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Integrated Exam 3/9 > Histo: Skeletal, Cardiac, and Smooth Muscles (smooth not complete) > Flashcards

Histo: Skeletal, Cardiac, and Smooth Muscles (smooth not complete) Flashcards

1
Q

What are elongated muscle cells called and how are they oriented?

A
  • Myocytes
  • Parallel to each other in organized bundles
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2
Q

What is muscle cytoplasm called and what is it occupied by?

A
  • Sarcoplasm
  • Actin and myosin myofilaments
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3
Q

What tissue type?

A
  • skeletal
  • look for striations and cells on outside
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4
Q

What tissue type?

A
  • cardiac
  • look for circular dots with lots of space
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5
Q

What tissue type?

A
  • smooth
  • 2 different sheets
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6
Q

Skeletal muscle activity fastest

A

strong
quick
discontinuous
voluntary contraction
striated

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7
Q

Cardiac muscle activity

A

strong
quick
continuous
involuntary contraction
striated
speed can be modulated

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8
Q

Smooth muscle activity

A

weak
slow
involuntary contraction
no striations
speed can be modulated

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9
Q

Skeletal muscle general features

A
  • made up of dense fibers that are organized and have high metabolic activity
  • syncytium (share a cytoplasm)
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10
Q

Connective tissue investment layers

A

(outermost) Epimysium -> Perimysium -> Endomysium -> muscle fiber

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11
Q

Epimysium

A
  • outer layer
  • fuses and becomes tendon which moves bone
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12
Q

Perimysium

A
  • invests fascicles (groups of myocytes)
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13
Q

Endomysium

A
  • CT element that surrounds individual myocytes/fibers
  • thin and small
  • contains capillaries
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14
Q

Capillary network

A
  • exists in endomysium
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15
Q

What is essential for the force of transduction of muscle fibers/bundles?

A

CT surrounding mus fiber

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16
Q

Classification of skeletal muscle fibers is based on 3 things:

A
  • contractile speed: rate of contraction and relaxation
  • enzymatic velocity: rate of ATP breakdown by myosin ATPase during contraction
  • metabolic profile: capacity for ATP production by oxidative phosphorylation or glycolysis
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17
Q

T1 Muscle Fiber

A
  • Slow oxidative fibers
  • red
  • slow twitch / slow myosin ATPase
  • Many mitochindria and glycogen
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18
Q

What type of athlete has T1 muscle fibers?

A
  • Long distance runners
  • Meant for long, slow/sustained contraction needed to maintain posture
  • Fatigue resistant
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19
Q

What type of athlete has T2a muscle fibers?

A
  • 400-800m Sprinters, hockey players
  • Fatigue resistant
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20
Q

What type of athlete has T2b muscle fibers?

A
  • Short-distance sprinters, weight lifters
  • Meant for rapid contractions and fine, precise movements
  • Fatigue prone
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21
Q

T2a Muscle Fiber

A
  • Fast oxidative, glycolytic fibers
  • medium pink color
  • fast twitch
  • high glycogen mitochondria and myoglobin content
    *Capable of anaerobic metabolism
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22
Q

T2b Muscle Fiber

A
  • Fast glycolytic fibers
  • white/light pink color
  • fast twitch
  • less mitochondria and myoglobin content (less metabolically active)
  • high glycogen and anaerobic activity
    *Myosin ATPase fastest of all fibers
    *Last fibers to be recruited by nervous system
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23
Q

What is the structural and functional subunit of the myofiber?

A

Myofibrils

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24
Q

What is a myofibril?

A
  • short, linear repeating unit of a sarcomere
  • principle sarcoplasmic component of the muscle fiber
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25
Q

What are the functional contractile apparatus of skeletal and cardiac muscles?

A

Sarcomeres (bounded by z-lines)

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26
Q

What 2 types of myofilaments are myofibrils composed of?

A

-thin filaments (actin)
-thick filaments (myosin II)

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27
Q

Add labeled Z,I,M

A

Add labeled Z,I,M

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28
Q

What is a sarcomere bounded and centered by?

