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HEAL1500 > UNIT 9 - MUSCULAR SYSTEM > Flashcards

UNIT 9 - MUSCULAR SYSTEM Flashcards

1
Q

what are the 3 types of muscle tissue?

A

-smooth
-cardiac
-skeletal

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2
Q

what are the cells of muscle tissue called?

A

-muscle fibers/myofibers

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3
Q

what are the characteristics of smooth muscle fibers?

A

-fibers are shaped like cylinders with pointed ends
-uninucleated
-arranged in parallel lines forming sheets
-not striated

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4
Q

where is smooth muscle located in the body?

A

-located in the walls of hollow internal organs and blood vessels (causes contraction)

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5
Q

what kind of contraction does smooth muscle have? how does this compare to other muscle types?

A

-involuntary contraction
-slower to contract than skeletal muscle
-can sustain prolonged contractions and does not fatigue easily

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6
Q

what does cardiac muscle form?

A

-the heart wall

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7
Q

what are the characteristics of cardiac muscle fibers?

A

-uninucleated
-striated
-branched and tubular

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8
Q

what interlocks the cardiac muscle fibers?

A

-intercalated discs

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9
Q

what junctions are within intercalated discs?

A

-gap junctions
-permit contractions to spread through the heart wall

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10
Q

how does cardiac muscle prevent fatigue?

A

-relaxes completely between contractions

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11
Q

what kind of contraction does cardiac muscle have?

A

-involuntary contraction
-occurs without CNS stimulation (SA node)
-rhythmic

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12
Q

what are the characteristics of skeletal muscle fibers?

A

-long and tubular (run the entire length of the muscle)
-multinucleated
-striated

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13
Q

what are the functions of skeletal muscles?

A

-support (muscle contraction opposes gravity, allows us to remain upright)
-movements of bones and body
-body temp maintenance (contraction breaks down ATP, releases heat throughout the body)
-fluid movement (blood + lymph)
-protection of internal organs
-stabilization of joints (muscle tendons hold bones together at joints)

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14
Q

what attaches muscles to bones?

A

-tendons

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15
Q

what do vertebrates such as humans possess?

A

-internal vertebral column
-skeleton
-jointed appendages

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16
Q

what kind of contraction does skeletal muscle have?

A

-voluntary contraction
-can become fatigued

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17
Q

what is a fasicle?

A

-bundle of skeletal muscle fibers

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18
Q

what is the connective tissue layer surrounding the individual muscle fibers?

A

-endomysium

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19
Q

what is the connective tissue layer surrounding the fasicle?

A

-perimysium

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20
Q

what is the connective tissue layer surrounding the entire muscle? what does this create? what does it seperate?

A

-epimysium
-extends to create its tendon
-separates muscles from internal organs

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21
Q

what is the origin of a muscle?

A

-attachment site to the stationary bone

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22
Q

what is the insertion of a muscle?

A

-attachment site to the bone that moves

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23
Q

what happens when a skeletal muscle contracts?

A

-pulls on the tendons at its insertion and the bone moves
-ex: biceps brachii contracts and raises the forearm (radius insertion)

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24
Q

what is the agonist?

A

-prime mover
-muscle that does most of the work for a specific movement

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25
Q

what is the synergist?

A

-assists the agonist in movement

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26
Q

what is the antagonist?

A

-muscle that acts opposite to the agonist
-ex: triceps brachii and biceps brachii

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27
Q

what would happen if both the agonist and antagonist contracted at once?

A

-there would be no movement

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28
Q

what are the types of naming used for skeletal muscles?

A

-size
-shape
-location
-direction of fibers
-attachment
-number of attachments/origins
-action

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29
Q

what are examples of muscles named for size?

A

-gluteus maximus
-gluteus minimus

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30
Q

what are other terms that are used for naming that indicate size?

A

-vastus (huge)
-longus (long)
-brevis (short)

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31
Q

what are examples of muscles named for shape?

A

-trapezius (trapezoid)
-deltoid (greek letter delta)

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32
Q

what are examples of muscles named for location?

A

-frontalis (overlies the frontal bone)
-external obliques
-internal obliques

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33
Q

what are other terms that are used for naming that indicate location?

