Skeletal and Smooth Muscle Flashcards
(74 cards)
1
Q
What are the types of muscle?
A
skeletal, smooth, cardiac
2
Q
What is the makeup of skeletal muscle from big to small?
A
large muscle bundles> myocytes/fibers> myofibrils> sarcomeres> actin and myosin
3
Q
What are thin filaments composed of in skeletal msucle?
A
actin helix with tropomyosin and troponin complex attached
4
Q
What are thick filaments composed of in skeletal muscle?
A
myosin 2
5
Q
Thin and thick filaments interact to produce what in skeletal muscle?
A
force
6
Q
What is the organization of a sarcomere?
A
2 z lines, I band, H zone
7
Q
What is the I band made out of?
A
thin filaments ONLY; actin
8
Q
What is the H zone made out of?
A
thick filaments ONLY; myosin heads
9
Q
What is the neuromuscular junction of skeletal muscle cells?
A
- nerve axon innervating each muscle fiber
- releases Ach
- Ach binds to the AchR on muscle cell which is permeable to Na, K, Ca
10
Q
What receptor causes depolarization in skeletal muscle cells?
A
AchR
11
Q
What is the process of the initiation of a muscle contraction?
A
- Ca release from SR
- Ca binds to troponin C and initiates a conformational change
- tropomyosin slides into the groove between the actin strands
- myosin can bind actin
12
Q
What are the 5 states of cross bridge cycling?
A
- attached
- released
- cocked
- cross-bridge
- power-stroke
13
Q
What occurs during the attached state?
A
- ATP binds to myosin head
- dissociation of actin-myosin complex
14
Q
What occurs during the released state?
A
- ATP is hydrolyzed
- myosin heads return to resting conformation
15
Q
What occurs in between the released and cocked states?
A
myosin heads relax
16
Q
What occurs during the cocked state?
A
cross-bridge forms and myosin head binds to a new position on actin
17
Q
What occurs during the cross-bridge state?
A
- phosphate is released
- myosin heads change conformation, resulting in power stroke
18
Q
What occurs during the power-stroke state?
A
ADP is released
19
Q
What happens between the power-stroke state and returning to the attached state (beginning of cycle)?
A
- myosin heads are arched
- myosin heads attach
20
Q
Is the influx of Ca through receptors necessary for contraction?
A
NO
21
Q
What are the steps in excitation-contraction coupling?
A
- charge carried along the plasma membrane of transverse tubules
- depolarization activates L-type Ca channels in transverse tubules leading to a conformational change
- physical conformational change induced in ryanodine receptors that are adjacent to the L-types but in SR
- RyR release Ca into cytosol
22
Q
What occurs when muscles are relaxed during the sliding filament theory?
A
- Z bands become widen
- I bands widen
- A bands remain the same
- H bands widen
23
Q
What occurs when muscles are contracted during the sliding filament theory?
A
- Z bands narrow
- I bands narrow
- A bands remain the same
- H bands narrow
24
Q
What is the SERCA pump in skeletal muscle relaxation?
A
Ca pump that sequesters myoplasmic Ca into the SR
25
Where does SERCA pump Ca into?
lumen
26
What is calsequestrin?
Ca binding protein near RyR
27
What is sarcalumenin?
transfers Ca from uptake sites to release sites
28
What is considered a shuttle protein in muscle relaxation?
sarcalumenin
29
What is smooth muscle composed of?
* thick filament: 1/4 of the one found in skeletal muscle
* thin filament: actin, tropomyosin, NO troponin
30
Does smooth muscle have sarcomeres and Z lines?
NO
31
What are the components of a smooth muscle contraction?
hormones, neural, mechanical, spontaneous electrical activity (AP)
32
What type of junction aloows unitary smooth muscle cells to act together?
GAP
33
How is the smooth muscle cell contraction initiated?
by Ca bindign to calmodulin
34
What is required to phosphorylate myosin?
myosin light chain
35
What is the process of excitation-contraction coupling for smooth muscle?
1. Ca enters cytoplasm through channels located in caveoli
2. Ca release from SR via IP3 activation of SR Ca channels
## Footnote
CIRCA (Ca induced -> Ca released)
36
What happens during smooth muscle relaxation?
1. pump Ca back into SR using CIRCA
2. activate myosin ligth chain phosphatase
37
What are the factors affecting force production in skeletal muscle?
