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KIN 267 > Chapter 10 > Flashcards

Chapter 10 Flashcards

1
Q

Functions of Muscle Tissue (4)

A

1) excitable/irratable →
2) **contractile **→ can shorten in length
3) **extensible **→ extend/stretch
4) **elastic **→ can return to original shape

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2
Q

Other Functions of Muscle Tissue (5)

A

1) create motion
2) stabilize body positions & maintain posture
3) store substances within body using sphincters
4) move substances by contractions
5) generate **heat **through **thermogenesis **

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3
Q

(3) types of muscular tissue

A

1) Skeletal
2) Cardiac
3) Visceral

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4
Q

1) Skeletal muscle

  1. location
  2. function
  3. appearance
  4. control
A
  1. skeleton
  2. movement, heat posture
  3. striated, multi-nucleated (eccentric)
  4. fibers parallel
  5. voluntary
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5
Q

2) Cardiac muscle

  1. location
  2. function
  3. appearance
  4. control
A
  1. heart
  2. pump blood continuously
  3. striated, 1 central nucleus
  4. involuntary
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6
Q

3) **Visceral **muscle

  1. location
  2. function
  3. appearance
  4. control
A
  1. GI tract, uterus, eye, blood vessels
  2. peristalsis, BP, pupil size, erects hairs
  3. no striations, 1 central nucleus
  4. involuntary
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7
Q

Organization of Muscle Tissue

A

epimysium, perimysium & endomysium

→ all continuous with CT that forms tendons & **ligaments **

**→ **extend from **fascia **

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8
Q

Fascia

  • function
A

dense sheet/broad band of irreg CT that lines body wall/limbs & supports/surrounds muscles/other organs

  • holds muscles of similar functions together
  • (connects muscles to other muscles to form groups)
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9
Q

Epimysium

A

outermost layer of **dense irregular CT **

  • encircles entire muscle
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10
Q

Perimysium

A

layer of dense irregular CT surrounding groups of 10-100 muscle fibers seperating them in bundles (fascicles)

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11
Q

Endomysium

A

mostly reticular fibers

  • seperates individual muscle fibers
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12
Q

What seperates muscle from skin?

A

Subcutaneous layer

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13
Q

Tendon

A

ropelike structure that extends beyond muscle fibers to attach muscle to periosteum of bone

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14
Q

Sarcolemma

A

plasma membrane of muscle cell beneath endomysium

  • encloses sarcoplasm & myofibrils (striated)
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15
Q

Sarcoplasm

A

**cytoplasm **of muscle fiber within sarcolemma

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16
Q

Myofibrils

A

striated contractile organelles of skeletal muscle

(in the sarcoplasm)

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17
Q

Transverse (T) Tubules

A

tiny invaginations of sarcolemma filled with interstitial fluid *(open to outside of fiber) *

  • tunnel in from surface toward center of each muscle fiber
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18
Q

Triad

A

T tubule + 2 terminal cisternae

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19
Q

Sarcoplasmic Reticulum (SR)

A

fluid-filled system of membranous sacs

  • encircles each myofibril
  • has **terminal cisternae **
  • stores Ca2+ in relaxes muscle fiber
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20
Q

Terminal Cisternae

A

dilated end sacs of SR that butt against T tubule from both sides

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21
Q

What triggers muscle contraction?

A

Release of Ca2+ from **terminal cisternae **of **SR **

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22
Q

Sarcomere

A

basic functional units of myofibrils

  • arrangement of thick & thin filaments sandwiched between 2 Z discs
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23
Q

Myofibrils

  • composed of?
A

filaments

  • thick filaments (myosin)
  • thin filaments (actin)
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24
Q

Z disc

A

*narrow, plate-shaped region of dense protein material *

  • seperates one sarcomere from the next
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25
Q

Sarcomere extends from?

A

one Z disc to the next Z disc

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26
Q

Extent of overlap of thick & thin filaments depends on?

