UMN Syndrome; Muscle Tone

Question 1

Muscle performance is mostly concerned with ___ neurons. With pathology, what is its definition?

Answer 1

LMN

Inability to generate force on muscle in primary disorder.

Question 2

Motor control is usually a(n) ___ disorder. Name 4 components of motor control.

Answer 2

UMN

1. Dexterity
2. Coordination
3. Agility
4. Fractionated movement

Question 3

What is a classic sign of UMN syndrome?

Answer 3

Loss of fractionated movement (being able to move a single muscle group independently).

Question 4

With UMN syndrome, there is typically increased muscle tone, what’s happens to the reflexes?

Answer 4

Hyperreflexia.

Question 5

What is a movement synergy?

Answer 5

Trying to move your hand and the whole limb moves in flexion or ext.

Question 6

Why can’t a person with a cortical stroke move?

Answer 6

UMN’s can’t recruit LMN for movement because higher centers can’t generate APs.

Question 7

With paresis, there is decreased activation of the antagonist or agonist?

Answer 7

Antagonist.

Question 8

With an UMN injury, is muscle atrophy greater or lesser than LMN injury?

Answer 8

Less.

Question 9

What is learned non-use?

Answer 9

Not using a limb that works resulting in negative neuro-plastic changes.

Question 10

Which spinal tract activates muscles that control individual joint movements?

Answer 10

Cortical spinal.

Question 11

What area of the brain would you cut to eliminate fractionated movement alone?

Answer 11

Pyramids in the rostral medulla (corticospinal tract).

Question 12

What spinal tract is the hand mostly innervated by?

Answer 12

Lateral corticospinal.

Question 13

What does the bulbar-spinal tract control?

Answer 13

Gross movements of the trunk and girdle muscles.

Question 14

Is a DTR polysynaptic? T/F

Answer 14

False, monosynaptic.

Question 15

What is diaschiasis and what is its relationship with DTRs and why?

Answer 15

Spinal shock lasting hours to days after injury. It can result in hyperative reflexes due to:

1. Upregulation on neurotransmitters
2. Loss of UMN control of inhibitory circuits

Question 16

Rehabilitation after nerve injury is optimal in the sub acute phase. What is the goal?

Answer 16

To drive neuroplasticity, specifically competition-driven collateral growth from IA afferents of LMN onto the alpha MN. You want the UMN to produce more collaterals than the IA afferent.

Question 17

What is the mathematical relationship between DTRs and muscle strength?

Answer 17

Inversely related.

Question 18

What is a practical use of the tonic stretch reflex?

Answer 18

Can give insight into the level of spasticity of a muscle, as this reflex is not usually seen.

Question 19

When would you see a clasp knife reflex?

Answer 19

Only with UMN lesion.

• resistance drops off after a break point, like a jack knife.
• only with slow, passive stretch

Question 20

What types of receptors are responsible for tonic reflexes (incl jack knife)?

Answer 20

Type II afferents, joint capsule and touch receptors.

Question 21

How is muscle tone defined?

Answer 21

Resistance to passive stretch.

Question 22

What are the factors that contribute to muscle tone?

Answer 22

1. Active factors, like UMN firing
2. Instrinsic factors like weak actin myosin bonds at rest
3. Passive factors: titin - keeps the ends of sarcomeres together.

Question 23

Is there a neural component to the slow stretch reflex in a normal person?

Answer 23

No, tonic, slow stretch reflex is inhibited. Most resistance is from titin, the passive element.

Question 24

How do you lose sarcomeres?

Answer 24

Contractures from immobility.

• also lose titin
• more actin-myosin bonds at rest (why you get stiffer)

Question 25

What is hypertonia and what causes it?

Answer 25

Increased resistance to passive stretch. - overactive neural input: a) hyperreflexia b) increased UMN activity

Question 26

Which muscle fiber types are more resistant to atrophy?

Answer 26

Type I fibers; also more resistant to stretch.

Question 27

When does hypotonia occur? What is the most extreme form called?

Answer 27

Usually after diaschiasis with UMN lesion. -movement also generally impaired Extreme = flaccidity -usually w/ complete LMN lesion

Question 28

What is the H reflex?

Answer 28

Loop from politeal fossa via tibial nerve. Stimulation of the alpha MN to ensure loop is intact.

Question 29

What is spasticity?

Answer 29

Hypertonia; velocity dependent increases in phasic stretch reflex

Question 30

How do you measure muscle tone?

Answer 30

DTRs, H Reflex, Ashworth scale (0-5): 0=normal

Question 31

In the medical management of hypertonia, where in the brain is baclofen injected?

Answer 31

The subarachnoid space. Intrathecal release that spreads locally.

Question 32

Dystonia is horrible, as highlighted by the video we saw in class. It can have different triggers. What is thought to be its cause?

Answer 32

Basal ganglia dysfunction, but poorly understood.

Question 33

Rigidity is a form of dystonia and hypertonia. What are the two different types?

Answer 33

LEAD PIPE -resistance is uniform through ROM ``` COG WHEEL (Parkinson's) -resistance is interrupted by a series of "jerks" ```

Question 34

What is the difference between resting and essential tremor?

Answer 34

RESTING (Parkinson's) -there at rest, disappears with initiation of task ESSENTIAL -no tremor at rest, only with task Also physiologic (not normally visible) and intention (target related, Cb disorders)