Week 1- Biomechanics of Skeletal and Nervous Tissue Flashcards
What process is responsible for adaptation in the human movement system?
Mechanotransduction
Mechanotransduction
- The process by which the body converts physical stress into cellular responses
What is the result of the cellular responses?
Structural and functional adaptations
Characteristic tissue responses
- Maintenance of physical stress tolerance
- Increased physical stress tolerance
- Decreased physical stress tolerance
- Injury
- Death
How does bone respond to low physical stress levels?
- Decreased bone mineral density
- Decreased strength
How does bone respond to normal physical stress levels?
No change
How does bone respond to high physical stress levels?
- Increased bone mineral density
- Increased strength
How does bone respond to excessive physical stress levels?
Fracture
How does cartilage respond to low physical stress levels?
- Decreased proteoglycan content
- Decreased thickness
- Decreased stiffness
How does cartilage respond to normal physical stress levels?
No change
How does cartilage respond to high physical stress levels?
- Increased proteoglycan content
- Increased thickness
- Increased stiffness
How does cartilage respond to excessive physical stress levels?
Tear or degeneration
How do ligaments respond to low physical stress levels?
- Decreased cross-sectional area
- Decreased stiffness
- Decreased strength
How do ligaments respond to normal physical stress levels?
No change
How do ligaments respond to high physical stress levels?
- Increased cross-sectional area
- Increased stiffness
- Increased strength
How do ligaments respond to excessive physical stress levels?
Sprain
How do tendons respond to low physical stress levels?
- Decreased cross-sectional area
- Decreased stiffness
- Decreased strength
How do tendons respond to normal physical stress levels?
No change
How do tendons respond to high physical stress levels?
- Increased cross-sectional area
- Increased stiffness
- Increased strength
How do tendons respond to excessive physical stress levels?
Strain
How does muscle respond to low physical stress levels?
- Decreased contractile protein
- Decreased fiber diameter
- Decreased peak tension
- Decreased peak power
How does muscle respond to normal physical stress levels?
No change
How does muscle respond to high physical stress levels?
- Increased contractile protein
- Increased fiber diameter
- Increased peak tension
- Increased peak power
How does muscle respond to excessive physical stress levels?
Strain
How do neurons respond to low physical stress levels?
- Decreased max discharge rate
- Increased recruitment threshold
- Decreased activation w/ MVC
- Loss of neurons
How do neurons respond to normal physical stress levels?
No change
How do neurons respond to high physical stress levels?
- Increased max discharge rate
- Decreased recruitment threshold
- Increased activation w/ MVC
- Increased motor unit synchronization
- Increased dendtritic arborization
- Increased serotonergic neural activity
- Increased synaptic transmission
- Neurogenesis
How do neurons respond to excessive physical stress levels?
Axonal demyelination and degeneration
How does the heart respond to low physical stress levels?
- Decreased cardiac muscle mass
- Decreased capillary density
- Decreased stroke volume
How does the heart respond to normal physical stress levels?
No change
How does the heart respond to high physical stress levels?
- Increased cardiac muscle mass
- Increased capillary density
- Increased stroke volume
- Increased metabolic activity
How does the heart respond to excessive physical stress levels?
- Fibrosis
- Aneurysm
- Ventricular hypertrophy
How do blood vessels respond to low physical stress levels?
- Decreased vascular diameter
- Decreased arterial compliance
How do blood vessels respond to normal physical stress levels?
No change
How do blood vessels respond to high physical stress levels?
- Increased vascular diameter
- Inecreased arterial compliance
How do blood vessels respond to excessive physical stress levels?
- Fibrosis
- Aneurysm
How does the skin respond to low physical stress levels?
- Decreased collagen content
- Decreased collagen fiber diameter
- Decreased strength
- Decreased thickness
How does the skin respond to normal physical stress levels?
No change
How does the skin respond to high physical stress levels?
- Increased collagen content
- Increased collagen fiber diameter
- Increased strength
- Increased thickness
How does the skin respond to excessive physical stress levels?
Abrasion or wound
Determinants of muscle force production
- Motor unit recruitment
- Muscle fiber type
- Muscle length
- Speed of contraction
- Muscle action
- Torque potential
- Muscle architecture
Motor unit recruitment
- Small units recruited first (conserves energy)
- Small are usually stabilizers
- Large are usually “movers”
Muscle fiber type
- Type I: small, oxidative, low force
- Type IIa: intermediate size, oxidative glycolytic, intermediate force
- Type IIx: large, fast glycolytic, high force
Passive tension
- Stretch on a muscle by extending a joint
- Generates a spring resistance (stiffness)
- Develops the elastic component of muscle
- No active contraction
Activee tension
- Initiated by cross-bridge formation
- Tension produced by contraction
Length-Tension Relationship
There is an ideal overlap of myofilaments to maximize tension through contraction
Active Insufficiency
Reduced capacity to produce active tension when muscles are placed on slack across multiple joints
Passive Insufficiency
Inability of a multi-joint muscle to lengthen to a degree that allows full ROM of all the joints it crosses simultaneously
Speed of contraction- eccentric
- Velocity increases as weight increases
- Lower heavy quickly, lower light slowly
Speed of contraction- concentric
- Velocity increases as weight decreases
- Lift heavy slowly, lift light quickly
Muscle action
- Concentric < Isometric < Eccentric
- We can lower more than we can hold
- We can hold more than we can lift
Torque potential
Moment arm changes during movement, altering the torque potential of the muscle
Muscle architecture
- Fibers of pennate muscles run at an angle, allowing more fibers in the muscle
- This produces more force
Determinants of mechanical properties of nervous tissue
- Continuity of nervous tissue tract
- Supporting connective tissue
- Peripheral nervous system factors
- Central nervous system factors
Mechanical factors of the peripheral NS
- Inter- and intra neural plexus formation
- Quantity of fascicles
Mechanical factors of the central NS
- Folding and twisting of axons
- Movement in relation to bony segments
Interneural plexus formation
Distribution of forces within a combo of nerves
Intraneural plexus formation
Distribution of forces within a specific nerve
How does the quantity pf nerve vesicles affect the mechanics of the peripheral NS?
Greater pressure is required to affect the nerves in a neuron w/ smaller number of fascicles
What role does the folding and twisting of axons play?
- Creates a redundancy within the tissue
- Allows the neural structures to elongate prior to exposure to significant tensile forces
How should nerves relate to the surrounding bony segments?
Nervous tissue needs to be able to move past adjacent structures in which they are housed
Physical stresses placed on nerves
- Compression
- Tension
- Excursion
How do nerves respond to compression?
Compression is normal, within certain limits
Is neural tissue elastic?
No
What happens if a nerve experiences tension?
- Leads to decreased cross-section area
- Increased intraneural pressure
What is excursion?
The ability to “slide” relative to the adjacent interfacing extraneural structures
