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ANAT 261 > Muscle > Flashcards

Muscle Flashcards

1
Q

in multicellular organisms what is movement assumed by

A

specialized cells = muscle fibers
contract upon appropriate stimulation

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2
Q

name the 3 types of muscle

A

skeletal striated muscle
cardiac muscle
smooth muscle

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3
Q

is a muscle cell and fiber the same

A

yesss

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4
Q

describe skeletal muscle generally

A

elongated multi-nucleated cell
cross striations (appearance of bands)
associated with many capillaries
collagen fibers
satellite cells
quick contraction and forceful
voluntary control
fibrocytes

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5
Q

why is skeletal muscle multinucleated

A

nuclei divide but cell does not separate and nuclei become embedded

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6
Q

why is skeletal muscle striated

A

myofibrils - cytoplasm filled with them

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7
Q

why is skeletal muscle associated with many capillaries

A

need blood to contract

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8
Q

what type of collagen fibers are found in skeletal muscle

A

type 3
reticular fibers

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9
Q

what is a satellite cell in skeletal muscle

A

located between sarcolemma (muscle fiber/cell) and BM
stem cell
mononucleated spindle cells
can repair muscle (like when pull muscle)
only in skeletal
limited regeneration via satellite cells
only seen in EM

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10
Q

describe bands of sarcomere

A

A band = darker
I band = paler
Z line = line in center, middle of I band

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11
Q

describe cardiac muscle generally

A

one nucleus in center
striated myofibrils
contained between intercalated disks
many capillaries
nuclei surrounded by halo
involuntary contraction
Vigorous and rhythmic

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12
Q

describe myofibrils of cardiac muscle

A

irregular
heterogenous shapes

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13
Q

what is intercalated disk

A

point of initiation of cell and other disk = end of cell

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14
Q

why does cardiac muscle need many capillaries

A

needs more than brain
during myocardial infarction (MI) cardiac tissue dies fast without oxygen - needs lots

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15
Q

describe halo that surrounds nuclei of cardiac muscle

A

golgi apparatus and glycogen
does not react well with H&E staining

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16
Q

what is hypertrophy and describe

A

occurs in striated muscle
hyper = above
trophy = nourishment

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17
Q

what does hypertrophy result from

A

above nourishment of new myofibrils in skeletal muscle

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18
Q

when is hypertrophy abnormal or normal

A

normal in skeletal
Abnormal in cardiac

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19
Q

why is hypertrophy abnormal in cardiac muscle

A

Muscle of heart wall will not contract properly

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20
Q

why is hypertrophy normal in skeletal muscle

A

gym - change in activity
will synthesize myoglobin (proteins) and oxygen binds - since cells need more oxygen
Myofibrils and muscle becomes bigger

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21
Q

describe smooth muscle generally

A

spindle shaped cells
nucleus centrally located (not always visible due to cross section POS)
will not see myofibrils
corkscrew nucleus
slow contraction
involuntary

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22
Q

does smooth muscle only have actin

A

NOOOO
some myosin
mainly actin

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23
Q

why will you not see myofibrils in smooth muscle

A

made of actin filaments
small

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24
Q

describe the spindle shaped cells of smooth muscle

A

smaller
shorter
thicker

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25
Q

why does smooth muscle have corkscrew nucleus

A

retracts a bit when fixed with chemicals

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26
Q

why is smooth muscle being involuntary good

A

body needs contraction all the time
like in vessels and stomach

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27
Q

what is hyperplasia and describe

A

normal in smooth muscle
hyper = above
plasis = molding
ex = uterine wall during pregnancy
number and size of cells increase
only in smooth muscle since these cells can divide by mitosis

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28
Q

what is epimysium of skeletal muscle

A

divide muscles into groups of cells

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29
Q

what are skeletal tissues surrounded by

A

dense ct = bundle or fascicle

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30
Q

what is perimysium of skeletal muscle

A

thin layer ct
fibrocytes surround bundle
special - connected by gap junctions

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31
Q

what is endomysium of skeletal muscle

A

BM that surrounds and separates individual cells
very thin
reticular fibers
capillaries
some fibrocytes

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32
Q

what is the role of CT around muscle cells in skeletal muscles

A

mechanical transducer to the forces generated by contracting muscle cells
associated to tendons and ligaments (produce movement and transduce)

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33
Q

describe breakdown of muscle (fascicle to filaments)

