Exam I Flashcards
(164 cards)
1
Q
what are a couple examples of external forces?
A
gravity and body weight
2
Q
what is the difference between stress and pressure?
A
pressure has no vectors (affects whole system); stress has vectors (affects specific area and direction)
3
Q
what are the 5 different types of loads?
A
(1) tension
(2) compression
(3) bending
(4) shear
(5) torsion
4
Q
what substances does stress apply to?
A
solids
5
Q
what substances does pressure apply to?
A
fluids and gases
6
Q
is temperature a scalar, vector, or tensor quantity?
A
scalar
7
Q
is velocity a scalar, vector, or tensor quantity?
A
vector
8
Q
is mass a scalar, vector, or tensor quantity?
A
scalar
9
Q
is pressure a scalar, vector, or tensor quantity?
A
scalar
10
Q
is force a scalar, vector, or tensor quantity?
A
vector
11
Q
is stress a scalar, vector, or tensor quantity?
A
tensor
12
Q
what is the difference between a scalar, vector, and tensor quantity?
A
(1) scalar: magnitude
(2) vector: magnitude and direction
(3) tensor: magnitude, direction and plane
13
Q
what are the 3 types of stress a solid can undergo?
A
(1) compression
(2) tension
(3) shear
14
Q
what is strain?
A
the change of an object in relation to it’s initial shape
ALWAYS a PERCENTAGE of deformation
15
Q
what is the difference between elastic and plastic strain?
A
elastic: deformation occurs but returns to original shape once external force is removed
plastic: deformation occurs but does not return to original shape
16
Q
which human tissues have elastic properties? which tissues have plastic properties?
A
ALL tissues in the human body have both elastic and plastic properties
17
Q
what does the yield point on the stress/strain curve signify?
A
where the structure goes from elastic to plastic (permanent deformation begins to occur)
18
Q
what does the slope of the model of elasticity on the stress/strain curve indicate?
A
the stiffness of the material
- more vertical line indicates a stiffer material
- more horizontal indicates a less stiff material
19
Q
an object that has a larger slope on the stress/strain curve indicates what?
A
more stiffness; the less likely an object is to give in before it tears
20
Q
where is the ‘ultimate stress’ point on the stress/strain curve? what does this mean?
A
the highest point on the curve (highest stress); once you pass the ‘ultimate stress’ point, less than 50% of the structure is intact (micro-failure)
21
Q
what occurs at the end of the stress/strain curve where the stress completely drops off?
A
complete failure (complete tear)
22
Q
what are two factors that lead to a structure being more stiff?
A
(1) greater density of collagen fiber bonds
(2) greater covalent cross-links between fibers
23
Q
what are the concepts of fragility vs. toughness?
A
toughness is the ability to absorb energy; fragile structures don’t absorb energy well, while tough ones do
24
Q
what is resiliency?
A
the ability to absorb energy when elastically deformed and RELEASE it (think basketball against a wall; tendons use SSC)
25
what is dampening?
the ability to absorb energy when elastically deformed but doesn't release it; opposite of resiliency
26
what happens to resiliency overtime?
it decreases; this leads to mechanical fatigue; if you keep loading a ligament the resiliency eventually decreases
27
regarding mechanical wear, how does stress, force and surface area relate?
Stress = force/area
| this means that as surface area decreases (such as erosion of a tendon), the force on that material increases
28
what are some ways to recover resiliency and prevent injury?
(1) decrease stress
| (2) allow more rest time
29
what is mechanical wearing in regards to human? how does it occur?
removal of the superficial layers of a structure; friction or corrosion of tissues (inflammation, cortisone injections, friction between tissues)
30
what type of tissue deformation occurs without permanent structural damage? what type of tissue deformation does cause permanent damage?
elastic: no permanent damage
plastic: permanent damage
31
what are 3 ways fatigue can occur?
(1) repetitive low magnitude loading
(2) loss of material resiliency overtime
(3) mechanical wearing
32
define viscosity
the ability of a fluid to resist flow
33
what is viscoelasticity?
a material that displays viscous and elastic characteristics when undergoing deformation (a material that has both fluid and solid properties)
34
what parts of musculoskeletal system are viscoelastic?
all parts (tendons, ligaments, cartilage, bone, etc.)
