Week 2 Flashcards
What is a lever?
Any rigid segment that rotates around a fulcrum
When does a lever system exist?
Exists whenever two forces are applied to a lever in a way that produces opposing
torques
What are the components of a lever system?
- Effort force (EF)
- Resistance Force (RF)
- Effort Arm (EA)
- Resistance Arm (RA)
What is effort force?
Force that is producing the resultant torque(acting in the direction of rotation)
What is resistance force?
Force creating an opposing torque
What is the effort arm?
Moment arm for the effort force
What is the resistance arm?
Moment arm for the resistance force
The ___ force is always the winner in the torque game
The effort force is always the winner in the torque game
The first class lever is where the axis lies somewhere between the ____ and the ___
The first class lever is where the axis lies somewhere between the point of application of the effort force and the point of application of the resistance force
In the first class lever within the body, the effort arm may be ___ than the resistance arm as long as they are in ___ side of the axis
In the first class lever within the body, the effort arm may be equal to, greater, less than the resistance arm as long as they are in opposite side of the axis
The second class lever system, is where the resistance force has a point of application between the ___ and ____
The second class lever system, is where the resistance force has a point of application between the axis and the point of application of the effort force
In the second class lever system, the effort arm is always ___ the resistance arm
In the second class lever system, the effort arm is always greater than the resistance arm
The second class lever system, is where the effort force has a point of application between the ___ and ____
The second class lever system, is where the effort force has a point of application between the axis and the point of application of the resistance force
In the third class lever system, the effort arm is always ___ the resistance arm
In the third class lever system, the effort arm is always less than the resistance arm
What is the mechanical advantage?
Measure of the mechanical efficiency of a lever system or the relative effectiveness of the effort force in comparison with the resistance force
Mechanical advantage is related to the ___
Mechanical advantage is related to the classification of a lever
Mechanical advantage provides an understanding of the relationship between the ___ and ___
Mechanical advantage provides an understanding of the relationship between the torque of an external force and the torque of a muscular force
How is mechanical advantage calculated?
The ratio of the effort arm to the resistance arm
What is the mechanical advantage when the effort arm is greater than the resistance arm?
It is greater than 1
What happens when the mechanical advantage is greater than 1?
The magnitude of the effort force working through the larger moment arm can be smaller than the magnitude of the resistance force, yet still create greater torque
What is the advantage of mechanical advantage?
A smaller force can defeat a larger force
The mechanical advantage of a first class lever system in the body can be/is ___
The mechanical advantage of a first class lever system in the body can be/is greater than, less than, or equal to one
The moment arm of the muscle in a first class lever system within the body is ___ to the moment arm of the external force
The moment arm of the muscle in a first class lever system within the body is shorter to the moment arm of the external force
Muscles working at the first class lever system within the body tend to be at a ___
Muscles working at the first class lever system within the body tend to be at a mechanical disadvantage
The mechanical advantage of a second class lever system in the body can be/is ___
The mechanical advantage of a second class lever system in the body can be/is greater than one
The magnitude of the ___ can be, but is not necessarily less than the magnitude of the ____
The magnitude of the effort can be, but is not necessarily less than the magnitude of the resistance
The mechanical advantage of a third class lever system in the body can be/is ___
The mechanical advantage of a third class lever system in the body can be/is less than one
In the third-class lever system within the body, the effort arm is always ____ the resistance arm
In the third-class lever system within the body, the effort arm is always less than the resistance arm
The magnitude of the effort force must be ___ than the magnitude of the resistance force for the effort to produce greater torque
The magnitude of the effort force must be greater than the magnitude of the resistance force for the effort to produce greater torque
Why is a third-class lever system mechanically inefficient/working at a disadvantage?
The magnitude of the effort force must always be greater than the magnitude of the resistance force in order for the torque of the effort force to exceed the torque of the resistance force
What are the limitations of analysis of forces by lever systems?
- Discussion of lever systems ignored the established fact that the rotation of a lever requires at least one force couple
- Requires oversimplification that fails to take into consideration key elements that affect function and structural integrity
- Torques on human segments are not simply produced by muscles and external forces
True or false
An effort and resistance force are a force couple
False.
An effort and resistance force are not a force couple, because they move in opposite directions rather than the same
What are the 3 main methods of manipulating external forces to maximize torque?
- Torque of an external force can be increased by increasing the magnitude of the applied force
- Torque of an external force can be increased by applying the force perpendicular to the lever
- Torque of an external force can be increased by increasing the distance of the point of application of the force from the joint axis
A force applied to a lever produces its greater torque when the force is applied at ___ to the lever, presuming that there is a second part of the force couple
A force applied to a lever produces its greater torque when when the force is applied at 90 deg to the lever presuming that there is a second part of the force couple
What are the components of total force?
- Perpendicular component
- Parallel component
What is the perpendicular component of a total force?
The portion of a force that is applied at 90 deg to a segment
What is the parallel component of a total force?
