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WQ24 - A&P I > Articulations & Muscles > Flashcards

Articulations & Muscles Flashcards

1
Q

what is an articulation? why are they necessary?

A

bones are essentially immobile; joints allow them to move
- structure of joint determines type and amount of movement that may occur
- there is compromise between need for strength and need for mobility
- classified according to anatomical organization and range of motion (ROM)

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2
Q

describe the articulation btwn adj. vertebrae. what type of joint is it?

A

gliding joint with slight flexion and rotation of vertebral column
- btwn superior and inferior articular processes of adj vertebrae
- fibrous cartilage = intervertebral disc (roughly 1/4 length of vertebral column)
- as we age and lose water, disc compress and shrink in height
- injury prone to age due to less cushion ability

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3
Q

shoulder joint

A

glenohumeral–
- stability sacrificed for mobility
- greatest range of all joints (weakest)
- most frequently dislocated
- ball-n-socket joint
- rotator cuff muscles: primary mechanism for supporting shoulder joint and limiting ROM
- ligaments and shape of acromion and corocoid process help stabilize
- dislocation can occur due to impact or violent muscle contraction
- contains several important bursae; can lead to infections

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4
Q

where is the origin of the shoulder joint rotator cuff muscles?

A

originates at trunk, pectoral girdle, and humerus

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5
Q

where do the shoulder joint rotator cuff muscles insert?

A

onto scapula

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6
Q

what movements are allowed on the shoulder joint?

A

flexion/extension, adduction/abduction, circumduction and rotation

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7
Q

elbow joint

A

complex hinge joint; involves humerus, ulna, and radius
- largest and strongest articulation at elbow is humero-ulnar joint: trochlea of humerus with trochlear notch of ulna

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8
Q

what is nursemaid’s elbow?

A

partial dislocation due to upward twisting pull on toddler by parents in a rush

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9
Q

why is the elbow joint so stable?

A
  • the bony surfaces of humerus and ulna interlock
  • single, thick articular capsule surrounds humero-ulnar and proximal radio-ulnar joints
  • articular capsule reinforced by strong ligaments
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10
Q

what movement occurs at elbow joint?

A

flexion/extension–
- shape of trochlear notch of ulna determines plane of movement
- combination of notch and olecranon limits degree of extension
- humeroradial joint: capitulum of humerus articulates with head of radius

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11
Q

hip joint

A

ball-n-socket diarthrosis
- very stable (for ball-n-socket) due to articulating bone shapes, ligaments, and muscles
- permits flexion/extension, abduction/adduction, circumduction and rotation

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12
Q

what articulating surfaces allow the movement within the hip joint?

A

acetabulum articulates with head of femur

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13
Q

what holds the head of the femur in place?

A

articular capsule is an extremely dense and strong cavity which holds the head in place

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14
Q

what is more common: hip dislocation or fracture of neck of femur?

A

fracture femur neck due to direction of transfer of weight

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15
Q

knee joint

A

very complicated hinge diarthrosis
- transfer weight from femur to tibia
- permits flexion/extension and very limited rotation
- rounded condyles of femur roll across the superior surface of the tibia, so the points of contact are constantly changing

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16
Q

what are the articulations within the knee joint?

A

2 articulations between femur and tibia (1. medial condyle to medial condyle; 2. lateral condyle to lateral condyle) and 1 between patella and patellar surface of femur

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17
Q

what does the articular capsule of the knee look like?

A

thin and incomplete but strengthened by ligaments and tendons

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18
Q

is a complete dislocation rare or common?

A

rare due to 7 major ligaments that stabilize knee

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19
Q

what is the most common injury in the knee joint?

A

lateral surface of leg is driven medially, tearing medial meniscus

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20
Q

what muscle cell is large in diameter, long in length, and run parallel to e/o?

A

skeletal

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21
Q

what muscle cell is multi-nucleated?

A

skeletal

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22
Q

do skeletal muscle cells have striations?

A

yes

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23
Q

what do striations tell you?

A

actin and myosin are organized into myofibrils and sarcomeres AND cell shortens when it contracts

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24
Q

is the NS required for contraction of skeletal muscle?

A

Yes–
control is voluntary; neural control at single neuromuscular junction (NMJ)/cell

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25
Q

does skeletal muscle have muscle tone?

A

Yes–
has tone or resting tension due to always a few motor units always contracting in resting muscle
- contractions do not cause enough tension for movement, but aids in posture, resting body temperature

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26
Q

where does skeletal muscle get its energy?

