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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
Sarcoplasmic reticulum
This is like ER but it is specific to muscle cells
26
Sarcomere contraction
Leads to a change in the overlap of actin and myosin NOT in their individual lengths
27
Functional units of a sarcomere
Z line, I band, A band
28
Z line
Form end points of sarcomere; when myosin heads pull actin two are sarcomere z lines are being pulled closer together
29
I band
Reflects location of actin filament this is lighter region on slide
30
A band
Reflects location of myosin filaments this is darker region on slide
31
Action potential path
Surface -> deeper level -> sarcomere -> contraction
32
Thick filaments
Myosin
33
Thin filaments
Actin
34
T tubules
Transverse tubules; Invagination of cell membrane that brings action potentials to the surface to the core of cell (invagintation of endomysium)
35
Actin and myosin relative movement
Myosin head pulls actin toward middle of sarcomere; relative lengths of I bands shorten while A bands remain constant
36
Key to making a muscle work
Everything contracting at the same time; 1 axon goes to multiple muscle fibers leading to all fibers contracting together
37
How to increase muscle force
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
Fatigue
Can have fatigue of muscle and also fatigue of nerve (at muscle level its due to lactic acid)
39
Motor units
Single motor neuron going to group of muscle fibers
40
Slow twitch fiber
Holding notebook up, precise control like itching an eye brow
41
Fast twitch fiber
Sprinting, larger diameter, more force
42
Neuromuscular junction
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
Extrafusal muscle fibers
Make up the bulk of muscles
44
Resting length
Sarcomeres contract most efficiently over a predictable range of lengths, on average optimum rest length is 2.5um
45
Triad
Adjacent transverse tubules and terminal cisternea as triads which are at A band I band junction
46
Termination of muscle contraction
SR reabsorbs Ca2+ terminating contraction
47
Motor nerve
Motor nerve to a muscle may contain many axons supplying many muscle fibers some axons may split to provide innervation to multiple fibers
48
Muscle spindles and Golgi tendon organs
Provide feedback to CNS to modulate muscle activity
49
Muscle spindles
Sensory receptors of muscles; often concentrated in muscles associated with slow contractions
50
Action potential separation
Separated by nerve endings associated with muscle spindle, goes DR -> DV -> VH -> VR -> response
51
Intramural fibers
Shorter than extrafusal fibers can be distributed at various positions along muscle length and across its girth
52
Satellite cells
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
Neuromuscular disease histology
See varroa this sizes of fibers
54
Changing fiber types
Can change with with exercise and steroids but there is a genetic component
55
Skeletal muscle overview
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
Cardiac muscle
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
Intercalated discs
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
Gap junctions
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
Can heart regenerate
No no satalite cells
60
Cardiac muscle fiber features
Short, have gap junctions to communicate
61
Pace of cardio myocyte contraction
Coordinated by autonomic input via cardiac nerves (parasympathetic from vagus sympathetic from thoracic spinal nerves)
62
Pacemaker potential of cardiomyocytes
Common to all cardimyocytes but SA node with autonomic input sets overall pace for entire heart
63
Purkinje cells
Part of intracardiac bundle system distributing action potential throughout heart wall
64
Heart muscle regeneration
No potential for regeneration no satalite cells
65
Cardiac myocyte nuclei
Central; may be two nuclei per monocytes
66
Myosin in heart
Myosin found in heart is unique compared to that found in most skeletal muscle
67
Cardiac myocyte fiber features
Short and branched
68
Smooth muscle
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
Smooth muscle cell types
Small spindle shaped cells that form sheets of muscle tissue; short muscle cells (20-200um long); unbrahcned
70
Smooth muscle cell force
Can all produce a small amount of force for a long period of time
71
Smooth muscle nuclei
Single nucleus centrally located
72
Ca2+ smooth muscle
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
Surface receptors and smooth muscle
Can alter the intrinsic pacing of smooth muscle via signal transduction pathway
74
Innervation of smooth muscle
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
Actin and myosin interactions smooth muscle
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
Dense bodies
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
Smooth muscle control
Involuntary control; pacing is intrinsic can be modulated by autonomic input
78
Smooth muscle regeneration
Has potential for regeneration via population of stem cells

Block One (31 decks)

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