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Block 3 Up To Quiz 1 > Skeletal Muscle Pt1 > Flashcards

Skeletal Muscle Pt1 Flashcards

After card 36 these are flash cards from end of lecture starting at plasticity of muscle

1
Q

Skeletal muscle fnxs

A
  • move its body and its of body
  • weight bearing and maintenance of posture
  • for its thoracic and abdominal cavities and contribute to visceral fxs (breathing, change abdominal pressure)
  • crucial role whole body metabolism
  • contributes to basal energy metabolism
  • storage depot carbs and amino acids
  • produces heat to maintain core body temp
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2
Q

major consumer oxygen and fuel during exercise

A

skeletal muscle

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3
Q

skeletal muscle consists of

A

fibers (or myocytes), ct, blood vessels, lymphatics, nerves

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4
Q

musculotendinous junction

A

myocyte connected to tendon fibers at longitudinal ends ; allows muscle fiber to transmit mechanical force to skeleton; this
- this is vulnerable to injury

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5
Q

epimysium

A

dense ct sheet covers muscle as whole

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6
Q

perimysium

A
  • binds groups of muscle fibers and associated tendon fibers into fascicles; perimysium is continuous with epimysium
  • provides passage for nerves and small blood vessels
  • allows for movement of fascicles against each other
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7
Q

endomysium

A
  • surrounds each muscle fiber
  • consists of fine reticular fibers supporting capillaries and nerve fibers
  • allows individual fibers within fascicle to move against each other
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8
Q

outside to inside coverings muscle

A

epimysium, perimysium, endomysium

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9
Q

feed artieries

A
  • beginning of vascular supply to skeletal muscle
  • last branches arterial system
  • begins externaly to tissue
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10
Q

arteriolar skeletal muscle

A
  • origin= site at which feed artery enters muscle

- within muscle arterioles undergo branching until reach terminal arterioles

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11
Q

microvascular unit

A
  • group of capillaries supplied by terminal arterioles
  • each unit = 15-20 capillaries running in parallel with muscle fibers
  • muscle fibers= longer than capillaries -> many microvascular units arranged in series to span distance each fiber
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12
Q

collecting venule

A

capillaries of microvascular unit drain into this

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13
Q

pennation

A
  • in most muscles fibers join tendon at acute angle= pinnation
  • orientation muscle fiber relative to tendon affects fx muscle
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14
Q

pennation fx

A
  • allows greater number fibers packed into given volume -> increased muscle power
  • greater pinnation -> greater lifting capacity and greater capacity for prolonged contraction
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15
Q

increased pinnation cost

A
  • decreased fiber length

- decreased lifting height

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16
Q

myocyte general description

A
  • multinucleate cell resulting from fusion myoblasts during development
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17
Q

nuclei of myocyte

A
  • each nucleus control protein synth in that region of cell
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18
Q

protein expression myocyte

A

generally protein expression coordinated so same protein isoforms expressed for full length fiber

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19
Q

myofibrils

A
  • bulk cytoplasm of myocyte= myofibril

- cylindrical structures composed of long repeated chains sarcomeres

20
Q

sarcomere consists of

A
  • array myofilamentz anchored at each end by z-discks
21
Q

microscopic appearance sarcomere

A
  • dark band= A band = thick myosin filaments

- light band= I band= thin actin filaments

22
Q

Z disk fx

A
  • transmit mechanical force generated by individual actin-myosin cross bridges to myotendinous junction
23
Q

z discs consist of

A
  • multiple proteins some of which serve as attachment points for actin myofilamentz, some connect to sarcolemma and elements in ECM
24
Q

accessory proteins myofilaments

A
  • accessory proteins organize myofilamentz

- responsible for uniformity of organization, length, spacing of filament in sarcomere