A

aerobic at resting and moderate levels; anaerobic (glycolysis) during max activity (peak tension)

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27
Q

what kind of muscle fatigue does this muscle tissue experience?

A

rapid onset, rapid fatigue at peak tensions

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28
Q

what muscle cell is branched?

A

cardiac

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29
Q

are cardiac muscle cells multi-nucleated?

A

no, they are generally single-nucleated and located in the center of the cells

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30
Q

are cardiac cells striated?

A

yes–
also contains intercalated discs (gap junctions and desmosomes) which are important for cells to act as a single functional unit

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31
Q

is the NS required for contraction of cardiac muscle?

A

no, control is involuntary

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32
Q

what is automaticity?

A

presence of pacemaker cells which can generate an electrical signal without need of NS
- hormones and NS can influence pacemaker cells but not always required

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33
Q

does cardiac muscle have muscle tone?

A

no, there are no cells contracting in background or in resting tension
- cardiac muscle cells have a distinct pattern of contracting then relaxing before contracting again

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34
Q

where does cardiac muscle get energy?

A

aerobic, usually lipid or carbs as substrates

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35
Q

does cardiac muscle experience fatigue?

A

muscle fatigue is slower onset, as cardiac muscle is resistant

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36
Q

what muscle tissue is spindle-shaped, thickest in the middle, and taper at the ends?

A

smooth muscle

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37
Q

are smooth muscle cells multi-nucleated?

A

no, they are generally single and located in the center

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38
Q

is smooth muscle striated?

A

no, actin and myosin are not organized into myofibrils and sarcomeres; cells do not shorten when they contract
- cells do a twisting motion instead

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39
Q

is the NS required for smooth muscle contraction?

A

no, control is involuntary; pacemaker cells generate an electrical signal without the need for NS

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40
Q

does smooth muscle have muscle tone?

A

yes– occurs because there are always some contractions of smooth muscle cells at rest
example:
blood vessels, muscle tone causes resting amount of vasoconstriction and allows blood to move
- gives resting tone to tracts: GI, respiratory, urinary, etc.

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41
Q

where does the smooth muscle gain energy?

A

aerobic respiration

42
Q

does smooth muscle experience contractions and muscle fatigue?

A

yes–
slow onset, but resistent to fatigue

43
Q

where is skeletal muscle found?

A

forms large muscles and are responsible for gross body movements and locomotion

44
Q

where is cardiac muscle found?

A

only in the heart

45
Q

where is smooth muscle found?

A

walls of visceral organs, lining blood vessels, glands

46
Q

what are intercalated discs?

A

specialized junctions between cardiac muscle fibers that allow for rapid electric transmission (action potential) and nutrient exchange.

47
Q

why are intercalated discs so important?

A

allows heart to beat in unison = functional syncytium due to cells mechanically, chemically, and electrically connected; entire tissue resembles single enormous cells

48
Q

how is skeletal muscle organized? (tissue level)

A

three layers are part of each muscle, collagen fibers from each come together at end of muscle to form tendon (aponeurosis): attaches muscle to bone

49
Q

what is the epimysium?

A

connective tissue surrounding entire muscle; and is a dense layer of collagen
- separates muscle from surrounding tissues and organs
- connected to deep fascia

50
Q

what is the perimysium?

A

divides muscle into compartments
- each compartment contains bundle of fibers/cells = fasicle
- contains collagen, elastic fibers, BV, and nerves (supplies individual fibers within fasicle)

51
Q

what is the endomysium?

A

surrounds individual muscle fibers and loosely connects
- within fasicle
- flexible elastic layer containing capillaries, myosatellite cells, and nerve fibers controlling muscle

52
Q

what is the structure of a skeletal muscle fiber?

A

multi-nucleate
- 100s of nuclei, just internal to PM
- genes in nuclei control enzyme production and structural proteins required for contraction

53
Q

what is the sarcolemma?

A

plasma membrane of skeletal muscle fiber
- surrounds sacroplasm (cytoplasm of muscle fiber) and contains numerous myofibrils
- has transmembrane potential due to unequal distribution of (+) and (-) charges across membrane

54
Q

what are t-tubules?

A

invaginations of external membrane of skeletal muscle fibers
- helps all regions of large cell to contract simultaneously
- narrow tubes continuous with sarcolemma
- extends into sarcoplasm at right angles to cell surface
- filled with extracellular fluid and have same properties as sarcolemma

55
Q

how does action potential get to the interior of a cell?

A

electrical impulses (AP) are conducted by sarcolemma and travel along t-tubules into the interior of the cell

56
Q

What are the structural components of a sarcomere?