A

Bounded: Z, I
Centered: A, H, M

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29
Q

Actin:

A
  • principal contractile protein of thin myofilaments
  • pair of helically entwined polymers (f-actin) of G-actin molecule
  • associated with troponin & tropomyosin
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30
Q

What binds actin?

A

TnI

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31
Q

What binds Ca+?

A

TnC

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32
Q

What binds tropomyosin?

A

TnT

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33
Q

Myosin II:

A
  • composed of 2 polypeptide heavy chains, each with a “head” and rod-like “tail” portion
  • 4 light chains associated with the head of heavy chain
  • head has ATPas activity and actin binding site
  • the projecting globular heads form the cross- bridges between the thick & thin filament
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34
Q

Titin

A
  • anchors myosin filaments in the Z lines
  • very large, has elasticity
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35
Q

a-actinin

A
  • short
  • major component of Z line
  • anchors actin to Z line
36
Q

Nebulin

A
  • an inelastic protein
  • assists in stabilizing a-actinin/actin interactions at z line
37
Q

Tropomodulin

A
  • “caps” actin to regulate its length at its free end
38
Q

Myomesin

A
  • myosin binding protein
  • holds myosin in register at the M line
39
Q

C protein

A
  • myosin binding protein
  • lies adjacent to myomesin
  • holds myosin in register at the M line
40
Q

What makes up the M-line in chromatography

A

Myomesin and C protein

41
Q

Sarcomere labeled

A
42
Q

Do actin and myosin interact at rest?

A

NO

43
Q

What band is not visible during muscle contraction?

A

I band

44
Q

What occurs during muscle contraction?

A

Thin (A) filaments slide past thick (M) filaments, resulting in greater penetration into A bands

45
Q

Costamere

A

Connects the sarcomere of the myocyte to the cell membrane

46
Q

Dystrophin

A

Links actin to laminin in the basal lamina, is dysfunctional in muscular dystrophy

47
Q

Desmin

A

Surrounds sarcomere at the Z-line attaching them to the sarcolemma

48
Q

Sarcolemma

A
  • cell membrane of muscle fiber
  • invested with a basal lamina
49
Q

Sarcoplasm

A
  • cytoplasm of a muscle fiber
  • many mitochondria
50
Q

Sarcoplasmic reticulum (SR)

A
  • special form of smooth er in muscles
  • sequesters calcium during contractions
  • rich in calsequestrin (binds calcium)
  • triad is functional unit
51
Q

What is a triad composed of?

A
  • 1 T-tubule (has voltage sensitive proteins to control depolarization of sarcolemma)
  • 2 Terminal cisternae (reservoir for calcium w/ voltage sensitive calcium channels)
52
Q

Triad image

A
53
Q

What is a motor unit?

A

A single alpha motor neuron/axon
and the skeletal muscle fibers it innervates

54
Q

Properties of the Motor Unit:

A
  • all or none law (either muscle cell contracts or it does not)
  • muscle fibers of the same motor unit contract in unison
  • the force generated by a muscle depends on the # of motor units contracting, the types of muscle fibers activated, and the rate and duration of motor neuron input
  • fine control muscles: 1 motor axon can innervate 1-3 muscle fibers
  • course control muscles: 1 axon can innervate 100s of muscles
55
Q

What is the motor end plate?

A

A specialized synapse where a
motor axon terminates onto a myofiber

56
Q

Where does communication occur in skeletal muscles?

A

motor end plate

57
Q

Properties of the Motor End Plate:

A
  • only 1 MEP per muscle fiber
  • axons can branch and invaginate sarcolemma to form junctional folds (high SA)
  • ACh is present on the presynaptic side of the junctional folds
  • depolarization of the nerve causes
    exocytosis, spilling ACh into the
    synaptic cleft
  • this activates ACh receptors on the sarcolemma
  • results in depolarization of the muscle
    fiber and contraction occurs
58
Q

EM of neuromuscular junction labeled

A
59
Q

What are the sensory receptors in muscle?

