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A&P II > Chapter 12 > Flashcards

Chapter 12 Flashcards

1
Q

what are skeletal muscles connected to?

A

two or more bones by tendons

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2
Q

What tissue surrounds muscle (epimysium) and tendon connective tissue?

A

continuous

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3
Q

what divides muscle into bundles (fascicles) of muscle cells?

A

Perimysium

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4
Q

What surrounds muscles fibers?

A

endomysium

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5
Q

Sarcolemma

A

plasma membrane

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6
Q

Are muscle fibers multinucleated?

A

yes

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7
Q

Sarcoplasm

A

cytoplasm

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8
Q

label a muscle diagram

A
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9
Q

components of a muscle fiber

A
  • myofibrils
  • mitochondria
  • sarcoplasmic reticulum (Ca storage)
  • T tubules
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10
Q

Lateral sacs

A
  • terminal cisternae
  • store calcium (increasing the capacity of the sarcoplasmic reticulum to release calcium) and release it when an action potential courses down the transverse tubules, eliciting muscle contraction
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11
Q

triad

A
  • T tubule + two lateral sacs
  • responsible for the regulation of excitation-contraction coupling
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12
Q

myofibrils

A
  • Give skeletal and cardiac muscle striated appearance
  • Orderly arrangement of thick and thin filaments
  • Actin (thin)
  • Myosin (thick)
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13
Q

Filaments form ?

A

sarcomeres (like car that are linked together)

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14
Q

A band

A

Dark band
Thick filaments
myosin

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15
Q

H zone

A

Thick filaments
No overlap

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16
Q

M line

A

Links thick filaments

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17
Q

I band

A

Light band
Thin filament
actin
No overlapping

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18
Q

Z line

A

Links thin filaments

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19
Q

Sarcomere

A

Functional unit
Z line to Z line

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20
Q

label sarcomere diagram

A
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21
Q

Actin

A
  • Contractile protein
  • Each G (globular monomer proteins) actin has a binding site for myosin
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22
Q

Tropomyosin

A
  • Regulatory protein
  • Overlaps binding sites on actin for myosin
  • Blocks myosin binding
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23
Q

Troponin

A
  • Regulatory protein
  • Ca2+ binding to troponin regulates skeletal muscle contraction
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24
Q

Name the three protein complexes of troponin

A

Attaches to actin
Attaches to tropomyosin
Binds Ca2+ reversibly

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25
Q

Thick myofilament

A
  • Myosin tail is toward the M line
  • Myosin head is toward the I band
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26
Q

Myosin head binding sites

A
  • Actin binding site
  • Nucleotide-binding site for ATP and ATPase
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27
Q

Titin

A
  • Is a very elastic protein
  • Supports protein in muscle
  • Anchors thick filaments between the M line and the Z line
  • Provides structural support and elasticity
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28
Q

Sliding filament

A
  • Muscle contraction
  • Shortening of muscle
  • Thick and thin filaments overlap
  • Neither thick nor thin filaments shorten
  • Filaments slide past each other
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29
Q

What happens within a sarcomere during contraction?

A
  • A band stays the same length
  • I band shortens
  • H zone shortens (basically disappears)
  • Sarcomere shortens (Z move closer together)
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30
Q

Sliding filament is due to

A

cyclical formation and breaking of cross bridges = crossbridge cycle

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31
Q

Look at figure 12.7!

A
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32
Q

What sequence of events whereby an action potential in the sarcolemma causes contraction must occur?

A
  • Dependent on neural input from the motor neuron
  • Requires Ca2+ release from the sarcoplasmic reticulum
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33
Q

Each motor neuron innervates?

A

several muscle cells

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34
Q

Each muscle fiber receives input from?

A

a single motor neuron

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35
Q

Acetylcholine released and bind to receptors on?

A
  • Motor end plate
  • High density of acetylcholine receptors
  • Highly folded
  • End-plate potential
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36
Q

Motor neuron AP always creates a?