A
  • highly ordered repeating units of actin and myosin
  • smallest functional unit of muscular fiber (that can contract)
  • 10,000 end-to-end per myofibril
  • extends from one Z-disk to another Z-disk (protein fibers forming an attachment site for actin myofilaments)
  • M-line: dark line that runds down the center of a sarcomere acting as an anchor for thick filaments
  • Dark bands = A bands
  • Light bands = I bands
57
Q

what is the sarcoplasmic reticulum?

A

abbreviated SR; related to the SER (smooth endoplasmic reticulum) as the membrane complex
- tightly bound to T-tubules
- forms tubular network around each myofibril
enlarge, fuse and form expanded chambers on either side of T-tubules = terminal cisternae
- Ca2+ actively pumped from sarcoplasm into terminal cisternae of SR

58
Q

what is the terminal cisternae?

A

specialized compartments in skeletal muscle cells that store and release calcium ions (Ca2+) when an action potential courses down the t-tubules, causing muscle contraction

59
Q

when a muscle is at rest, what do the [Ca2+] look like?

A

in the sarcoplasm: low [Ca2+]; SR: [Ca2+]

60
Q

when a muscle is contracting, what do the [Ca2+] look like?

A

in the sarcoplasm: high [Ca2+]

61
Q

what are myofibrils?

A

consists of bundles of protein filaments aka myofilaments
- cylindrical structure inside fiber
- encircled by t-tububles
- 1-2 µm in diameter, as long as fiber
- can actively shorten as they are responsible for fiber contraction
- anchored into inner surface of sarcolemma at ends
- consist of scattered mitochondria and granules of glycogen

62
Q

what are the two types of myofilaments?

A

thin filaments: primarily made of actin
thick filaments: primarily made of myosin

63
Q

what is glycogen?

A

storage form of glucose

64
Q

what is thin myofilament?

A
  • actin resembles two tiny strands of pearls twisted together
  • actin has active site for myosin
  • tropomyosin filaments located along groove btwn twisted strands of actin myofilament (covers active sites for myosin)
  • troponin molecules attached at specific intervals along actin myofilament and binds to Ca2+
65
Q

what is a thick myofilament?

A

made of myosin
- resembles bundles of tiny golf clubs
- 2 subunits twisted around e/o; each with a tail and head
- tail points towards M-line
- head projects outward toward nearest thin filament
- myosin head interacts with exposed attachment sites on thin filament during contraction

66
Q

what is a cross-bridge?

A

refers to the attachment of myosin with actin within muscle cell

67
Q

how does the cross-bridge cycle work?

A
  1. myosin heads bind to actin
  2. myosin heads use chemical energy from ATP to generate a pulling force against actin filaments
  3. the myosin heads detach and prepare to bind again
  4. the actin-myosin cross-bridge formation pulls the actin inward, shortening sarcomere length, which results in contraction
  5. as active muscle lengthens or shortens, cross bridges repeatedly detach and reattach in new positions
68
Q

what two factors are necessary for cross-bridge formation?

A
  • elevated [Ca2+]
  • adequate supply of ATP
69
Q

what is the A band?

A
  • located in center of the sarcomere
  • length = length of thick filament
  • also includes portion of thin filament
  • contains 3 subdivisions
    1. M line (center portio of each thick filament)
    2. H band (on either side of M line, contains only of thick filaments)
    3. zone of overlap (area of overlap between thin and thick filaments; Ca2+ released from SR into this area)
70
Q

What is the I band?

A
  • made of thin filaments, not thick
  • extends from A band of 1 sarcomere to A band of adj. sarcomere
  • contains Z-disk
    • marks boundary of sarcomere
    • thin filament extends from Z line toward M line and into zone of overlap
71
Q

identify the components of a neuromuscular junction (NMJ)

A
  • presynaptic terminal: enlarged axon terminal of nerve
  • synaptic cleft: space btwn presynaptic and postsynaptic terminals
  • postsynaptic terminal = motor end plate
    • muscle fiber membrane
    • convoluted to increase surface area
72
Q

what is the presynaptic terminal?

