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MSK Week 5 > ICL 3.2: Histology of Muscle > Flashcards

ICL 3.2: Histology of Muscle Flashcards

1
Q

what are the layers of a muscle?

A

muscle –> fascicle –> muscle fibers/myocyte –> myofibril –> myofilaments (thick and thin)

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2
Q

what are thick and thin myofilaments also called?

A

thin = thin actin filaments

thick = thick myosin filaments

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3
Q

what are the boundaries of a sarcomere?

A

z line to z line is a sarcomere

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4
Q

what is the I band composed of?

A

ONLY actin thin filament

the Z band is also in the I band

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5
Q

what is the H band composed of?

A

ONLY myosin thick filament

the M line is also in the H band so think M and M

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6
Q

what is the sarcolemma?

A

the membrane surrounding a muscle fiber/myocyte

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7
Q

what is the function of the sarcoplasmic reticulum?

A

storage of calcium

it’s a network inside of a muscle fiber the goes in-between all the myofibrils in the sarcoplasm

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8
Q

what is the terminal cisternae?

A

a dilation of the sarcoplasmic reticulum that hug T tubules

T tubules are an invagination of the sarcolemma which allows depolarization to get to all the myofibrils

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9
Q

what is a muscle triad?

A

a T tubule + 2 cisternae

located at the AI junction

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10
Q

what is the connective tissue covering the layers of muscle?

A
  1. epimysium = covers the entire muscle
  2. perimysium = covers each fasicle
  3. endomysium = covers individual muscle fibers
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11
Q

what does skeletal muscle look like on histology slides?

A

you can see fascicles arraigned in parallel fashion

you can also see a clear/lighter pink epimysium

skeletal muscle also has a lot of peripheral nuclei!

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12
Q

what is thick filament made of?

A

myofibrils are either thick or thin – thick filaments are often called myosin

so thick filament is made up of multiple myosin molecules

1 myosin molecule = 4 light chains and 2 heavy chains

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13
Q

what is thin filament made of?

A

myofibrils are either thick or thin – thin filaments are often called actin

1 thin filament = actin + tropomyosin + troponin

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14
Q

what are the 3 components of troponin?

A

Tc = binds calcium

Tt = binds tropomyosin

Ti = binds actin

Ca binds and changes configuration of troponin so the myosin binding sites on actin get exposed so that myosin can bind

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15
Q

what are the 2 types of skeletal muscle fibers?

A

type I and type 2

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16
Q

what are type I skeletal muscle fibers?

A
  1. fatigue-resistant
  2. large amounts of myoglobin and mitochondria
  3. aka red muscle
  4. use oxidative phosphorylation
    ex. postural muscles
17
Q

what are type II skeletal muscle fibers?

A
  1. they use anaerobic glycolysis
  2. fatigue-prone but they’re the fast muscles for quick precise movement
  3. large number of glycolytic enzymes
  4. aka white muscle
18
Q

what is dystrophin?

A

it’s found in the sarcolemma of a muscle fibers and it helps to anchor actin to transmembrane proteins

19
Q

what happens when there’s a dystrophin mutation/deficiency?

A

duchenne and becker’s muscular dystrophy –> duchenne is more severe and is a frameshift mutation

they result from defective dystrophin proteins formation which inhibits muscle regeneration

patients often have giant calves

20
Q

what is a cardiac diad?

A

T tubule + 1 terminal cisternae

the diad is located at the z-line1/2020-1/2021

21
Q

how many nuclei does cardiac muscle fiber have?

A

1 nuclei

skeletal muscle usually has multiple

22
Q

what does cardiac muscle look like on histology?

A

branching muscle fibers; not as parallel as muscle fibers

nuclei are centrally located

there are intercalated discs too

23
Q

what are the two types of smooth muscle?

A
  1. multi-unit

2. visceral (main type)

24
Q

what is multi-unit smooth muscle?

A

it is found only in a select few areas of the body, e.g. ciliary muscle, muscles of iris, and arrector pili muscle of the skin

25
Q

what is visceral smooth muscle?

A

more abundant that multi-unit smooth muscle

it is found in the walls of most viscera of the body, including the gastrointestinal tract, bile ducts, ureters, uterus, and many blood vessels

26
Q

what are dense bodies?

A

smooth muscles don’t have z-disks, they have dense bodies but they serve the same function

27
Q

what are caveolae?

A

they take place of T tubules in smooth muscle

smooth muscle fibers are smaller so we don’t need the extensive invagination as we see in the T tubules in skeletal and cardiac muscle

28
Q

what does smooth muscle look like histologically?

A

TONS of nuclei all throughout the cytoplasm

29
Q

what are the striations, nucleus, T-tubules, type of innervation and cell-to-cell junction seen in skeletal muscles?

A

striations = present

nucleus = multiple, peripheral

T-tubules = present

innervation = voluntary

cell-to-cell junction = none

30
Q

what are the striations, nucleus, T-tubules, type of innervation and cell-to-cell junction seen in cardiac muscles?

A

striations = present

nucleus = one or a few, centrally located

T-tubules = present

innervation = involuntary

cell-to-cell junction = intercalated discs

31
Q

what are the striations, nucleus, T-tubules, type of innervation and cell-to-cell junction seen in smooth muscles?

A

striations = absent

nucleus = single, centrally located

T-tubules = absent

innervation = involuntary

cell-to-cell junction = gap junctions

32
Q

how does smooth muscle contract?

A

actin filaments of smooth muscle slide in opposite directions due to arrangement of myosin heads

this allows smooth muscle to contract really really well which we need like in our GI!

33
Q

what’s the difference in the thick filament of the different muscles?

A

skeletal and cardiac muscle have bipolar thick filament which makes them limited in their movement and they can only go to the M line

smooth muscle on the other had has side-polar thick filament which can contract all the way to opposing sides which allows it to contract stronger

34
Q

when skeletal muscle contracts, do the following structures shorten, stay the same length, or elongate?

Sarcomere
H band
I band
A band
M line
Myofilaments
A

Sarcomere = shortens

H band = shortens

I band = shorten

A band = stay the same length

adjacent M lines = shorten; get closer together

myofilaments = stay the same length

35
Q

during marathon training, percentage of what would increase?

A

type I muscle fibers!

36
Q

the i band is bisected by what?

A

z line

37
Q

the M line is located in the middle of what structure, band or line?

A

A band, H band and sarcomere!

MSK Week 5 (7 decks)

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