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Hysteresis
The energy loss (and deformation) seen with repeated load and unload cycles on the disc.
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Creep
Deformation of the disc that occurs with a to sustained load.
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Hilton's Law
A nerve trunk which supplies the muscles of any given joint also supplies the muscles that move the joint, and the skin distal to the insertions of the, muscles.
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Bell-Magendie
anterior horn of the cord is motor, posterior horn is sensory.
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Gate theory
Activation of large diameter afferent nerves may inhibit smaller afferent pain fibers in the substantia gelatinosa on the dorsal horn of the cord.
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Head's Law
When a painful stimulus is applied to a part of low sensibility in proximity with a part of much higher sensibility, the pain produced is felt in the area of higher sensibility rather than in the area to which the stimulus was applied.
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Vitalism
The principle that maintains the laws of physics and chemistry cannot explain the nature of life.
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Motor unit or functional spinal segment
A pair of adjacent vertebrae, connecting disc and ligamentous structures
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Anterior motor unit
The portion of the motor unit that includes the PLL and the structures anterior to it (weight bearing)
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Posterior motor unit
All the structures posterior to the PLL: posterior joints, articular capsule. Neural arches and the interconnecting ligaments.
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Sclerotome
An area of bone, fascia, and joints innervated by a single nerve root. (Sclerotogenous- referred pain originating from a sclerotome, e.g. facet syndrome or spondylolisthesis).
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Myotome
A group of muscles innervated by a single nerve root. (C7 myotome = wrist flexors, finger extensors, triceps)
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Dermatome
An area of skin innervated by single nerve root.
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Axoplasmic transport (AXT)
is important in nerve growth and maturation, sensory signaling and modulation of inflammation.
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Antegrade
(FAXT) Fast transport of nutrients (for nerve growth and trophic) from cell body to axon and terminals (proximal to distal).
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Retrograde
(SAXT) Slow or bulk. Transport from terminal to cell body. (distal to proximal) less common. Recycles NGF and neurotransmitters.
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ANS- Sympathetics
- T1-L2 (lateral horns)
- "fight or flight"
- short pre-ganglionic/ white rami
- long post-ganglionic/ gray rami
- sudomotor, pilomotor, responses
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ANS- Parasympathetics
- CN 3,7,9,10, S2-4
- "rest and digest"
- long pre-ganglionic
- short post-ganglionic
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Myelinated nerve fibers
- General (sensory and motor) A(alpha)
- Larger, faster
- Sensory Ia, Ib
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Unmeylinated nerve fibers
- General (sensory and motor) C fiber
- Smaller, slower
- Sensory IV
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Afferent/ Sensory neurons types
- Ia, Ib proprioception, kinesthsia (big/ fast)
- II proprioception, mechanoceptors
- III, IV mechanoceptors, hot, cold nociceptos (slow)
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Golgi tendon organs
- Receptors located at the end of muscle that detect muscle tension. When stimulated inhibits muscle contraction.
- Golgi tendon organ=>Ib afferent=>inhibitory internucial=> inhibits (alpha) motor neuron => extrafusal fiber
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Muscle spindles
- Intrafusal receptors that sensitive to length of intrafusal fibers.
- Annulo spiral/ flower spray endings=> Ia afferent=> distal horn=> (alpha) motor neuron=> extrafusal fiber
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Gamma motoneuron
- Innervates muscle spindle, increasing Group Ia afferents. Affects background muscle tone.
- Annulo spiral/flower spray ending=> Ia afferent=> dorsal horn=> (gamma) motorneuron=> muscle spindle
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Nociceptors
Sensory receptors responsive to pain, hot and cold mechanoreceptors (C-fibers)
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Proprioceptors
Receptors found in muscles, tendons, and joints that detect position and motion of the body.
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Substance P
A excitatory neurotransmitter involved with nociception (pain) and associated with mood disorders, anxiety, stress and fibromyalgia. (capsaicin relieves arthitic pain as it reduces the level of Substance P).
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Facilitation
Increased afferent bombardment causing a decreased threshold for firing, with continued stimulation resulting in hyperactive responses.
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