Spasticity and Neural plasticity Flashcards
define muscle tone
resistance to muscle to passive stretch, encountered when the joint of a relaxed pt is moved. it is an UMN syndrome
what is a negative impairment
those that represent a loss of previous function e.g weakness
what is a positive impairment
new or additional problems e.g proprioceptive reflexes/cutaneous reflexes
define the term ‘spasticity
a motor disorder characterised by a velocity -dependent increase in tonic stretch reflexes with exaggerated stretch reflexes resulting from hyper-excitability of the stretch reflex. Also a component of the UMN syndrome
define the term ‘rigidity’
an increased resistance to relatively slow passive movements, present in both extensors and flexors and independent of direction.
what are the differences between spasticity and rigidity?
SPASTICITY: normally UL flexors
RIGIDITY: flexors and extensors equally
SPASTICITY: velocity-dependent increase in tone
RIGIDITY: constant throughout ROM
SPASTICITY: increased tendon relexes
RIGIDITY: normal reflexes
SPASTICITY: UMN pyramidal sign
RIGIDITY: extrapyramidal sign
what is a phasic stretch reflex?
a quick, unsustained contraction of the muscle that occurs in response to a rapid stretch of the muscle. mechanoreceptors are stimulated.
what are the determinants of tone?
Degree of motor unit activity
Intrinsic elastic properties of the muscle, tendons and connective tissue
Environmental and sensory input
list the inhibitory influences
- reciprocal inhibition
- autogenic inhibition from golgi tendon organs
- pain inhibits extensors
- recurrent (Renshaw cell) inhibition
define reciprocal inhibition
the relaxation of the antagonistic muscle evoked by contraction of the agonist muscle
define autogenic inhibition
the sudden relaxation of a muscle in response to the development of high tension. Golgi tendon organs are responsible
define presynaptic inhibition
when neurotransmitter acts on inhibitory receptors on the nerve axon to reduce the likelyhood of an action potential firing
define Reccurrent/Renshaw cell Inhibition
the phenomenon in which Renshaw cells (responsible for regulating the firing of the alpha motor neurones) terminate on motorneurones, inhibiting their firing
list the facilitatory influences
- a stretch to the muscle with activate the muscle spindle
- annulospiral influence
- flower spray endings
-activation of synergist muscles - pain facilitates flexors
define annulospiral influence
nerve endings of intrafusal muscle fibers called the annulospiral ring activate stretch-activated channels that depolarise the neuron and thus increase its firing rate