The portion of a force that is applied at parallel to a segment
The parallel component of total force tends to create ___ motion
The parallel component of total force tends to create translatory motion
The perpendicular component of total force tends to create __ motion
The perpendicular component of total force tends to create rotation and horizontal translation motion
The sum of the magnitude of the perpendicular and parallel component of a force will always be ___ than the resultant force
The sum of the magnitude of the perpendicular and parallel component of a force will always be greater than the resultant force
The parallel component of most muscle forces contributes to ___, making muscles important joint stabilizers
The parallel component of most muscle forces contributes to joint compression, making muscles important joint stabilizers
Most of the force generated by a muscle contributes to joint compression rather than ___
Most of the force generated by a muscle contributes to joint compression rather than joint rotation
Rotation around a joint axis requires that the sum of the ____ equals zero
Rotation around a joint axis requires that the sum of the parallel and perpendicular components equals zero
What happens when the sum of the parallel or perpendicular components of a joint axis do not equal zero initially?
Translatory motion will continue to occur alone or in combination with rotatory motion until checked by a capsule ligamentous force or a joint reaction force
Majority of torque on a segment will be produced by forces or force components that are applied ___ to the segment and at some distance from the ___
Majority of torque on a segment will be produced by forces or force components that are applied 90 deg to the segment and at some distance from the joint axis
The greater the net unbalanced torque, the greater the ___
The greater the net unbalanced torque, the greater the angular acceleration of the segment
What is an open chain activity?
One end of a segment or set of segments is free to move in space
What are the characteristics of an open chain activity?
- Independent motion
- Allows isolation
- Typically non-weight bearing
- Mobility is greater than stability
- More functional in the upper extremity than in the lower extremity
What is a closed chain activity?
Both ends of a segment or set of segments are constrained in some way and are not free to move in space
What are the characteristics of a closed chain activity?
- Interdependent motion
- Shared load
- Typically weight bearing
- Stability is greater than mobility
- More functional in the lower extremity than in the upper extremity
What is stress?
Resistance of a material to deformation
What is strain?
Deformation that occurs in a material in response to the application of an external load quantified as a percentage of change in some dimension of the material
What are the characteristics of an isotropic material?
- Homogenous
* Exhibit uniform properties when loaded in different directions
What are the characteristics of an anisotropic material?
- Heterogenous
* Exhibit non-uniform properties when loaded in different directions
What is load?
Application of a force, moment, or combination of them to a material
What is tension?
Equal and opposite loads applied away from the surface of a structure
What is compression?
Equal and opposite loads applied toward the surface of a structure
What is shear?
Opposing loads applied parallel to the surface of a structure
What is torsion?
Opposing loads are applied to the surface of a structure resulting in twisting about an internal axis
What is bending?
Combination of three or more loads applied to a structure causing it to bend about an axis external to itself
When does combined loading occur?
Combination of two or more loading modes applied to a structure at the same time
What is deformation?
Change occurring in some dimension of the
material in response to an applied load
What is viscosity?
Ability of a material to resist flow and dampen shear forces
What is elasticity?
Ability of a material to return to its original shape following deformation after the removal of the deforming load
What allows meaningful movement of the human movement system to occur?
The articulations/joint of the skeletal system
What do human joints comprise?
Living tissues that change their structure to in response to changing environmental or functional demands
What are the 4 classes of connective tissue?
- Connective tissue proper
- Cartilage
- Bone
- Blood
____ are considered to be dense regular connective tissues
Tendons and ligaments are considered to be dense regular connective tissues
Connective tissue is characterized by…?
Widely dispersed cells and a large volume of extra-cellular matrix
___ is considered to be a highly specialized an mineralized form of connective tissue
Bone is considered to be a highly specialized an mineralized form of connective tissue
A microscopic levels, the extra-cellular matrix of connective tissues have both __ and ___ components
A microscopic levels, the extra-cellular matrix of connective tissues have both inter-fibular and fibular components
What determines the function of most connective tissue?
Extra -cellular components
The mechanical behavior of tissues involve the study of…?
The mechanical behavior of tissues involve the study of * how different materials and structures are able to provide support in response to changing forces*
The mechanical behavior of tissues deals with the relationship between ___ and ___
The mechanical behavior of tissues deals with the relationship between stress and strain
Stress occurs as a reaction force within…?
Stress occurs as a reaction force within the substance of the structure in the presence of an applied load
How can stress be quantified?
Force/unit area that develops within the material being tested.
What is ultimate stress?
The stress/load at the point of failure
What is ultimate strain?
The strain or deformation at the point of failure
What is isotropy?
A measure of the uniformity of the material when loaded from different directions
What is an example of an isotropic material?
Metals
What is an example of an anisotropic material?
Biological tissues
Which is more anisotropic: tendon, ligament, joint capsule, fascia?
Tendon more than ligament, joint capsule, and fascia
Tension results in…?
Tension results in lengthening and narrowing of the structure and causes tensile stresses to occur within the structure
What does compression result in?
Shortening and widening of the structure and causes compression stresses to occur within the structure
What does shear result in?
Internal angular deformation of the structure and causes shear stresses to occur within the structure
What does torsion cause?
A combination of compression, tension, and shear stresses to occur within the structure
What does combined loading cause?
Multiple combinations of stresses to occur within the structure
What is a load deformation curve?
