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musculoskeletal system Flashcards

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1
Q

why do skeletal muscles appear striated under the microscope?

A
  • highly organised nature of sarcomeres
  • actin & myosin are arranged in an orderly structure within the sarcomeres
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2
Q

what are actin & myosin?

A

contractile proteins

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3
Q

why are smooth muscles not striated?

A

actin & myosin are arranged irregularly so they appear uniform under a microscope

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4
Q

3 types of muscle tissue

A
  • skeletal
  • cardiac
  • smooth
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5
Q

skeletal muscle

A
  • long cylindrical cells
  • many nuclei per cell (lots of satellite cells fused together)
  • striated due to sarcomeres
  • voluntary
  • rapid contractions
  • limbs, face…
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6
Q

cardiac muscle

A
  • branching cells
  • 1 or 2 nuclei per cell
  • striated
  • involuntary
  • medium speed contractions
  • only in the heart
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7
Q

why does cardiac muscle have branching cells?

A

to facilitate uniformal contractions

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8
Q

why are cardiac muscles always slightly contracted?

A

to prevent fully emptying a chamber in the heart

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9
Q

smooth muscle

A
  • fusiform cells
  • one nucleus per cell
  • non striated (actin & myosin irregularly arranged)
  • involuntary
  • slow, wave like contractions
  • GI tract / organs
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10
Q

what is an isometric contraction?

A
  • produces no movement
  • while standing, sitting & posture
  • force produced with no change
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11
Q

what is an isotonic contraction?

A
  • produces movement
  • walking, moving anything in the body
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12
Q

what is an isokinetic contraction?

A

moving with the same constant velocity

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13
Q

what does the Z disc do?

A
  • stabilised / hold actin filaments together
  • allows transfer of forces between sarcomeres
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14
Q

what does a myosin molecule consist of?

A
  • 2 twisted together
  • has a tail and head
  • head = attaches to actin molecules
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15
Q

what does the thin (actin) filament consist of?

A
  • 2 twisted actin molecules
  • troponin complex
  • tropomyosin
  • G actin
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16
Q

what does the thick (myosin) filament consist of?

A

myosin molecules with globular heads (pointing outwards) which form cross-bridges with / can attach to actin molecules

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17
Q

troponin complex

A
  • protein needed for muscle contraction
  • calcium binds to it to trigger musclular force
  • in thin filament
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18
Q

tropomyosin

A
  • proteins
  • regulates muscle contraction by mediating interactions between troponin complex and actin
  • in thin filament (actin)
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19
Q

H band

A
  • zone of thick filaments with no actin
  • M line in H band
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20
Q

M line

A
  • middle of sarcomere
  • formed by cross connecting elements of cytoskeleton
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21
Q

what does the addition of calcium trigger?

A
  • activates the contractile proteins (troponin complex)
  • muscle contraction
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22
Q

what is meant by the term motor unit?

A

motor unit describes a functional group comprised of a motor neuron and its axons (branching into the muscle) and the innervated muscle fibres

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23
Q

what do cardiac muscle fibres determine?

A

they organise how cardiac output is produced

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24
Q

parts of the skeletal system

A
  • bones
  • joints
  • cartilages
  • ligaments
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25
Q

the skeletal system is divided into 2 divisions

A
  • axial skeleton
  • appendicular skeleton
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26
Q

what is the axial skeleton?

A
  • skull, vertebral column, rib cage
  • forms longitudinal part of the body
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27
Q

what is the appendicular skeleton?

A

limbs and girdle

(girdle: either of two more or less complete bony rings at the anterior and posterior ends of the vertebrate trunk supporting the arms and legs respectively)

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28
Q

functions of bone

A
  • support
  • protection
  • assisting in movement
  • mineral storage
  • red blood cell production
  • chemical energy storage (fats)
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29
Q

how does the skeleton support the body?

A
  • it is the body framework
  • supports soft tissue
  • provides attachment points for most skeletal muscle
  • helps allow simple movement without the expanditure of too much energy
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30
Q

how does the skeleton protect the body?

