UNIT 9 - MUSCULAR SYSTEM Flashcards
(116 cards)
1
Q
what are the 3 types of muscle tissue?
A
-smooth
-cardiac
-skeletal
2
Q
what are the cells of muscle tissue called?
A
-muscle fibers/myofibers
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
4
Q
where is smooth muscle located in the body?
A
-located in the walls of hollow internal organs and blood vessels (causes contraction)
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
6
Q
what does cardiac muscle form?
A
-the heart wall
7
Q
what are the characteristics of cardiac muscle fibers?
A
-uninucleated
-striated
-branched and tubular
8
Q
what interlocks the cardiac muscle fibers?
A
-intercalated discs
9
Q
what junctions are within intercalated discs?
A
-gap junctions
-permit contractions to spread through the heart wall
10
Q
how does cardiac muscle prevent fatigue?
A
-relaxes completely between contractions
11
Q
what kind of contraction does cardiac muscle have?
A
-involuntary contraction
-occurs without CNS stimulation (SA node)
-rhythmic
12
Q
what are the characteristics of skeletal muscle fibers?
A
-long and tubular (run the entire length of the muscle)
-multinucleated
-striated
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)
14
Q
what attaches muscles to bones?
A
-tendons
15
Q
what do vertebrates such as humans possess?
A
-internal vertebral column
-skeleton
-jointed appendages
16
Q
what kind of contraction does skeletal muscle have?
A
-voluntary contraction
-can become fatigued
17
Q
what is a fasicle?
A
-bundle of skeletal muscle fibers
18
Q
what is the connective tissue layer surrounding the individual muscle fibers?
A
-endomysium
19
Q
what is the connective tissue layer surrounding the fasicle?
A
-perimysium
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
21
Q
what is the origin of a muscle?
A
-attachment site to the stationary bone
22
Q
what is the insertion of a muscle?
A
-attachment site to the bone that moves
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)
24
Q
what is the agonist?
A
-prime mover
-muscle that does most of the work for a specific movement
25
what is the synergist?
-assists the agonist in movement
26
what is the antagonist?
-muscle that acts opposite to the agonist
-ex: triceps brachii and biceps brachii
27
what would happen if both the agonist and antagonist contracted at once?
-there would be no movement
28
what are the types of naming used for skeletal muscles?
-size
-shape
-location
-direction of fibers
-attachment
-number of attachments/origins
-action
29
what are examples of muscles named for size?
-gluteus maximus
-gluteus minimus
30
what are other terms that are used for naming that indicate size?
-vastus (huge)
-longus (long)
-brevis (short)
31
what are examples of muscles named for shape?
-trapezius (trapezoid)
-deltoid (greek letter delta)
32
what are examples of muscles named for location?
-frontalis (overlies the frontal bone)
-external obliques
-internal obliques
33
what are other terms that are used for naming that indicate location?
-pectoralis (chest)
-gluteus (buttocks)
-brachii (arm)
-sub (beneath)
34
what are examples of muscles named for direction of fibers?
-orbicularis oculi (circular)
-rectus abdominis (rectus=straight)
35
what are other terms that are used for naming that indicate direction of fibers?
-transverse (across)
-oblique (diagonal)
36
what are examples of muscles named for attachment?
-sternocleidomastoid (attached to the sternum, clavicle, and mastoid process)
-brachioradialis (attached to the brachium (arm) and radius)
37
what are examples of muscles named for number of attachments/origins?
-biceps brachii (2)
-quadriceps femoris (4 origins)
38
what are examples of muscles named for action?
-adductor longus (adducts the thigh)
-extensor digitorum (extends the digits)
39
what are other terms that are used for naming that indicate action?
-flexor (to bend)
-masseter (to chew)
-levator (to lift)
40
what is the longest muscle?
-sartorius
41
what are the cellular components of a muscle fiber?
-sarcolemma
-sarcoplasm
-sarcoplasmic reticulum
-t tubules
-myofibrils
42
what is the sarcolemma?
