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COT - Exam 1 > 6.1 - Lecture - Muscle > Flashcards

6.1 - Lecture - Muscle Flashcards

1
Q

Endomysium

A
  • Sounds fibers
  • immediately surrounds muscle fibers - primary reticular fibers
  • transmit force laterally within muscle
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2
Q

Perimysium

A
  • Surrounds fasicles

- recognizable for its major blood vessels found in its thicker CT layer

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3
Q

Epimysium

A
  • Connects fasicles
  • Surrounds muscle as a whole
  • connects body of muscle to tendon (dense regular CT connecting muscle to bone)
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4
Q

Myotubes

A
  • early myofibers

- they are smaller and still have centrally located nucleus and free cytoplasm

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5
Q

Cardiac Myocyte

A
  • basic unit of cardiac muscle - can have primary nuclei (often just 1)
  • joined at the ends by fascia adherens (adhering plate)
  • have gap JXN along membranes between adjacent cardiomyocytes - allows for contraction in unison
  • have intercalated discs
  • sarcoplasmic cone - cytoplasmic space devoid of myofibrils (b/c they bend around central nucleus): filled with mitochondria and cellular organelles
  • dyads
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6
Q

Striated Muscle

A
  • general term for muscle in which actin and myosin is organized into parallel bundles of myofibrils
  • subtypes : Cardiac muscle and skeletal muscle
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7
Q

Skeletal Muscle

A
  • subtype of muscle typically found connected to bones - generally generates force under direct command of NS
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8
Q

Sarcolemma

A

cell membrane of a muscle cell

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9
Q

Myofiber

A

= basic unit of skeletal muscle - bound by sarcolemma
- different from muscle cell because develops from union of several myocytes in order to form syncytium (cells sharing one outer membrane + common cytoplasm)

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10
Q

Myocyte

A

= muscle cell

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11
Q

Satellite Cells

A

= adult myocytes persisting outside the cell membrane of the myofiber, but still inside of the external membrane

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12
Q

Describe the parallel arrangement of skeletal muscle

A
  • Adjacent myofibers that travel in the same direction form fasicles - the basic unit of muslce from an anatomical perspective
  • within 1 myofiber there are numerous distinct unit of myofibrils containing orderly parallel arrangements of my filaments (thin filament actin and thick filament myosin)
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13
Q

Fascicle

A
  • the basic unit of muscle from an anatomical perspective

- formed by adjacent myofibers that travel in the same direction

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14
Q

Myofibrils

A
  • the numerous distinct units forming one myofiber

- each contains orderly parallel arrangements of myofilaments

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15
Q

Myofilaments

A
  • thin filament actin

- thick filament myosin

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16
Q

Sarcomeres

A
  • repeating organized units within myofibrils

- within a sarcomere actin and myosin are held in an orderly hexagonal packing by structural proteins

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17
Q

Alpha-actinin

A
  • one of the structural proteins of a sarcomere
  • holds actin
  • forms the Z-line
  • arranged perpindicular to the myofilaments
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18
Q

Myomesin and C-protein

A
  • structural proteins of a sarcomere
  • holds myosin
  • forms the M-line
  • arranged perpindicular to the myofilaments
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19
Q

Nebulin and titin

A
  • structural proteins of a sarcomere
  • run in the parallel direction with the myofilaments
  • binds actin to the alpha-actinin of the Z-line
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20
Q

Troponin and tropomyosin

A
  • regulate the binding of actin and myosin
21
Q

A-band

A
  • formed by thick myosin molecules
22
Q

I-band

A
  • formed by the absence of myosin

- will change with contraction

23
Q

H-band

A
  • formed by the absence of actin at the center of the sarcomere
  • will change with contraction
24
Q

Costameres

A

= intermediate filaments

  • bind adjacent myofibrils to the cell membrane
  • a clinically important protein that is part of this = dystrophin
25
Q

Dystrophin

A
  • A clinically important protein that is included in the costmeres (intermediate filaments that connect to the cell membrane and myofibrils)
26
Q

What are the three types of skeletal muscle

A

Type I = Red
Type IIa = intermediate
Type IIb = white

  • each muscle has a characteristic ratio of the three, which may change through exercise or disease state
27
Q

Type I fibers

A
  • slow contracting
  • non-fatiguing
  • aerobic fibers
  • mainly derive energy from oxidative metabolism
28
Q

