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Block One > Introduction To Muscles > Flashcards

Introduction To Muscles Flashcards

1
Q

3 muscle types

A

Skeletal, smooth, cardiac

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2
Q

Where do muscles come from

A

Muscle cells migrate to dorsal and ventral part of ___ limb and start seeing cleavage that is moving out as developing myocyte

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3
Q

Myoblast

A

Undifferentiated cell with central nucleus, cytoplasm, looks like generic cell

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4
Q

Differentiating myoblast

A

Will start differentiating and you will start to see actin and myosin forming in the cytoplasm, this is still a myoblast just a differentiating myoblast

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5
Q

Muscle

A

A contractile tissue that may perform “work” in course of normal function

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6
Q

Myotubules

A

Myoblast serially aggregate into elongate microtubes in this process they accumulate nuclei which are accommodated via lengthening; as these mature contractile proteins are expressed; has receptors on outside where axons will come in and send signals

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7
Q

Myofilaments

A

Parallel orientation and arrangement of myotubules

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8
Q

Primary myotubules

A

Early myofibres, first generation of cells to develope will be surrounded by smaller less well developed secondary myotubules

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9
Q

Adult myocute or myofiber

A

Have linear organization, have neuromuscular junction, for from centraly nucleared cell to peripheral nucleated cell

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10
Q

Peripheral nuculeared muscle cell

A

If contracting don’t want a nucleus in the way

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11
Q

Syncytium

A

Single cellular construct with multiple nuclei

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12
Q

Secondary myotubules

A

Form around primary myotubules like scaffolding, have central nuceli

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13
Q

Muscle cell innervation fetus

A

Polyneuromal Innervation: innervation by multiple axons for each muscle cell; as development progresses shed polyneuromal innervation and now have innervation via one nerve fiber

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14
Q

Sarcomere

A

Contractile units of muscles themselves; repeating contractile units that appear in register across width of muscle fiber and appear serially along length of muscle fiber

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15
Q

Late forming myotubules

A

Some will become satalite cells and herald a regenerative function later in life

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16
Q

Neutral cell adhesion molecule

A

Gene expression thought to regulate number of active myocytes in the muscle (no new myocytes added to muscle after fetal differentiation stops)

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17
Q

Muscle cell size in fetus vs in adult

A

In a fetus you will see primary type I myofibers (larger) and surrounding this second generation of smaller secondary fast type II mycofibers; in adult you will see much larger fibers, fast twitch fiber population will be equal type I fibers

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18
Q

How does a muscle contract

A

Every little piece contractions leading to an overall contraction

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19
Q

Endomysium

A

Around individual muscle fibers

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20
Q

Perimysium

A

Surrounds fascicles

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21
Q

Epimysium

A

Surrounds outer edge of muscles

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22
Q

Fascicles

A

Muscle fibers packaged into fascicles

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23
Q

Blood vessels and muscles

A

Need ample blood supply to muscles

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24
Q

Action potential in muscle

A

Causes shortening of sarcomere which bc of serial arrangement and synchronous activation effects a rapid and powerful shortening of entire muscle ; Ca2+ will be released into sarcoplasmic reticulum and this will change actin and myosin interaction

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25
Q

Sarcoplasmic reticulum

A

This is like ER but it is specific to muscle cells

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26
Q

Sarcomere contraction

A

Leads to a change in the overlap of actin and myosin NOT in their individual lengths

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27
Q

Functional units of a sarcomere

A

Z line, I band, A band

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28
Q

Z line

A

Form end points of sarcomere; when myosin heads pull actin two are sarcomere z lines are being pulled closer together

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29
Q

I band

A

Reflects location of actin filament this is lighter region on slide

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30
Q

A band

A

Reflects location of myosin filaments this is darker region on slide

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31
Q

Action potential path

A

Surface -> deeper level -> sarcomere -> contraction

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32
Q

Thick filaments

A

Myosin

33
Q

Thin filaments

A

Actin

34
Q

T tubules

A

Transverse tubules; Invagination of cell membrane that brings action potentials to the surface to the core of cell (invagintation of endomysium)

35
Q

Actin and myosin relative movement

A

Myosin head pulls actin toward middle of sarcomere; relative lengths of I bands shorten while A bands remain constant

36
Q

Key to making a muscle work

A

Everything contracting at the same time; 1 axon goes to multiple muscle fibers leading to all fibers contracting together

37
Q

How to increase muscle force

A

Have more nervus input so more muscle fibers are stimulated by different axons to contract (ie if every other fiber was being stimulated stimulate every one ect)

38
Q

Fatigue

A

Can have fatigue of muscle and also fatigue of nerve (at muscle level its due to lactic acid)

39
Q

Motor units

A

Single motor neuron going to group of muscle fibers

40
Q

Slow twitch fiber

A

Holding notebook up, precise control like itching an eye brow

41
Q

Fast twitch fiber

A

Sprinting, larger diameter, more force

42
Q

Neuromuscular junction

A

This is usually in middle of muscle fiber (usually half way between origin and insertion); this is a chemical synapse between motor neuron and muscle fiber

