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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
Q

to what receptors does ACh bind?

A

nicotinic ACh receptors

26
Q

where are the nicotinic ACh receptors located?

A

on the plasma membrane of the muscle cell in junctional folds

27
Q

what is the purpose of junctional folds?

A

junctional folds increase surface area for reception of ACh signals

28
Q

what does the binding of ACh receptors accomplish?

A

binding of ACh receptors will open voltage gated Na channels that will lead to depolarization of the muslce cell

29
Q

what are T tubules?

A

T tubules are invaginations in the plasma membrane of muscle cells that allows for the depolarization to quickly reach DHP/RyR-1

30
Q

what is the only source of Ca in skeletal muscle contraction?

A

calcium comes from the sarcoplasmic reticulum via an association between the DHP receptor and RyR-1 receptor.

31
Q

what is the function of calcium in skeletal muscle contraction?

A

calcium binds to troponin-C that results in a conformational change to remove TnI and expose myosin-binding sites on actin

32
Q

what happens to calcium following muscle contraction?

A

it is actively transported back into sarcoplasmic reticulum vis SERCA pumps

33
Q

what are muscle spindles?

A

specialized stretch receptors in muscle

34
Q

what composes muscle spindles?

A

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
Q

describe neuronal activity of muscle spindle

A

sensory- degree of stretch

motor- info from spinal cord that helps regulate sensitivity of stretch receptor

36
Q

what are golgi tendon organs?

A

golgi tendon organs are a type of sensory receptor that respond to increased mm tension (sensory only)

37
Q

describe the appearance of cardiac muscle?

A

striated

38
Q

what are intercalated discs?

A

attachments of adjacent cardiac muscle cells

39
Q

what is the structure and function of intercalated discs?

A

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
Q

describe the nuclei of cardiac muscle cells

A

reside inside the cell (unlike skeletal muscle)

41
Q

why do cardiac muscle cells appear branched?

A

branching comes from the association of 2+ cardiac mm cells through intercalated discs

42
Q

what features of cardiac muscle convey that it has high energy needs?

A

high glycogen and mitochondria

43
Q

describe T tubules in cardiac muscle cells?

A

cardiac muscle cells have only 1 T tubule per sarcomere, located at the z-line

44
Q

where are the pacemaker cells located?

A

SA node, AV node

45
Q

how many nuclei per cardiac muscle cell?

A

1-2 centrally located nuclei

46
Q

describe the appearance of smooth muscle

A

uninucleated, not striated

47
Q

what is the shape of smooth mm nuclei?

A

“corkscrew”, centrally located

48
Q

what neurotransmitters in smooth mm?

A

ACh and NE

49
Q

describe repair of smooth mm cells

A

smooth mm cells will rapidly divide and replace damaged cells (unlike cardiac mm)

50
Q

what does calcium bind in smooth mm?

A

calcium binds to calmodulin

51
Q

what is the function of the camodulin-calcium complex?

A

calcium-calmodulin complex will activate MLCK

52
Q

what is the function of MLCK?

A

MLCK will phosphorylate and activate myosin light chains, enabling them to bind actin and cause contraction

53
Q

what is the arrangement of myosin in smooth muscle?

A

side-polar arrangement

54
Q

describe side-polar arrangement

A

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
Q

describe Duchenne Muscular Dystrophy

A

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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