A graph utilized to determine the strength properties and materials in which the load applied is plotted against the deformation material
What type of information does a load deformation curve provide?
Elasticity, plasticity, ultimate strength and stiffness, failure point, and the amount of energy prior to failure
What does the toe region of the load deformation curve signify?
Signifies the removal of slack within the structure as the tensile load is applied
What is a crimp?
A wavy configuration of collagen fibers found in most relaxed connective tissue
When does a crimp disappear?
When the collagen fibers in connective tissue are loaded
Where in the load deformation curve does a crimp occur?
In the toe region
What does the elastic region on the load deformation curve represent?
The range in which the stress is directly proportional to the strain
All the deformation occurring in the elastic region is ___
All the deformation occurring in the elastic region is reversible
Is the structure in the elastic region able to return to its normal dimensions after the load has been removed?
Yes, structures in the elastic region are able to return to its normal dimensions after the load has been removed
What does the elastic limit/ yield point signify?
The end of the elastic region where the material begins to undergo permanent deformation
What does the plastic region on the load deformation curve represent?
The range in which materials begin to deform at a rate disproportional to the stress
What is occurring in the plastic region?
Permanent deformation, although the structure is still intact and it may return to similar dimension with time
What does the ultimate failure point represent on the deformation curve?
Represents the continued load in the plastic range, but the maximum load that the tissue can tolerate has been reached.
What is happening with deformation and load at the ultimate failure point?
Deformation continues until it fails and load equals failure load
True or false
Tissue size can affect response to loading
True
Increased cross-sectional area of a tissue means that the tissue can withstand ___ force at any given length
Increased cross-sectional area of a tissue means that the tissue can withstand more force at any given length
An increased cross-sectional area of a tissue leads to ___
Greater strength and stiffness
Does the elongation to failure and length of a tissue changes when the cross sectional area is increased?
No, it stays the same
What does an increased tissue length mean?
It means that it can elongate further under the same load of condition as a shorter tissue
What is the status of strength and stiffness when the tissue length has been increased?
- Strength is the same
- Stiffness is reduced
What is young’s modulus/modulus of elasticity?
The linear portion of the curve that occurs in the elastic region of the load deformation curve.
The ____ is the measure of stiffness or resistance to external loads
The modulus of elasticity is the measure of stiffness or resistance to external loads
The _____ is the measure of compliance to external load
The reverse of the modulus of elasticity is the measure of compliance to external load
What does it mean when the slope through the young modulus is steep?
The modulus of elasticity is said to be high
A high modulus of elasticity correlates with ___?
A high modulus of elasticity correlates with high stiffness, and low compliance
Ex: cortico tissue
What does it mean when the slope through the young modulus is gradual?
The modulus of elasticity is said to be low
A low modulus of elasticity correlates with ___?
A low modulus of elasticity correlates with low stiffness and high compliance
Ex: Adipose tissue*
What is the stress-strain curve?
Load-deformation curve in which load is expressed as load per unit area and strain is expressed as deformation per unit of length or percentage of deformation
What happens in the toe region of the stress-strain curve for collagenous materials?
There is very little force to deform tissue in straightening crimp
What happens in the elastic region of the stress-strain curve for collagenous materials?
Collagen fibrils are being stretched and are resisting applied force
____ reflects type of collagen, fibril size, and cross-linking among collagen molecules
The elastic region of the stress-strain curve for collagenous materials reflects type of collagen, fibril size, and cross-linking among collagen molecules
What happens when load is removed in the elastic region of the stress-strain curve for collagenous materials?
When the load is removed, structure will return to its pre-stressed dimensions, although this return will take some time
The level of loading in the elastic region of the stress-strain curve for collagenous materials includes ____ and typically extends to about ____
The level of loading in the elastic region of the stress-strain curve for collagenous materials includes stresses and strains that
occur with normal activities and typically extends to about 4% strain
What happens in the plastic region of the stress-strain curve for collagenous materials?
Micro failure of collagen fibers begins and structure no longer capable of returning to original length after force removed
What does the recovery in the plastic region of the stress-strain curve for collagenous materials require?
Recovery after this level of loading requires considerable time as it involves aspects of healing
What are the aspects of healing in the plastic region of the stress-strain curve for collagenous materials require?
- Synthesis of new tissue
* Cross-linking of collagen molecules
What happens in the beyond ultimate failure point of the stress-strain curve for collagenous materials?
Remaining collagen fibrils experience increased stress and rapidly rupture sequentially
What is created in the beyond ultimate failure point of the stress-strain curve for collagenous materials?
Overt failure of the tissue
What type of tissue failure is created in the beyond ultimate failure point of the stress-strain curve for collagenous materials?
- Rupture
- Avulsion
- Fracture
What is a rupture?
Failure through middle of ligament or tendon
What is an avulsion?
Failure at bony attachment of ligament or tendon
What is a fracture?
Failure within bony tissue
A rupture is typically a response of ___
A rupture is typically a response of a fast loading rate
An avulsion is typically a response of ___
An avulsion is typically a response of a slow loading rate
Deformation prior to failure in the beyond ultimate failure point of the stress-strain curve for collagenous materials varies on?