A

whether muscle is contracted, relaxed or stretched

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27
Q

A band

A

dark middle region

  • extends length of thick filaments

(includes part of overlap with thin filaments)

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28
Q

I band

A

lighter, less dense area

  • contains rest of thin filaments

but NO thick filaments

  • Z disc passes through center
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29
Q

Zone of overlap

A

Toward each **end of A band **

  • where thin & thick filaments lie side by side
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30
Q

H Zone

A

center of A band containing ONLY thick filaments

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31
Q

M line

A

center of **H zone **

marks middle of sarcomere

formed by supporting proteins that hold thick filaments **together **

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32
Q

Z line is really __ __ when considered in 3D

A

Z disc

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33
Q

Muscle Proteins

**Myofibrils **built from (3) groups of proteins

  • functions?
A

1) **Contractile **→ generate force during contraction
2) Regulatory→ help switch contraction process on/off
3) Structural→ keeps thick & thin filaments in proper alignment & links myofibrils to sarcolemma & ECM

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34
Q

1) Contractile Proteins

A

Actin

Mysoon

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35
Q

2) Regulatory Proteins

A

troponin

tropomyosin

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36
Q

3) Structural Proteins

A

Titan

Dystrophin

Myomesin

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37
Q

Myosin

  • parts
A

main component of **thick **filaments

-functions as motor protein in all 3 types of muscle tissue

**myosin tail → **twisted gold club handles

  • point toward M line in center of sarcomere
  • form **shaft **

**myosin head **→ 2 projections of each myosin molecule

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38
Q

Actin

A

main component of **thin filaments **(anchored to Z discs)

  • bead of pearls twisted into helix

myosin-binding site → where myosin head attaches

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39
Q

Tropomyosin

A

strands of **tropomyosin **cover **myosin-binding site **on actin

  • held together by **troponin **molecules
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40
Q

Troponin

A

hold **tropomyosin strands **in place

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41
Q

When Ca2+ binds to troponin?

A

**troponin **undergoes change in shape

→ moves **tropomyosin **away from **myosin-binding sites **on actin

  • muscle contraction begnis as myosin binds to actin
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42
Q

Structural Proteins → functions? (4)

A

contribute to **alignment, stability, elasticity & extensibility **of myofibrils

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43
Q

Titin

A

3rd most plentiful protein in muscle (after actin & myosin)

  • extends from Z disc to M line & accounts for much of the elasticity of myofibrils
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44
Q

Dystrophin

A

links filaments to integral membrane proteins

reinforces **sarcolemma & **transmits tension from **sarcomeres **to tendons

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45
Q

Myomesin

A

binds to titin & links adjacent thick filaments

  • forms **M line **
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46
Q

Troponin-Tropomyosin Complex

A

can slide back & forth depending on presence of Ca2+

  • slides down into “gutters” of actin molecules ot unblock **myosin-binding sites **on actin
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47
Q

Levels of **Organization **within Skeletal Muscle

A

skeletal muscle

fascicle

muscle fibers (cells)

myofibrils

filaments

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48
Q

Sliding-Filament Mechanism

A

muscle contraction occurs b/c myosin heads attach to & walk along thin filaments at both ends of sarcomere

  • progressively pulling thin filaments towards M line
  • thin filaments meet at center of sarcomere
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49
Q

What happens to each band/zone as muscle contracts?

A

H Zone → disappears (thin filaments overlap more & more)

**I Band → **shortens & disappears (Z discs come closer together)

A Band → does not shorten (extends length of thick filaments which does not shorten)

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50
Q

Contraction Cycle

A

repeating sequence of events that cause filaments to slide

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51
Q

Contraction Cycle

at onset of contraction…

A

**SR **releases Ca2+ into sarcoplasm

→ bind to troponin → moves tropomyosin away from myosin-binding sites on actin

→ once binding sites are free - **contraction cycle **begins

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52
Q

Contraction Cycle

**- (4) steps **

A

1) ATP hydrolysis
2) **Attachment of myosin **to **actin **to form cross-bridges
3) Power stroke
4) Detachment of myosin from actin

53
Q

1) ATP hydrolysis

A

myosin head include ATP-binding site & ATPase

hydrolysis rxn reorients & energizes myosin head

  • ADP & P group still attached to myosin head
54
Q

2) Attachment of myosin to actin to form cross-bridges

A

energized myosin head attached to myosin-binding site on actin (cross-bridge)

  • releases P group
55
Q

3) Power stroke

A

after cross-bridges form, power stroke occurs

during power stroke:

  • site on cross-bridge where ADP is bound opens
  • cross-bridge rotates & releases ADP
  • cross-bridge generates force as it rotates towards center of sarcomere, sliding thin filament past thick filament toward M line
56
Q

4) Detachment of myosin from actin

A

at end of power stroke, **cross-bridges **remain firmly attached to actin **until it binds another ATP molecule **

  • as ATP binds to ATP-binding site on myosin head, myosin head detaches from actin
57
Q

Steps of Contraction Cycle (4)