-plasma membrane of a muscle cell
-contains many myofibrils
43
what is the sarcoplasm?
-cytoplasm of a muscle cell
-contains glycogen for energy for muscle contraction
-contains myoglobin
44
what is the sarcoplasmic reticulum?
-endoplasmic reticulum
-calcium storage site
45
what are t-tubules?
-extensions of the sarcolemma that penetrate the cells
-come close to the portions of sarcoplasmic reticulum (causes calcium to be released by conveying impulses)
46
what is myoglobin?
-red pigment that stores oxygen for muscle contraction
47
what is a myofibril?
-a bundle of myofilaments that contracts
-runs the entire length of the muscle
48
what is a myofilament?
-an actin or myosin filament whose structure and functions account for muscle striations and contractions
49
what is the breakdown of a muscle fiber?
-muscle fiber is a set of small cylinders (myofilaments) assembled into larger cylinders (myofibrils) that cluster to form the muscle fiber
50
what are striations within muscle?
-stripes formed by the placement of myofilaments within myofibrils
51
what are the 2 types of myofilaments?
-thick myofilaments
-thin myofilaments
52
what are thick filaments made of?
-the protein myosin
-rod like portion with a globular head
-heads have ATP binding sites
53
what are thin filaments made of?
-two intertwining strands of the protein actin
-also contains tropomyosin and troponin
54
what are myofibrils divided into?
-sarcomeres
55
what are the different aspects of sarcomeres?
-Z lines
-I band
-A band
-H band
56
what are the Z lines?
-where sarcomeres extend from
-lie between two Z lines
57
what is the I band?
-isotropic
-light coloured
-made of only thin myofilaments
58
what is the A band?
-anisotropic
-made of overlapping thick and thin myofilaments
59
what is the H band?
-centered within the A band
-contains only thick myofilaments
60
what occurs as the muscle fiber contracts?
-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
how is a muscle contraction supplied with energy?
-ATP
-myosin filaments break down ATP
-globular heads pull the actin filament toward the center of the sarcomere
62
what is a nervous system cell that stimulates muscle fibers to contract?
-motor neuron
63
what is a nerve?
-group of neurons
64
what is an axon?
-the part of a neuron that stimulates a muscle fiber
-has branches so it can stimulate several muscle fibers
65
what is a neuromuscular junction?
-where an axon terminal comes near the sarcolemma
-region
66
what is a synaptic cleft?
-space separating the 2 (axon terminal and sarcolemma)
67
what do axon terminals contain?
-synaptic vessels filled with the neurotransmitter acetylcholine (ACh)
68
what happens when nerve signals reach the axon terminals?
-ACh is released into the synaptic cleft
-ACh subsequently is destroyed by cholinesterase enzyme (to stop nervous stimulation of contraction)
69
what occurs once ACh has been released into the synaptic cleft?
-binds to receptors in the sarcolemma (acetylcholine ligand-gated ion channels)
-allows Na+ to rush into the muscle cell
70
what effect does Na+ going into the cell have?
-generates electrical signals that spread across the sarcolemma through opening voltage-gated ion channels and down T-tubules
71
what occurs when Na+ enters T-tubules?
-electrical signal arrives on the dihydropyridine receptor
-pulls the ryanodine receptors on the sarcoplasmic reticulum membrane
-causes calcium to be released
72
what is a triad?
-structure formed by a t-tubule and terminal cisternae on either side
73
what occurs when calcium is released?
-muscle contraction occurs
-calcium binds to troponin
-the tropomyosin threads move and expose myosin-binding sites on the actin
74
what are the steps following the binding of calcium within muscle contraction?
-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
what is rigor mortis?
-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
what is a motor unit?
-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
how do the number of fibers within a motor unit vary?
-fine control motor units contain only a few fibers
-motor units for strength contain many fibers
78
what is a muscle twitch?
-a single contraction of a muscle fiber
-lasts only a fraction of a second
79
what are the 3 stages of a muscle twitch?
