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AGRC1041 > muscle > Flashcards

muscle Flashcards

1
Q

muscle cells are

A

muscle fibres

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2
Q

myofilaments

A

actin and myosin

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3
Q

muscle cells contain myoglobin:

A
  • structured related to hemoglobin
  • O2 storage and release to working muscle
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4
Q

specialized muscle terms for cytoplasm, endoplasmic reticulum, plasma membrane

A
  • sarcoplasm
  • sarcoplasmic reticulum
  • sarcolemma
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5
Q

3 types of muscle

A

skeletal, smooth, cardiac

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6
Q

skeletal muscle

A
  • voluntary
  • striated
  • movement of skeleton, eye, tongue, etc
  • sphincters of digestive and urinary tracts
  • maintains body temp
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7
Q

smooth muscle

A
  • visceral muscle
  • main component of viscera
  • controlled by autonomic NS and endocrine system
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8
Q

cardiac muscle

A
  • heart
  • contraction inherent
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9
Q

skeletal muscle cells are what type in terms of nucleus

A

multinucleate

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10
Q

skeletal muscle fibres surrounded by reticular connective tissue

A

endomysium

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11
Q

skeletal muscle;
groups of fibres (fascicles) are separated by dense connective tissue called

A

perimysium

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12
Q

skeletal muscle
enveloping the entire muscle is a thick layer of dense connective tissue

A

epimysium (fascia)

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13
Q

endomysium:
perimysium:
epimysium:

A
  • surrounds fibers
  • surrounds fascicles
  • surroundeds entire muscle, continues as tendon
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14
Q

in transverse section skeletal muscles

A
  • fibres appear roundish in transverse section
  • flattened peripheral nuclei (remember multinucleate within the fibre)
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15
Q

striations of skeletal muscle

A

caused by organizations of actin and myosin

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16
Q

satellite cells/ Stem cells; likely mesenchymal stem/ stromal cells

A

Differentiate into muscle cells in response to damage

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17
Q

embryological development of skeletal muscle; fibers develop from chains of

A

myoblasts

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18
Q

embryological development of skeletal muscle; chains of myoblasts fuse end to end to form multinucleate syncytia called

A

myotubes

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19
Q

steps of embryological development of skeletal muscle

A
  • Fibres develop from chains of myoblasts
  • Fuse end to end to form multinucleate syncytia: myotubes
  • Lay down actin & myosin
  • Nuclei become displaced to periphery
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20
Q

once myoblasts have fused to form a fiber, their nuclei can no longer

A

synthesize DNA and so they cannot divide (so can’t create new muscle fibres but they can grow bigger)

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21
Q

skeletal muscle grows via

A

hypertrophy (so they can’t grow new fibers, but they can grow bigger)
- Increase in sarcoplasm
- Number of myofibrils

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22
Q

what inhibits muscle growth

A

gene myostatin;
so if mutation of myostatin can grow huge muscles

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23
Q

Satellite cells (MSCs)

A
  • Mesenchymal stem cells
  • for Growth in the young
  • for Repair in adults
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24
Q

3 types of skeletal muscle fibers

A
  • Red fibers (type I: slow oxidative fibers) endurance
  • White fibers (Type IIX; fast glycolytic fibers) sprint
  • Intermediate fibers (Type IIA; fast ox/ glyx fibers), mix of red and white
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25
Q

Red fibers (type I: slow oxidative fibers) endurance

(skeletal muscle)

A
  • Fewer myofibrils, rich in myoglobin and mitochondria
  • Extensive blood supply
  • Aerobic
  • Slow, powerful and sustained (tonic) contractions
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26
Q

White fibers (Type IIX; fast glycolytic fibers) sprint

(skeletal muscle)

A
  • Less myoglobin and sarcoplasm, simple mitochondria
  • Relatively poor blood supply; why they are white
  • Rich in glycogen
  • Anaerobic
  • Rapid (twitch) contractions, easily exhausted
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27
Q

Intermediate fibers (Type IIA; fast ox/ glyx fibers), mix of red and white

A
  • Properties intermediate between red and white fibers
  • Rich in myoglobin and mitochondria
  • Rich in glycogen
  • extensive blood supply
28
Q

Example; breast meat on roast chicken;

what fibers is is dominated by

A

flap wings briefly to escape; short burst of flight powered by white (fast) fibers, white meat

(vs in ducks Long flights so meat tends to be darker red than chicken breast meat)

29
Q

aerobic muscle fibers:
anaerobic muscle fibers:

A
  • red, slow
  • white, fast
30
Q

Striations

A
  • Each fiber (muscle cell): myofibrils in parallel
  • Each myofibril; myosin and actin laid down in an orderly pattern, in register with each other, forming A and I bands
31
Q

A bands

A
  • dark
  • anisotropic, means they stay constant length
  • made up of myosin
  • Pale central H band within, bisected by dark M line where myosin filaments joint
32
Q

I bands

A
  • light
  • isotropic; means they change their length, do this when muscle contracts
  • made up of actin
  • Bisected by a dark Z line; where actin filaments join
33
Q

Sarcomere;

A

regions between Z lines

34
Q

Myofibrils during contractions (sliding filament theory)