25
Q

titin

A
  • large elastic protein
  • attaches Z disc fo myosin filaments
  • serves as template for sarcomere assembly
  • acts as molecular spring
26
Q

titin template sarcomere assembly

A
  • positions thick filaments midway between z discs
27
Q

titin as molecular spring

A
  • prevents over stretching muscle fibers retiring myosin filament to original position following muscle contraction
28
Q

cytoplasm of muscle cell

A

sarcoplasm

29
Q

additional cellular elements in sarcoplasm of muscle fiber

A
  • transfer tubular system (T-tubules)
  • sarcoplasmic reticulum
  • mitochondria
  • glycogen garnules
  • lipid droplets
30
Q

T-tubules

A
  • invaginations sarcolemma (plasma membrane)

- penetrate deep into muscle fibers

31
Q

sarcoplasmic reticulum fx

A
  • storage, release, reuptake Ca2+
32
Q

terminal cisternae

A
  • specialized regions of repeating patterns that form mesh like network enveloping myofibril (this = sarcoplasmic reticulum)
  • these in close association with specific regions each sarcomere
33
Q

triad

A
  • each T tubule flanked by 2 cisternae

- 2 triads per sarcomere

34
Q

Muscle mass depends on

A

balance between protein synthesis and protein degradation which are influenced by physical activity, nutritional status, hormone balance, and injury or dx

35
Q

increase in muscle mass depends on

A

hypertrophy (increase cell size) rather than hyperplasia (cell division) b/c muscle cells are post-mitotic

36
Q

stem cells and muscle cells

A

muscle cells contain stem cell population of stellite cells that can proliferate and differentiate into new muscle fibers under certain circumstances

37
Q

exercise effect on muscle

A
  • induces significant structural and metabolic changes in muscle tissue
  • nature of changes depends on particular type of training (endurance or strength)
38
Q

what does endurance training require of muscles

A
  • activates large muscle groups to sustain activity for prolonged period without excess fatigue
  • requires efficient delivery O2 to muscle fiber and enhanced ability fiber to utilize O2
39
Q

response of muscle to endurance training

A
  • increase capillary supply
  • increased number and size mitochondria in myocytes
  • fat and glycogen storage enhanced
  • concentration oxidative enzymes for aerobic production ATP increased
  • does not cause changes muscle size or force-generating capacity
40
Q

strength training effect on muscle

A
  • causes increased capacity to generate force
  • size individual muscle fibers increases bc increased protein synth
  • increased protein synth -> addition of myofilaments, sarcomeres, and myofibrils
  • satellite cells activated -> new fibers produced
41
Q

mechanisms by which increased load leads to changes in protein expression and muscle growth

A
  • not yet fully eludicated
  • mTOR pathway involved
  • GPCR pathway involved
  • myostatin implicated
42
Q

atrophy

A
  • reduction in muscle mass bc decrease in size and/ or umber of muscle fibers
43
Q

atrophy main causes

A
  • disuse
  • denervation
  • cachexia
  • sarcopenia
44
Q

denervation and disuse (lack of activity)

A

mechanical stimulation of muscle normally -> activation signaling pathway that promotes protein synthesis lack of stimulation from denervation and disuse -> fewer stimuli for protein production so muscles turn over and are not replaced

45
Q

Cachexia

A
  • loss lean body mass associated with many chronic dxs
  • multiple factors contribute to weight loss:
  • increased energy demapnds
  • decreased energy intake
  • decreased energy absorption
  • shift to amino acid use for source of energy
46
Q

Sarcopenia at whole body level

A
  • loss lean body mass associated with gaining in absence of dx
  • often loss lean body mass accompanied by increased fat mass
47
Q

Sarcopenia at cellular level

A
  • decrease myosin synthesis
  • post translational modifications myosin -> decreased ability to form cross-bridges
  • sarcoplasmic reticulum undergoes structural change so calcium stores no longer in close proximity to sarcomeres
  • muscle fibers contain fewer mitochondria
  • satellite cells do not respond as effectively to myogenic stimuli

Block 3 Up To Quiz 1 (24 decks)

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