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Histology block 2 > muscle > Flashcards

muscle Flashcards

1
Q

3 general characteristics of skeletal mm

A

multinucleated, nuclei lie outside the muscle fiber and skeletal mm is striated

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2
Q

contract endomysium, perimyseium and epimysium

A

endomesium- loos CT surrounding individual muscle fibers
perimysium- thicker CT surrounding groups of fibers to form fascicles
epimysium- dense CT that surrounds a groups of fascicles

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3
Q

why are their folds at the myotendinous junction?

A

folds will increase surface area for integrin receptors and dystrophin-glycoprotein complexes that link the actin cytoskeleton of muscle to basal lamina/collagen of tendon

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4
Q

what is an example of slow twitch type I muscles?

A

back extensors

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5
Q

what is an example of fast twitch type IIA muscles?

A

hamstrings

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6
Q

what type of metabolic process do type IIA use?

A

mainly aerobic (oxidative) but are capable of glycolysis

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7
Q

what are a few examples of fast twitch type IIB muscles?

A

extraocular mm, finger mm

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8
Q

what are the progenitor cells for muscle?

A

myoblasts

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9
Q

what are the 2 fates of myoblasts?

A

1- multinucleate myotubes

2- satellite cells

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10
Q

what are the functions of muscular satellite cells?

A

regeneration, repair mm by dividing and fusing with skeletal mm fibers if basal lamina is intact

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11
Q

what is the functional unit of a myofibril?

A

sarcomere

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12
Q

what are the general functions of accessory proteins? (3)

A

regulation of spacing
attachement
alignment

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13
Q

function of tropomodulin

A

actin-binding protein that regulates the length of actin in the sarcomere, important for the length-tension relationship

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14
Q

function of desmin

A

forms stabilizing cross-linages of adjacent myofibrils forming a lattice around sarcomeres at z line

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15
Q

function of myomesin

A

binds thick filament and anchors to m line

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16
Q

function of c protein

A

binds thick filament and anchors to m line, two present, flanking myomesin

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17
Q

dystrophin function

A

links basal lamina to actin filaments (focal adhesion proteins)

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18
Q

name the hypothesis for mm contraction

A

sliding filament hypothesis

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19
Q

what nerves innervate skeletal mm?

A

motor neurons from the ventral horn of the spinal cord

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20
Q

where do nerves and skeletal muscle meet?

A

neuromuscular junction

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21
Q

who many neuromuscular junctions per muscle fiber?

A

one

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22
Q

define motor unit

A

a motor unit consists of one motor neuron and all of the muscle fibers that are innervated by its branches

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23
Q

compare large vs. small motor units

A

large motor units seen in large, coarse movement muscles (like back), small motor units seen in small, fine movement muscles, like fingers or eyes

24
Q

what is the neurotransmitter released at the NMJ in skeletal muscle?

A

acetylcholine (ACh)

25
to what receptors does ACh bind?
nicotinic ACh receptors
26
where are the nicotinic ACh receptors located?
on the plasma membrane of the muscle cell in junctional folds
27
what is the purpose of junctional folds?
junctional folds increase surface area for reception of ACh signals
28
what does the binding of ACh receptors accomplish?
binding of ACh receptors will open voltage gated Na channels that will lead to depolarization of the muslce cell
29
what are T tubules?
T tubules are invaginations in the plasma membrane of muscle cells that allows for the depolarization to quickly reach DHP/RyR-1
30
what is the only source of Ca in skeletal muscle contraction?
calcium comes from the sarcoplasmic reticulum via an association between the DHP receptor and RyR-1 receptor.
31
what is the function of calcium in skeletal muscle contraction?
calcium binds to troponin-C that results in a conformational change to remove TnI and expose myosin-binding sites on actin
32
what happens to calcium following muscle contraction?
it is actively transported back into sarcoplasmic reticulum vis SERCA pumps
33
what are muscle spindles?
specialized stretch receptors in muscle
34
what composes muscle spindles?
spindle cells and neuron terminals surrounded by an internal capsule that is suspended in a fluid-filled space and bordered by an external capsule
35
describe neuronal activity of muscle spindle
sensory- degree of stretch | motor- info from spinal cord that helps regulate sensitivity of stretch receptor
36
what are golgi tendon organs?
golgi tendon organs are a type of sensory receptor that respond to increased mm tension (sensory only)
37
describe the appearance of cardiac muscle?
striated
38
what are intercalated discs?
attachments of adjacent cardiac muscle cells
39
what is the structure and function of intercalated discs?
contain gap junctions that allow for the rapid conduction of signals along cardiac mm fibers also contain fascia and macula adherens that transmit force of contraction between cells
40
describe the nuclei of cardiac muscle cells
reside inside the cell (unlike skeletal muscle)
41
why do cardiac muscle cells appear branched?
branching comes from the association of 2+ cardiac mm cells through intercalated discs
42
what features of cardiac muscle convey that it has high energy needs?
high glycogen and mitochondria
43
describe T tubules in cardiac muscle cells?
cardiac muscle cells have only 1 T tubule per sarcomere, located at the z-line
44
where are the pacemaker cells located?
SA node, AV node
45
how many nuclei per cardiac muscle cell?
1-2 centrally located nuclei
46
describe the appearance of smooth muscle
uninucleated, not striated
47
what is the shape of smooth mm nuclei?
"corkscrew", centrally located
48
what neurotransmitters in smooth mm?
ACh and NE
49
describe repair of smooth mm cells
smooth mm cells will rapidly divide and replace damaged cells (unlike cardiac mm)
50
what does calcium bind in smooth mm?
calcium binds to calmodulin
51
what is the function of the camodulin-calcium complex?
calcium-calmodulin complex will activate MLCK
52
what is the function of MLCK?
MLCK will phosphorylate and activate myosin light chains, enabling them to bind actin and cause contraction
53
what is the arrangement of myosin in smooth muscle?
side-polar arrangement
54
describe side-polar arrangement
myosin heads are staggered and the polarity of the heads is that same along one side of the filament and opposite on the other side
55
describe Duchenne Muscular Dystrophy
mutation in dystrophin that leads to decreased force of mm contraction, tearing of the membrane, eventual degeneration of the fibers and fibrosis

Histology block 2 (9 decks)

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