A

muscle cell AP

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37
Q

If there’s no Ca2+ what happens?

A
  • troponin holds tropomyosin over myosin binding sites on actin
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38
Q

If there’s no Ca2+ are there any crossbridges?

A
  • No crossbridges form between actin and myosin
  • Muscle relaxed
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39
Q

If Ca2+ present what occurs

A
  • it binds to troponin, causing movement of troponin, causing movement of tropomyosin, exposing binding sites for myosin on actin
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40
Q

If Ca2+ is present are there any crossbridges?

A
  • Yes, crossbridges form between actin and myosin
  • Cycle occurs; muscle contracts
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41
Q

Steps of excitation-contraction coupling

A
  1. Action potential in sarcolemma
  2. Action potential down T tubules
  3. DHP receptors of T tubules open Ca2+ channels (ryanodine receptors) in lateral sacs of SR
  4. Ca2+ increases in cytosol
  5. Ca2+ binds to troponin, shifting tropomyosin
  6. Crossbridge cycling occurs
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42
Q

Memorize figure 12.8

A
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43
Q

what type of gating are on the sarcoplasmic reticulum Ca2+ channels

A
  • Voltage-gated opening
  • Coupled to T tubules by ryanodine and DHP receptors
    Ca2+ -induced opening
    Ca2+ -induced closing
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44
Q

what must occur for a muscle contraction to end?

A

Ca2+ must leave troponin, allowing tropomyosin to cover myosin binding sites on actin

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45
Q

What must occur to remove Ca2+ from cytosol

A
  • Ca2+ -ATPase in the sarcoplasmic reticulum
  • Transports Ca2+ from cytosol into the sarcoplasmic reticulum
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46
Q

Twitch

A
  • Contraction produced in a muscle fiber in response to a single action potential
  • An all-or-nothing event for a muscle fiber at rest
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47
Q

Phases of a twitch

A
  • Latent period
  • Contraction phase
  • Relaxation phase
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48
Q

Latent period

A
  • Time from action potential in muscle cell to onset of contraction (few milliseconds)
  • Excitation-contraction coupling
49
Q

Contraction phase

A
  • Time tension is increasing (10–100 msec)
  • Crossbridge cycling (as long as theres still Ca2+)
50
Q

Relaxation phase

A
  • Time tension is decreasing back to zero (longer than contraction phase)
  • Ca2+ reuptake to SR
  • Fewer crossbridges less force
51
Q

Isometric twitch contraction

A
  • Length constant
  • Contractile elements contract, generating tension
  • When load > tension
  • Muscle does not shorten, load not lifted
52
Q

Isotonic twitch contraction

A
  • Constant tension
  • When tension > load
  • Load is lifted as muscle shortens
53
Q

during normal muscle contractions which contractions are rare and which ones mostly occur?

A
  • Purely isotonic contractions are rare
  • purely isometric contractions occur
54
Q

Even if the load is constant, isometric precedes?

A

isotonic phase of contraction

55
Q

Isometric continues (tension increases) until?

A
  • tension exceeds load
  • Then isotonic contraction begins
56
Q

Tension remains constant as

A

muscle shortens

57
Q

Graded muscle contractions depend on what factors:

A
  • Tension produced by each fiber (Number of active crossbridges that bind to actin)
  • Number of fibers contracting
  • Frequency of stimulation
58
Q

if more crossbridges that bind?

A

more force is generated

59
Q

Frequency of stimulation

A
  • increases in the frequency of action potentials in muscle fibers increase tension in two ways
  • Treppe (step-wise)
  • Summation
60
Q

summation

A

Action potential
2 msec

61
Q

Contraction

A

10–200 msec
Contractions can overlap and sum

62
Q

Factors that affect the force generated by individual muscle fibers

A
  • Fiber diameter
  • Number of thick and thin filaments/area = constant
  • Fiber length
  • Optimal length
63
Q

Force-generating capacity =

A

inherent ability of muscle to generate force

64
Q

Force-generating capacity depends on

A

the number of crossbridges in each sarcomere and the geometric arrangement of sarcomeres

65
Q

More crossbridges/sarcomere ->

A

more force

66
Q

Larger diameter-> _____ -> ________

A

more filaments-> more force

67
Q

At the onset of contraction what affects force generated?