- Tissue type
- Tissue size
What is viscoelasticity?
A characteristic exhibited by all tissues
of the body in which the properties of
viscosity and elasticity are combined
Viscoelasticity makes tissue behavior ___ dependent
Viscoelasticity makes tissue behavior time-, rate-, and history-dependent
What is creep?
Progressive strain or deformation of a structure under the influence of a constant stress or load
What are the determinants of mechanical properties of a fibrous connective tissue?
- Size and density of the structure
- Mechanical properties of the collagen and elastin fibers contained in the structure
- Proportion of collagen and elastin fibers
- Orientation of fibers in the tissue
What are the time dependent properties illustrated by the viscoelasticity of connective tissue?
- Creep
- Hysteresis
- Stress-relaxation
How does creep apply in the clinic?
Stretching shortened tissue
How is creep tested in cartilage and bone and why?
Compressive loading.
So that the depth of indentation represents creep and covering
What is stress-relaxation?
Decrease in the stress within a structure in the presence of a constant strain or deformation
What happens if a tissue stretched to a fixed length, while the force required to maintain the length is measured?
The force needed will be decreased over time
When does hysteresis occur?
When the force and length are measured as forces are loaded and unloaded and the resulting load deformation curves do not follow the same path
In hysteresis, energy is often lost as ___
In hysteresis, energy is often lost as heat
What are the rate dependent properties illustrated by the viscoelasticity of connective tissue?
Strain-rate sensitivity
What is strain-rate sensitivity?
Resistance to deformation relative to rate of load application
Increased rate of load application is associated with ___
Increased rate of load application is associated with increased resistance to deformation
Decreased rate of load application is associated with ___
Decreased rate of load application is associated with Decreased resistance to deformation
Less deformation prior to failure occurs with ____
Less deformation prior to failure occurs with load application at a higher rate for a brief duration
What are the mechanical properties of fibrous connective tissue?
- High tensile strength
- Anisotropic
- Fails at strains as low as 9% for structures with little or no elastin fiber content
- Fails at strains of up to 70% for structures with high elastin content
What are some of the mechanical properties of fibrous connective tissue?
- Ultimate load and strain increase with increasing speed of loading
- Stiffness does not change with changes in speed of loading
- Significant viscoelastic characteristics, especially in first 6-8 hours of loading
- Compared to tendons, ligaments must withstand forces in all directions
In the clinic, the viscoelastic characteristics of fibrous connective tissue can be exploited for ___
In the clinic, the viscoelastic characteristics of fibrous connective tissue can be exploited for increasing tissue length without tearing or failure
What can fatigue type failures result from in a fibrous connective tissue?
Fatigue type failures can result from exposure to loads that are too high, too numerous, or too frequent with management requiring a reduction in one or more of these variables
___ results in a general loss of collagen content, but an increase in collagen cross-linking
Aging results in a general loss of collagen content, but an increase in collagen cross-linking
The use of NSAIDs can cause an/a ___ in the tensile strength of connective tissues due to an increase in overall collagen content and in the proportion of non-soluble collagen
The use of NSAIDs can cause an increase in the tensile strength of connective tissues due to an increase in overall collagen content and in the proportion of non-soluble collagen
The final trimester of pregnancy is accompanied by a significant release of the hormone relaxin resulting in a ____ making the tissues more susceptible to injury
The final trimester of pregnancy is accompanied by a significant release of the hormone relaxin resulting in a general loss of stiffness and strength of the connective tissues making the tissues more susceptible to injury
What are the determinants in the mechanical properties of cartilage?
- Type of cartilage (i.e. hyaline cartilage, fibrocartilage, elastic cartilage)
- Structural composition (i.e. Type I vs. Type II collagen)
- Proportions of structural components (i.e. water, collagen, elastin, proteoglycans)
What is the boundary mechanism in the lubrication of cartilage?
Monolayer of glycoproteins carries load and provides separation of cartilage surfaces for lubrication
What is the fluid film mechanism in the lubrication of cartilage?
Fluid pressure provides separation of articular surfaces and, thus, provides lubrication
What are the mechanical properties of cartilage?
- Anisotropic
- Biphasic
- Capable of large viscoelastic deformation due to processes of fluid exudation and redistribution
What does biphasic mean?
When something has both fluid and solid phases
Cartilage depends upon ____ through its substance via cyclic compression and decompression as well as motion
Cartilage depends upon diffusion and the pumping of fluids through its substance via cyclic compression and decompression as well as motion
Compromise of cartilage health should be expected following ____ due to an alteration in nutritional supply mechanisms
Compromise of cartilage health should be expected following immobilization due to an alteration in nutritional supply mechanisms
Injury of cartilage can often occur without ___ and can progress until ___ is quite advanced before pain is experienced
Injury of cartilage can often occur without initial awareness and can progress until tissue destruction is quite advanced before pain is experienced
What are the determinants of the mechanical property of bone?
- Size, density, and geometric characteristics of bone specimen
- Mode of loading applied
- Rate and frequency of loading
What does the type of mechanical property of a bone depend upon?
The type of bone in consideration
What are the two types of bone?
