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Biol 66 - Human Physiology > Chapter 12 Muscles > Flashcards

Chapter 12 Muscles Flashcards

1
Q

what are the 3 muscle types and their characteristics

A

skeletal muscle - striated, voluntary (somatic), attached to bones
smooth muscle - non-striated, involuntary (autonomic), in organs and skin
cardiac muscle - striated, involuntary (autonomic), in heart

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2
Q

what is a skeletal muscle cell called

A

muscle fiber

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3
Q

muscle fiber

A

multiple nuclei
up to 20cm long
usually shorter than entire muscle, some as long

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4
Q

skeletal muscle

A

multiple muscle fibers with connective tissue bound together

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5
Q

what is the muscle attached to the bone by

A

tendons

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6
Q

what does each muscle fiber contain

A

myofibrils, which contain myofilaments (myosin and actin)

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7
Q

what is responsible for the striated appearance in a skeletal muscle

A

dark A bands (thick filaments, myosin)

and light I bands (thin filaments, actin)

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8
Q

what is a neuromuscular junction

A

location where muscle fiber and neuron meet

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9
Q

pathway of Action Potential in muscle

A

AP in motor neuron - release of acetylcholin (ACh) into neuromuscular junction - ACh binds to nicotinic ACh receptor (NAchR) in the muscle fiber - AP occurs and results in contraction of fiber

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10
Q

motor unit

A

one motor neuron and all the muscle fibers it controlls

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11
Q

what do smaller motor units allow

A

finer muscle control

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12
Q

what is recruitment

A

increase the # of active motor units in a muscle = increase the strength of a contraction

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13
Q

what is summation

A

stimulation of motor units at different time, results in summation of contraction and increased muscle strenght

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14
Q

myofibril

A

bundle of myofilaments

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15
Q

different section of myofibril

A

sarcomere

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16
Q

what are the striations in myofibrils due to

A

thick and thin protein myofilaments

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17
Q

thick myofilament

A

dark appearance
Myosin
has two globular heads that form cross-bridges (contact actin during contraction)

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18
Q

thin myofilament

A 
light appearance
actin
regulate contraction
composed of troponin C
Tropomyosin
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19
Q

what does troponin C bind

A

Calcium

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20
Q

what does troponin T bind

A

Tropomyosin

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21
Q

what does troponin I bind

A

actin

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22
Q

what does tropomyosin do

A

blocks myosin binding site on actin

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23
Q

what is a sarcomere

A

the basic contractile unit in striated muscle

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24
Q

characteristics of sarcomere

A

section of myofibril
Z lines at each end
composed of Actin(connected to Z lines) and Myosin (connected in place by titin)