A

Length of fiber

68
Q

Optimal length

A

Resting length of muscle at which the fiber can develop the greatest amount of tension

69
Q

situ

A

most muscles are at optimal length

70
Q

More muscle fibers contracting =

A

greater force

71
Q

Recruitment

A
  • Stimulating more muscle fibers to contract
  • occurs at the level of the motor unit
72
Q

Motor unit recruitment

A
  • Activation of the motor neuron activates all muscle fibers in the motor unit
  • Increases in tension occur in steps proportional to the size of the motor unit
73
Q

Muscles for delicate movements

A

Small motor units

74
Q

Muscles for strength

A

Large motor units

75
Q

Small motor units

A
  • small fibers
  • Small motor neuron cell bodies
  • Small axon diameters
76
Q

Large motor units

A
  • Large fibers
  • Large motor neuron cell bodies
  • Large axon diameters
77
Q

Order of motor unit recruitment is related to?

A

size of motor units

78
Q

Small units recruit? Large units recruit?

A

first ; last

79
Q

Larger neurons are more difficult to?

A
  • depolarize to threshold
  • Requires greater synaptic input
  • Small neurons excited first (low input), then large neurons (high input)
80
Q

What is required for muscles to generate work?

A

ATP, drives crossbridge cycling

81
Q

Sources of ATP

A
  • Phosphorylation of ADP by creatine phosphate
  • Oxidative phosphorylation of ADP in mitochondria
  • Anaerobic glycolysis
82
Q

Role of the creatine/phosphate system

A
  • At rest, small store of ATP
  • Must quickly increase ATP synthesis
  • Use of ATP drives the reaction to the right
83
Q

creatine/phosphate reaction

A

Creatine + ATP-> creatine + ATP

84
Q

creatine/phosphate can supply up to _____the quantity of resting ATP

A

5 times

85
Q

What energy system is initially used during exercise?

A
  • Oxidative phosphorylation
  • Initially, glycogen stores supply glucose
  • Up to 30 min, glucose and fatty acids in blood
86
Q

why must O2 supply be kept adequate?

A
  • Increases ventilation
  • Increases heart rate and contraction
  • Dilates vessels to muscle
  • Transient increase in GLUT4
87
Q

Exercise of heavy intensity involves what?

A
  • Anaerobic glycolysis
  • Lactate
  • Only 2 ATP molecules per glucose molecule
88
Q

Basis for skeletal muscle classification

A

*Velocity of contraction
- Fast versus slow
*Primary energy source
- Oxidative versus glycolytic

89
Q

Differences in speed of contraction are dependent on what?

A
  • Dependent on rate of myosin ATPase activity
  • Higher rate = faster crossbridge cycling
90
Q

ATP hydrolysis =

A

rate-limiting step of cycle

91
Q

Fast fibers

A

Myosin with fast ATPase activity

92
Q

Slow fibers

A

Myosin with slow ATPase activity

93
Q

Fast fibers contract ___times more rapidly than slow fibers

A

2-3

94
Q

Fast fibers relax ___ rapidly compared to slow fibers

A

more

95
Q

Rate of Ca2+ -ATPase is ___ in fast twitch fibers

A

faster

96
Q

Slow fiber contractions last approximately ___ times longer than fast fiber contractions

A

10

97
Q

Glycolytic fibers

A

Anaerobic glycolysis
Fewer mitochondria
Many glycolytic enzymes
High glycogen stores
Use little oxygen—anaerobic
Large diameter
Quick to fatigue

98
Q

Oxidative fibers

A

Oxidative phosphorylation
Many mitochondria
Myoglobin (red)
Small diameter
Resistant to fatigue
Many capillaries