- Cortical (compact) bone
- Cancellous (trabecular or spongy) bone
What are the mechanical properties of cortical (compact bone)?
- Very high ultimate strength in compression and tension
- Very high stiffness
- Anisotropic
- Fractures at approximately 2% strain
- Stiffness and ultimate load increase with increased speed of loading
What are the mechanical properties of cancellous (trabecular or spongy) bone?
• Moderate to low ultimate strength depending upon porosity
• Moderate to low stiffness
• Anisotropic
• Typically fractures at approximately 7%
strain, but can sustain strains as high as
75% before failure in some instances
• Stiffness and ultimate load tolerance increase with increased speed of loading
Changes in the mechanical properties of
bone generally parallel changes in ___
Changes in the mechanical properties of
bone generally parallel changes in bone
mass, aging and osteoporosis
Stresses on bone are due to ____
Stresses on bone are due to *weight bearing
and muscle loading*
____ can considerably modify the exposure of bones to loading, but become less effective in doing so with fatigue
Muscles can considerably modify the
exposure of bones to loading, but become
less effective in doing so with fatigue
Bone is subject to stress (fatigue) fracture relative to ____of loading
Bone is subject to stress (fatigue) fracture relative to magnitude, quantity, and
frequency of loading
When does the bone being subject to stress (fatigue) fracture relative to magnitude, quantity, and frequency of loading occur?
Occurs with shift in balance of bone
formation and absorption toward osteoclastic activity
What does the management of bone being subject to stress (fatigue) fracture relative to magnitude, quantity, and frequency of loading require?
Management requires the modification of
one or more of the contributing factors
Taking advantage of the mechanical advantage of _____, a dynamic splint can be used to aide in increasing joint ROM
Taking advantage of the mechanical advantage of creep, a dynamic splint can be used to aide in increasing joint ROM
What is a dynamic splint?
A spring loaded tensioning device that provides for the application of low load, long duration stretch.
What does the dynamic splint mechanism provide?
A constant tensioning force to be applied,, while linked changes occur in the tissues
____ uses elastic components
Dynamic splints uses elastic components
____ uses inelastic components to apply torque to a joint in order to statically position it as close to the end of ROM as possible.
Static progressive splinting uses inelastic components to apply torque to a joint in order to statically position it as close to the end of ROM as possible.
What mechanical advantage does a static progressive splint take advantage of?
Stress- relaxation
Skeletal muscle function provides both __ and ____
Skeletal muscle function provides both mobility and stability
Skeletal muscle can produce or control movement of the ___ around the joint axis, where they can resist extraneous movement of joint surfaces through the ___
Skeletal muscle can produce or control movement of the bony lever around the joint axis, where they can resist extraneous of joint surfaces through the approximation of joints
The total muscle force vector can be approximated by…?
The total muscle force vector can be approximated by putting the point of application at the muscle’s attachment and then drawing an action line symmetrically towards the middle of the muscle’s fibers
The direction of pull of any muscle is always towards the ____ of the muscle
The direction of pull of any muscle is always towards the center of the muscle
What are the determinants of muscle force production?
- Recruitment of motor units
- Muscle fiber type
- Muscle length
- Speed of contraction
- Muscle Action
- Torque Potential
- Muscle architecture
____ is fundamental to the recruitment of motor units
Size principle is fundamental to the recruitment of motor units
Which motor units are recruited 1st?
Motor units with small cell bodies and few motor fibers
What are the other factors influencing motor unit recruitment?
- Nature of task performed
- Variable within individual muscles of synergistic group
- Firing frequency
- Fatigue
Small distal muscles rely on ____
Small distal muscles rely on increased frequency of firing
Large proximal muscles rely on ___
Large proximal muscles rely on the recruitment of additional motor units
____ can also affect force production during muscle contraction
muscle fiber types can also affect force production during muscle contraction
Muscle fiber types is reflective of the ___
Muscle fiber types is reflective of the physiologic characteristics of muscle fibers
The physiologic characteristic of muscle fibers can affect the ____
The physiologic characteristic of muscle fibers can affect the potential speed of contraction, the potential magnitude of force generation, and determines the fatigueability of the muscle fiber
What are the characteristics of type 1 slow oxidative fibers?
- Diameter: Small
- Color: Red
- Capillarity: Dense
- Myoglobin content: High
- Speed of contraction: Slow
- Rate of fatigue: Slow
What are the characteristics of type 2a fast oxidative glycolitic fibers?
- Diameter: Intermediate
- Color: Red
- Capillarity: Dense
- Myoglobin content: Intermediate
- Speed of contraction: Fast
- Rate of fatigue: Intermediate
What are the characteristics of type 2x fast glycolitic fibers?
- Diameter: Large
- Color: White
- Capillarity: Sparse
- Myoglobin content: Low
- Speed of contraction: Fast
- Rate of fatigue: Fast
What is muscle tension?
Ability to develop tension and to exert a force on the bony lever is most important characteristic of muscle
Total tension in a muscle includes both ___ and ____ components
Total tension in a muscle includes both active and passive components
Total tension is a vector quantity possessing magnitude, ____, an ___, and a direction of pull
Total tension is a vector quantity possessing magnitude, two points of application, an action line, and a direction of pull
____ tension is developed in the parallel elastic component of the muscle.
Passive tension is developed in the parallel elastic component of the muscle.