A

protects delicate organs:
- ribs protect the heart and lungs
- skull protects the brain

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31
Q

why do the ribs need to be flexible?

A
  • to allow the dissipation of energy throughout the body
  • to distribute force
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32
Q

how does the skeleton help movement?

A

muscles contract and pull on bones which gives rise to movement

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33
Q

bones and mineral storage

A
  • outer layer of bony tissue used for mineral storage
  • mainly calcium and phosphorus
  • can be taken from bone (osteoclasts) -> blood stream if blood levels to low
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34
Q

bones and blood cell production

A
  • red, white blood cells and platelets made in bones
  • red bone marrow = in ends of long bones and some other bones like ribs, femur, humerus & vertebrae bones
  • blood cells produced in red bone marrow
  • yellow bone marrow = in the shaft of long bones
  • no blood cells produced in yellow bone marrow
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35
Q

where is fat stored in bones?

A

in adipocytes in yellow bone marrow

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36
Q

role of spongy bone

A
  • balances the dense and heavy compact bone -> makes bone lighter -> muscles can move them easier
  • when load is put on bones it helps distribute it
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37
Q

how many bones are in the skeleton?

A

206

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38
Q

what are the 2 basic types of bone tissue?

A
  • compact bone (homogenous)
  • spongy bone (small, needle-like pieces of bone with many open spaces for blood supply)
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39
Q

are bones easy to repair? why?

A
  • yes (better than tendons and cartilage)
  • due to high vascularisation
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40
Q

long bones

A
  • longer than they are wide
  • movement
  • arms, legs…
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41
Q

short bones

A
  • square, cube like
  • stability & support instead of movement
  • wrist, ankle…
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42
Q

flat bones

A
  • flat, curved
  • protection
  • skull, sternum…
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43
Q

irregular bones

A
  • odd shapes
  • vertebrae, pelvis (wide area where many muscles come togethet)
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44
Q

types of bone cells

A
  • osteocytes
  • osteoblasts
  • osteoclasts
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45
Q

osteocytes

A
  • mature bone cells
  • constantly being replaced by osteoblasts
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46
Q

osteoblasts

A
  • bone-forming cells
  • rebuilds bone if fractured
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47
Q

osteoclasts

A
  • bone-destroying cells
  • break down bone matrix for re-modeling and release calcium
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48
Q

what does bone re-modeling require?

A
  • osteoblasts
  • osteoclasts
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49
Q

what is the skeleton in embryos?

A

hyaline cartilage
-> replaced by bone during development

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50
Q

where did cartilage not get replaced by bone during development?

A
  • bridge of the nose
  • parts of the ribs -> flexibility
  • joints
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51
Q

how many bones does the skull have?

A

22

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52
Q

the hyoid bone

A
  • only bone that does not articulate with other bones
  • moveable base for the tongue and othr muscle attachments
  • broken when being chocked -> changes in breathing pattern as a result
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53
Q

the hyoid bone

A
  • only bone that does not articulate with other bones
  • moveable base for the tongue and othr muscle attachments
  • broken when being chocked -> changes in breathing pattern as a result
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54
Q

what is a joint?

A
  • an articulation
  • where two bones come together
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55
Q

types of joints

A
  • fibrous
  • cartilaginous
  • synovial
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56
Q

fibrous joint

A
  • immovable / no movement
  • connects bones
  • skull & pelvis
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57
Q

cartilaginous joint

A
  • slightly moveable
  • bones attached by cartilage
  • spine & ribs
58
Q

synovial joints

A
  • freely moveable
  • cavities between bones filled with synovial fluid
59
Q

role of synovial fluid

A

lubricate and protect
between bones

60
Q

the two major pathways that axons from the brain descend along

A
  • lateral = side of the spinal cord
  • ventromedial = front and center
61
Q

spinal tracts

A
  • bundles of nerves
  • from brain to peripheral muscles
  • stretch detectors = sense how fast and much a muscle is lengthened or shortened
62
Q

