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Human physiology > Chapter 12: Muscles > Flashcards

Chapter 12: Muscles Flashcards

1
Q

are large, multinucleate cells that appear striped or striated under the microscope

A

skeletal muscle fibers

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2
Q 
-striated but they are smaller,
branched, and uninucleate
-Cells are joined in series by
junctions called intercalated
disks
A

cardiac muscle

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3
Q

fibers are small and lack striations

A

smooth muscle

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4
Q

moves bones closer together

A

flexion

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5
Q

moves bones away from each other

A

extension

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6
Q
  • The tissue surrounding muscle (epimysium) and tendon connective tissue are continuous
  • perimysium
  • fascicles
A

skeletal muscles

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7
Q

extends into the muscle body, dividing muscle into bundles (fascicles) of muscle cells

A

perimysium

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8
Q

contain 100s-1000s of muscle cells—muscle fibers, which extend the length of the muscle

A

fascicles

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9
Q

what are the components of a muscle fiber?

A

-many myofibrils
-sarcoplasmic reticulum
-many mitochondria ~ high energy
-transverse tubules (T tubules)
-lateral sacs (terminal cisternae)
~ Ca2+
-triad

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10
Q

T tubule + 2 lateral sacs

A

triad

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11
Q

-Give skeletal and cardiac muscle striated appearance
-Orderly arrangement of thick and thin filaments
~actin
~myosin

A

myofibrils

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12
Q

due to thick and thin filaments that run parallel to the long axis

A

striations

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13
Q

form sarcomeres

A

filaments

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14
Q

what is the structure of a sarcomere?

A
  • A band
  • H zone
  • M line
  • I band
  • Z line
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15
Q
  • dark band

- thick filaments

A

A band

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16
Q
  • thick filaments

- no overlap

A

H zone

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17
Q

links thick filaments

A

M line

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18
Q
  • light band
  • thin filament
  • no overlapping
A

I band

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19
Q

links thin filaments

A

Z line

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20
Q 
has acces-
sory proteins that link
the thin filaments
together, similar to
the accessory proteins
shown for the M line
A

Z disk

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21
Q

contractile protein

A

actin

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22
Q

has binding site for myosin

A

each G actin

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23
Q
  • regulatory protein

- overlaps binding sites on actin for myosin

A

tropomyosin

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24
Q

-regulatory protein
-complex of 3 proteins
~Attaches to actin
~Attaches to tropomyosin
~Binds Ca2+ reversibly

A

troponin

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25
Q

-Myosin tail is toward the M line
-Myosin head is toward the I band
-Myosin head binding sites
~actin binding site
~ATPase activity

A

thick myofilament

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26
Q
  • 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
A

titin

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27
Q
  • crossbridge cycle
  • excitation-contraction coupling
  • muscle cell metabolism
A

sliding filament model

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28
Q

how muscles generate force

A

crossbridge cycle

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29
Q

how muscle contractions are turned on and off

A

excitation contraction coupling

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30
Q

how muscle cells provide ATP to drive the crossbridge cycle

A

muscle cell metabolism

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31
Q
  • shortening of muscle
    • thick & thin filaments overlap
    • neither thick nor thin filaments shorten
    • filaments slide past each other
A

muscle contraction

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32
Q

what happens within a sarcomere during contraction?

A
  • A band stays the same length
  • I band shortens
  • H zone shortens
  • Sarcomere shortens
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33
Q

due to cyclical formation and breaking of cross bridges = crossbridge cycle

A

sliding

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34
Q

what happens to actin and myosin during contraction?

A

do not change length but instead slide past one another

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35
Q

do not change length but instead slide past one another

A

Cyclical formation of links between actin and myosin

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36
Q

what happens to myosin during the cyclical formation of links between actin and myosin (sliding)?

A

*myosin head undergoes conformation changes
-high energy form
~ADP and Pi bound to myosin
~High affinity for actin
-low energy
~ADP and Pi released from myosin
*relies on hydrolysis of ATP

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37
Q

myosin head moves, propelling thin filament toward center of muscle

A

power stroke

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38
Q

detach when ATP binds

A

thick and thin filaments

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39
Q

returns to the initial cocked position when ATP is hydrolyzed.

