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histology exam 1 > skeletal muscle > Flashcards

skeletal muscle Flashcards

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1
Q

myocyte

A

indiv. muscle cell

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2
Q

muscle fiber

A

many myocytes fused together

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3
Q

myofibrils

A

contractile elements

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4
Q

sarcoplasm

A

muscle cytoplasm

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5
Q

muscle plasma membrane

A

sarcolemma

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6
Q

skeletal muscle appearance

A

-cells are multinucleate
-nuclei migrate to periphery of cell
-striated fibers
-assembled into sarcomeres

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7
Q

can skeletal muscle proliferate?

A

no

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8
Q

endomysium

A

CT that surrounds individual muscle fibers

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9
Q

fascicles

A

several fibers bound together

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10
Q

perimysium

A

CT that surrounds fascicles

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11
Q

muscle

A

formed from many fascicles

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12
Q

epimysium

A

CT that surrounds entire muscle, continuous with tendinous attachment

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13
Q

where do blood vessels tend to follow in skeletal muscle?

A

along CT (epi- and perimysium for support)

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14
Q

two major types of skeletal Mm fibers

A

fast twitch & slow twitch

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15
Q

type I skeletal muscle fibers

A

slow twitch

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16
Q

slow twitch fibers

A

-“slow” myosin
-small fibers w/ large amount of myoglobin
-use 1’ aerobic respiration for oxidative metabolism
-large # of mitochondria (ATP for energy)
-resistant to fatigue
-generate only moderate muscle tension
-common in peripheral limbs

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17
Q

type II skeletal muscle fibers

A

fast twitch

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18
Q

fast twitch fibers

A

-“fast” myosin
-large fibers with less myoglobin & fewer mitochondria
-use 1’ anaerobic glycolysis for energy production
-abundant glycogen
-extensive sarcoplasmic reticulum for rapid Ca release
-fatigue rapidly, but generate high muscle tension for short bursts of activity

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19
Q

what types of skeletal muscle fibers present in muscle?

A

both (type I and type II)

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20
Q

where are you most likely to see more type I skeletal muscle fibers?

A

in muscles used constantly
ex: leg muscles for standing

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21
Q

type IIA skeletal muscle fibers

A

oxidative & fatigue resistant

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22
Q

type IIB skeletal muscle fibers

A

glycolytic & fatigue sensitive

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23
Q

what happens during peak periods of exertion for skeletal muscle?

A

both type I and type II fibers metabolize glycogen via anaerobic glycolysis to produce ATP –> intermediate metabolites (e.g., lactic acid) –> precipitate as crystals in Mm –> tearing of Mm fibers & pain after heavy exertion

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24
Q

what happens during severe oxygen debt?

A

ischemia, muscle cramps, and even cell death

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25
extreme exertion can lead to...
rhabdomyolysis (breakdown of actin & myosin) & subsequent kidney failure due to release of myoglobin & clogging of glomeruli
26
during normal exercise Mm fibers can develop...
micro-tears
27
hypertrophy
increase in cell size
28
what causes hypertrophy of muscle cells?
exercise causes an increase in number of mitochondria & increase in volume of contractile proteins; splitting & branching of individual Mm fibers
29
hyperplasia
production of new Mm fibers *relatively rare*
30
atrophy
decrease in cell size
31
what causes atrophy of muscle cells?
-disuse -immobilization can cause denervation
32
sarcopenia
loss of skeletal muscle fibers and Mm mass *comes with increasing age*
33
satellite cells
-small cells adjacent to sarcolemma -proliferate following injury and then differentiate into myoblasts
34
what are the two types of mechanoreceptors in skeletal muscle?
neuromuscular spindles & neurotendinous spindles
35
what do mechanoreceptors do in skeletal muscle?
-prevent overstretching & tearing of Mm -used in postural reflexes -coordination
36
neuromuscular spindles
-located within belly of Mm -sensitive to changes in length
37
neurotendinous spindles
-located within the tendon -sensitive to changes in tension
38
skeletal muscle ultrastructure
-individual Mm fibers composed of myofibrils -myofibrils composed of numerous myofilaments (or contractile proteins) in parallel bundles -myofibrils arranged in sarcomeres
39
what are the two types of myofilaments?
actin & mysoin
40
actin
thin filament
41
myosin
thick filament
42
sarcomere structure
-A band: actin & myosin overlap -I band: only actin -Z-discs: located in I band -M line: middle line of sarcomere; located in A band
43
Z-discs
act as anchoring points for actin myofilaments
44
during Mm contraction ___ shorten, but ____ remain the same length
sarcomeres; myofilaments
45
sliding filament theory of Mm contraction
-thick & thin filaments slide over one another via energy from ATP -sarcomere is shortened due to repeated binding & unbinding of actin & myosin filament -ratchet-like, or "walk-along" mechanism
46
neuromuscular junction
site where skeletal muscle innervated by nerves
47
motor end plate (NMJ)
terminal portion of axon surrounded by myelin that rests on sarcolemma
48
terminal bouton
similar to motor end plate by unmyelinated
49
synaptic cleft
space b/w motor end plate & sarcolemma
50
what bridges the synaptic cleft?
chemical neurotransmitter *generally acetylcholine*
51
transverse tubule system (T-tubules)
-extensive network of tubules continuous with sarcolemma -indirectly links extracellular space with ER & intracellular environment
52
triad
ends of T-tubules bounded by terminal cisternae of ER on either side
53
what travels down the T-tubules?
electrical stimulation of neuron --> influx of Na+ into neuron --> wave of depolarization down axon --> release of neurotransmitter, binding to receptor proteins --> wave of depolarization of Mm fiber
54
Ca reservoirs in skeletal muscle
sarcoplasmic reticulum & terminal cisternae
55
sliding filament mechanism
influx of Na+ ions into cytoplasm from T-tubules triggers depolarization of sarcolemma --> release of Ca from ER & terminal cisternae into cytoplasm during contraction --> Ca causes conformational change in troponin, which interacts with tropomyosin (bound to actin), exposing myosin-binding sites on actin filament --> myosin binding causes conformational change in myosin head & sliding of myosin past actin *myosin heads repeatedly bind & unbind to actin in presence of Ca and Pi, causing contraction*
56
what ions activate sliding filament mechanism?
Ca
57
each muscle fiber exhibits what type of response?
all or none; either it contracts or it doesn't
58
graded response
total number of muscle fibers contracting @ any given time determine strength of overall contraction
59
motor unit (skeletal muscle)
-group of muscle fibers supplied by single motor neuron -stimulation of a motor neuron results in contraction of all muscle fibers within that motor unit
60
recruitment (skeletal muscle)
increase in number of motor units firing within a muscle
61
muscular dystrophy
-degenerative wasting disease -Mm weakness due to genetic defect in Mm protein -can cause cell death -one form affects the protein dystrophin
62
myasthenia gravis
-autoimmune disease caused by production of antibodies to Ach receptors -causes Mm weakness -treatment with Achase inhibitors

histology exam 1 (13 decks)

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