Muscle tone Flashcards
1
Q
define normal postural tone
A
a continuous state of mild contraction, or a state of preparedness of the muscle
2
Q
what is normal postural tone characterized by?
A
- effective co-activation (stabilization) at axial and proximal joints
- ability to move against gravity and resistance (it is high enough to resist gravity and low enough to allow mobility)
- ability to maintain the limb in a position
- balanced tone between agonist and antagonistic muscles
- ease of ability to shift from stability to mobility and reverse as needed
- allows automatic postural adjustments to movement
3
Q
what is muscle tone?
A
the degree of tension (contraction) in a skeletal muscle
- it is dependent on the integrity of the peripheral and CNS mechanisms and the properties of the muscle
4
Q
what determine muscle tone?
A
- elastic properties of connective tissue
- visco-elastic properties of muscle fibers
- motor unit activity (neural)
5
Q
on what does normal muscle tone rely?
A
- normal functioning of the cerebellum
- motor cortex
- basal ganglia
- midbrain
- vestibular system
- spinal cord
- neuromuscular system
- on a normally functioning stretch reflex
6
Q
characteristics of normal muscle tone
A
- effective coactivation at axial and proximal joints
- ability to move against gravity ad resistance
- ability to maintain the position of the limb if it is placed passively by the examiner and then released
- balanced tone between agonistic and antagonistic muscles
- ease of ability to shift from stability to mobility and reverse as needed
- ability to use muscles in groups or selectively with normal timing and coordination
- resilience or slight resistance in response to passive movement
7
Q
explain the upper motor neuron control of muscles
A
- motor cortex
- descending motor cortex
- anterior horn of spinal cord grey matter
- additional brain areas
8
Q
explain the lower motor neuron control of muscles
A
motor unit:
- motor neuron
- motor (efferent) nerve fibers
- spinal nerves
- muscle fibers it supplies
9
Q
results of lesions of upper motor neuron
A
- weakness of the specific movement (extension of upper limbs and flexion of lower limbs pyramidal weakness)
- spasticity or high tone
- overactive stretch reflex
- hyperactivity of motor neurons
10
Q
results of lesions of lower motor neuron
A
- weakness (paresis)
- wasting (atrophy)
- flaccidity
- low muscle tone
- suppressed/ absent reflexes
11
Q
causes of abnormal muscle tone
A
hypertonicity
- secondary to CNS pathology (stroke/ trauma)
- changes in the ascending tracks (efferent) inhibiting motor neurons
- range of postural tone
\+ no anti-gravity control
\+ no gradation of movement
\+ = total reciprocal inhibition
- muscle tone
\+ increased resistance to passive stretch and movement
\+ hyperactive reflexes
\+ changes in mechanical structures
\+ types
= spasticity
= rigidity
= dystonia
= clonus
= spasms
hypotonicity
-cerebellum pathology
- abnormality in lower motor neuron
- neuromuscular junction pathway
- muscle pathology
- range of postural tone
\+ no postural adjustments
\+ movement blocked
\+ = total co-contraction
- muscle tone
\+ associated with:
= weakness
= atrophy
= absent/ decreased reflex response
\+ types
= flaccidity
= hypotony
= ataxi
12
Q
what influences assessment of muscle tone?
A
- speed
- effort
- emotional stress
- temperature
- fatigue
- position of head
- sensory stimulation
13
Q
causes of hypotonia
A
- usually occurs in newborn babies up to age of 6 weeks and is accompanied by phasic reflexes
- most children with cerebral impairment start with hypotonia
- muscle disease can cause hypotonia (muscular dystrophy or polio myositis
- damage of motor fibers of peripheral nerves
- damage of dorsal or ventral nerve roots usually occurs in isolation, but together with a spinal cord injury
- spinal cord injuries like paraplegia
- when cerebellum is affected, tone is lowered, although active movement can still occur, albeit in an abnormal manner
- traumatic brain/spinal injury, flaccidity initially exists and could change to hypertonicity within a few weeks
14
Q
what is flaccidity and its characteristics?
A
- refers to absence of tone
- deep tendon reflexes and active movement are absent
- can result in LMN dysfunction
- muscles feel soft and offer not resistance to passive movement
15
Q
what can be observed in ataxia?
A
- decomposition of movement
+ when client reaches for object, movement is jerky or broken up - dysmetry
+ when client reaches for object, they go beyond it or stop in front of it - disdiadokokinesia (DDK)
+ client cannot perform quick alternating movements like pronation and supination - intension tremor
+ tremor usually occurs at the end of a movement in distal muscles, causing rhythmic oscillation of hands when they near the object. this usually aggravates with complicated or difficult movement - nystagmus
+ rhythmic oscillation of both eyes - heel-knee test
+ when client is asked to move heel over tibia, they cannot do so in a coordinated movement and it is poorly coordinated