Passive tension may add to the ____ produced by the muscle when the muscle is lengthened
Passive tension may add to the active tension produced by the muscle when the muscle is lengthened
Passive tension may become slack and not produced to the total tension when the muscle is _____
Passive tension may become slack and not produced to the total tension when the muscle is shortened
Passive tension is create by___
Passive tension is create by lengthening the muscle beyond slack length of the tissues
Active tension refers to the tension developed by ___
Active tension refers to the tension developed by the contractile elements of the muscle
Active tension is initiated by ____
Active tension is initiated by cross bridge formation and movement of thick and thin filaments
The amount of active tension that a muscle can generate depends on ___
The amount of active tension that a muscle can generate depends on neural factors and mechanical properties of muscle fibers
What are the neural factors included in the amount of active tension that a muscle can generate?
- Frequency of motor units firing
- Number of motor units firing
- Size of motor units firing
What are the mechanical properties included in the amount of active tension that a muscle can generate?
- Isometric length tension relationship
- Force velocity relationship
A direct relationship exist between the isometric tension development in a muscle fiber and the ____
A direct relationship exist between the isometric tension development in a muscle fiber and the length of the sarcomeres of the muscle fiber
When does an optimal sarcomere length exist?
When a muscle fiber is capable of developing maximal isometric tension.
Why does a muscle fiber obtain maximal isometric tension at an optimal sarcomere length?
Because thick and thin filaments are positioned so that maximum number of cross bridges within the sarcomere can be formed.
What happens if the muscle fibers is shortened or lengthened beyond optimal length?
The amount of active tension that a muscle fiber is able to generate when stimulated decreases
Sarcomere length-tension relationship only applies to ___
Sarcomere length-tension relationship only applies to isometric muscle contraction
During dynamic contractions, length-tension relationship must be combined with ____ to determine the effect that both length and velocity have on muscle tension
During dynamic contractions, length-tension relationship must be combined with force-velocity relationship to determine the effect
that both length and velocity have on muscle tension
Force-velocity relationship describes relationship between ___ and ___
Force-velocity relationship describes relationship between velocity of muscle contraction and force produced
Force-velocity relationship provides an explanation for what happens during ___ and ___ muscle contractions
Force-velocity relationship provides an explanation for what happens during concentric and eccentric muscle contractions
What is the speed of shortening?
The rate at which myo-filaments are able to slide pass one another to be able to form and reform cross bridges
Speed of shortening is related to ___ and ___
Speed of shortening is related to muscle fiber type and length
As load increases on a muscle, concentric contraction velocity ___ at isometric maximum
As load increases on a muscle, concentric contraction velocity slows to zero at isometric maximum
In concentric muscle contraction, as the shortening speed decreases, the tension in muscle ___
In concentric muscle contraction, as the shortening speed decreases, the tension in muscle increases
In isometric muscle contraction, the speed of shortening is ___ and tension is ___ than in a concentric contraction
In isometric muscle contraction, the speed of shortening is zero and tension is greater than in a concentric contraction
In an eccentric contraction, as the speed of muscle lengthening increases, the tension in the muscle ___ and then ____
In an eccentric contraction, as the speed of muscle lengthening increases, the tension in the muscle increases and then plateaus
____ contraction occurs with the active shortening of a muscle
Concentric contraction occurs with the active shortening of a muscle
Concentric contraction involves sliding of the ___
Concentric contraction involves sliding of the thin filaments toward and past the thick filaments
Concentric contraction is accompanied by the ___ and results in ___
Concentric contraction is accompanied by the formation and reformation of cross bridges in each sarcomere and results in shortening of the muscle and the generation of tension
A ____ contraction is one in which muscle fibers do not change
An isometric contraction is one in which muscle fibers do not change
What muscle action is happening when the whole muscle is activated and bones to which it is attached to do not move?
Isometric contraction
During a concentric contraction, bones move ____
During a concentric contraction, bones move closer together as the whole muscle shortens
During an eccentric contraction, bones move ____ as the muscle tries to control descent of the weight and the muscle ____ as the joint moves through the ROM
During an eccentric contraction, bones move away from each other as the muscle tries to control descent of the weight and the muscle lengthens as the joint moves through the ROM
Amount of tension that can be developed in a muscle varies according to ___
Amount of tension that can be developed in a muscle varies according to type of contraction
In which contraction is tension the greatest in general?
Eccentric contraction
What are the factors affecting torque potential?
