Muscle Tissue Flashcards
(59 cards)
1
Q
Layers of skeletal muscle?
A
- epimysium: external sheath of dense irregular connective tissue w/ septa that extend inwards w/ nerves/vessels/lymphs
- perimysium: thin connective tissue around each bundle of mm fibers (fascicle/functional unit)
- endomysium: thin, delicate layer of reticular fibers and fibroblasts arr external lamina of each mm fiber; hold capillaries for O2
2
Q
Where are mm layers cont w/ tendon connective tissue?
A
Myotendinous junctions
3
Q
Describe features of myofibrils
A
- dark bands = A bands
- light bands = I bands, bisected by Z disc
4
Q
Boundaries of sarcomere?
A
Z disc to Z disc
5
Q
Composition and location of thick/thin myofilaments?
A
- thick = myosin @ A-band
- thin = F-actin
6
Q
What are the 2 regulatory proteins of thin filaments?
A
- Tropomyosin, located in groove b/w 2 twisted actin strands
- Troponin; complex of TnT (binds tropomyosin), TnC (binds Ca2+), and TnI (regulates actin-myosin sys)
7
Q
Types of collagen in skeletal mm tissue?
A
Types 1 and 3 (reticulin)
8
Q
What protein anchors actin filaments to Z disc?
A
alpha actinin binding protien
9
Q
Purpose of titin?
A
- supports thick myofilaments
- connects them to Z disk
10
Q
Functions of nebulin? (2)
A
- binds each thin myofilament laterally
- anchors them to alpha actinin
- specifies length of actin polymers during myogenesis
11
Q
What is not found in H zone w/i A band?
A
Thin filaments
12
Q
Location and composition of M line?
A
- bisects H zone
- holds myomesin and creatine kinase
13
Q
Function of myomesin?
A
- binds myosin to hold it in place
14
Q
Function of creatine kinase?
A
- transfers phos groups from phosphocreatine to ADP –> ATP production
15
Q
Function of transverse (T) tubules?
A
- in sarcoplasmic reticulum
- helps trigger release of Ca2+ from SR and contraction
- invaginations of PM that insert onto sarcoplasm to encircle each myofibril
16
Q
Location and function of terminal cisternae?
A
- adjacent to each T-tubule
- T-tubule + 2 terminal cisternae = triad
- triad –> depolarization of sarcolemma in T-tubule –> Ca2+ release
17
Q
When is contraction induced? (2)
A
- AP arrives @ neuromuscular junction (NMJ or motor end plate – MEP)
- transmitted along T-tubules to terminal cisternae of SR –> Ca2+ release
18
Q
Why can myosin not bind actin in the resting state?
A
Blocked by troponin-tropomyosin complex
19
Q
What is a motor unit?
A
- 1 axon and all the mm fibers in contact w/ its branches
20
Q
Mechanism of myasthenia gravis? (4)
A
- autoimmune disorder
- Ab’s against proteins of ACh receptors
- receptors can’t be activated by ACh
- intermittent skeletal mm weakness
- extraocular mm of eyes are first affected
21
Q
Motion of titin molec’s during contraction?
A
Compressed
22
Q
Function and description of muscle spindles? (4)
A
- stretch detectors
- concentric layers of flattened cells w/ interstitial fluid and intrafusal fibers
- penetrated by sensory axons
- monitor changes in length (distension) of surr (extrafusal) mm fibers
23
Q
Function and description of Golgi tendon organs? (3)
A
- enclose sensory axons that penetrate collagen bundles @ myotendinous junction (MTJ)
- detect changes in tension w/i tendons
- inhibit motor nn activity in xs tension
24
Q
Mechanism of Duchenne musc dystrophy? (3)
A
- mutations in dystrophin gene
- defective linkages b/w cytoskeleton and ECM
- mm contractions disrupt linkages –> mm fiber atrophy
25
3 types of skeletal mm fiber?
1. Slow oxidative: slow contractions over long pd's w/o fatigue; many mitochond and capillaries (dark red)
2. Fast glycolytic: rapid, short-term contraction; few mitochond or capillaries (white)
3. Fast oxidative-glycolytic: intermediates
26
How many nuclei in each cardiac mm cell?
1
27
Describe intercalated discs (3)
- interfaces b/w adjacent cells
- transverse regions contain desmosomes and fascia adherens junctions
- longitudinal regions have gap junctions for ionic cont.
28
Major fuel of heart?
Fatty acids
29
Do terminal cisterns and T-tubules form dyads or triads in heart mm?
Dyads
30
Function of atrial natriuretic factor (ANF) peptide hormone?
- released in secretory granules from heart
| - acts on target cells in kidney to affect Na+ secretion and H2O balance
31
Major features of smooth mm cells? (4)
- tapering cells w/ many gap junction
- 1 elongated nucleus
- lack T-tubules
- caveolae = plasmalemma invaginations
32
What proteins produce contraction in smooth mm fibers?
- calmodulin
| - Ca2+ sensitive myosin light chain kinase (MLCK)
33
What part of skeletal mm are dense bodies structurally similar to?
Z discs
34
What else do smooth mm do besides contraction?
- produce collagen, elastin, and proteoglycans
| - confer major influence on ECM
35
What are lelomyomas? (3)
- benign tumors that dvp from smooth mm fibers
- most often found in wall of uterus (known as fibroids)
- painful pressure and bleeding
36
Regenerating tools of each muscle type? (3)
- satellite cells for skeletal mm
- fibroblasts for cardiac mm --> cardiac scars
- smooth mm cells replace damaged tissue for smooth mm
37
T/F: skeletal mm fibers are held together by cell junctions
False, they are bound by connective tissue
38
What holds together fascicles?
Perimysium
39
What ensheaths entire skeletal mm?
Epimysium (also carries major vasc/nn supply)
40
Position of nuclei in skeletal mm cells?
Peripheral placement
41
What protein masks myosin-binding sites on F-actin in resting mm?
Tropomyosin
42
What protein changes shape in presence of Ca2+ and pulls tropomyosin away from actin?
Troponin
43
What is A band full of?
Thick filaments
44
What is I band made of?
Thin filaments
45
Where is H band?
- middle of A band, thick filaments only
46
Purpose of M line?
Anchors thick filaments
47
What band does not change length during contraction?
A band, b/c myofilaments don't shorten
48
Relationship b/w motor unit and coarseness of movement?
Fewer mm fibers in a unit = finer movement
49
What type of collagen fiber makes up most tendons?
Type 1 collagen
50
IM filaments found in smooth mm? (2)
- desmin
| - vimentin
51
How are smooth mm cells connected?
Gap junctions
52
Importance of side-polar thick filaments? (3)
- found in smooth mm
- myosin filaments aligned in opposite directions on either side of filament
- no central bare zone like in bipolar thick filaments
53
During voluntary contraction of skeletal mm, the sarcomere:
Gets shorter
54
Basal lamina of a mm fiber is part of which structure?
Endomysium
55
What characteristic is unique to cardiac mm?
Often branched
56
What feature typifies T-tubules?
Carry depolarization to mm fiber interior
57
T/F: Smooth muscle cells of the multiunit type are connected by GAP junctions and can contract spontaneously
False
58
T/F: Individual skeletal muscle fibres are surrounded by perimysium, which is a delicate network of reticular fibres
False
59
T/F: The H-band of the sarcomere corresponds to the part in which actin and myosin filaments overlap
False