the lateral descending spinal tract

A
  • voluntary movement
  • originates in the cortex
  • composed of the:
    • corticospinal tract (pyramidal tract)
    • rubrospinal tract (extra-pyramidal)
63
Q

the effects of corticospinal lesions

A
  • deficit in fractionated movement of arms and hands
  • paralysis on contralateral side due to crossing over
  • recovery if rubrospinal tract is intact
  • subsequent rubrospinal lesion reverses recovery
64
Q

crossing over

A
  • also called pyramidal decussation
  • results in e.g. left side of the brain managing things on the right side of the body
65
Q

what are the descending spinal tracts?

A
  • the ventromedial pathways
  • the vestibulospinal tract
  • the tectospinal tract
66
Q

the ventromedial pathways

A
  • posture and locomotion
  • originate in the brainstem
  • pontine and medullary recticulospinal tract
  • involved in reflexes
67
Q

the vestibular tract

A
  • head balance
  • head turning
68
Q

the tectospinal tract

A

orientating

69
Q

the pontine recticulospinal tract

A

enhances postural reflex
-> to maintain a constant posture in relation to a dynamic external environment

70
Q

the medullary recticulospinal tract

A

liberated postural muscles from reflex

71
Q

where is movement initiated?

A

the motor cortex
- areas 4 & 6 of the frontal lobe

72
Q

area 4 of the motor complex

A
  • primary motor cortex / M1
  • simpler movements
  • not as much of the brain is needed for simpler movements
73
Q

area 6 of motor cortex

A
  • higher motor area
  • more complex movements
  • actions converted into signals specifying how actions will be performed
74
Q

what does the supplementary motor area do (SMA)?

A
  • additional movement
  • found in the medial region of motor cortex
  • intentional preperation for movement
75
Q

what does the premotor area do (PMA)?

A
  • found in the lateral region of motor cortex
  • sensory guidance of movement
76
Q

what do the posterior parietal and prefontal cortex do?

A
  • highest level of motor control
  • descisions made about their outcomes
  • area 5 & 7
77
Q

role of the anterior frontal lobes of cerebral cortex

A
  • abstract thought
  • decision making
  • anticipating consequences of action
  • should I do this movement?
78
Q

proprioception definiton

A
  • sense of position and strength of effort
  • awareness of body in space
  • pressure put on and orientation of the body
79
Q

what does muscle shortening depend on?

A
  • the type of muscle
  • the architecture / structure of the muscle (internally and attachments to skeleton)
  • which muscle fibres are activated
  • force and speed of movement depends on this
80
Q

what determines what we move and the direction of movement?

A
  • the amount of cells and area of the motor cortex activated
  • need to coordinate activity between 2 sides of the brain
81
Q

motor units

A
  • combination of a motor neuron and all of the muscle fibres that it innervates
  • recruited in a precise order
  • small units recruited first
82
Q

why are small motor units recruited first?

A
  • henneman´s size principle
    -> task appropriate recruitment to minimize fatigue
  • The small units don’t produce much force, they are slow to act, and they are resistant to fatigue.
83
Q

cerebellum

A
  • balance
  • movement
  • coordination
84
Q

how does information reach the CNS?

A
  • via afferent/sensory pathways
  • signal needs to be sent back to the brain for coordination…
85
Q

during proprioception where does the brain receive signals from?

A
  • vestibular organs
  • eyes
  • stretch receptors
86
Q

vestibular organs & proprioception

A
  • in the inner ear
  • send information about rotation, acceleration, position
87
Q

eyes & proprioception

A

send visual information

88
Q

stretch receptors & proprioception

A
  • in skin, muscles and joints
  • send info about position of body parts
  • also sense pressure
89
Q

what information do tendons tell you?

A
  • joint angle
  • how much pressure is put on joints
90
Q

proprioceptors in the limbs

A
  • sensors
  • provide information about joint angle, muscle length & muscle tension
  • position of limb in space
91
Q

what does the muscle spindle tell you?