A
  • muscle spindle (fuse) -> gives rise to reflexes and movement
  • golgi tendon organ (GTO) -> innervates the tendon
60
Q

muscle spindle (fuse)

A
  • detects changes in muscle length
  • contain both sensory and motor fibers
  • stretch reflex (stretch on muscle causes contraction)
61
Q

golgi tendon organ (GTO)

A
  • monitors tension developed in muscle
  • afferent (sensory) fibers only
  • prevents damage during excessive force generation (stimulation causes relaxation of muscle via inhibition of a-motorneurons)
62
Q

Intrafusal muscle spindle

A
  • innervated by gamma motor neurons (sensory and motor fibers)
  • contract slightly, but NO force around a joint
  • maintain LENGTH of the fuse
63
Q

Extrafusal muscle spindle

A
  • innervated by alpha motor neurons
  • highly contracting fibers that generate force and supply the muscle with power
64
Q

Muscle spindle image

A
65
Q

Muscle spindle fuse image

A
66
Q

Fuse image (longitudinal section)

A
67
Q

GTO image (tendon of achilles)

A
68
Q

How do skeletal muscles develop?

A
  • fusion of myoblasts (single cells)
69
Q

What tissue type do myoblasts come from?

A

mesoderm

70
Q

What is myostatin?

A

a regulatory protein that negatively controls muscle size (growth and differentiation)

71
Q

What is myoD?

A

a regulatory factor that activates the expression of muscle-specific genes

72
Q

Development of skeletal muscle order

A

mesoderm -> myoblast -> multinucleated myotubes -> muscle fiber

73
Q

What are satellite cells?

A
  • muscle stem cells
  • present in adults
  • sit on edge of myocyte
  • monitor damage
74
Q

Satellite cell image

A

a = nucleus of satellite cell
b = collage
arrows = basal lamina

75
Q

Satellite cell in EM

A
76
Q

Role of satellite cells?

A

induce repair

77
Q

Cardiac Muscle: Overview

A
  • under involuntary nervous control (autonomic)
  • no regenerative capacity, damaged heart muscle is replaced by CT scar
  • fibers are NOT syncytial network, but rather individual cells
  • contain striations and sarcomeres
78
Q

Cardiac Muscle: Cellular Structure

A
  • one or two centrally arranged nuclei
  • cells are joined to each other by intercalated discs
  • mitochondria and glycogen granules are enriched at the poles of the nucleus and referred to as sarcoplasmic cone
79
Q

Cardiac Muscle: Ultrastructural Organization

A

Intercalated discs:
- junctional complexes that appear as dark transverse lines between muscle fibers
- 2 portions: lateral and transverse

Transverse portion:
- runs across fibers
- possesses 2 junctional specializations: fasciae adherentes and maculae adherentes (desmosomes)

*fasciae adherentes = anchor thin filaments

*macular adherentes = bind cells to prevent separation during contractions

Lateral portion (gap junctions):
- provide direct electrical communication between cells

80
Q

Cardiac muscle organization labeled

A
81
Q

Atrial granules

A
  • found in atrial cardiac muscle cells
  • contain the hormones atrial
    natriuretic actor (ANF) and brain natriuretic factor (BNF)
  • both are diuretic hormones
82
Q

Cardiac Muscle: Nervous Investment

A
  • cardiac muscle fibers contract spontaneously
  • initial stimulus for contraction is by sinoatrial node
  • when stimulus reaches purkinje fibers which spread out the timing from the SA node
  • innervation is modulatory: speeds up or slows down the intrinsic beat
82
Q

T tubule system: cardiac vs skeletal

A
  • cardiac muscle has larger t-tubules than skeletal muscle
  • sarcoplasmic reticulum of cardiac muscle is poorly developed relative to the SR in skeletal muscle
  • each cardiac cell T tubule is associated with one terminal cistern, forming dyads
    instead of triads
83
Q

What are purkinje fibers?

A
  • modified cardiac muscle cells located
    in the atrioventricular bundle of His
  • larger than ordinary cardiac muscle cells
  • have a large number of gap junctions
  • LOW myofibril content and HIGH glycogen content
84
Q

EM of purkinje fiber

A

Integrated Exam 3/9 (8 decks)

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