A

myosin head

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40
Q
  1. ATP binds to myosin; Myosin releases actin
  2. Myosin hydrolyzes ATP; Energy from ATP rotates the myosin head to the cocked position. Myosin binds weakly to actin.
  3. Power stroke begins when tropomyosin moves off the binding site.
  4. Myosin releases ADP at the end of the power stroke.
A

contraction cycle

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41
Q
  1. binding of myosin to actin
  2. power stroke
  3. rigor (myosin in low energy form)
  4. unbinding of actin and myosin
  5. cocking of the myosin head (myosin in high energy form)
A

crossbridge cycle

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42
Q
  • Sequence of events whereby an action potential in the sarcolemma causes contraction
    • Dependent on neural input from the motor neuron
    • Requires Ca2+ release from the sarcoplasmic reticulum
A

excitation contraction coupling

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43
Q

what is the role of the neuromuscular juncton in excitation-contraction coupling?

A

-Each motor neuron innervates several muscle cells
-Each muscle fiber receives input from a single motor neuron
-Acetylcholine released
-Motor end plate
~High density of acetylcholine receptors
-End-plate potential
-Motor neuron AP always creates a muscle cell AP

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44
Q

what is the role of Ca2+ in excitation contraction coupling?

A

If no Ca2+ → troponin holds tropomyosin over myosin binding sites on actin

- no crossbridges form between actin & myosin
- muscle relaxed
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45
Q

what happens in excitation contraction coupling if Ca2+ is present?

A

If Ca2+ present → binds to troponin, causing movement of troponin, causing movement of tropomyosin, exposing binding sites for myosin on actin

- Crossbridges form between actin and myosin
- Cycle occurs; muscle contracts
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46
Q

what are the 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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47
Q

how is muscle action potential initiated?

A
  1. somatic motor neuron releases ACh at neuromuscular junctions
  2. Net entry of Na+ through ACh
    receptor-channel initiates a
    muscle action potential.
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48
Q

what are the 3 metabolic pathways to obtain energy?

A
  • phosphocreatine breakdown
  • anaerobic glycolysis
  • aerobic respiration
49
Q

short burst of energy

A

Phosphocreatine breakdown

50
Q
  • produces lactate and acid

- quick, no oxygen required, small amount of energy released

A

anaerobic glycolysis

51
Q
  • citric acid cycle and electron transport chain

- slow, requires oxygen, large amount of energy released

A

aerobic respiration

52
Q
  • psychological effects

- protective reflexes

A

central fatigue

53
Q
  • decrease in neurotransmitter release
  • decrease in receptor activation
  • at neuromuscular junction
A

peripheral fatigue

54
Q

change in muscle membrane potential

A

excitation-contraction coupling

55
Q

what is the basis for skeletal muscle classification?

A

-velocity of contraction
-primary energy source
~oxidative vs glycolytic

56
Q

what are the differences in speed of contraction?

A
  • fast twitch

- slow twitch

57
Q

what are the differences in speed of contraction dependent on?

A
  • dependent on rate of myosin ATPase activity
    • ATP hydrolysis= rate limiting step of cycle
    • Higher rate = faster crossbridge cycling
58
Q

myosin with fast ATPase activity

A

fast fibers

59
Q

myosin with slow ATPase activity

A

slow fibers

60
Q
  • contract 2-3 times more rapidly than slow fibers

- relax more rapidly

A

fast fibers

61
Q

why do fast fibers relax more rapidly?

A

rate of Ca2+-ATPase is faster

62
Q

contractions last 10 times longer than fast fiber contractions

A

slow fibers

63
Q

what are the 3 skeletal muscle fiber types?