A

-pectoralis (chest)
-gluteus (buttocks)
-brachii (arm)
-sub (beneath)

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34
Q

what are examples of muscles named for direction of fibers?

A

-orbicularis oculi (circular)
-rectus abdominis (rectus=straight)

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35
Q

what are other terms that are used for naming that indicate direction of fibers?

A

-transverse (across)
-oblique (diagonal)

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36
Q

what are examples of muscles named for attachment?

A

-sternocleidomastoid (attached to the sternum, clavicle, and mastoid process)
-brachioradialis (attached to the brachium (arm) and radius)

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37
Q

what are examples of muscles named for number of attachments/origins?

A

-biceps brachii (2)
-quadriceps femoris (4 origins)

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38
Q

what are examples of muscles named for action?

A

-adductor longus (adducts the thigh)
-extensor digitorum (extends the digits)

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39
Q

what are other terms that are used for naming that indicate action?

A

-flexor (to bend)
-masseter (to chew)
-levator (to lift)

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40
Q

what is the longest muscle?

A

-sartorius

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41
Q

what are the cellular components of a muscle fiber?

A

-sarcolemma
-sarcoplasm
-sarcoplasmic reticulum
-t tubules
-myofibrils

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42
Q

what is the sarcolemma?

A

-plasma membrane of a muscle cell
-contains many myofibrils

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43
Q

what is the sarcoplasm?

A

-cytoplasm of a muscle cell
-contains glycogen for energy for muscle contraction
-contains myoglobin

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44
Q

what is the sarcoplasmic reticulum?

A

-endoplasmic reticulum
-calcium storage site

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45
Q

what are t-tubules?

A

-extensions of the sarcolemma that penetrate the cells
-come close to the portions of sarcoplasmic reticulum (causes calcium to be released by conveying impulses)

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46
Q

what is myoglobin?

A

-red pigment that stores oxygen for muscle contraction

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47
Q

what is a myofibril?

A

-a bundle of myofilaments that contracts
-runs the entire length of the muscle

48
Q

what is a myofilament?

A

-an actin or myosin filament whose structure and functions account for muscle striations and contractions

49
Q

what is the breakdown of a muscle fiber?

A

-muscle fiber is a set of small cylinders (myofilaments) assembled into larger cylinders (myofibrils) that cluster to form the muscle fiber

50
Q

what are striations within muscle?

A

-stripes formed by the placement of myofilaments within myofibrils

51
Q

what are the 2 types of myofilaments?

A

-thick myofilaments
-thin myofilaments

52
Q

what are thick filaments made of?

A

-the protein myosin
-rod like portion with a globular head
-heads have ATP binding sites

53
Q

what are thin filaments made of?

A

-two intertwining strands of the protein actin
-also contains tropomyosin and troponin

54
Q

what are myofibrils divided into?

A

-sarcomeres

55
Q

what are the different aspects of sarcomeres?

A

-Z lines
-I band
-A band
-H band

56
Q

what are the Z lines?

A

-where sarcomeres extend from
-lie between two Z lines

57
Q

what is the I band?

A

-isotropic
-light coloured
-made of only thin myofilaments

58
Q

what is the A band?

A

-anisotropic
-made of overlapping thick and thin myofilaments

59
Q

what is the H band?

A

-centered within the A band
-contains only thick myofilaments

60
Q

what occurs as the muscle fiber contracts?

A

-sarcomeres shorten
-I band shortens
-Z lines move inward
-H band almost disappears
-filaments themselves keep the same length (thin filaments slide past thick filaments)

61
Q

how is a muscle contraction supplied with energy?

A

-ATP
-myosin filaments break down ATP
-globular heads pull the actin filament toward the center of the sarcomere

62
Q

what is a nervous system cell that stimulates muscle fibers to contract?

A

-motor neuron

63
Q

what is a nerve?

A

-group of neurons

64
Q

what is an axon?

A

-the part of a neuron that stimulates a muscle fiber
-has branches so it can stimulate several muscle fibers

65
Q

what is a neuromuscular junction?

A

-where an axon terminal comes near the sarcolemma
-region

66
Q

what is a synaptic cleft?