  • general concept
A

1) myosin heads hydrolyze ATP → become reoriented & energized **
2) myosin heads bind to actin forming cross-bridges
3) mysoin cross-bridges rotate toward center of sarcomere (power stroke**)
4) as myosin head binds ATP, cross-bridges detach from actin

58
Q

Rigor Mortis

A

muscles remain in a state of rigidity because no ATP to bind to myosin head

  • can’t detach from actin
59
Q

Length-Tension Relationship

A

indicates how forcefulness of muscle contraction depends on length of sarcomeres within muscle before contraction begins

max tension occurs when zone of overlap b/w thick & thin extends from edge of H zone to 1 end of thick filament

understretched - compressed thick filaments

overstretched - limited contact b/w actin & myosin

60
Q

Neuromuscular Junction (NMJ)

A

synapse between somatic motor neuron & **skeletal muscle fiber **

61
Q

Somatic motor neurons

A

neurons that stimulate muscle fibers to contract

62
Q

Somatic Motor Neuron - axon

A

extends from brain/spinal cord to group of skeletal muscle fibers

63
Q

Synapse

A

region where communication occurs between 2 neurons or between neuron & target cell

64
Q

Synaptic cleft

A

small gap at most synapses that seperates the 2 cells

65
Q

Neurotransmitter

A

chemical released that transmit signals across **synapse **

66
Q

Axon Terminal

A

End of **motor neuron **at NMJ

67
Q

Synaptic end bulbs

A

neural part of NMJ

    • axon terminal divides into cluster of synaptic end bulbs*
  • expanded distal end of axon terminal that contains **synaptic vesicles **
68
Q

Synaptic Vesicles

A

Hundreds of membrane-enclosed sacs in synaptic end bulbs that are suspended in the cytosol

  • contain **Acetylcholine (ACh) **
69
Q

Acetylcholine

A

neurotransmitter within synaptic vesicles that are released at NMJ

70
Q

Motor End Plate

A

muscle fiber part of NMJ

region of sarcolemma opposite of synaptic end bulbs

- **contain millions of **ACh receptors **(integral transmembrane proteins) - **ligand-gated ion channels **

  • gated Na+ channels that respond to ACh
71
Q

Nerve impulse (nerve AP) elicits muscle action potential in **(4) steps **

A

1) Release of ACH
2) Activation of ACh receptors
3) Production of muscle action potential
4) Termination of ACh activity

72
Q

1) Release of ACh

(7)

A

nerve impulse arrives at synaptic end bulbs

stimulates voltage‐gated channels to **open **

b/c [Ca2+] is higher in ECF, Ca2+ flows inward

Ca2+ stimulates synaptic vesicles to undergo exocytosis

synaptic vesicles fuse with motor neuron’s PM

release ACh into synaptic cleft

diffuses across synaptic cleft b/w motor neuron & motor end plate.

73
Q

2) Activation of ACh receptors

A

2 ACh molecules bind to receptor on **motor end plate **→ ion channel **opens **

Na+ flows inward

74
Q

3) Production of Muscle AP

A

inflow of Na2+ → inside of muscle fiber **more (+) **

→triggers muscle AP

→propogates along sarcolemma into T tubules

→ causes SR to release Ca2+ into sarcoplasm

muscle fiber contracts

75
Q

4) Termination of ACh activity

A

ACh broken down by **acetylcholinesterase (AChE) **

  • attached to collagen fibers in ECM of synaptic cleft
76
Q

when APs in motor neuron stop…

A

ACh no longer released - broken down in synaptic cleft

**Ca2+ moves form sarcoplasm back into SR **

Ca2+ release channels in SR close

77
Q

Where is NMJ?

A

usually near midpoint of skeletal muscle fiber

  • muscle APs that arise at NMJ propogate towards ends of fiber
78
Q

location of

  1. Presynaptic membrane
  2. postsynaptic membrane
A

1) on neuron
2) motor end plate on muscle cell

79
Q

Conscious thought (to move muscle) causes?