35
what has an effect on viscoelastic tissues? (5)
(1) how long the load is applied
(2) how quickly the load is applied
(3) temperature
(4) hysteresis
(5) thixotropy
36
what is creep?
the continued deformation of a material under constant load over time
37
what is the Stress-Relaxation response in regards to deformation?
a material held at a constant length will experience a decreased magnitude of stress over time
(ex. hold a hamstring stretch for 5 minutes, at first the stretch is tough, but then becomes easier)
38
what happens to viscoelastic tissues under higher temperatures?
will deform quicker and relax easier; cooling tissues has inverse effect
39
what is thixotrophy?
viscoelastic property in which the system displays mechanical properties of a gel when undisturbed, and properties of a liquid when moved (vibration and motion will make a structure easier to move)
40
what is hysteresis?
behavior of a tissue will depend upon what you were doing before the load is applied (go to play soccer – warm-up beforehand and change tissue behavior during game)
41
what does adult hyaline cartilage do? (3)
(1) provides bearing surface for synovial joints
(2) increases surface loading area
(3) provides friction-less gliding surface
42
what makes up 70-85% of the weight of cartilage?
water
43
what type of substance makes up cartilage?
type II collagen
44
what is the purpose of elastin?
helps recoil
45
how are collagen fibers oriented in the deep zone of cartilage? superficial zone?
deep zone: vertical orientation (compressive force)
| superficial zone: horizontal orientation (shear force)
46
what are the two macromolecules that make up cartilage? what's each function?
(1) collagen - provides shape and tensile properties (meshwork)
(2) proteoglycan - resists compressive forces
47
what type of charge is found on proteoglycans that push them closer together and increase the compressive stiffness of the cartilage?
negative
48
what type of collagen is considered the strongest type?
type I
49
what type of collagen is present after an injury and eventually matures into type I collagen?
type III
50
type I collagen is the primary component of what tissues?
tendons and ligaments
51
type II collagen is the primary component of what
cartilage, meniscus, disc
52
why do tendonopathy injuries result in pain at the attachment sites?
because the tendon is close to the periostium, which has a nerve innervation
53
when force is applied to cartilage, what resists the compressive forces? what resists the sheer forces?
proteoglycans resist compressive forces, while the collagen resists sheer forces (due to lateral displacement)
54
how does cartilage get its nutrition since it's a-vascular for the most part?
compressive force causes fluid to leak out and then back in when the force is removed (motion provides nutrition to joint)
55
at what percentage of stretch will an ACL fail?
8%
56
what happens when ligaments/tendons are immobilized?
the ability for that structure to absorb energy is significantly decreased
57
what does a decrease of GAGs in cartilage result in?
decreased GAGs = decreased stiffness
| the cartilage becomes weaker
58
what effect does exercise have on cartilage? (2)
(1) increased surface area
| 2) increased GAGs in deep zones (increased ability to resist compressive forces
59
what type of loading is ideal for the nutrition of cartilage tissue?
cyclic, intermittent motion
60
which scenario is more likely to cause deformation of cartilage?
(1) Adding an extra 10 pounds of force to cartilage 24/7 (think an obese person carrying excess weight)
(2) squatting 315 for reps 3x per week
scenario #1; low magnitude, constant loading is much more likely to cause damage
61
is the knee, hip, or ankle most resistant to OA?
the ankle
62
what can be said about the elastic/plastic properties of cartilage (type II collagen)?
there is no plastic range for type II collagen
63
what is the strongest type of bone?
cortical
64
where are cortical and trabecular bone located?
cortical bone is the outer portion of bone and trabecular bone is within cortical bone
65
what bone can strain more before it breaks?
trabecular bone; cortical bone doesn't deform much, and suffers much less strain before breaking
66
what makes up 60-70% of bones?
minerals (calcium and phosphate)
67
what musculoskeletal tissue is the most vascular?
bone; trabecular bone is more vascular than cortical bone
68
what type of bone is OA more prevalent in?
trabecular bone
69
what type of load does bone handle well? the worst?
bone handles compression loads the best, while shear and torsion loads aren't tolerated as well
70
what is wolf's law?
bone density increases in areas where stress is applied (if you don't use it, you lose it)
71
what demographics typically have lower bone density?
women and elderly
72
what is anisotropy as it relates to bone?
bone is strongest when load is applied parallel to trabecular bone and weakest when applied perpendicular
73
how do muscle contractions help reduce stress tension in bones?
muscle contractions pull origin and insertion closer together, causing compression as opposed to tension
74
do bones handle tension or compression better?
compression
75
what is one reason stress fractures are thought to occur?
in areas where tension stress on the bones is higher
76
when muscles fatigue and they can't contract properly what can happen to bone?
when muscles fatigue, they can't contract and compressive strength is reduced, while tension strength is increased; this is why fatigue leads to stress fractures
77
is bone stronger when it's loaded quickly or stronger?
quickly; bone can handle a higher stress when applied fast than a lower stress applied slow
78
when does an avulsion fracture occur?
when the tendon is stiffer than bone when loaded, the bone fails before tendon (seen more in slow loading)
79
what are the stages of healing for a tendon/ligament? (4)
Days 2-4: cellular stage
Days 5-21: fibroplastic stage
Days: 21-60: consolidation stage
Days 60-360: maturation stage
80
what should be done during the cellular stage of ligament/tendon healing?
protection from any tensile loads; union is fragile
81
what should be done during the fibroplastic stage of ligament/tendon healing?
low tensile loads, slow PROM; low tensile stress help organize/align collagen fibrils
82
what should be done during the consolidation stage of ligament/tendon healing?
progressively increase tensile forces, AROM/PROM
83
what should be done during the maturation stage of ligament/tendon healing?
more aggressive but progressive increase
| tensile forces via AROM/PROM and; resistive exercises
84
what are the active components of skeletal muscle?
actin and myosin found in the sarcomere
85
sarcomeres can only create what type of force within itself?
tension
86
what are the passive components of skeletal muscle?