A

-space separating the 2 (axon terminal and sarcolemma)

67
Q

what do axon terminals contain?

A

-synaptic vessels filled with the neurotransmitter acetylcholine (ACh)

68
Q

what happens when nerve signals reach the axon terminals?

A

-ACh is released into the synaptic cleft
-ACh subsequently is destroyed by cholinesterase enzyme (to stop nervous stimulation of contraction)

69
Q

what occurs once ACh has been released into the synaptic cleft?

A

-binds to receptors in the sarcolemma (acetylcholine ligand-gated ion channels)
-allows Na+ to rush into the muscle cell

70
Q

what effect does Na+ going into the cell have?

A

-generates electrical signals that spread across the sarcolemma through opening voltage-gated ion channels and down T-tubules

71
Q

what occurs when Na+ enters T-tubules?

A

-electrical signal arrives on the dihydropyridine receptor
-pulls the ryanodine receptors on the sarcoplasmic reticulum membrane
-causes calcium to be released

72
Q

what is a triad?

A

-structure formed by a t-tubule and terminal cisternae on either side

73
Q

what occurs when calcium is released?

A

-muscle contraction occurs
-calcium binds to troponin
-the tropomyosin threads move and expose myosin-binding sites on the actin

74
Q

what are the steps following the binding of calcium within muscle contraction?

A

-myosin heads attach to actin and form temporary bonds called cross bridges (ATP binding breaks this)
-ADP and P are released and myosin heads bend (ATP broken) (power stroke pulling the actin filament towards the sarcomere center)
-ATP binding restarts the process

75
Q

what is rigor mortis?

A

-relaxing the muscle is impossible because ATP is needed to break cross bridges
-appears 2 hours after death (completes 6-8 hours after death)
-lasts 12 hours (24 hours after death) and disappears
-starts in the face and moves down

76
Q

what is a motor unit?

A

-a nerve fiber and all the muscle fibers it innervates
-all muscle fibers in a motor unit are stimulated at once (all contract or all don’t)
-number of fibers within a unit varies

77
Q

how do the number of fibers within a motor unit vary?

A

-fine control motor units contain only a few fibers
-motor units for strength contain many fibers

78
Q

what is a muscle twitch?

A

-a single contraction of a muscle fiber
-lasts only a fraction of a second

79
Q

what are the 3 stages of a muscle twitch?

A

-latent period
-contraction period
-relaxation period

80
Q

what is the latent period?

A

-time between stimulation and initiation of contraction
-beginning events of muscle contraction are occurring (ACh diffusing and spreading down t-tubules)

81
Q

what is the contraction period?

A

-calcium leaves the sarcoplasmic reticulum and cross bridges form

82
Q

what is the relaxation period?

A

-cross bridges are broken
-cholinesterase dissociates ACh in synaptic cleft (no more action potential)
-calcium returns to the sarcoplasmic reticulum
-force diminishes as muscle returns to its former length

83
Q

what returns calcium to the sarcoplasmic reticulum?

A

sarcoendoplasmic reticulum calcium ATPase (SERCA) pump

84
Q

what is summation?

A

-occurance of additional twitch contractions before the previous twitch has completely relaxed
-achieved by increasing frequency of stimulation or by recruiting additional muscle fibers within a muscle

85
Q

how long does summation occur?

A

-can occur until tetanus is achieved

86
Q

what is tetanus?

A

-maximal sustained contraction
-continues until muscle fatigue (depletion of energy reserves)
-fatigue happens when a muscle relaxes even though stimulation continues
-maximum contraction requires that all motor units be in tetanus

87
Q

what is recruitment?

A

-activation of more motor units in a muscle because of nervous stimulation intensity increases

88
Q

why is maximum contraction rare? what occurs instead?

A

-all motor units would fatigue at the same time
-some motor units contract while others rest

89
Q

what are the 2 main causes of muscle fatigue?

A

-limitations of a nerves ability to generate a sustained signal (neural fatigue)
-reduced ability of the muscle fiber to contract (metabolic fatigue)

90
Q

what is muscle tone? what does the amount depend on?

A

-muscle firmness
-amount depends on muscle contraction
-some motor units are always contracted but not enough to cause movement

91
Q

what are the 4 different sources of energy for the muscles?

