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Unit 3 > BIOMED 10/31 Muscle Histology > Flashcards

BIOMED 10/31 Muscle Histology Flashcards

1
Q

skeletal muscle function

A

contraction due to interactions of actin and myosin

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2
Q

skeletal muscle structure/function relationship

A
  1. large enough to accommodate contractile proteins
  2. multinucleated
  3. needs mitrochondria for ready energy supply
  4. needs space for CT and insfrastructure for blood supply
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3
Q

shape of skeletal muscle cells

A

long and cylindrical

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4
Q

CT that lies in between muscles

A 
Loose
it has:
-capillaries
-venules
-endomysium
-nuclei o skeletal muscle
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5
Q

why are skeletal muscle multinucleated?

A
  • fibers are very long

- needs to communicate

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6
Q

3 subparts of CT of skeletal muscle?

A
  • Epimysium: above/outer layer that encompasses entire muscle
  • Perimysium: Compartmentalized fascicles (each fascicle has perimysium around it)
  • Endomysium: layer around each individual cell
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7
Q

what is the purpose of CT in skeletal muscle?

A
  1. vehicle for blood supply, nerve supply, and lymph supply to muscle
  2. organizational structure integrity
  3. plentiful/abundant
  4. aids in contraction and relaying stress of tension forces (active or passive)
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8
Q

what is the significance of myotendinous junction?

A

allows for communication between CT and muscle tissue and relays contractile forces/information to the bone through tendons

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9
Q

organization within skeletal muscle cell/fiber

A

muscle fiber cell > myofibrils > myofilaments

external to internal each fiber with a fascicle has that structure

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10
Q

Sarcoplasmic Reticulum

A

internal mesh bag that contains calcium and where it is sequestered between contractions

within each myofibril

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11
Q

T-Tubules

A

carries the extracellular fluid

-because entrance is from outside of the cell

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12
Q

myofibrils

A

highly organized, pentagonal shaped structures

  • actin
  • myosin
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13
Q

where do the nuclei of the muscle fibers sit?

A

they are pushed to the edge to allow room for contraction

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14
Q

cell membrane of the fiber

A

made of two layers

  1. sarcolemma
  2. external lamina (outside layer and contains extracellular fluid)
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15
Q

triad of skeletal muscle

A

T: t-tubule + lateral sacs of SR

- no actual physical connection

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16
Q

why don’t t-tubule and SR connect

A

T-tub has extracellular fluid

SR has intracellular fluid and calcium

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17
Q

junctional feet

A

DHP - proteins that reside on t-tubuel side of connection

RyR - portion of the connection that resides on SR

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18
Q

what happens when there is an AP along a muscle cell?

A

there is a voltage change that travels down t-tubule and as it passes RyR, it communicates a stimulus to mechanically open channels on SR

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19
Q

what are sarcomeres?

A

functional unit of the muscle fiber

from z-line to z-line

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20
Q

what causes the striation appearance on muscle fiber?on light micrograph

A

I band and A band

21
Q

Z - line

A

where actin is attached

muscle contraction

22
Q

portion on either side of z-line

A

actin only coming from I-band

23
Q

I-band

A

actin only band within muscle fiber

lighter striation

24
Q

H-band

A

has m-line down the middle of it

region of myosin that has only tails

25
Q

m-line

A

place where myosin is connected to

26
Q

myosin goes ____ direction/s off of the center

A

both

27
Q

what happens during contraction?

A

actin comes in over myosin heads and pulls ends toward the middle

  • I-bands may get smaller
  • H-bands, depending on contraction, may be obscured
  • A-band doesn’t change
28
Q

what are thin myofilaments system proteins

A

Actin
Troponin
Tropomysosin

29
Q

purpose of tropinin complex (troponin I and tropomyosin)

A

physical blocks to binding sites of myosin

30
Q

troponin c

A

where calcium binds

31
Q

after calcium binds to troponin C, what happens to troponin T?

A

get mechanical movement after calcium binding and it pulls (rolls/exposes) the tropomyosin off of binding sites

32
Q

myosin is a ___ myofilament made of ____ and ___ regions

A

thick
head
tail

33
Q

where does all of the action occur in myosin?

A

Head region

  • has binding site for actin
  • binding site for ATP
  • has ATPase
  • meaningfully arranged, repeating spiral pattern (all have the potential to interact with actin)
  • enzyme on myosin head is fiber dependent
  • fast twitch(close together)
  • slow twitch(far apart)
34
Q

other proteins in the sarcomere

A
  1. titin
  2. nebulin
  3. desmin
  4. dystrophin protein complex
35
Q

what is titin

A

(connectin)

  • Role: protein that goes from z line and travels to mline and to the z line continuously
  • physical connection from one part of sarcomere all the way down
  • supportive structure from one end to the next; importance in relaying contractile info to the ends of the muscle fiber
36
Q

what is nebulin

A

structural protein that is a support to actin

37
Q

what is desmin?

A

connects one z line to the next z line from one side of the cell to the other

  • keeps the z lines in register and generates banding pattern
  • connects one myofibril to the next at z-lines
38
Q

what is dystrophin protein complex

A

part of protein complex that attaches myofibrils to skeletal muscle membrane

39
Q

sensory receptors in skeletal muscle

A

muscle spindles

GTOs

40
Q

what do muscle spindles do?

A

detect changes in length

  • in parallel with extrafusal fibers
  • relay stretch of muscle back to CNS
41
Q

what do GTOs do?

A
  • detect tension

- like force transducers at the myotendinous junction

42
Q

different types of skeletal muscle growth and regeneration

A

hyperplasia

hypertrophy

43
Q

what is the significance of hyperplasia?

A

increase in number (one cell divides into 2 cells)

-main strategy during development of muscle up until first year of adult life

44
Q

after the age of 1, what is the main vehicle for growth of the muscle?

A

hypertrophy
-increases in size by increasing the number of myofilaments organized in myofibrils thus increasing the size of the muscle (increased amount of contractile proteins and supporting structures)

45
Q

what are satellite cells of muscle?

A
  1. myoblasts that are in stasis
  2. sit outside the sarcolemma, but inside the external lamina in close approximation with skeletal muscle cell
  3. most of the content in the cell is occupied by the nucleus
46
Q

main purpose of satellite cells

A

protein synthesis, thus main part of cell is the nucleus

-when activated, causes ramp up of myofibril production by fusing with the muscle fiber

47
Q

what is Duchenne’s muscular dystrophy?

A

indicate that there is a problem with protein dystrophin (attaches myofibrils to skeletal muscle membrane)

-genetic mutation that creates an injury at the muscle fiber whenever there is muscle activation (b/c the thing that is supposed to support and convey it is not functional)

48
Q

in Duchenne’s muscular dystrophy, this is what happens: in an attempt to regenerate the myofibrils, ____ cells try to _____ new _____. BUT, once the ____ cells exceed capacity, we get _____ ____ ____ and muscle becomes ____ and _____

A 
satellite 
regenerate/restore
myofibrils
satellite 
scar tissue formation
non contractile
non functional

Unit 3 (6 decks)

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