(1) parallel elastic components
| (2) series elastic components
87
what are some example of parallel elastic components?
epimysium, perimysium, endomysium
88
what are some example of series elastic components?
titin, tendons
89
what is the ratio of actin to myosin in a sarcomere?
6 actin: 1 myosin
90
when a muscle contraction occurs, what structures are pulled closer together?
z-discs
91
what is the concept of the length tension curve? (as it relates to active tension)
there is an ideal length where muscle can generate the most force; muscles can't generate high forces when the muscle is fully stretched, nor when it is fully contracted
92
what is the active force per unit of cross-sectional area?
30 N/cm2
93
what is the concept of the length tension curve? (as it relates to passive tension)
tension increases as the sarcomere length increases
94
is titin an active or passive component?
passive; titin functions most during passive stretching and eccentric contraction
95
what is the purpose of titin?
to maintain the structural integrity of the sarcomere; titin is attached to myosin, and wraps around actin to elastically increase passive stiffness
96
what are endomysium, perimysium, and epimysium primarily composed of?
type 1 collagen
97
what is the relationship between connective tissue in muscle and the vascular components?
nerve and blood supply are guided by connective tissue within muscles; more connective tissue allowed for improved healing capabilities
98
what are the major roles of connective tissue in muscles? (4)
(1) structural role to cover surface of muscle cells, bundles, and muscles
(2) passively transfer forces from muscle to tendon
(3) provide conduit for blood supply and nerves
(4) generate passive tensile resistance to stretch
99
what is the myotendinous junction? what's its purpose?
```
specialized structure to transfer force from muscle to tendon
Purpose:
(1) increase surface area
(2) reduce stress
(3) improves viscioelastic properties
(4) ready muscle for contraction
```
100
how does isometrically contracting a muscle affect the subsequent lengthening of that muscle?
a muscle that is preconditioned with an isometric contraction can lengthen more before it ruptures when compared to a muscle that wasn't preconditioned
101
does a muscle that is contacted or relaxed tolerate more stress before rupturing?
a contracted muscle can resist more outside load (tensing muscles before a car accident better protects your muscles)
102
where in the muscle do tears most commonly occur? what types of muscles are more prone to tearing?
(1) distal insertion at the muscule-tendon junction (typically because the distal insertion has less surface area)
(2) long, biarticular muscles are more likely to tear
103
what are the 3 types of acute injuries to the muscle-tendon unit?
(1) laceration (shear stress)
(2) contusion (compression stress)
(3) strain (tension stress)
104
where are tears and overuse injuries common?
tears are much more common in the muscle, while overuse injuries are more common in tendons
105
how does muscle fatigue lead to an increased risk of a muscle tear?
as a muscle fatigues it fires (contracts) less, thus it has less protective ability
106
what happens to the sarcomere and components during isometric contractions?
(1) sarcomere shortens
| (2) series component lengthens
107
what happens to the sarcomere and components during eccentric contractions?
(1) sarcomere lengthens
| (2) series component lengthens
108
what happens to the sarcomere and components during concentric contractions?
(1) sarcomere shortens
| (2) parallel component shortens
109
where do muscle strains most frequently occur?
muscle-tendon junction
110
what is the advantage of pennated muscles?
power/strength production
111
what is the advantage of fusiform muscles?
high shortening velocity
112
what is the relationship between the number of muscle fibers and force generation?
the more muscle fibers, the greater force can be produced
113
what is the relationship between the muscle fiber orientation and force generation?
the more parallel fibers are to the tendon the better the ability to generate force
*Note: pennate muscle fibers may have slightly reduced force, but pennation allows for more fibers, which typically outweigh the loss of force due to pennation
114
do short or long muscle fibers generate more force throughout a larger ROM?
long muscle fibers
115
how much can muscle fibers shorten?
between 30 – 50% of their
| length
116
do short or long muscle fibers have a greater muscle shortening velocity?
long muscle fibers
117
do concentric or eccentric contractions use more ATP?
concentric contractions use more ATP; more muscle activation
118
do concentric or eccentric contractions create a higher amount of tension?
eccentric contractions (think elongation of muscle)
119
why does eccentric exercise cause more DOMS than concentric exercise?