A
  • synaptic vesicles: numerous & small in size
    • contain neurotransmitter called acetylcholine (Ach)
    • Ach: stimulus for a skeletal muscle fiber
  • Ca2+ channels
    • Ca2+ must enter presynaptic terminal for exocytosis of Ach into synaptic cleft
    • AP traveling down neuron to presynaptic terminal causes Ca2+ channels to open
73
Q

what is the postsynaptic terminal

A
  • Na+ channels
    • have Ach receptor
    • Ach binds leading to Na+ channel opening
    • Na+ enters muscle fiber resulting in AP
  • Ach is broken down by acetylecholinesterase (AchE)
    • enzyme found in synaptic cleft and sarcolemma
    • ensures that one AP in neuron yields only one AP in muscle
74
Q

What are the events involved in the neural control of skeletal muscles? How is an
electrical signal in the nerve changed to a chemical sign and then back to an
electrical signal in the muscle fiber sarcolemma?

A
  1. arrival of AP at presynaptic terminal causes sudden change of transmembrane potential (TMP) = causes Ca2+ channels to open
  2. Release of Ach = Ca2+ enters presynaptic terminal and causes synaptic vesicles to relese Ach into synaptic cleft via exocytosis
  3. Ach binds to postsynaptic terminal and diffuse across synaptic cleft and bind to AchR (receptor) site on Na+ channels in muscle fiber membrane
    • Ach binding increases permeability to Na+, Na+ channels open
    • Na+ rushes into cell = AP initiates and continues until AchE breaks down Ach
  4. Appearance of AP in sarcolemma
    • Na+ causes AP in sarcolemma
    • AP originates at edges and sweeps across membrane surface travelling inward along t-tubules
  5. return to initial state
    • before AP spreads across sarcolemma, AchE breaks down Ach and reabsorbs it to resynthesize Ach for repeated release
75
Q

describe sliding filament theory of muscle contraction

A

lengths of actin and myosin do not change, only the bands/zone change size
- H and I bands gets smaller
- zones of overlap get larger
- z lines move closer together
- length of A band remains constant
- thin filaments slide toward center of each sarcomere, alongside thick filaments
- sliding occurs in every sarcomere along myofibril = myofibril gets shorter
- myofibril attached to sarcolemma at each Z-line and at either end of muscle fiber, thus when myofibril gets shorter so does entire muscle fiber

76
Q

what is the first step of the contraction cycle?

A

exposure of the active site
- Ca2+ binds to troponin (lock)
- Causes troponin-tropomyosin complex to move and expose active site on actin for myosin

77
Q

what is the second step of the contraction cycle?

A

formation of cross-bridges
- myosin head bound to ADP+Pi (energized)
- energized myosin head binds w/ actin

78
Q

what is the third step of the contraction cycle?

A

pivoting of myosin heads
- at rest, myosin heads points away from M line requires ATP; ADP+Pi bound to myosin
- energy released as head pivots toward M-line (power-stroke) and ADP+Pi is released

79
Q

what is the fourth step of the contraction cycle?

A

detachment of cross-bridges
- ATP binds to myosin and breaks down cross-bridges
- active site exposed and another cross-bridge can form

80
Q

what is the fifth step of the contraction cycle?

A

reactivation of myosin
- free myosin head splits ATP to ADP+Pi
- E released as head is “cocked”
- repeat cycle several times/sec (dependent on [Ca2+] and ATP availability)

81
Q

how does the relaxation of a muscle happen?

A
  • no more AP as AchE breaks down Ach
  • Ca2+ actively taken up into SR
  • No Ca2+, troponin-tropomyosin moves over actin active sites
  • no exposed active sites, no cross-bridge formation
    -no cross-bridge formation, no sliding of filaments
    -no sliding of filaments, muscle passively lengthens
    -muscle lengthens, muscle relaxes
82
Q

what happens in rigor mortis?

A

during death, blood circulation decreases and skeletal muscle is deprived of nutrients and O2
- within few hours, muscle runs out of ATP and SR cannot actively transport Ca2+ out of sarcoplasm
- cross-bridges that formed cannot break
- muscles become rigid
- lasts until lysosomal enzymes released by autolysis break down proteins and sarcomere components
- occurs 15-25 hrs after death, until 72+ hours
- body goes limp afterwards

83
Q

How is insecticide an AchE inhibitor?

A

inhibition of AchE promotes the accumulation of Ach; constant stimulus of muscle fiber
- insect will die, respiratory cannot relax and will continue to fatigue until death

84
Q

how is curare an Ach inhibitor?

A

curare: poison used by native americans in south america on arrows
- binds to AchR on muscle cell membrane
- prevents endogenous (inner cell) Ach from binding
- muscle fibers can’t be stimulated and do not contract
- leads to paralysis

85
Q

what is a twitch?

A

how much tension a single muscle fiber can produce due to one stimulus
- varies in duration, depending on type of muscle and other factors

86
Q

what is the latent period?

