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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
Q

cross-bridges

A

myosin contacts actin during contraction

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26
Q

contraction

A

activation of the force-generating sites (cross-bridges) in muscle fibers

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27
Q

what is the sliding filament mechanism

A

overlapping thick and thin filaments in sarcomere move past each other to contract the muscle

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28
Q

what happens during the sliding filament machanism

A

myosin binds to actin
myosin pulls Z lines closer together
reduction of width of I-bands

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29
Q

what happens to the binding site in actin in a relaxed muscle

A

it is blocked by tropomyosin

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30
Q

what does troponin do

A

holds tropomyosin in blocking position

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31
Q

what is troponin

A

a heterotrimer (wihtin 3 substunits - CTI)

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32
Q

what needs to happen that the myosin cross-bridge can bin to actin

A

tropomyosin must move away from blocking position

33
Q

what happens during contraction of a muscle

A

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
Q

trigger for contraction

A

Ca2+

35
Q

3 thin filaments

A

troponin, tropomyosin, actin

36
Q

activation of myosin head

A

ATP binds to myosin head

head becomes “cocked” - ready to bind to actin

37
Q

cross bridge power stroke

A

phosphate is released

cross bridge produces power stroke

38
Q

what is the result of a power stroke

A

myosin head moves actin filaments

39
Q

pathway of a power stroke

A

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
Q

role of calcium in muscle contraction

A

Ca2+ released by sarcoplasmic reticulum into sarcoplasm
binds with tropomin C
Tropomyosin moves away from blocking position

41
Q

what brings AP into skeletal muscle fiber

A

transvers tubule (T-tubule)

42
Q

what is the period between the AP and the contraction called

A

Latent period

43
Q

when is calcium released

A

as a consequence of an arriving AP

44
Q

how long does AP in fiber last

A

1-2 ms, ends before contraction

45
Q

what does an AP stimulize

A

membrane close to the sarcoplasmic reticulum

46
Q

why is the sarcoplasmic reticulum surrounded by extensive meshwork

A

to assure that all the released Ca2+ ions diffuse to all the toponin C

47
Q

pathway from AP to muscle contraction

A 
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
Q

what means tension

A

force pulling on an object by a contracting muscle

49
Q

what is a load

A

force exerted (anüben) on muscle by an object

50
Q

relationship of load and tension

A

opposing forces

51
Q

what is a twitch

A

contaction of a muscle fiber to single AP

52
Q

summation

A

increase in muscle tension

successive (following) APs during contraction

53
Q

recruitment

A

increased activation of muscle fibers due to stronger AP

54
Q

what are the types of contraction

A

isometric contraction

insotonic contraction

55
Q

characteristics of isometric contraction

A

“same size” contraction
muscle develops tension but does not change length
tension = load
can be converted into isotonic contraction
holding a box

56
Q

characteristics of isotonic contraction

A

“same tension” contraction
tension remains constant and muscle changes length
tension > load
lifting or lowering a weight

57
Q

length tension relationship

A

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
Q

by what are skeletal muscle fibers differentiated

A 
contraction speed (fast or slow twitch)
pathway used to form ATP (oxidative, glycolytic)
59
Q

oxidative muscle fibers

A

red due to many blood vessels
use oxydative phosphorylation
high capacity for aerobic respiration
a lot of mitochondria

60
Q

glycoliytic fibers

A

anaerobic respiration of glycogen
white, few blodd vessels
larger diameter
little amount of mitochndria

61
Q

3 muscle fiber types

A

type I slow oxidative fibers
type II A fast oxidative fibers
type IIX fast glycoliytic fibers

62
Q

charcteristics of type I slow oxidative fibers

A 
fatigue-resistant
small diameter, red
many mitochondria
oxidative, low glycolytic
body posture
63
Q

characteristics of type II A fast oxidative fibers

A 
fatigue-resistant
response quickly
intermediate diameter, red
many mitochondria
oxidative, intermediate glycolytic
walking
64
Q

characteristics type IIX glycolytic fibers

A 
fatigable
large diameter, white
high glycolytic
fewer mitochondria
sprinting
65
Q

what is muscle fatigue

A

decrease in muscle tension due to previous contraction

66
Q

reasons for fatigue

A

conduction failure
lactic acid builup
reduced ability of sarcoplasmatic reticulum to release Ca2+
use of all muscle glycogen during low intensity

67
Q

muscle cramps

A

involuntary tetanic contraction due to electrolyte imbalance or persistant dehydration

68
Q

hypocalcemic tetany

A

involuntary contraction due to low extracellular Ca2+ concentration

69
Q

muscular dystrophy

A

deterioration (Verschlechterung) of muscle

70
Q

myasthenia gravis

A

paralysis due to increased # of ACh receptors

71
Q

cardiac muscle

A

only in heart
involuntary
similarities to skeltal and smooth muscle
muscle cells join end to end at intercalted disks

72
Q

pathway from AP to muscle contraction

A 
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
Q

why is the sarcoplasmic reticulum surrounded by extensive meshwork

A

to assure that all the released Ca2+ ions diffuse to all the toponin C

74
Q

cardiac muscle contraction

A

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
Q

characteristics of smooth muscle

A

no striation, no myofibrils, no sarcomeres
arranged in layers, not long fibers
involuntary - nervous part of autonomic nervous system
no troponin needed

76
Q

what is the key difference in the cross brodge activation in smooth muscles

A

no troponin C
tropomyosin doesn´t block cross-bridge access to actin
changes in thick filaments due to Ca2+ activate cross-bridges

77
Q

where does calcium come from - smooth muscle

A

internal- (SR) and external source (ECF)

78
Q

what causes the contraction of smooth muscles

A

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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