A
  • slow oxidative (type 1)
  • fast oxidative-glycolytic (type 2A)
  • fast glycolytic (type 2X)
64
Q

-slow myosin ATPase
-high oxidative capacity-aerobic
~mitochondria
~rich blood supply
~myoglobin (red)
-small diameter
~little tension
-fatigue slowly

A

slow oxidative fibers (type 1)

65
Q

-fast myosin ATPase activity
-high glycolytic capacity
~high glycogen stores
~many glycolytic enzymes
-no myoglobin (white)
-large diameter
~greater tension
-fatigue rapidly

A

fast glycolytic fibers (2X)

66
Q
  • intermediate myosin ATPase activity
  • high oxidative capacity-aerobic
  • myoglobin
  • slow to fatigue, but more rapid than slow oxidative fibers
  • intermediate diameter
A

fast oxidative fibers (type 2A)

67
Q

what are the long term responses to aerobic exercise?

A
  • increased oxidative capacity
  • some fast glycolytic fibers can be converted to fast oxidative fibers
  • increase in size & # of mitochondria
  • increase in # of capillaries surrounding muscle fibers
68
Q

what are the long term responses to high intensity exercise?

A
  • decreased oxidative capacity
  • some fast oxidative fibers can be converted to fast glycolytic fibers
  • decrease in size & # of mitochondria
  • increase in fiber diameter
  • reduced resistance to fatigue
69
Q

the mechanical response of an individual muscle cell to a single action potential.

A

twitch

70
Q

Graded muscle contractions depend on two factors, what are they?

A

-tension produced by each fiber
~# of active crossbridges that bind to actin
~more crossbridges that bind–>more force
-number of fibers contracting

71
Q

what are the Factors affecting the number of active crossbridges and thus the force generated by the contraction of individual muscle fibers?

A
  • frequency of stimulation
  • fiber diameter
  • changes in fiber length
72
Q

Frequency of stimulation: increases in the frequency of action potentials in muscle fibers increase tension in two ways, what are they?

A
  • treppe

- summation

73
Q

-Amount of tension developed depends on amount of Ca2+ bound to troponin
-At high frequencies, release exceeds reuptake
~Ca2+ increases in cytosol
-eventually saturates system
~All troponin has Ca2+ bound to it
~Crossbridge cycling maxed out
~Maximum tetanic contraction

A

cause of summation and tetanus

74
Q

how does fiber diameter affect force generating capacity?

A

-fiber diameter varies
-larger diameter–> more filaments –> more force
~more crossbridges –> more force
~more sarcomeres in parallel –> more force

75
Q

Length of fiber at the onset of contraction affects force generated

A

fiber length

76
Q
  • Resting length of muscle at which the fiber can develop the greatest amount of tension
  • Due to maximum overlap of thick filament crossbridges and thin filaments
A

optimal length

77
Q

Decrease crossbridge overlap

A

nonoptimal lengths

78
Q

what does more muscle fibers contracting result in/

A

greater force

79
Q

-More fibers contracting → greater tension
-Recruit motor units
~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

A

motor unit recruitment

80
Q

what are motor unit sizes like?

A

-number of motor units varies in different muscles
~small: delicate movements (3-5 fibers)
~large: strength movements (100s-1000s)
-all muscle fibers in a single motor unit are of the same fiber type
~fast twitch
~slow twitch

81
Q 
-Order of motor unit recruitment is related to size of motor units
   ~small units recruited first
   ~large units recruited last
-asynchronous recruitment
   ~avoids fatigue and maintains tension
A

size principle

82
Q 
-create force and moves a load
  ~concentric action
  ~eccentric action
-the muscle contracts, 
shortens, and creates enough force to move the load.
A

isotonic contractions

83
Q

is a shortening action

A

Concentric action

84
Q

is a lengthening action

A

eccentric action

85
Q 
-create force without moving a load
  ~series elastic elements
  ~sarcomeres
-the muscle contracts 
but does not shorten. The force created cannot move the load
A

isometric contractions

86
Q

elastic components of muscles

A

Series elastic elements

87
Q

what do sarcomeres and elastic elements do during isometric contractions?

