Lecture 28: Reflexes and muscle tone Flashcards
Describe the myotatic stretch reflex:
This is reflex muscle contraction when the muscle is lengthened.
Two components:
- Phasic (brisk, brief - tendon reflex)
- Tonic (weaker, long-lasting - tone)
Write some notes on tendon reflexes:
- Involuntary
- Stereotyped
- Non-fatiguing
- Response determined by stimulus strength
- Normal variations between individuals
- Increased muscle activation in same segment and other muscles (re-enforcement)
- Increased anxiety and decreased sleep
Name some tendon reflexes and the nerves:
Jaw jerk -> Trigeminal Biceps -> C5/6 nerve root Brachioradialis -> C6 Triceps -> C7 Fingers -> C8 Knee -> L3/4 Ankle -> S1
What is the grading of reflexes?
0 = absent \+ = Normal \++ = Normal brisk \+++ = Exaggerated \++++ = Clonus (Repeated contraction)
What is tone?
Resistance of muscle to passive lengthening
What are the components of tone?
- Muscle elasticity
- Neural (Tonic or stretch reflex)
How is tone assessed?
Passive flexion and extension of limb at varying speeds
May be:
- Normal
- Reduced
- Increased
Why are tone and reflexes important?
- They change in disease
- Recognised the pattern of change localises the site of the lesion i.e
- > Upper motor neuron
- > Basal ganglia
- > Lower motor neuron
‘Hypotonia’ , reduced tone suggests a lesion where?
Lower motor neuron
Increased tone;
- Spasticity
- Rigifity
Suggests lesions where:
Spasticity = Upper motor neuron
Rigidity = Basal ganglia
How do reflexes change with lesions?
Reduced / absent = lower motor neuron
Increased = upper motor neuron
No change = basal ganglia
Describe the impact of peripheral nerve lesons:
- Reduced or absent reflexes
- Reduced tone
- Muscle wasting
- Muscle fasciulations (Twitching)
- Babinski reflex flexor (big toe goes down)
Where can the peripheral nerve lesions occur?
Sensory axon
Cell body of LMW
motor axon
Muscle
Describe the pattern of UPN lesions:
- Increased reflexes
- Increased tone
- Babinski reflex extensor (big toe goes up)
- Upper Motor neuron reflex changes in
- > Strokes
- > Brain tumours
- > Spinal cord lesions
Describe how the tone changes with upper motor neuron lesions?
- lesions and descending upper motor neuron pathways leads to changes in stretch reflexes.
- most common change is exaggerated stretch reflexes
- > Increased tone, Spastic catch
Write some notes on the increase tone and spasticity of upper motor neuron lesions:
Increased tone and spasticity
- Depend on the speed of muscle stretch
- > Slow muscle stretch may lead to little resistance
- > Faster muscle stretch -> Increases resistance, Increase tone
- > Rapid stretch -> Increased resistance then sudden loss of reflex contraction - Like a clasp knife
What do lesions in the brain result in (recap)?
- Increased tone
- Increased reflexes
- Upgoing babinski response
What do peripheral nerve lesions result in? (Recap)
- Decreased tone
- Absent reflexes
- Normal downgoing babinski response
What would you expect to see in a pt with C5 lesion in terms of tone and reflex?
Reflexes reduced or absent at the level of the lesion
- Biceps and supinator jerk (C5 and C6)
Tone at the elbow is reduced