Type IIa

A
  • have properties intermediate to types I and IIb
29
Q

Type IIb

A
  • fast contracting
  • easily fatiguing
  • anerobic
  • mainly derive energy from glycolytic pathways
30
Q

External membrane

A
  • analogous in structure to basement membrane of the epithelia
  • separates skeletal muscle fibers from the surrounding CT
31
Q

Endomysium

A
  • CT connected to the external membrane
32
Q

Perimysium

A
  • surrounds each fascicle

- is thicker, tube-shaped layer of CT (compared to endomysium)

33
Q

Epimysium

A

= CT fascia that binds the anatomical form of the muscle to the surrounding tissues
- is external to the perimysium

34
Q

Cardiac muscle

A

= type of striated muscle specific to the heart

  • specialized to support rhythmic contraction
  • cardiac myocytes are smaller than skeletal muscle myofibers
  • typically larger than smooth muscle myocytes
  • one or sometimes two nuclei - centrally located
  • arrangement of myofilaments, myofibrils, sarcomeres is identical to skeletal muscle
  • have sarcoplasmic cone (space without myofilaments - filled with mitochondria and other organelles)
  • adjacent myocytes are connected by gap jxns and bound physically by fascia adherens (which creates intercalated disc pattern in LM)
35
Q

Sarcoplasmic Cone

A
  • space devoid of myofilaments
  • created due to the central nucleus in cardiac myocytes
  • filled with mitochondria and other organelles
  • only in cardiac myocytes
36
Q

Fascia adherens

A
  • physical connection between adjacent cardiac myocytes
  • usually longitudinally physically binding them?
  • only in cardiac myocytes?
37
Q

Intercalated disc

A
  • specific to cardiac myocytes?

= the name for the pattern created by the appearance of the fascia adherens in the LM

38
Q

Purkinje Fibers

A

= modified cardiac myocytes

  • contain fewer myofilaments
  • run in characteristic anatomical pathways in the subendocardium
  • deliver electric potentials to cardiac muscle
39
Q

Smooth muscle

A

= evolutionarily oldest muscle

  • consists of fibroblast-like cell that expresses myosin
  • an involuntary muscle
  • forms layers in many organs such as the GI, Bladder, uterus, prostate
40
Q

What are the two types of smooth muscle

A

Unitary

Multiunit

41
Q

Unitary Smooth muscle

A
  • smooth muscle acts as one mechanical unit
  • transmitting signals from relatively few axons among cells via gap JXNs
    (ratio of axons - cells is greater than 1/10?)
42
Q

Multiunit Smooth Muscle

A
  • Contains closer to a 1:1 ratio of axons to muscle cells

- allows for finer, graded control in places where it is needed (i.e. Iris)

43
Q

Random fact about smooth muscle cells in the uterus from the syllabus (p.114)

A

Smooth muscle cells in the uterine myometrium are hormonally responsive and grow up to 200 microns in length during pregnancy

44
Q

NMJ

A
  • a specialized structure joining a motor nerve axon with a muscle
  • is most specialized in skeletal muscle
  • also exists in rudimentary form in smooth muscle
45
Q

Junctional folds

A
  • local invaginations of the sarcolemma underneath the point of contact with the axon
  • designed to increase surface area + the number of Ach Receptors present
46
Q

Muscle spindles

A

= sensory structures in muscle designed to sense the position and state of stretch of the muscle
- composed of modified muscle fibers (bag and chain fibers)

47
Q

Bag and Chain fibers

A

= modified muscle fibers that compose the muscle spindles

  • FXN in sensing stretch of the muscle
  • sensory fibers originate at the surface of the bag and chain fibers to sense stretch
  • motor fibers (including gamma motor neurons) innervate the bad and chain fibers to alter their sensitivity
48
Q

Gamma motor neurons

A
  • unique motor fiber that innervates the bag and chain fibers comprising the muscle spindles
  • FXN: alter the sensitivity of the bag and chain fibers
49
Q

Golgi Tendon Organ

A
  • functionally similar structure to the muscle spindles
  • positioned between the muscle fibers and their connected tendon (i.e. in parallel with the muscle fiber)
  • primarily associated with reflexive responses of the muscles

COT - Exam 1 (26 decks)

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