* initial length of muscle fiber
* fiber type
* mtoor unit recrutiment
* speed of contraction
* muscle fiber arrangement
38
What are the type of muscle actions?
dynamic and static
39
What are the types of dynamic actions?
concentric and eccentric
40
What is a concentric action?
* muscle develops tension and shortens
* muscle force > extrenal force
## Footnote
example: lifting a weight
41
What is an eccentric action?
* muscle develops tension and lenghtens
* muscle force < external force
## Footnote
examples: braking force = hiking downhill; putting weight down
42
What is a type of static action?
isometric
43
What happens during an isometric action?
* muscle develops tension with NO change in length
* muscle force = external force
## Footnote
example: doing a planck
44
How can a muscle generate force without shortening?
with the use of contractile elements and connective/elastic components
45
How do isometric and eccentric actions help the muscle generate force without shortening?
* elastic components are stretched; contributes passively to total muscle force
* sarcomeres ratchet and pull toward their center which actively generates force
46
What is titin?
elastic protein that runs from Z lines to M line of sarcomere
47
What is the largest protein and 3rd most abundant protein in muscle?
titin
48
How is titin responsible for producing the passive force in muscle?
acts as a molecular spring
49
What are the metabolic properties of fasta nd slow twitch fibers?
1. primary energy pathways utilized to make ATP (oxidative, glycoytic)
2. determined by differences in mitochondria, capillary density, myoglobin conc., enzymatic activity
50
What are the contractile properties of fast and slow twitch fibers?
1. speed of contraction
2. maximal force production
3. fatigue resistance
51
What happens in the speed of contraction for fast and slow twicth fibers?
* myosin ATPase activity: faster in type 2 isozyme
* Ca cycling
52
What is the maximal force production for fast and slow twicth fibers?
* # of cross bridges formed/cross sectional area
* fiber diameter
* rate of cross bridge formation
53
What does the fatigue resistance for fast and slow twicth fibers depend on?
energy pathways utilized
54
What is the difference in faitgue for slow and fast twitch fibers?
* slow type 1: resistant
* fast type 2a: resistant
* fast type 2b: fatigable
55
What is the difference in color for slow and fast twitch fibers?
* slow type 1: red (myoglobin)
* fast type 2a: red (myoglobin)
* fast type 2b: white (low myoglobin)
56
What is the difference in metabolism for slow and fast twitch fibers?
* slow type 1: oxidative
* fast type 2a: oxidative
* fast type 2b: glycolytic
57
What is the difference in mitchondria for slow and fast twitch fibers?
* slow type 1: high
* fast type 2a: higher
* fast type 2b: fewer
58
What is the difference in glycogen for slow and fast twitch fibers?
* slow type 1: low
* fast type 2a: abundant
* fast type 2b: high
59
Whatis the name when ALL muscle fibers are innervated by a single motor neuron?
the motor unit
60
What is the difference bewteen temporal and spatial summation?
* temporal: increased frequency of stimulation of motor units
* spatial: increased # of motor units that are recruited
61
What is summation?
how muscle increases force
62
What is recruitment?
NOT ALL muscle fibers are participating all the time, some are inactive
63
What exactly happens during temporal summation?
singl AP releases Ca for short duration to cause a twitch and can summated
64
Stimulating a muscle with an AP before it has had time to relax leads to what?
* increased Ca duration
* new contraction occurs before preceding one is over
* force progressivle increases
* fusion of the twitch contractions
* sustained contraction
* force is amplified
65
What exactly occurs in spatial summation?
all muscle fibers in a motor unit are activated simultaneously
66
What is creatine phosphate ?
ATP buffer system that keeps ATP constant
67
How is glycogen a muscle energy source during exercise?
plays part in glycolysis (3ATP + lactic acid) and aerobic oxidation (37 ATP)
68
Plasma fatty acid, adipose create what as a muscle energy source?
oxidative phosphorylation
69
What are the muscle energy sources during exercise?
* ATP
* creatine phosphate
* glycogen
* plasma glucose + glycogen
* plasma fatty acid, adipose
70
What is the difference between tonic and phasic muscles?
* tonic: continuously active to maintain a level of tone
* phasic: rhythmic or intermittent contractions
71
What is an exmple of a tonic muscle?
blood vessels, respiratory tract, sphincters
72
What is an example of a phasic muscle?
GI tract, urogenital, lymphatic
73
What is the unit for tonic muscles?
multiunit: tone associated with action potentials
74
What is the unit for a phasic muscle?
single unit: AP propagates from cell-to-cell