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25
cross-bridges
myosin contacts actin during contraction
26
contraction
activation of the force-generating sites (cross-bridges) in muscle fibers
27
what is the sliding filament mechanism
overlapping thick and thin filaments in sarcomere move past each other to contract the muscle
28
what happens during the sliding filament machanism
myosin binds to actin myosin pulls Z lines closer together reduction of width of I-bands
29
what happens to the binding site in actin in a relaxed muscle
it is blocked by tropomyosin
30
what does troponin do
holds tropomyosin in blocking position
31
what is troponin
a heterotrimer (wihtin 3 substunits - CTI)
32
what needs to happen that the myosin cross-bridge can bin to actin
tropomyosin must move away from blocking position
33
what happens during contraction of a muscle
muscle fiber depolarizes due to arriving AP release from Ca2+ from sarcoplasmic reticulum Ca2+ binds to troponin C troponin T chnages shape -> tropomyosin moves away from blocking actin myosin cross-bridge binds to actin
34
trigger for contraction
Ca2+
35
3 thin filaments
troponin, tropomyosin, actin
36
activation of myosin head
ATP binds to myosin head | head becomes "cocked" - ready to bind to actin
37
cross bridge power stroke
phosphate is released | cross bridge produces power stroke
38
what is the result of a power stroke
myosin head moves actin filaments
39
pathway of a power stroke
ATP hydrolysis myosin gets "cocked" (active) binding of myosin to actin releases energy comformation change in myosin = power stroke actin is pulled toward center of sarcomere new ATP attaches to myosin head to break it away
40
role of calcium in muscle contraction
Ca2+ released by sarcoplasmic reticulum into sarcoplasm binds with tropomin C Tropomyosin moves away from blocking position
41
what brings AP into skeletal muscle fiber
transvers tubule (T-tubule)
42
what is the period between the AP and the contraction called
Latent period
43
when is calcium released
as a consequence of an arriving AP
44
how long does AP in fiber last
1-2 ms, ends before contraction
45
what does an AP stimulize
membrane close to the sarcoplasmic reticulum
46
why is the sarcoplasmic reticulum surrounded by extensive meshwork
to assure that all the released Ca2+ ions diffuse to all the toponin C
47
pathway from AP to muscle contraction
``` AP arrives at motor neuron release of ACh ACh binds to nicotinic ACh in sarcolemma Na+ diffueses in - causes AP AP enters Transverse tubules Ca2+ channels open Ca2+ diffuses out into sarcoplasm Ca2+ binds to troponin - stimulates contraction in myofibrils ```
48
what means tension
force pulling on an object by a contracting muscle
49
what is a load
force exerted (anüben) on muscle by an object
50
relationship of load and tension
opposing forces
51
what is a twitch
contaction of a muscle fiber to single AP
52
summation
increase in muscle tension | successive (following) APs during contraction
53
recruitment
increased activation of muscle fibers due to stronger AP
54
what are the types of contraction
isometric contraction | insotonic contraction
55
characteristics of isometric contraction
"same size" contraction muscle develops tension but does not change length tension = load can be converted into isotonic contraction holding a box
56
characteristics of isotonic contraction
"same tension" contraction tension remains constant and muscle changes length tension > load lifting or lowering a weight
57
length tension relationship
optimal length = lots of actin-myosin overlap & plenty of room to slide - max. tension short & long sarcomere = lack of room to slide or actin-myosin don´t overlap enough - little tension
58
by what are skeletal muscle fibers differentiated
``` contraction speed (fast or slow twitch) pathway used to form ATP (oxidative, glycolytic) ```
59
oxidative muscle fibers
red due to many blood vessels use oxydative phosphorylation high capacity for aerobic respiration a lot of mitochondria
60
glycoliytic fibers
anaerobic respiration of glycogen white, few blodd vessels larger diameter little amount of mitochndria
61
3 muscle fiber types
type I slow oxidative fibers type II A fast oxidative fibers type IIX fast glycoliytic fibers
62
charcteristics of type I slow oxidative fibers
``` fatigue-resistant small diameter, red many mitochondria oxidative, low glycolytic body posture ```
63
characteristics of type II A fast oxidative fibers
``` fatigue-resistant response quickly intermediate diameter, red many mitochondria oxidative, intermediate glycolytic walking ```
64
characteristics type IIX glycolytic fibers
``` fatigable large diameter, white high glycolytic fewer mitochondria sprinting ```
65
what is muscle fatigue
decrease in muscle tension due to previous contraction
66
reasons for fatigue
conduction failure lactic acid builup reduced ability of sarcoplasmatic reticulum to release Ca2+ use of all muscle glycogen during low intensity
67
muscle cramps
involuntary tetanic contraction due to electrolyte imbalance or persistant dehydration
68
hypocalcemic tetany
involuntary contraction due to low extracellular Ca2+ concentration
69
muscular dystrophy
deterioration (Verschlechterung) of muscle
70
myasthenia gravis
paralysis due to increased # of ACh receptors
71
cardiac muscle
only in heart involuntary similarities to skeltal and smooth muscle muscle cells join end to end at intercalted disks
72
pathway from AP to muscle contraction
``` AP arrives at motor neuron release of ACh ACh binds to nicotinic ACh in sarcolemma Na+ diffueses in - causes AP AP enters Transverse tubules Ca2+ channels open Ca2+ diffuses out into sarcoplasm Ca2+ binds to troponin - stimulates contraction in myofibrils ```
73
why is the sarcoplasmic reticulum surrounded by extensive meshwork
to assure that all the released Ca2+ ions diffuse to all the toponin C
74
cardiac muscle contraction
AP goes through T-tubules Ca2+ enters cell through gates depolarization release of more Ca2+ through sarcoplasmatic reticulum thin filament-, cross-brige activation and force generation same as in skeletal muscle
75
characteristics of smooth muscle
no striation, no myofibrils, no sarcomeres arranged in layers, not long fibers involuntary - nervous part of autonomic nervous system no troponin needed
76
what is the key difference in the cross brodge activation in smooth muscles
no troponin C tropomyosin doesn´t block cross-bridge access to actin changes in thick filaments due to Ca2+ activate cross-bridges
77
where does calcium come from - smooth muscle
internal- (SR) and external source (ECF)
78
what causes the contraction of smooth muscles
Ca2+ binds to calmodulin calmodulin activates enzyme (myosin light-chain kinase) phosphorylated myosin bind to actin cross-bridges generate force

Biol 66 - Human Physiology (13 decks)

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