A

changes in muscle length

92
Q

what does the golgi tendon organ tell you?

A

information about changes in muscle tension

93
Q

what is the muscle spindle?

A
  • small sensor organs enclosed in a capsule
  • modified muscle fibres with sensory nerves wrapped around them
  • found throughout the body of a muscle, parallel with extrafusal fibres (muscle fibres)
  • have several small specialised muscle fibres known as intrafusal fibres which have contractile proteins (thick & thin filaments) at either end, with a central region
94
Q

the central region of a muscle spindle

A
  • made up of contractile proteins
  • wrapped by the sensory dendrites of the muscle spindle afferent nerves
95
Q

what happens to the muscle spindle when the muscle lengthens?

A
  • muscle spindle is stretched
  • ion channels opened
  • this triggers the action potentials in the muscle spindle afferents
  • which sends info to the brain to say that muscle has stretched
96
Q

intrafusal fibres

A
  • innervated by an efferent neuron called the gamma motor neuron (MN)
  • found within a muscle spindle
97
Q

extrafusal fibres

A
  • innervated by efferents known as alpha MN
  • stimulated to contract by aphla MN activation
98
Q

what does the gamma MN do?

A
  • maintains muscle spindle sensitivity
  • innervate intrafusal fibres
  • regardless of muscle length
  • also excited when alpha MN is activated
  • stimulates contractions in the two ends of the intrafusal fibre -> readjusting its length & keeping central region of intrafusal fibre taut
99
Q

the golgi tendon organ

A
  • in a series with muscle fibres
  • located in tendons
  • sensory dendrites of golgi tendon organ afferent = interwoven with collagen fibres in the tendon
  • muscle contraction is a good stimulus for it
100
Q

what happens when the muscle contracts?

A
  • collagen fibres are pulled tight
  • this activated the golgi tendon organ afferent
  • changes in this muscle tension = provide different degrees of pull on the tendon
  • golgi tendon organ tells you about that info on muscle tension
  • most of the force of a stretch is absorbed by the muscle itself -> muscle contraction better stimulus for golgi tendon organ than muscle stretch
101
Q

tactile receptors

A

provide sensation of:
- touch
- pressure
- vibration

102
Q

baroreceptors

A

detect blood volume & pressure changes

103
Q

4 types of mechanoreceptors (other proprioceptors)

A
  • merkel receptors
  • meissner corpuscles
  • ruffini cylinders
  • pacinian corpuscles
104
Q

what makes the 4 mechanoreceptors differ?

A
  • location in kin
  • physical features
  • speed of adaptation to stimulation
  • size of receptive fields
  • type of mechanical stimulation to which they respond
105
Q

mechanoreceptors

A
  • each type responds to a range of frequencies of mechanical stimulation
  • range = 0.3Hz - 500Hz
  • detect touch, pressure, vibration and sound
106
Q

slow adapting (SA) fibres

A
  • merkel disks
  • ruffini cylinders
  • respond when the stimulus is present
  • active / firing till contact to the stimulus stops
107
Q

rapidly adapting fibres

A
  • meissner corpuscles
  • pacinian corpuscles
  • respond to stimuli with burst of firing at beginning and end of stimulation
108
Q

where are receptors with small receptive fields found?

A

close to skin surface

109
Q

where are receptors with large receptive fields found?

A

deeper in skin
- e.g. when you stand on a big stone pressure is distributed more

110
Q

do simple reflexes involve the CNS?

A

no

111
Q

do complex reflexes involve the CNS?

A

yes
-> could require a desicion or a choice

112
Q

what is dizziness a result of?

A
  • vestibulo-ocular reflex gone wrong
  • spinning causes sensory cells to keep signalling after we stop
  • inputs from balance organs normally compensated by movements of the eye
113
Q

which stimuli do merkel receptors respond best to?

A

steady pressure from small objects

114
Q

which stimuli do meissner corpuscules respond best to?