43
Q

Extrafusal muscle fibers

A

Make up the bulk of muscles

44
Q

Resting length

A

Sarcomeres contract most efficiently over a predictable range of lengths, on average optimum rest length is 2.5um

45
Q

Triad

A

Adjacent transverse tubules and terminal cisternea as triads which are at A band I band junction

46
Q

Termination of muscle contraction

A

SR reabsorbs Ca2+ terminating contraction

47
Q

Motor nerve

A

Motor nerve to a muscle may contain many axons supplying many muscle fibers some axons may split to provide innervation to multiple fibers

48
Q

Muscle spindles and Golgi tendon organs

A

Provide feedback to CNS to modulate muscle activity

49
Q

Muscle spindles

A

Sensory receptors of muscles; often concentrated in muscles associated with slow contractions

50
Q

Action potential separation

A

Separated by nerve endings associated with muscle spindle, goes DR -> DV -> VH -> VR -> response

51
Q

Intramural fibers

A

Shorter than extrafusal fibers can be distributed at various positions along muscle length and across its girth

52
Q

Satellite cells

A

Stem cells found along periphery of skeletal myocytes, separate from main myocyte yet bound to it with in its basal lamina; these allow for muscle regeneration

53
Q

Neuromuscular disease histology

A

See varroa this sizes of fibers

54
Q

Changing fiber types

A

Can change with with exercise and steroids but there is a genetic component

55
Q

Skeletal muscle overview

A

Multiple nuceli per fiber (cell) located peripherally in adult
long cells < (or=to) 40cm
unbranded cells in normal state
Capable of regeneration via satalite cells
Highly vascular
Each muscle cell innervated by single motor axon
Sensory feedback is provided by muscle spindles and Golgi tendon organs

56
Q

Cardiac muscle

A

Found only in the heart DOES NOT extend to blood vessels or veins; striated bc serially arranged sarcomere; highly oxidative requires rich blood supply; cappilaries between cardiomyocytes, mitocondria also plentiful; have a central nuclei

57
Q

Intercalated discs

A

Specialized membrane connections of cardiomyocytes which contain gap junctions located between adjacent cells. Intercalated discs serve to anchor cells and allow movement of ions between cells; synchronize cell contractions; perpendicular to long axis of cell

58
Q

Gap junctions

A

Aka Nexi Contained in intercalated disks, these are where electrical action potential can be directly communicated form cell to cell; these essentially allow leakage of action potential and lead to synchronicity

59
Q

Can heart regenerate

A

No no satalite cells

60
Q

Cardiac muscle fiber features

A

Short, have gap junctions to communicate

61
Q

Pace of cardio myocyte contraction

A

Coordinated by autonomic input via cardiac nerves (parasympathetic from vagus sympathetic from thoracic spinal nerves)

62
Q

Pacemaker potential of cardiomyocytes

A

Common to all cardimyocytes but SA node with autonomic input sets overall pace for entire heart

63
Q

Purkinje cells

A

Part of intracardiac bundle system distributing action potential throughout heart wall

64
Q

Heart muscle regeneration

A

No potential for regeneration no satalite cells

65
Q

Cardiac myocyte nuclei

A

Central; may be two nuclei per monocytes

66
Q

Myosin in heart

A

Myosin found in heart is unique compared to that found in most skeletal muscle

67
Q

Cardiac myocyte fiber features

A

Short and branched

68
Q

Smooth muscle

A

Found throughout body generally associated with involuntary functions such as peristalsis, arterial tone, and pupillary sphincter diameter; associated with vascular structures, tubular organs, and other organ system

69
Q

Smooth muscle cell types

A

Small spindle shaped cells that form sheets of muscle tissue; short muscle cells (20-200um long); unbrahcned

70
Q

Smooth muscle cell force

A

Can all produce a small amount of force for a long period of time

71
Q

Smooth muscle nuclei

A

Single nucleus centrally located

72
Q

Ca2+ smooth muscle

A

Stored in SR or alveolar adjacent to sarcolemma; when distributed into cytoskeleton binds to calmodulin and activates a myosin light chain kinase which allows myosin to bind to actin effection contraction

73
Q

Surface receptors and smooth muscle

A

Can alter the intrinsic pacing of smooth muscle via signal transduction pathway

74
Q

Innervation of smooth muscle

A

Efferent neurons don’t necessarily contact every smooth muscle cell nerve ending can be adjacent to one or several smooth muscle cells and initiate action potential in those cells which in turn transmit action potential to adjacent smooth muscle cells within compartment to facility synchronous contraction and relaxation

75
Q

Actin and myosin interactions smooth muscle

A

Actin interspersed throughout thick myosin filaments throughout cytoplasm and is located adjacent to cell membrane; interactions throughout skeleton of cell make it change shape during contraction

76
Q

Dense bodies

A

Focal densities; consist of alpha-actinin tied in with sarcolemma and some myofilaments throughout cell; analogous fo z lines of striated muscles; adjacent cells communicate through gap junctions allowing synchronicity of contraction throughout region

77
Q

Smooth muscle control

A

Involuntary control; pacing is intrinsic can be modulated by autonomic input

78
Q

Smooth muscle regeneration

A

Has potential for regeneration via population of stem cells

Block One (31 decks)

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