99
Q

Three skeletal muscle fiber types

A

Slow oxidative
Fast oxidative
Fast glycolytic

100
Q

Properties of slow oxidative fibers

A
  • Low myosin ATPase
  • High oxidative capacity—aerobic
  • Small diameter
  • Fatigue slowly
101
Q

Properties of fast glycolytic fibers

A
  • High myosin ATPase activity
  • High glycolytic capacity
  • No myoglobin (so they appear white)
  • Large diameter
  • Fatigue rapidly
102
Q

Properties of fast oxidative fibers

A
  • Intermediate myosin ATPase activity
  • High oxidative capacity—aerobic
  • Myoglobin
  • Slow to fatigue, but more rapid than slow oxidative fibers
  • Intermediate diameter
103
Q

Recruitment order:

A
  1. Slow oxidative fibers
  2. Fast oxidative fibers
  3. Fast glycolytic fibers (sprinting)
104
Q

Resistance to fatigue: High-intensity exercises

A
  • Glycolytic fibers
  • Buildup of lactate
  • Altered enzyme activity
  • Recovery within minutes to hours
105
Q

Strong contractions cause

A

compression of blood vessels

106
Q

Resistance to fatigue: Low-intensity exercises

A
  • Depletion of energy reserves (glycogen)
  • Long time to recover
  • Psychological fatigue
  • Will to win
107
Q

Muscle Receptors for Coordinated Activity

A

Muscle spindle
Golgi tendon organ

108
Q

Smooth muscle

A
  • Lacks striations
  • Found in internal organs and blood vessels
  • Under involuntary control by the autonomic nervous system
  • Spindle-shaped
  • Small—approximately 1/10 the size of skeletal muscle
  • Contains actin and myosin
  • No sarcomeres
  • Dense bodies
109
Q

Smooth muscle steps of excitation-contraction coupling

A
  1. Most Ca2+ comes from outside the cell
  2. Voltage-gated Ca2+ channels in plasma membrane
  3. Ca2+ triggers release of Ca2+ from sarcoplasmic reticulum
  4. Ca2+ binds to calmodulin
  5. Ca2+ -calmodulin activates myosin light-chain kinase
  6. MLCK phosphorylates myosin
  7. Crossbridge cycling
110
Q

Relaxation of smooth muscle

A
  • Phosphatase removes phosphate from myosin
  • Ca 2+ is removed from cytoplasm
111
Q

Myosin ATPase contraction is ____times ____ in smooth muscle than in skeletal muscle

A

10–100 ; slower

112
Q

Neural regulation of smooth muscle contraction

A
  • Innervated by autonomic nervous system
  • Sympathetic and/or parasympathetic
  • May be excitatory or inhibitory
  • Precise response depends on the receptor type
  • Neurotransmitter is released from varicosities
  • Diffuse binding of neurotransmitter to receptors
113
Q

Classification of smooth muscle

A

Single-unit smooth muscle
Multi-unit smooth muscle

114
Q

Single-unit smooth muscle

A
  • Most common type
  • Intestinal tract
  • uterus
  • Muscle fibers activated synchronously
  • Fibers connected by gap junctions
  • Contract together as a single unit
115
Q

Multi-unit smooth muscle

A
  • Located in large airways and arteries, eye (ciliary muscle, iris)
  • Few, if any, gap junctions
  • Each fiber acts individually
    Receives own innervation
116
Q

Smooth Muscle: Pacemaker

A

Single-unit smooth muscle
Slow-wave potentials
Cycles in resting Vm
Pacemaker potentials

117
Q

Cardiac Muscle

A
  • striated with same sarcomeres
  • Troponin-tropomyosin regulation
  • Gap junctions (within intercalated disks)
  • Pacemaker cells
  • Innervated by autonomic nervous system
118
Q

Ca2+ in cardiac muscles comes from

A

extracellular fluid and sarcoplasmic reticulum

A&P II (8 decks)

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