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NYCC MSP > Muscle Structure > Flashcards

Muscle Structure Flashcards

1
Q

What is the term given to skeletal muscle due to the presence of multiple nuclei within a single cytoplasm?

A

syncytia

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2
Q

Thick filaments of skeletal muscle are called ____

A

myosin

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3
Q

Thin filaments of skeletal muscle are called ____

A

actin

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4
Q

Actin filaments are aligned and connected to the Z-line by ____

A

Nebulin (guidewire for actin)

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5
Q

Myosin filaments are connected to the Z-line by ____

A

Titin (tightens myosin)

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6
Q

What are extrafusal fibers responsible for?

A

movement (contraction)

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7
Q

What are intrafusal fibers responsible for?

A

stretch reception (ie., proprioception) by muscle spindles

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8
Q

Extrafusal fibers contain (sensory/motor/both) neurons

A

motor neurons

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9
Q

Intrafusal fibers contain (sensory/motor/both) neurons

A

motor AND sensory neurons

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10
Q

The fascial layer covering the entire skeletal muscle is called ____

A

epimysium

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11
Q

A skeletal muscle is composed of multiple ____

A

fascicles

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12
Q

The fascial layer surrounding each fascicle is called ____

A

perimysium

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13
Q

A fascicle is composed of multiple ____

A

muscle fibers (muscle cells)

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14
Q

The fascial layer surrounding each muscle fiber is called ____

A

endomysium

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15
Q

A muscle fiber is composed of multiple ____

A

myofibrils

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16
Q

A myofibril is a bundle of ____

A

myofilaments (myosin & actin)

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17
Q

What part of skeletal muscle is involved in compartment syndrome?

A

epimysium
(treatment = fasciotomy)

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18
Q

When at rest, the myosin binding site on thin filaments is physically blocked by the ____

A

troponin-tropomyosin complex

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19
Q

What event unblocks the binding sites on actin?

A

Ca2+ binds to troponin

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20
Q

What is the function of the sarcoplasmic reticulum?

A

Ca2+ storage (relaxation) & release (contraction)

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21
Q

What travels through the sarcoplasmic reticulum to trigger calcium release?

A

Na+

22
Q

What is the functional unit of a muscle fiber?

A

sarcomere

23
Q

What defines the length of a sarcomere?

A

Z-line to Z-line

24
Q

What is the Z-line/band?

A

electron dense band that anchors thin actin filaments
(ends of sarcomere)

25
Q

What is the I-band?

A

actin filaments extend from Z-band to A-band

26
Q

What is the A-band?

A

composed of entire length of myosin filaments + overlapping actin filaments

27
Q

____ filaments form a hexagonal array around each ____ filament

A

thin; thick

28
Q

What is the H-zone?

A

pale region in midportion of A band where actin filaments end (ONLY contains myosin)

29
Q

What is the M-line?

A

zone of intermolecular bridging & thickening of myosin at the midline of the A band, which forms a thin, slightly darker electron-dense band

30
Q

Each thin filament is equidistant from how many thick filaments?

A

3

31
Q

What happens to Ca2+ with cessation of neural activity?

A

SR actively transports Ca2+ back into terminal cisternae

32
Q

What happens to Ca2+ with depolarization of a muscle cell?

A

SR passively releases Ca2+ into muscle cell –> binds to troponin

33
Q

A muscle fiber is innervated by a single ____

A

LMN ending

34
Q

What is a motor unit?

A

a single motor neuron and all the muscle fibers it innervates

35
Q

What determines muscle fiber type?

A

LMN conduction speed

36
Q

T/F:
muscle fibers in a motor unit are a combination of type I and type II fibers

A

FALSE
all fibers in a MU are same type

37
Q

Type I fibers are ____ twitch

A

slow

38
Q

Type II fibers are ____ twitch

A

fast

39
Q

T/F:
In humans, all muscles consist of a combination of type I and type II fibers

A

TRUE
i.e., postural muscles (eg. soleus) still have fast twitch;
fast twitch muscles (eg. gastrocs, EDL) still have slow twitch

40
Q

What muscle fiber type are red/dark?

A

type I

41
Q

What muscle fiber type are white?

A

type II

42
Q

Postural muscles contain mostly type ____ fibers

A

I

43
Q

Describe the properties of motor neurons innervating type I fibers.

A

Alpha 2 motor neuron
- low threshold
- slower conduction velocity

44
Q

Describe the properties of motor neurons innervating type II fibers.

A

Alpha 1 motor neuron
- high threshold
- faster conduction velocity

45
Q

Describe the metabolic properties of type I fibers

A

Aerobic
- ^myoglobin
- ^mitochondria

46
Q

Describe the metabolic properties of type II fibers

A

Anaerobic
- less myoglobin
- less mitochondria

47
Q

What is the endurance level of type I and II fibers?

A

type I = high
type II = low

48
Q

What would happen to muscle fibers if innervation were crossed between soleus (type I) and EDL (type II)?

A

Fiber types would switch over time
(innervation determines fiber type)

49
Q

What happens to type I fibers with training?

A
  • no hypertrophy due to endurance training
  • ^mitochondria
50
Q

What happens to type II fibers with training?

A

hypertrophy with strength training

NYCC MSP (44 decks)

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