A
  • Actin filaments (thin, attached to Z line) slide over the myosin filaments (thick, attached to M line)
  • Shortening of the sarcomere (and also the I band)
35
Q

sliding filament theory where myofibrils move during contraction is dependent on

A

ATP and CA2+

36
Q

Sarcolemma

A
  • Aka plasmalemmal/ membrane
  • Sends tubular extensions into muscle fiber called T tubules
  • Surround each myofibril at junction of the A and I bands
  • Continuous with extracellular environment
37
Q

Sarcoplasmic reticulum

A
  • Aka endoplasmic reticulum
  • Network that encircles myofibrils between T tubules
  • Form flattened cisternae on either side of T tubules
  • Triad; cisternae, T tubule, cisternae
38
Q

Ca2+ stored in

A

sarcoplasmic reticulum

38
Q

During nervous stimulation sarcolemma becomes

A

depolarized, transmitted throughout entire fiber via T tubule system

39
Q

depolarization of sarcolemma causes

A

release of Ca2+ form the sarcoplasmic reticulum; flows into sarcoplasm that surrounds the actin and myosin filaments; causes their contraction

40
Q

Triad

A

cisternae, T tubule, cisternae

41
Q

what provides energy for contraction

A

Mitochondria located within I bands

42
Q

Innervation of skeletal muscle via

A

motor nerves from CNS

43
Q

Each motor nerve divides within the muscle, branches supply separate groups of fibers and the branches end in

A

specialized synapses called neuromuscular junctions (motor end plates)

44
Q

motor unit=

A

Nerve and fibers it innervates

45
Q

Sensory nerve endings =

A
  • neuromuscular spindles
  • Convey info to CNS
  • Rate and extent of muscle stretch
  • Tendo-muscular junction
46
Q

Least specialized of the 3 muscle types

A

smooth muscle

47
Q

smooth muscle fibers have how many nuclei

A

one, central, oval/round

48
Q

smooth muscle fibres may be found

A
  • Singly
  • Groups: Sheets or layers
    Fasciculi
49
Q

many smooth muscle fibers form

A

irregular branching fasciculi ; fasciculi function as contractile units

50
Q

Fibers within a fasciculus are roughly

A

parallel

51
Q

does smooth muscle have myofibrils/ sarcomeres?

A

No myofibrils, no sarcomeres

52
Q

3 types of myofilaments in smooth muscle

A
  • Actin (thin)
  • Myosin (thick)
  • Intermediate filaments
53
Q

in smooth muscle actin anchored at

A

dense bodies: connect to intermediate filaments

54
Q

how do smooth muscle contract

A

also sliding filament theory

55
Q

in smooth muscle _______ spread the force of contraction throughout cell

A

Intermediate filaments

56
Q

Innervation of smooth muscle

A
  • Contraction is inherent
  • Coordinated via gap junctions between adjacent cells
  • Rate of contraction modulated by the ANS and hormones
  • Smooth muscles surrounding blood vessels regulated by vasomotor nerves
57
Q

Cardiac muscle made up of chains of branching cells with how many nuclei

A

1-2 central nuclei

form a 3D branching network

58
Q

cardiac muscle cells joined at specialized junctions=

A

intercalated discs

59
Q

Intercalated discs;

A
  • specialized junction where cardiac muscle cells joined
  • allow cells to be linked physiologically and mechanically, rapid spread of contraction and anchorage of myofilaments
60
Q

are cardiac muscle striated

A
  • yes, arrangement of myofilaments similar to skeletal muscles
  • Cross striation present
    (Not as distinct as skeletal muscles)
  • Longitudinal striations
    (Due to rows of mitochondria)
61
Q

Each cardiac muscle cell contacts other via

A

intercalated discs

62
Q

cardiac muscle , how its different to skeletal muscle

A
  • while actin and myosin are arranged into myofibrils, they have fan-like arrays rather than cylindrical structures
  • Separated by sarcoplasm containing many mitochondria; aerobic metabolism
  • T tubules are larger; penetrate myofilaments at Z lines, all parts of fiber no more than 2 microns from sarcolemma, no triads
63
Q

4 types of cardiac muscle

A
  • Ventricular muscle (described above)
  • Atrial muscle; cells have a smaller diameter, T tubules absent
  • Conducting fibers; smaller than contractile cells, embedded in dense connective tissue to form nodes, intercalated discs and myofilaments not well developed, coordinate electrical events
  • Purkinje fibers; modified conducting fibers in ventricle, not purkinje neurons!
64
Q

Innervation of cardiac muscle

A
  • Contraction is inherent; independent of neural control
  • No neuromuscular junctions
  • No sensory endings
  • However it is modulated by neural signals
  • ANS
  • Nerves terminate in nodes formed by conducting fibers
65
Q

Which of the following statements about muscle is INCORRECT?

The contraction of cardiac muscle is dependent on neural control and so it is extensively supplied with neuromuscular junctions and sensory nerve endings

In skeletal muscle cells, depolarisation of the sarcolemma is transmitted throughout the fibre via the organisation of T-tubules

In skeletal muscle, neuromuscular spindles convey information to the central nervous system about the rate and extent of muscle stretch

The contraction of smooth muscle is inherent and is coordinated by gap junctions between adjacent cells

A

The contraction of cardiac muscle is dependent on neural control and so it is extensively supplied with neuromuscular junctions and sensory nerve endings

AGRC1041 (20 decks)

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