A

-glycogen (stored in muscle)
-triglycerides (stored in muscle)
-glucose (from blood)
-fatty acids (from blood)

92
Q

what does the energy source used depend on?

A

-exercise intensity and duration
-when exercise time increases, use of stored energy decreases and use of blood energy increase

93
Q

how do muscles produce ATP?

A

-creatine phosphate (CP) pathway
-fermentation
-cellular respiration
-muscle cells store limited amounts of ATP

94
Q

which of the 3 ways of producing ATP requires oxygen?

A

-cellular respiration
-aerobic

95
Q

which of the 3 ways of producing ATP does not require oxygen

A

-fermentation
-CP pathway
-anaerobic

96
Q

what is cellular respiration?

A

-the slowest of the 3 ways but the most efficient
-occurs in the mitochondria
-uses glucose from either stored glycogen or blood glucose
-makes use of fatty acids
-includes glycolysis

97
Q

how many ATP molecules does cellular respiration produce?

A

-30

98
Q

what is myoglobin?

A

-protein in muscle cells that delivers oxygen to the mitochondria

99
Q

what is fermentation?

A

-hormones signal cells to break down glycogen for glucose
-fast acting
-results in a buildup of lactate
-produces 2 ATP

100
Q

what is the creatine phosphate pathway?

A

-simplest and fastest way for muscle to make ATP
-consists of only one reaction
-creatine phosphate is only formed when a muscle cell is resting (limited amount stored)

101
Q

when is the CP pathway used?

A

-at the beginning of exercise
-ex: energy for a play in a football game comes principally from the CP system

102
Q

what pathway for ATP is used for activities longer than 5 seconds?

A

-fermentation
-ex: sprint or powerlifting

103
Q

what are fast twitch fibers?

A

-designed for strength (explosions of energy)
-motor units contain many fibers
-helpful in sprinting or weight lifting
-greater maximum tension
-dependent on anaerobic energy (CP + fermentation) (vulnerable to accumulation of lactate)
-fatigue quickly

104
Q

why are fast twitch fibers lighter in colour than slow twitch fibers?

A

-have fewer mitochondria
-little myoglobin
-fewer blood vessels

105
Q

which type of twitch fiber develops maximum tension faster?

A

-fast twitch fibers

106
Q

what are slow twitch fibers?

A

-motor units have fewer muscle fibers
-have more stamina
-helpful in endurance sports
-produce energy aerobically (only tire when fuel supply is gone)
-tension develops slowly
-resistant to fatigue

107
Q

why are slow twitch fibers darker in colour than fast twitch fibers?

A

-have many mitochondria
-contain myoglobin

108
Q

what surrounds slow twitch fibers? what does this allow for?

A

-by dense capillary beds
-draw more blood and oxygen than fast twitch fibers

109
Q

how are slow twitch fibers able to maintain a steady production of ATP in their mitochondria?

A

-have a reserve of glycogen and fat

110
Q

do skeletal muscles pull or push on bones to cause movement?

A

-pull
-NEVER PUSH

111
Q

what does the pulling of skeletal muscle allow us to do?

A

-response to changes in the environment
-allows for chewing and swallowing

112
Q

what moves food through the digestive tract?

A

-rhythmic smooth muscle contractions

113
Q

how does muscle aid the cardiovascular and lymphatic systems?

A

-contractions of the heart propel blood into blood vessels and push blood toward the heart
-helps squeeze interstitial fluid into lymphatic capillaries

114
Q

how does muscle provide protection of body parts?

A

-skeletal muscles pad and protect bones
-abdominal muscles of the abdominal wall protect internal organs

115
Q

what are examples of how muscles regulate body temp?

A

-when cold, smooth muscle constricts inside blood vessels of the skin (conserves heat)
-shivering is caused by involuntary skeletal muscle contraction (uses ATP which generates heat)
-goose bumps are caused by arrector pili muscles contracting, hairs will stand up and close pores (limits heat loss) (more effective in other mammals)

116
Q

how do goosebumps insulate?

A

-create an air pocket sealing warm air around the follicle to create a layer of insulation

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