A

activation of motor neuron

→ release of neurotransmitter acetylcholine (ACh) at NMJ

→ Enzyme Acetylcholinesterase breaks down ACh after short period of time

80
Q

ACh Receptors

A

on **ligand-gated Na+ channels **on motor end plate

81
Q

Muscle AP

  • phases (3)
A

Resting Potential → (-70 mV)

ACh stimulus at motor end plate → (-55 = Threshold)

Depolarizing phase → (+30) - Na+ gates open → inflow

Action Potential

Repolarizing phase → back to (-70) - K+ gates open → outflow

(Na+ gates close)

**After-hyperpolarizing **phase → K+ channels take too long to close

82
Q

Generating AP on muscle membrane involves transfer of info from:

A

Electrical signal (down neuron) → chemical signal (at NMJ) → electrical signal (depolarization of sarcolemma)

83
Q

Excitation-Contraction Coupling

(8) steps

A

1) AP at axon terminal of motor neuron → release of ACh
2) **ACh **across synaptic cleft → binds to receptors in motor end plate → triggers muscle AP
3) AChE destroys ACh so only more ACh for AP
4) muscle AP: T Tubules → opens Ca2+ release channels in SR → Ca2+ into sarcoplasm
5) Ca2+ binds to troponin
6) Contraction Cycle
7) Ca2+ release channels in SR **close **→ transport pumps restore low Ca2+ in sarcoplasm
8) T-T complex back into position
9) muscle **relaxes **

84
Q

**Excitation-Contraction Coupling **

  • general process (6)
A
  1. Thought process going on in brain
  2. AP arriving at NMJ
  3. Regeneration of AP on muscle membrane
  4. Release of Ca2+ from SR
  5. Sliding of thick on thin filaments in sarcomeres
  6. Generation of muscle tension (work)
85
Q

Role Players in Excitation-Contraction Coupling

(16)

A

**brain →motor neuron **→ **ACh **→AChE

ACh receptors → **Na+/K+ channels ** → Na+ flow in → K+ flow out

Regenerate AP →T-Tubules → SR → Ca2+ release → T/T

ATP →myosin binding → filaments slide → muscles contract

86
Q

Sources of Muscle Energy (4)

A

1) stored ATP → 3 secs
2) Energy from **Creatine Phosphate → 12 secs
3) Anaerobic Glucose Use (Glycolysis) → 30-40 s
4) Aerobic ATP production (aerobic cellular resp**) → mins-hours

87
Q

Creatine Phosphate

A

relaxed muscle:

Creatine + ATP → Creatine Phosphate + ADP

contracting muscle:

Creatine Phosphate + ADP → Creatine + ATP

ATP → Energy for muscle contraction + ADP

88
Q

Anaerobic Glucose Use

A

Anaerobic Cellular Respiration = Anaerobic Glycolysis

Muscle Glycogen or Blood Glucose

Glucose → 2 ATP + 2 Pyruvic Acid → 2 Lactic Acid (→ into blood)

89
Q

Aerobic ATP production

A

**Aerobic Cellular Respiration **

FAs (from adipose cells)

Pyruvic acid (from glycolysis)

Amino acids (from protein breakdown)

Oxygen (from hemoglobin in blood/myoglobin in muscle fibers)

→ **36 ATP **+ CO2 + H2O + heat

90
Q

Muscle Fatigue

A

inability of a muscle to maintain force of contraction after prolonged activity

91
Q

Types of Fatigue (2)

A

1) Central
2) Peripheral

92
Q

1) Central Fatigue

A

**before actual muscle fatigue begins **

  • feeling tired & wanting to stop activity
  • caused by changes in **CNS **
93
Q

2) Peripheral Fatigue

A

inability to supply sufficient energy to contracting muscles to meet increased energy demands

94
Q

Sources of Fatigue (6)

A
  1. Inadequate release of Ca2+ from ** SR**
  2. Reduced O2
  3. Reduced Cr Ph
  4. Reduced glycogen
  5. Buildup of H+
  6. Problems with Ach receptors or release
95
Q

Oxygen Debt (**Excess Post-Exercise Oxygen Consumption - EPOC) **

A

amount of O2 repayment required after exercise in skeletal muscle to:

- replenish ATP, Creatine phosphate & myoglobin

  • convert lactic acid back into purivate (so it can be used for CAC to replenish ATP)
96
Q

Motor Unit

A

composed of **motor neuron + all muscle cells it innervates **

97
Q

Motor Units

1) high precision
2) low precision

A

1) fewer muscle fibers per neuron
- laryngeal & extraocular muscles (2-20)
2) many muscle fibers per neuron
- thigh muscles (2,000-3000)

98
Q

Force of muscle contraction depends on (4)

A

frequency of stimulation - rate at which APs arrive at NMJ (# of impulses/second)

size of motor units

# of motor units activated

type?

99
Q

Activities requiring extreme precision (subtle/rapid movements of eye) involve muscles with?