A

Sarcomeres shorten while elastic elements stretch, resulting in little change in overall length

88
Q

act as levers to enhance the speed or power of limb movements

A

long bones

89
Q

any elongated, rigid object that rotates around a fixed point called a fulcrum

A

lever

90
Q

occurs when an effort applied overcomes resistance (load) at some other point

A

rotation

91
Q

what are the 2 advantages conferred by a lever?

A

-To exert more force against a resisting object than the force applied to the lever
~Human moving a heavy object with help of crowbar

-To move the resisting object farther or faster than the effort arm is moved
~movement of rowing a boat

92
Q
  • Has fulcrum in the middle between effort and resistance (EFR)
  • Atlanto–occipital joint lies between the muscles on the back of the neck and the weight of the face
  • Loss of muscle tone occurs when you nod off in class
A

first class lever

93
Q
  • Resistance between fulcrum and effort (FRE)
  • Resistance from the muscle tone of the temporalis muscle lies between the jaw joint and the pull of the digastric muscle on the chin as it opens the mouth quickly
A

second class lever

94
Q
  • Effort between the resistance and the fulcrum (REF)
  • Most joints of the body
  • The effort applied by the biceps muscle is applied to the forearm between the elbow joint and the weight of the hand and the forearm
A

third class lever

95
Q
  • 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
A

smooth muscle

96
Q

located in Vascular, gastrointestinal, urinary, respiratory, reproductive, ocular systems

A

smooth muscle

97
Q

what are the contraction patterns of smooth muscle?

A
  • phasic (periodic)

- tonic (continuously)

98
Q

how does smooth muscle communicate with neighboring cells?

A
  • Single-unit smooth muscle, or visceral smooth muscle

- Multi-unit smooth muscle

99
Q

example of a phasic smooth muscle that is usually relaxed

A

esophagus

100
Q

example of a phasic smooth muscle that cycles between contraction and relaxation

A

intestine

101
Q

example of a tonic smooth muscle that is usually contracted

A

a spinchter that relaxes to allow material to pass

102
Q

a tonic smooth muscle whose contraction is varied as needed

A

vascular smooth muscle

103
Q

are connected by

gap junctions, and the cells contract as a single unit

A

Single-unit smooth muscle cells

104
Q

are not electrically linked,

and each cell must be stimulated independently.

A

Multi-unit smooth muscle cells

105
Q

are the slowest to contract and relax

A

smooth muscles

106
Q

-actin is more plentiful
-lacks troponin
-less myosin
~myosin filaments are longer
~entire surface of filament covered with myosin heads
-extensive cytoskeleton
~intermediate filaments and dense bodies
-amount of SR varies and is less organized
-no t-tubules but caveolae

A

smooth muscle

107
Q

membrane invaginations

A

caveolae

108
Q

-form a cytoskeleton
~Actin attaches to the dense bodies
~Each myosin molecule is surrounded by actin filaments

A

Intermediate filaments and protein dense bodies

109
Q

has

hinged heads all along its length

A

smooth muscle myosin

110
Q

what does smooth muscle contraction begin with?

A

Begins with increase in cytosolic Ca2+

111
Q

what happens in smooth muscle contraction after cytosolic Ca2+ increases?

A

Ca2+ binds to calmodulin and begins a cascade that results in contraction

112
Q

during smooth muscle contraction, what happens after the cascade started by Ca2+?

A

Dephosphorylated myosin may remain attached to actin for a period of time during a latch state

113
Q

Contraction (of smooth muscle) caused by electrical signaling (change in membrane potential)

A

electrochemical coupling

114
Q

Contraction (of smooth muscle) caused by chemical signaling

A

pharmacomechanical coupling

115
Q

the signal for contraction in smooth muscle

A

increased cytosolic calcium

116
Q

the first step of relaxation of smooth muscle

A

removal of Ca2+ from the cytosol

117
Q

fire action potentials when they reach threshold

A

slow wave potentials

118
Q

always depolarize to threshold

A

pacemaker potentials

Human physiology (17 decks)

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