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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
why does smooth muscle have corkscrew nucleus
retracts a bit when fixed with chemicals
26
why is smooth muscle being involuntary good
body needs contraction all the time like in vessels and stomach
27
what is hyperplasia and describe
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
28
what is epimysium of skeletal muscle
divide muscles into groups of cells
29
what are skeletal tissues surrounded by
dense ct = bundle or fascicle
30
what is perimysium of skeletal muscle
thin layer ct fibrocytes surround bundle special - connected by gap junctions
31
what is endomysium of skeletal muscle
BM that surrounds and separates individual cells very thin reticular fibers capillaries some fibrocytes
32
what is the role of CT around muscle cells in skeletal muscles
mechanical transducer to the forces generated by contracting muscle cells associated to tendons and ligaments (produce movement and transduce)
33
describe breakdown of muscle (fascicle to filaments)
fascicle (bundle of muscle fibers) --> muscle fiber (1-40nmx10-100um) -->1500 myofibrils (1-2um diameter) -->3000 thin filaments (F-actin), 1500 thick filaments (myosin)
34
what is center of pseudoband H
cross linking proteins forms M line H band = only thick filaments
35
what does myosin have
tail and head
36
what is sarcomere
smallest repetitive subunit of contractile apparatus Z line to Z line
37
what is Z line
alpha actinin anchors thin filament
38
what is M line
creatine kinase = cross linking - catalyses phosphocreatine + ADP --> ATP + creatine
39
describe thick filament
myosin 4 myosin heavy chains 2 myosin light chains
40
what happens when use chymotrypsin to split molecules of thick filament into fragments and separate
LMM = light meromysoin HMM = heavy meromyosin
41
describe HMM subunits and function
HMMS - 2 HMMS - 1 = 2 activities = binds ATP and has ATPase activity, actin binding site = wants to bind actin and activates ATPase
42
describe thin filament
actin globular proteins polarized molecule binds in active site
43
name the important components of broken down thin filament
tropomyosin troponin
44
name and describe the 3 troponin subunits
TnI = inhibit actin myosin interaction TnC = binds calcium TnT = anchors to tropomyosin *ONLY with calcium
45
where is tropomyosin present
in groove
46
what does troponin do
binds calcium and produces change in conformation of tropomyosin and can bind actin
47
describe mechanism of action of sarcomere - physically
thin slides over thick - no change in length pseudoband H becomes smaller and so does I band
48
describe mechanism of action of sarcomere - chemically
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
name and describe proteins involved in mechanism of contraction of sarcomere
titin = spring like, connects myosin to Z line and provides stability nebulin = surround actin filaments tropomodulin
50
describe terminal cisternae
sarcoplasmic reticulum - SER non granulated
51
describe connecting tubules
sarcoplasmic reticulum connect adjacent terminals mitochondria
52
describe T tubules
sarcolemma - PM invagination of PM follow between 2 terminal cisternae
53
what is a triad
2 terminal cisternae + t tubule
54
where is calcium ATPase
on membrane of terminal cisternae
55
what is calsequestrin
protein pumps calcium into sarcoplasmic reticulum dumps molecules without binding
56
describe when action potential fired in sarcomere
inside T tubule depolarization of membrane calcium released into sarcoplasm and will be available for contraction
57
describe STEPS = 5 when action potential fired in sarcomere
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
what are other words for neuromuscular junction
motor end plate myoneural junction terminal bouton
59
how does contraction occur in sarcomeres
Simultaneously in all sarcomeres, in all myofibrils of one muscle cell in all muscle cells in a bundle of muscle
60
how to ensure synchronous contraction
muscle fibers innervated by myelinated nerves fast due to myelin
61
describe myelinated motor nerves
branch out within perimysium and endomysium where each nerve gives rise to several terminal wings called terminal boutons
62
describe where the myelinated motor nerves penetrate
penetrates at level of epimysium axons branch in endomysium synapse between nerve and muscle cell (muscular tissue)
63
where is ACH receptor present (neuromuscular junction)
post synaptic membrane only gates - bind acetylcholine
64
describe synaptic vesicle (neuromuscular junction)
many when have action potential in neuron = stimulates exocytosis fusion with presynaptic membrane contain ACH (small molecules released in lumen synaptic cleft)
65
what happens when ACH binds (neuromuscular junction)
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
describe myelin - what its caused bypp
schwann cell - surrounded by BM, synthesis of myelin and wraps around axon
67
is BM continuous with muscle fiber of (neuromuscular junction)
yup
68
what is presynaptic membrane (neuromuscular junction)
membrane of axon - terminal bouton
69
what is synaptic cleft (neuromuscular junction)
space in between pre and post synaptic membranes
70
what is postsynaptic membrane (neuromuscular junction)
sarcolemma - PM of muscle cell
71
how would you visualize neuromuscular junction
immunochemistry to visualize proteins = one antibody for axon and one identifies terminal bouton
72
describe ACH receptor
molecular weight = 270.00 5 subunits = 2 alpha, 2 beta, 1 gamma, 1 delta under BM
73
what is myasthenia gravis
produces antibodies against acetylcholine receptor
74
describe ACH-cholinesterase
present in synaptic celft ACH after contraction has to be removed = breaks ACH to acetate (recycled) and choline
75
does cardiac muscle have sarcomeres
yuhhh
76
name and describe each part of intercalated disk
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
describe zonula adherens (intercalated disk)
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
describe mucula adherens - desmosomes (intercalated disk)
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
describe gap junctions (intercalated disk)
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
describe sarcoplasmic reticulum of cardiac muscle
sometimes has t tubules and terminal cisternae triad = at level of z line
81
what does one unit of smooth muscle look like
sarcomere - but not tho
82
what are smooth muscle cells not similar to
hemidemosomes
83
describe dense bodies of smooth muscle
anchoring of actin filaments alpha actinin like proteins - similar to z line but NOT
84
what is similar to t tubules in smooth muscke
little invaginations represent t tubule = vesicles/caveolae
85
where is myosin in smooth muscle cells
some myosin filaments all spread and floating in plasma membrane
86
what do smooth muscle cells have - specifics
dense bodies PM BM reticular fibers actin and myosin filaments = myosin head binds actin and bends
87
recall a hemidesmosome and why it is not similar to dense bodies of smooth muscle
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
describe elhers danlos syndrome
mutation of reticular fibers - which confer stability to smooth muscle cells can cause rupture of digestive system and an aneurysm of arteries
89
what are myosin heavy chains attached to in smooth muscle
attach to light chain head attached to tail = myosin cannot bind actin = no contraction
90
what does calcium initiate
myosin light chain kinase
91
describe myosin light chain kinase of smooth muscle
ATP --> ADP = generates phosphate = release tail/heavy chains from light chains now myosin head binds actin = bending of head
92
why is slow contraction of smooth muscle good
great for intestine - peristalsis
93
what does relaxation of smooth muscle depend on and explain process
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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