A

small motor units (1-4 muscle fibers/neuron)

100
Q

All-or-none principle of muscle contraction

(2)

A

When individual muscle fiber is stimulated to depolarization & AP propagates along its sarcolemma → must contract to it’s full force

Also, when single motor unit is recruited to contract, all muscle fibers in that motor unit must all contract at the same time

101
Q

twitch contraction

A

the brief contraction of all muscle fibers in motor unit in response to single AP in its motor neuron

102
Q

Latent period

A

brief delay as AP sweeps aover sarcolemma & Ca2+ released from SR (point of no return)

2 msec

  • delay between application of stimulus & beginning of contraction
103
Q

Contraction Period

A

10-100 msec

Ca2+ binds to troponin, myosin-binding site on actin exposed

cross-bridges form

peak tension develops in muscle fiber

104
Q

Relaxation Period

A

10-100 msec

Ca2+ **actively transported **back in SR

myosin-binding sites covered again by tropomyosin

myosin heads detach from actin

tension in muscle **decreases **

105
Q

Refractory Period

A

5 msec (skeletal) - 300 msec (cardiac)

**temporary loss of excitability **

muscle fibers in motor unit won’t respond to stimulus during this short time

106
Q

Wave Summation

A

phenomenon in which stimuli arriving at dif times causes **larger contractions **

  • after refractory period is over but **before skeletel muscle has relaxed **

(2nd contraction stronger than first)

107
Q

Unfused (incomplete) Tetanus

A

skeletal muscle fiber is stimulated at rate of **20-30 times/sec **

- can only partially relax between stimuli

result is sustained but wavering contraction

108
Q

Fused (Complete) Tetanus

A

when skeletal muscle fiber is stimulated at rate of **80-100 times/sec **

- does not relax at all

  • result = sustained contraction in which individual twitches can’t be detected
109
Q

Applying increased numbers of APs to muscle fiber (or **fascicle/muscle**/muscle group) results in?

A

fusion of contractions (tetanus) & performance of useful work

110
Q

Motor Unit Recruitment

A

process in which **# of active motor unit **increases

  • allows muscle to accomplish increasing gradations of contractile strength
111
Q

Muscle FIber Types by **appearance (2) **

A

1) Red Muscle Fibers
2) White Muscle Fibers

112
Q

1) Red Muscle Fibers

A

high myoglobin content

more mitochondria

more energy stores

greater blood suppluy

(dark meat)

113
Q

2) **White **muscle fibers

A

less myoglobin

less mitochondria

less blood supply

(white meat)

114
Q

Types of Muscle Fibers by function

A

1) Slow Oxidative
2) Fast Oxidative-Glycolytic
3) Fast Glycolytic

115
Q

1) Slow Oxidative

A

smallest, dark red

least powerful

very fatigue resistant

endurance (walking)

116
Q

2) Fast Oxidative-Glycolytic

A

intermediate, red-pink

moderately resistant to fatigue

jogging/most weightlifting activities

117
Q

3) Fast Glycolytic

A

large, white

powerful

intense anaerobic activity of short duration

118
Q

Within a particular motor unit, skeletal muscle fibers are…

A

all the same type

119
Q

Different motor units in muscle are recruited depending on?

A

task being performed

120
Q

Muscle Contractions

(2) types

A

1) Isotonic
2) Isometric

121
Q

1) Isotonic Contraction

A

tension (force of contraction) developed in muscle remains constant while muscle changes length

  • results in movement
122
Q

2) Isometric Contraction

A

tension generated not enough to exceed resistance of object being moved

tension = resistance

muscle does NOT change length

123
Q

(2) types of Isotonic Contraction

A

1) Concentric
2) Eccentric

124
Q

1) **Concentric **Isotonic Contraction

A

tension generated > resistance of object

muscle shortens while generating force

125
Q

2) **Eccentric **Isotonic Contraction

A

length of muscle **increases **

contraction in which muscle tension < resistance

126
Q

Aging - Muscle

A

partly due to decreased levels of physical activity…

humans undergo slow, progressive loss of skeletal muscle mass that is replaced largely by fibrous CT & adipose tissue

127
Q

Muscle Strength

age 85 **vs **age 25

muscle fiber types

A

Muscle strength at 85 is about 1/2 that at age 25

Compared to other 2 fiber types, relative # of slow oxidative fibers appears to increase

128
Q

Sarcopenia

A

degenerative loss of skeletal muscle mass, quality, and strength associated with aging

(0.5–1% loss per year after age 25)

KIN 267 (12 decks)

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