Muscle Tone Flashcards
What is hypotonic?
degree of resistance is less than normal
What is hypertonic?
degree of resistance is more than normal
What is muscle tone?
The resistance encountered when the joint of a relaxed subject is moved passively
What is postural tone?
The background level of muscle activity throughout the body
Maintained through automatic activity of descending motor systems (in response to internal and external environment)
Normal tone is variable and changes
from individual to individual
depends on internal & external factors
depends on the base of support
depends on the activity
what mechanical factors cause muscle tone?
Physical inertia of limb
Viscoelastic properties
Thixotropy
What neural factors cause muscle tone?
Active contraction
Reflex contraction
Causes of hypertonia
Caused by PNS lesion e.g. trauma to peripheral nerve CNS lesion e.g. cerebral shock, CVA
Features of hypertonia
Deficiency in generating force (weakness)
Deficiency in sustaining output (fatigue)
In CNS lesions:
Lack of excitation at the mn
Slowness in muscle activation
(motor unit recruitment)
Features of hypertonicity
Increased resistance to passive movement Spasm Spasticity Rigidity Dystonia Dyspraxia
what produces hypertonicity?
Neural factors
Altered descending input to mn
ed excitability of spinal motoneurons
Mechanical factors
If muscles are immobilised in their shortened position, there is loss of sarcomeres, with ed shortness and stiffness
Immobility results in remodelling of connective tissue, resulting in ed stiffness of muscle
spasticity
Muscle tightness / stiffness
The increased responsiveness to stretch
Associated with increased tendon reflexes
Involvement of characteristic muscle groups / patterns
Rigidity
Caused by an imbalance in neurotransmitters deep within the brain, resulting in uncontrolled motor output from the brain
Characterised by increased stiffness throughout range of passive movement
Resistance does not depend on velocity of stretch
Same intensity of resistance in both flexor and extensor muscles
What does abnormal tone result in?
Abnormal postures Impaired balance Abnormal patterns of movement Poor co-ordination of movement Loss of functional ability Secondary musculoskeletal problems
How to manage abnormal tone
To maintain soft tissue length
To maintain joint alignment
To prevent muscle shortening
Promote normal functional movement
Maintain independence
