
  • Parasympathetic inn activates Ca release, utilizing calmodulin and kinase cascade that encourages the formation of actin-myosin cross bridges
31
Q

Myoepithelial cells

A
  • Some tissues have these, with smooth muscle contraction mechanisms
  • Sweat glands, mammary glands, and salivary glands, iris, seminiferous tubules of testis
32
Q

Infectious disease that impact musculoskeletal system

A

-Necrotizing fasciitis, trichonosis, and botulism

33
Q

Trichonosis

A
  • Parasitic disease
  • Nemotode larval form in encystem within skeletal muscle
  • Muscle weakness as cyst impinge on nerve
  • Caused by consumption of undercooked pork or bear
  • Surgical cure
34
Q

Botulism

A
  • Caused by binding of a toxin from food with microbial contamination by Clostridium botulinum
  • Toxin blocks release of ACH at nerve cell, causing flaccid paralysis in the muscles served by that nerve
35
Q

Necrotizing fasciitis

A
  • Clostridium prefringens release enzymes that attack muscle tissue
  • Bacterial protease attack at demosomes
  • H2S gas is released causing gas bubbles

Histo & Embryo (8 decks)

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