-latent period
-contraction period
-relaxation period
80
what is the latent period?
-time between stimulation and initiation of contraction
-beginning events of muscle contraction are occurring (ACh diffusing and spreading down t-tubules)
81
what is the contraction period?
-calcium leaves the sarcoplasmic reticulum and cross bridges form
82
what is the relaxation period?
-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
what returns calcium to the sarcoplasmic reticulum?
sarcoendoplasmic reticulum calcium ATPase (SERCA) pump
84
what is summation?
-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
how long does summation occur?
-can occur until tetanus is achieved
86
what is tetanus?
-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
what is recruitment?
-activation of more motor units in a muscle because of nervous stimulation intensity increases
88
why is maximum contraction rare? what occurs instead?
-all motor units would fatigue at the same time
-some motor units contract while others rest
89
what are the 2 main causes of muscle fatigue?
-limitations of a nerves ability to generate a sustained signal (neural fatigue)
-reduced ability of the muscle fiber to contract (metabolic fatigue)
90
what is muscle tone? what does the amount depend on?
-muscle firmness
-amount depends on muscle contraction
-some motor units are always contracted but not enough to cause movement
91
what are the 4 different sources of energy for the muscles?
-glycogen (stored in muscle)
-triglycerides (stored in muscle)
-glucose (from blood)
-fatty acids (from blood)
92
what does the energy source used depend on?
-exercise intensity and duration
-when exercise time increases, use of stored energy decreases and use of blood energy increase
93
how do muscles produce ATP?
-creatine phosphate (CP) pathway
-fermentation
-cellular respiration
-muscle cells store limited amounts of ATP
94
which of the 3 ways of producing ATP requires oxygen?
-cellular respiration
-aerobic
95
which of the 3 ways of producing ATP does not require oxygen
-fermentation
-CP pathway
-anaerobic
96
what is cellular respiration?
-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
how many ATP molecules does cellular respiration produce?
-30
98
what is myoglobin?
-protein in muscle cells that delivers oxygen to the mitochondria
99
what is fermentation?
-hormones signal cells to break down glycogen for glucose
-fast acting
-results in a buildup of lactate
-produces 2 ATP
100
what is the creatine phosphate pathway?
-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
when is the CP pathway used?
-at the beginning of exercise
-ex: energy for a play in a football game comes principally from the CP system
102
what pathway for ATP is used for activities longer than 5 seconds?
-fermentation
-ex: sprint or powerlifting
103
what are fast twitch fibers?
-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
why are fast twitch fibers lighter in colour than slow twitch fibers?
-have fewer mitochondria
-little myoglobin
-fewer blood vessels
105
which type of twitch fiber develops maximum tension faster?
-fast twitch fibers
106
what are slow twitch fibers?
-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
why are slow twitch fibers darker in colour than fast twitch fibers?
-have many mitochondria
-contain myoglobin
108
what surrounds slow twitch fibers? what does this allow for?
-by dense capillary beds
-draw more blood and oxygen than fast twitch fibers
109
how are slow twitch fibers able to maintain a steady production of ATP in their mitochondria?
-have a reserve of glycogen and fat
110
do skeletal muscles pull or push on bones to cause movement?
-pull
-NEVER PUSH
111
what does the pulling of skeletal muscle allow us to do?
-response to changes in the environment
-allows for chewing and swallowing
112
what moves food through the digestive tract?
-rhythmic smooth muscle contractions
113
how does muscle aid the cardiovascular and lymphatic systems?
-contractions of the heart propel blood into blood vessels and push blood toward the heart
-helps squeeze interstitial fluid into lymphatic capillaries
114
how does muscle provide protection of body parts?
-skeletal muscles pad and protect bones
-abdominal muscles of the abdominal wall protect internal organs
115
what are examples of how muscles regulate body temp?
-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
how do goosebumps insulate?
-create an air pocket sealing warm air around the follicle to create a layer of insulation