A

fascicle (bundle of muscle fibers) –> muscle fiber (1-40nmx10-100um) –>1500 myofibrils (1-2um diameter) –>3000 thin filaments (F-actin), 1500 thick filaments (myosin)

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34
Q

what is center of pseudoband H

A

cross linking proteins
forms M line
H band = only thick filaments

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35
Q

what does myosin have

A

tail and head

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36
Q

what is sarcomere

A

smallest repetitive subunit of contractile apparatus
Z line to Z line

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37
Q

what is Z line

A

alpha actinin
anchors thin filament

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38
Q

what is M line

A

creatine kinase = cross linking - catalyses
phosphocreatine + ADP –> ATP + creatine

39
Q

describe thick filament

A

myosin
4 myosin heavy chains
2 myosin light chains

40
Q

what happens when use chymotrypsin to split molecules of thick filament into fragments and separate

A

LMM = light meromysoin
HMM = heavy meromyosin

41
Q

describe HMM subunits and function

A

HMMS - 2
HMMS - 1 = 2 activities = binds ATP and has ATPase activity, actin binding site = wants to bind actin and activates ATPase

42
Q

describe thin filament

A

actin
globular proteins
polarized molecule
binds in active site

43
Q

name the important components of broken down thin filament

A

tropomyosin
troponin

44
Q

name and describe the 3 troponin subunits

A

TnI = inhibit actin myosin interaction
TnC = binds calcium
TnT = anchors to tropomyosin
*ONLY with calcium

45
Q

where is tropomyosin present

A

in groove

46
Q

what does troponin do

A

binds calcium and produces change in conformation of tropomyosin and can bind actin

47
Q

describe mechanism of action of sarcomere - physically

A

thin slides over thick - no change in length
pseudoband H becomes smaller and so does I band

48
Q

describe mechanism of action of sarcomere - chemically

A

cleaves ATP –> ADP and releases phosphate (activated by calcium) = produces energy for bending of myosin head
since myosin head attached to actin= thin filament displaced and slides over thick = contraction

49
Q

name and describe proteins involved in mechanism of contraction of sarcomere

A

titin = spring like, connects myosin to Z line and provides stability
nebulin = surround actin filaments
tropomodulin

50
Q

describe terminal cisternae

A

sarcoplasmic reticulum - SER
non granulated

51
Q

describe connecting tubules

A

sarcoplasmic reticulum
connect adjacent terminals
mitochondria

52
Q

describe T tubules

A

sarcolemma - PM
invagination of PM
follow between 2 terminal cisternae

53
Q

what is a triad

A

2 terminal cisternae + t tubule

54
Q

where is calcium ATPase

A

on membrane of terminal cisternae

55
Q

what is calsequestrin

A

protein
pumps calcium into sarcoplasmic reticulum
dumps molecules without binding

56
Q

describe when action potential fired in sarcomere

A

inside T tubule
depolarization of membrane
calcium released into sarcoplasm and will be available for contraction

57
Q

describe STEPS = 5 when action potential fired in sarcomere

A

1 - muscle ap propagated
2 - in t tubule = calcium released from lateral sac
3 - calcium binds to troponin = removes blocking action of tropomyosin
4 - cross bridge moves, sliding of actin, head bending = contraction
5 - calcium leaving troponin restores tropomyosin blocking action with calcium resequestration

58
Q

what are other words for neuromuscular junction

A

motor end plate
myoneural junction
terminal bouton

59
Q

how does contraction occur in sarcomeres

A

Simultaneously in all sarcomeres, in all myofibrils of one muscle cell in all muscle cells in a bundle of muscle

60
Q

how to ensure synchronous contraction

A

muscle fibers innervated by myelinated nerves
fast due to myelin

61
Q

describe myelinated motor nerves

A

branch out within perimysium and endomysium where each nerve gives rise to several terminal wings called terminal boutons

62
Q

describe where the myelinated motor nerves penetrate

A

penetrates at level of epimysium
axons branch in endomysium
synapse between nerve and muscle cell (muscular tissue)

63
Q

where is ACH receptor present (neuromuscular junction)

A

post synaptic membrane only
gates - bind acetylcholine

64
Q

describe synaptic vesicle (neuromuscular junction)

A

many when have action potential in neuron = stimulates exocytosis
fusion with presynaptic membrane
contain ACH (small molecules released in lumen synaptic cleft)

65
Q

what happens when ACH binds (neuromuscular junction)