- Length of moment arm of muscle force
- Length of the muscle
- Velocity of shortening or lengthening during dynamic movements
Muscles produce force in the body by acting over a ___ at the joint to produce a torque
Muscles produce force in the body by acting over a moment arm at the joint to produce a torque
Moment arm of the muscle can change with ____ which affects the torque being produced
Moment arm of the muscle can change with joint position which affects the torque being produced
Single joint muscles tend to be recruited to produce force primarily in ____ contractions
Single joint muscles tend to be recruited to produce force primarily in concentric and isometric contractions
Multi joint muscles tend to be recruited to control the fine regulation of torque during dynamic movements involving ___ more than ___ muscle actions
Multi joint muscles tend to be recruited to control the fine regulation of torque during dynamic movements involving eccentric more than concentric muscle actions
Multi joint muscles tend to be recruited during more ___ motions requiring movements along multiple axis
Multi joint muscles tend to be recruited during more complex motions requiring movements along multiple axis
____ is a phenomenon related to muscle length- tension relationship and the multi joint nature of some muscles
Active insufficiency is a phenomenon related to muscle length- tension relationship and the multi joint nature of some muscles
What is active in sufficiency?
Reduced capacity in production of active tension across one joint occurring when muscles are placed on slack across another joint
When does passive insufficiency occur?
Occurs when an inactive, potentially antagonistic muscle is of insufficient length to permit full ROM at the joints crossed by the passive muscle
___ can measure the electrical activity of a muscle
EMG can measure the electrical activity of a muscle
The electrical activity of a muscle is directly proportional to the ___
The electrical activity of a muscle is directly proportional to the motor unit activity
The motor unit activity of a muscle is directly proportional to the __
The motor unit activity of a muscle is directly proportional to the isometric muscle force
The type and direction of motion that results from an active muscle contraction depends on ___
The type and direction of motion that results from an active muscle contraction depends on the net force and torques acting on each of the bony attachments
Muscle will move a segment in its direction of pull only when ___
Muscle will move a segment in its direction of pull only when the torque generated by the muscle exceeds opposing torques
What are the advantages of isokinetic exercise and testing?
- Maximal loading through ROM
- Safe
- Objective
- Reproducible measurement
What are the disadvantages of isokinetic exercise and testing?
- Isolation
- Non-weight bearing
- Limited acceleration
- Mono-planer
- Cost
- Not functional
- Differences in exertion by performer
___ is the basic functional unit of the nervous system
A neuron is the basic functional unit of the nervous system
The ___ is the neuron cell body
The perikaryon is the neuron cell body
____ is housed in ventral horn of spinal cord (motor at all levels, pre-ganglionic autonomic in levels T1 through L3), sympathetic trunk (postganglionic autonomic), and dorsal root ganglia (sensory)
Perikaryon is housed in ventral horn of spinal cord (motor at all levels, pre-ganglionic autonomic in levels T1 through L3), sympathetic trunk (postganglionic autonomic), and dorsal root ganglia (sensory)
___ are typically, a single fiber extending away from cell body with branches near
termination
Axons are typically, a single fiber extending away from cell body with branches near termination
The conduction speed of an axon increases with ___
The conduction speed of an axon increases with myelination
The conduction speed of an axon is positively correlated with ____
The conduction speed of an axon is positively correlated with fiber diameter
___ are branched structures from cell body and terminal axon that act to increase the number of available synapses, the surrounding
Dendrites are branched structures from cell body and terminal axon that act to increase the number of available synapses
The number of available synapses is further increased by the presence of ___ upon surface of dendrites
The number of available synapses is further increased by the presence of dendritic spines upon surface of dendrites
What are the gross structures of the nervous system?
- Brain
- Spinal cord
- Nerve roots
The brain is housed entirely within the ___
The brain is housed entirely within the cranium
___ is structured as a continuation of the medulla oblongata from foramen magnum, terminates at the conus medullaris at L2 level
Spinal cord is structured as a continuation of the medulla oblongata from foramen magnum, terminates at the conus medullaris at L2 level
The spinal cord attaches to the coccyx via ___
The spinal cord attaches to the coccyx via filum terminale
___ are transitional structure from central nervous system into peripheral nervous system
Nerve roots are transitional structure from central nervous system into peripheral nervous system
____ is a delicate and continuous layer of connective tissue meshwork surrounding all elements of the central nervous system
Pia mater is a delicate and continuous layer of connective tissue meshwork surrounding all elements of the central nervous system
___ is a delicate connective tissue meshwork housing cerebrospinal fluid between itself and pia mater. It connects into pia mater via arachnoid trabeculae
Arachnoid mater is a delicate connective tissue meshwork housing cerebrospinal fluid between itself and pia mater. It connects into pia mater via arachnoid trabeculae
____ is a tough outermost meningeal layer with high collagen content aligned in layers longitudinally. It is highly vascularized and innervated
Dura mater is a tough outermost meningeal layer with high collagen content aligned in layers longitudinally. It is highly vascularized and innervated
What is the structural hierarchy of the PNS?