A

rubbing against the skin or skin movement across a surface

115
Q

which stimuli do ruffini cylcinders respond best to?

A

steady pressure & stretching of the skin (joint movement)

116
Q

which stimuli do picinian corpuscles respond best to?

A

changing stimulation

117
Q

where are muscle spindles found?

A

in muscle tissue

118
Q

what are muscle spindles?

A

receptors

119
Q

what stimuli do muscle fibres detect?

A

changes in muscle fibre length

120
Q

where are golgi tendon organs found?

A

in tendons between muscle fibres and adjoining collagen fibres

121
Q

what stimuli do golgi tendon organs respond to?

A

changes in muscle fibre tension

122
Q

what are golgi tendon organs?

A

receptors

123
Q

which tissues are easiest to regenerate?

A
  • skeletal tissue
  • cardiac muscle does not regenerate well -> can lead to heart failure
124
Q

what happens during regeneration after injury?

A
  • growth of cells and tissue to replace lost structures
  • needs intact connective tissue scaffold
125
Q

types of cells

A
  • labile
  • stable
  • permanent
126
Q

labile cells

A
  • high rate of loss and replacement
  • high regeneration capacity / can regenerate fast
  • cells that may die off / fall off easily or frequently
  • squamous and glandular epithelia
  • haemopoeitic cells in bone marrow
127
Q

stable cells

A
  • non proliferative but can be stimulated to after damage
  • renal tubular cells
  • hepatocytes
  • osteoblasts
  • endothelial cells
  • fibroblasts
128
Q

permanent cells

A
  • cannot divide after initial development
  • cannot regenerate when damaged
  • neurons
  • cardiac muscle
  • skeletal muscle (around basal lamina, basal cells can produce satellite cells that can proliferate)
129
Q

what can signal changes in cell growth?

A
  • e.g. intracellular Ca2+ changes can affect satellite cell proliferation
130
Q

variables that influence healing

A
  • injury: type, intensity, duration
  • patient: age, comorbidity, medication
  • treatment: apposition, stabilisation, loading & motion
131
Q

how long does a ligament take to regenerate?

A

12-16 months

132
Q

how long does a tendon take to heal?

A

12 weeks - 14 weeks

133
Q

how long / after how many days does inflammation occur?

A

0-7 days
- cant recognize what happened only that a response is needed

134
Q

where do inflammatory cells migrate from?

A
  • epitendinous tissues (sheath, periosteum, soft tissues)
  • epitendon & endotendon
135
Q

what does the defected tissue/area fill with after injury / during inflammation?

A
  • granulation tissue
  • haematoma
  • tissue debris
  • fibronectin is laid down as scaffolding for collagen synthesis
  • form a “scab” above skin -> similar in muscles
136
Q

length of repair

A

3-60 days

137
Q

what occurs during repair?

A
  • fibroblasts migrate to zone of injury
  • they begin to synthesise collagen by day 5
  • initially collagen type 3 is produced which is laid down in a random orientation
  • week 4 = intrinsic fibroblasts proliferate and these cells take over the healing process synthesising and reabsorbing collagen (tendon callus)
  • switch to type 1 collagen production
  • vasuclar ingrowth via collagen / fibronectin scaffolding
138
Q

when does organisation occur?

A

28-180 days

139
Q

what happens during organisation?

A
  • final stability acquired during this phase by the normal physiological use of the tendon
  • full recovery of tendon & ligament can be difficult
  • cross linking between fibrils helps to further increase tendon tensile strength
  • complete regeneration never acheived
    -> defect remains hypercellular
    -> thinner collagen fibrils
140
Q

tendon healing

A

weakest: 7-10 days
regain most strength by 21-28 days
maximum strength after 6 months

141
Q

what can mobilisation do to a tendon injury?

A
  • increase ROM
  • decrease tendon repair strength if excessive stress placed on repair
  • immobilisation leads to increase tendon substance strength at expense of ROM
142
Q

what does RICE stand for?

A
  • rest
  • ice
  • compression
  • elevation

human biology (11 decks)

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