Lecture 28: Reflexes and muscle tone

Question 1

Describe the myotatic stretch reflex:

Answer 1

This is reflex muscle contraction when the muscle is lengthened.

Two components:

• Phasic (brisk, brief - tendon reflex)
• Tonic (weaker, long-lasting - tone)

Question 2

Write some notes on tendon reflexes:

Answer 2

• 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

Question 3

Name some tendon reflexes and the nerves:

Answer 3

Jaw jerk -> Trigeminal
Biceps -> C5/6 nerve root
Brachioradialis -> C6
Triceps -> C7
Fingers -> C8
Knee -> L3/4
Ankle -> S1

Question 4

What is the grading of reflexes?

Answer 4

0 = absent
\+ = Normal
\++ = Normal brisk
\+++ = Exaggerated
\++++ = Clonus (Repeated contraction)

Question 5

What is tone?

Answer 5

Resistance of muscle to passive lengthening

Question 6

What are the components of tone?

Answer 6

• Muscle elasticity

- Neural (Tonic or stretch reflex)

Question 7

How is tone assessed?

Answer 7

Passive flexion and extension of limb at varying speeds

May be:

• Normal
• Reduced
• Increased

Question 8

Why are tone and reflexes important?

Answer 8

• 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

Question 9

‘Hypotonia’ , reduced tone suggests a lesion where?

Answer 9

Lower motor neuron

Question 10

Increased tone;

• Spasticity
• Rigifity

Suggests lesions where:

Answer 10

Spasticity = Upper motor neuron

Rigidity = Basal ganglia

Question 11

How do reflexes change with lesions?

Answer 11

Reduced / absent = lower motor neuron
Increased = upper motor neuron
No change = basal ganglia

Question 12

Describe the impact of peripheral nerve lesons:

Answer 12

• Reduced or absent reflexes
• Reduced tone
• Muscle wasting
• Muscle fasciulations (Twitching)
• Babinski reflex flexor (big toe goes down)

Question 13

Where can the peripheral nerve lesions occur?

Answer 13

Sensory axon
Cell body of LMW
motor axon
Muscle

Question 14

Describe the pattern of UPN lesions:

Answer 14

• Increased reflexes
• Increased tone
• Babinski reflex extensor (big toe goes up)
• Upper Motor neuron reflex changes in
• > Strokes
• > Brain tumours
• > Spinal cord lesions

Question 15

Describe how the tone changes with upper motor neuron lesions?

Answer 15

• lesions and descending upper motor neuron pathways leads to changes in stretch reflexes.
• most common change is exaggerated stretch reflexes
• > Increased tone, Spastic catch

Question 16

Write some notes on the increase tone and spasticity of upper motor neuron lesions:

Answer 16

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

Question 17

What do lesions in the brain result in (recap)?

Answer 17

• Increased tone
• Increased reflexes
• Upgoing babinski response

Question 18

What do peripheral nerve lesions result in? (Recap)

Answer 18

• Decreased tone
• Absent reflexes
• Normal downgoing babinski response

Question 19

What would you expect to see in a pt with C5 lesion in terms of tone and reflex?

Answer 19

Reflexes reduced or absent at the level of the lesion
- Biceps and supinator jerk (C5 and C6)

Tone at the elbow is reduced