- Nerve fiber
- Fascicle
- Peripheral nerve trunk
____ axons housed within collagenous basement membrane and is surrounded by innermost connective tissue layer referred to as the endoneurium
Nerve fiber axons housed within collagenous basement membrane and is surrounded by innermost connective tissue layer referred to as the endoneurium
____ are bundles of nerve fibers that are surrounded by external epineurium
Fascicles are bundles of nerve fibers that are surrounded by external epineurium
Fascicles are separated by an ___
Fascicles are separated by an internal epineurium
Each fascicle is intimately surrounded by a connective tissue layer called ____
Each fascicle is intimately surrounded by a connective tissue layer called perineurium
Peripheral nerve trunk are bundle of fasciculi, enveloped by loose areolar tissue layer termed _____
Peripheral nerve trunk are bundle of fasciculi, enveloped by loose areolar tissue layer termed mesoneurium
The nervous system is highly integrated by ___
The nervous system is highly integrated by connective tissue
___ is the supporting cells between neurons of the nervous system and is involved in the myelination process
Neuroglia is the supporting cells between neurons of the nervous system and is involved in the myelination process
____ is the oligodendroglia of the central nervous system and the schwann’s cells of the peripheral nervous system
Neuroglia is the oligodendroglia of the central nervous system and the schwann’s cells of the peripheral nervous system
What are the connective tissue structures of the nervous system?
- Neuroglia
- Meninges
- Peripheral connective tissues
____ and ___ allow stretch and compression without kinking
Pia mater and arachnoid mater allow stretch and compression without kinking
____ provides tremendous axial loading strength as well as relative structural stability through osseus attachments
Dura mater provides tremendous axial loading strength as well as relative structural stability through osseus attachments
Peripheral connective tissues provide ____ as well as ____ to tensile and compressive forces
Peripheral connective tissues provide protection as well as resistance to tensile and compressive forces
What are the functions of connective tissue within the nervous system?
- Adds both tensile strength and elasticity to nervous tissue where movement is necessary
- Adds structural stability through attachments to adjacent structures
- Facilitates processes involved in nutrition, oxygenation, and waste removal (i.e. circulation)
- Influences interactions with endocrine and immune systems
- Highly innervated and nociceptive although nervous tissue itself is not
20% of the oxygen available in circulating blood utilized by the _____, which is 2% of body mass
20% of the oxygen available in circulating blood utilized by the nervous system, which is 2% of body mass
Both central and peripheral components of the nervous system have extensive intrinsic ___ supported by ____
Both central and peripheral components of the nervous system have extensive intrinsic vascular systems supported by connective tissues
The nervous system integration with the vascular system is susceptible to ____ and ____ which can alter blood flow
The nervous system integration with the vascular system is susceptible to mechanical compression and tensions forces which can alter blood flow
The vascular system within the nervous system are ___ innervated and nociceptive although nervous tissue itself is not
The vascular system within the nervous system are highly innervated and nociceptive although nervous tissue itself is not
What are the ways that the nervous system tissues is considered to be continuous throughout the body?
- Mechanical
- Electrical
- Chemical
How is the nervous system tissue continuous throughout the body mechanically?
Continuous via connective tissue associations
How is the nervous system tissue continuous throughout the body electrically?
Interconnected electrically via impulse generation and transmission
How is the nervous system tissue continuous throughout the body chemically?
Linked chemically via flow of neurotransmitters
What are the functions of the nervous system?
- Conducts and regulates impulses via continuous electrochemical antegrade and retrograde flow
- Associates physical, psychological, and environmental inputs
- Adapts dynamically to maintain and change its own function
- Facilitates coordinated conscious and unconscious reactions of multiple body systems
What are the determinants of the mechanical properties of the nervous system?
- Continuity of nervous tissue tract
- Supporting connective tissues
What are the determinants of the mechanical properties of the nervous system in the peripheral nervous system?
- Interneural and intraneural plexus formation
- Quantity of fascicles housed within nerve
What are the determinants of the mechanical properties of the nervous system in the central nervous system?
- Folding and twisting of axons
- Nervous tissue movement in relation to neighboring bony segments
Interneural plexus formation in the PNS serves to ___
Interneural plexus formation in the PNS serves to * distribute force within combinations of nerves*
Intraneural plexus formation in the PNS serves to ___
Intraneural plexus formation in the PNS serves to distribute force within specific
nerves
How does the quantity of fascicles housed within peripheral nerves determine of the mechanical properties of the nervous system?
Nerve compression with greater pressure
required to affect nerve fibers in a nerve with a smaller number of fascicles
How does the folding and twisting of axons
within the central nervous system determine of the mechanical properties of the nervous system?
Redundancy within the tissues of the central nervous system allows neural structures to elongate prior to being exposed to significant tensile forces
Normal movement of the body requires that
tissues of the ___ be able to move past adjacent structures in which they are housed
Normal movement of the body requires that
tissues of the central nervous system be able to move past adjacent structures in which they are housed
What are the mechanical load that nervous system tissues are exposed to?
- Compression
- Tension
- Excursion
Compression can lead to alterations in ____ which can occur at relatively low pressures
Compression can lead to alterations in fluid and blood flow within neural tissue which can occur at relatively low pressures
Exposure to compression is normal if ___ and ___ are not excessive
Exposure to compression is normal if magnitude of forces and duration of exposure are not excessive
True or false
Neural tissue is not elastic
True
Increased tensile loading leads to ___ cross sectional area and increased _____
Increased tensile loading leads to decreased cross sectional area and increased intraneural pressure
When does blood flow begin to decrease?
At 6-8% strain or elongation
When is blood flow completely arrested?
At 15% strain or elongation
What is excursion?
The ability of the neural tissue to “slide” relative to adjacent interfacing extraneural
tissues