eccentric exercise causes more damage to the connective tissue within a muscle than concentric exercise does
120
when is the relationship between force and velocity?
inverse relationship; as force decreases, velocity increases (and vice versa)
121
what is the size principle?
smaller motor neurons are recruited before larger motor neurons (smaller muscles before larger muscles)
122
what is rate coding?
the rate at which motor units fire
123
when a limb is immobilized or activity level is decreased, what type of muscle fibers atrophy more significantly?
type I muscle fibers
124
how do higher joint speeds affect concentric and eccentric activity?
high joint speed reduces tension in concentric activity and increase tension in eccentric activity (because higher speeds require more deceleration)
125
what type of muscle fibers do people tend to lose with age? what type of tissue do people tend to gain with age?
type II muscle fibers; increased connective tissue
126
what is stability?
a resistance to the change in state
127
what is posture?
the relative position of segments
128
what is the difference between static and mechanical stability?
static stability is when the line of gravity falls within the base of support
mechanical stability is the ability of an object to maintain equilibrium
129
what is joint stability?
maintain position of the articulating structures of a joint (not dislocating)
130
what is the line of gravity?
another way to say the force vector of gravity
131
what is the center of pressure?
the average location of foot to floor forces
132
what are 3 aspects involved with ideal standing posture?
(1) minimal muscle force
(2) minimal stress on joitns and CT
(3) maximal stability
133
what are most deviations in posture caused by in the frontal plane?
scoliosis
134
what is coxa valga? what can this result in?
an angle of inclination of the femur >135 degrees; a functionally longer leg
135
what is coxa vara? what can this result in?
an angle of inclination of the femur <120 degrees; a functionally shorter leg
136
how does lordosis affect moment arm?
normal lordosis small moment arm
| extreme lordosis: large moment arm
137
what are two factors that contribute to ideal standing posture in the sagittal plane?
(1) LOG falls near virtual axes
| (2) minimized moment arm
138
in the sagittal plane for the atlanto-occipital joint, where is the LOG? what is the external moment?
anterior; flexion
139
in the sagittal plane for the cervical spine, where is the LOG? what is the external moment?
posterior; extension
140
in the sagittal plane for the thoracic spine, where is the LOG? what is the external moment?
anterior; flexion
141
in the sagittal plane for the lumbar spine, where is the LOG? what is the external moment?
posterior; extension
142
in the sagittal plane for the SI joint, where is the LOG? what is the external moment?
anterior; nutation
143
in the sagittal plane for the hip joint, where is the LOG? what is the external moment?
posterior; extension
144
in the sagittal plane for the knee joint, where is the LOG? what is the external moment?
anterior; extension
145
in the sagittal plane for the ankle joint, where is the LOG? what is the external moment?
anterior; dorsiflexion
146
why do deviations from ideal posture affect the entire body?
the body is a closed kinematic chain, so altering one segment affects everything down the chain
147
when are postural muscle active in static posture?
always; they prevent excessive sway
148
what muscles work to resist gravity in relation to the line of gravity?
posterior to the line of gravity
149
what are the 3 components of the neurological system that contribute to balance?
(1) visual
(2) vestibular
(3) sensory-motor
150
what are 3 aspects required to control balance?
(1) sensing
(2) processing
(3) responding
151
what are examples of sensors in the body?
(1) mechanoreceptors: located in joints capsules. muscles, skin
(2) vision
(3) vestibular
152
what sensor is the fastest to respond in the body?
mechanoreceptors
153
what is the processor of the human body?
the CNS
154
what responds in the human body to sensory input?
muscle activate
155
what is perturbation?
sudden mechanical change that threatens stability
156
what are 2 ways in which the body responds to perturbation?
(1) Feed-forward (Proactive)
| 2) Feedback control (reactive
157
where does rotation occur? where does translation occur?
rotation occurs in a plane, about an axis
| translation occurs within a plane, along an axis
158
for all 3 levers, what is in the middle?
1st class: axis
2nd class: resistance (external force)
3rd: effort (internal force)
159
what are the 1st, 2nd, and 3rd class levers in the body?
1st: triceps, spine
2nd: gastroc/soleus (MTP joint)
3rd: everything else in the body
160
what are collagen and elastin designed to resist?
tension
161
do ligaments or tendons have more elastin? which structure has more stiffness?
ligaments generally contain more elastin
than tendons making them less stiff and
just slightly weaker than tendons
162
are tendons or ligaments more resilient?
tendons; absorb and release energy better than ligaments
163
based on the composition of tendons and ligaments, why are tendons stiffer than ligaments?
tendons have more type I collagen and less proteoglycans than ligaments
164
what can cause the mechanical failure of cartilage? (2)
(1) repeated shear stress
| (2) abnormal compressive joint loading
