Muscle Tone And Length

Question 1

Muscle tone

Answer 1

Sufficient tension to allow movement but maintain stability
Varies with posture - lying; lower tone, standing; higher tone
Neural - active muscle contraction and background activity even when the muscles is ‘relaxed’
Non-neural - non-elastic structures within the muscle (tendons), elastic properties and connective tissue

Question 2

Upper motor neurone syndrome: negative neural component

Answer 2

Weakness - low tone
Impaired motor control
Decreased range of movement

Question 3

Upper motor neurone syndrome: positive neural component

Answer 3

Spasticity - increased stretch response and co-activity, high tone
Associated reactions
Spasms
Clonus

Question 4

Upper motor neurone syndrome: second adaptive changes

Answer 4

Mechanical muscle stiffness
Contractures - decreased range of movement, high tone

Question 5

Spasticity

Answer 5

Motor disorder
A velocity dependent increase in tonic stretch reflexes
Faster speed of change of the muscle means a higher tone and spasticity but slower speed of change of the muscle means lower tone and spasticity
Exaggerated stretch reflexes
Co-activity of opposing muscle groups

Question 6

Characteristics of upper motor neurone syndrome

Answer 6

E.g. stroke and MS
Abnormal posture
Difficulty moving in an effective way
Stiffness - resistance to passive movement
Muscle and joint contractures - deformities
Pain
Spasms
Clonus - abnormal reflex that involves involuntary and rhythmic contractions

Question 7

Extrinsic factors affecting tone

Answer 7

Posture - based of support and centre of gravity
Temperature - hot means muscles are more relaxed and lower tone
Visual or auditory stimuli - affect alert scale
Emotional states - anxiety can increase the tone
Medical factors - UTIs, bowel impaction, skin irritation, ingrowing toe nails, increased sensory stimuli, pain

Question 8

Abnormal motor output

Answer 8

Under-active agonist
Over-active antagonist
Shortened antagonist

Question 9

Abnormal motor output: under-active agonist

Answer 9

Decreased neural drive to spinal neurones
Muscle weakness
Low tone

Question 10

Abnormal motor output: over-active antagonist

Answer 10

Increased tone/ spasticity - may still be weak due to lack of voluntary drive

Question 11

Abnormal motor output: shortened antagonist

Answer 11

Stiffness and contracture

Question 12

Muscle length: sarcomeres

Answer 12

Number of sarcomeres changes the muscle length
Reduced sarcomeres means a reduced length
Constant firing of the muscle means the sarcomeres contract meaning a decreased muscle length
Length will effect - range of movement, force generated and where in the range of movement

Question 13

Other contributors to stiffness

Answer 13

Immobilised muscles in the shortened position there is an increase in the proportion of collagen to contractile muscle
If the muscle is electrically stimulated in the shortened position sarcomere numbers still shorten but there are no connective tissue changes

Question 14

Common patterns of spasticity

Answer 14

Upper limb - usually flexor synergy; fingers flexed and adducted, thumb flexed and adducted
Lower limb - usually extensor synergy; hip flexed, internally rotated and adducted, knee extended, ankle plantar flexed with inversion

Question 15

Contractures

Answer 15

Prolonged maintenance of a muscle in a shortened position
Fixed shortening of the muscle and contracture of peri-articular structures
Reduced passive range of movement
May persistence even if spasticity is effectively treated

Question 16

Common contracture sites

Answer 16

Upper limb - loss of finger and wrist extension, loss of thumb extension, abduction and opposition
Lower limb - loss of ankle dorsiflexion and eversion, loss of hip abduction