A

sodium flows in and potassium out
changes polarity of membrane
Origination of ACH on potential - AP spreads to t tubules and sarcolemma
causes depolarization, calcium diffuses towards sarcoplasm = contraction

66
Q

describe myelin - what its caused bypp

A

schwann cell - surrounded by BM, synthesis of myelin and wraps around axon

67
Q

is BM continuous with muscle fiber of (neuromuscular junction)

A

yup

68
Q

what is presynaptic membrane (neuromuscular junction)

A

membrane of axon - terminal bouton

69
Q

what is synaptic cleft (neuromuscular junction)

A

space in between pre and post synaptic membranes

70
Q

what is postsynaptic membrane (neuromuscular junction)

A

sarcolemma - PM of muscle cell

71
Q

how would you visualize neuromuscular junction

A

immunochemistry to visualize proteins = one antibody for axon and one identifies terminal bouton

72
Q

describe ACH receptor

A

molecular weight = 270.00
5 subunits = 2 alpha, 2 beta, 1 gamma, 1 delta
under BM

73
Q

what is myasthenia gravis

A

produces antibodies against acetylcholine receptor

74
Q

describe ACH-cholinesterase

A

present in synaptic celft
ACH after contraction has to be removed = breaks ACH to acetate (recycled) and choline

75
Q

does cardiac muscle have sarcomeres

A

yuhhh

76
Q

name and describe each part of intercalated disk

A

fascia - zonula adherens (transverse part)
macula adherens (transverse part)
gap junctions (lateral part)
alpha actinin in center
plaque, desmosomes, thin filaments anchors into PM

77
Q

describe zonula adherens (intercalated disk)

A

goes all around 2 adjacent PM
bell junction
alpha-actinin/vinculin = actin anchoring of terminal web (into alpha-actinin)
·intercellular space =15 nm cadherins

78
Q

describe mucula adherens - desmosomes (intercalated disk)

A

trapped in small spot
bell like
intercellular space = 25nm
intermediate filaments
Transmembrane proteins: desmocollin & desmoglein (provide stability)
plaque: Desmoplakins 1 and 2, plakoglobin & desmocalmin

79
Q

describe gap junctions (intercalated disk)

A

coupled connexons (6 connexins)
Channels (1.5 nm diameters) for 2nd messengers like calcium
calcium diffuses through gap junctions = Rhythmic (everything at sametimes)
connexin 48 = predominant in cardiac muscle (if mutated baby will not survive)

80
Q

describe sarcoplasmic reticulum of cardiac muscle

A

sometimes has t tubules and terminal cisternae
triad = at level of z line

81
Q

what does one unit of smooth muscle look like

A

sarcomere - but not tho

82
Q

what are smooth muscle cells not similar to

A

hemidemosomes

83
Q

describe dense bodies of smooth muscle

A

anchoring of actin filaments
alpha actinin like proteins - similar to z line but NOT

84
Q

what is similar to t tubules in smooth muscke

A

little invaginations represent t tubule = vesicles/caveolae

85
Q

where is myosin in smooth muscle cells

A

some myosin filaments all spread and floating in plasma membrane

86
Q

what do smooth muscle cells have - specifics

A

dense bodies
PM
BM
reticular fibers
actin and myosin filaments = myosin head binds actin and bends

87
Q

recall a hemidesmosome and why it is not similar to dense bodies of smooth muscle

A

tonofilaments (intermediate filaments)
plaque BP-protein anchors to tonofilaments
integrins, laminin and anchoring fibrils (collagen VII) anchor near plaque

no alpha actinin or vinculin like in dense bodies

88
Q

describe elhers danlos syndrome

A

mutation of reticular fibers - which confer stability to smooth muscle cells
can cause rupture of digestive system and an aneurysm of arteries

89
Q

what are myosin heavy chains attached to in smooth muscle

A

attach to light chain
head attached to tail = myosin cannot bind actin = no contraction

90
Q

what does calcium initiate

A

myosin light chain kinase

91
Q

describe myosin light chain kinase of smooth muscle

A

ATP –> ADP = generates phosphate = release tail/heavy chains from light chains
now myosin head binds actin = bending of head

92
Q

why is slow contraction of smooth muscle good

A

great for intestine - peristalsis

93
Q

what does relaxation of smooth muscle depend on and explain process

A

depends on decrease of calcium levels causing subsequent inactivation of myosin light chain kinase = everything returned to normal (calcium removed)

ANAT 261 (27 decks)

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