A

first phase of a muscle twitch; where AP moves thru sarcolemma, causing Ca2+ release from SR

87
Q

what is the contraction phase?

A

second phase of a muscle twitch
- Ca2+ binds
- cross-bridge formation
- power-stroke
- tension builds to peak

88
Q

what is the relaxation phase?

A

third phase of a muscle twitch
- Ca2+ actively transported back into SR
- Ca2+ levels fall
- active sites are covered
- tension falls to resting levels

89
Q

how is the force of a contraction increased?

A

summation: increasing force of contraction of muscle fibers within muscle
recruitment: increasing number of muscle fibers contracting

90
Q

what is treppe?

A

muscle stimulation in which the 2nd stimulation takes place immediately after relaxation phase of 1st ended
- resulting contraction develops slightly higher max tension than first
- rise due to gradual increase in Ca2+ in sarcoplasm
- SR can’t actively transport Ca2+ fast enough

91
Q

what is wave summation and incomplete tetanus?

A

muscle stimulation in which 2nd stimulus arrives before relaxation phace has ended, and second more powerful contraction occurs
- twitches begin to summate
- if stimulus continues and muscle is never allowed to relax completely, tension rises
- reaches peak value 4x max produced by treppe
- in incomplete tetanus, it reaches near peak tension but does not max out

92
Q

what is complete tetanus?

A

muscle stimulation in which second stimulus happens early enough where relaxation phase is completely eliminated from the prev. twitch
- AP arrive rapidly enough that SR cannot reclaim Ca2+
- high [Ca2+] in sarcoplasm prolongs contraction

93
Q

what is a motor unit?

A

single motor neuron and all the skeletal muscle fibers it stimulates
- small precise muscles have 1 or few muscle fibers/unit (ie. eye muscles)
- large muscles have many muscle fibers/motor unit (ie. thigh muscle)

94
Q

what is summation?

A

force of contraction of individual muscle fibers is increased by rapid stimulation
- low stimulus frequency allows for complete relaxation of fibers btwn twitches
- increase frequency doesn’t allow for complete relaxation
- contractions start to summate and add on to previous one
- overall force of contraction increases

95
Q

what is recruitment?

A

strength of contraction increases as number of stimulated motor units increases
- few motor units stimulated = small force
- increase motor units = more fibers stimulated to contract = increase force of contraction
- max force produced in a given muscle when all motor units of muscle are stimulated
- motor units are added gradually to allow for smooth sustained contraction (avoids jerking action)
- limited by available ATP

96
Q

what is muscle tone?

A

the amnt of tension or resistance to movement in muscles; but not enough tension to cause movement
- helps stabilize bone and joints
- maintains body temperature
- heightened tone accelerates recruitment during voluntary contraction
- activated muscles use E (energy)
- high fitness, high E used at rest, high metabolism
- increased muscle mass, more fibers contracting, helps burn calories

97
Q

what is ATP?

A

adenosine triphosphate
- active energy molecule
- at rest, produces more than needed
- ATP cannot be stored, must be used

98
Q

what is CP?

A

creatine phosphate
- the storage molecule for excess ATP energy in resting muscle:
ATP + creatine = CP + ADP (enzyme used: CPK (creatine phosphokinase)
- energy stored in CP can “recharge” ADP when muscle requires ATOP for contraction
- when CP is depleted, ATP is generated for contracting muscle

99
Q

what is aerobic metabolism? what is required? how much ATP is produced? Pros? Cons?

A
  • requires oxygen
  • primary energy source for resting muscles and endurance activities
  • can use variety of nutrient molecules to produce ATP (1 glucose = 34 ATP; 1 fatty acid = 100 ATP)
  • sloww
  • occurs in mitochondria
  • 1 C6H12O6 (glucose) => ATP + H2O + CO2
100
Q

what is anaerobic glycolysis? what is required? how much ATP is produced? Pros? Cons?

A
  • does not require O2
  • primary energy source for peak intense muscular activity
  • inefficient: produces 2 ATP/glucose
  • glucose => ATP + Lactic acid
  • occurs in cytoplasm of cells
  • limited nutrients can be used (primarily glycogen reserves in sarcoplasm)
  • NASTY waste products (lactic acid byproduct lowers pH and causes pain)
101
Q

what is muscle fatigue?

A
  • when muscle can no longer perform required activity
  • ATP is used faster than produced and lactic acid builds up faster than it can be removed
  • force of contractions decrease
  • ATP can’t break cross-bridge formations, so no subsequent contractions occur

WQ24 - A&P I (4 decks)

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