Brainstem Motor Pathways

Question 1

What are the symptoms of a lesion to the lateral corticospinal tract?

Answer 1

1. produces paresis and a loss of voluntary movements, especially at the digits
2. positive Babinski sign
3. decreased cremaster reflex
4. produces hypotonia (loss of tonic stimulatory effect)
5. does not produce spasticity.

Question 2

What would result from a lesion of the anterior corticospinal tract?

Answer 2

1. manipulation of objects normal
2. frequent falling
3. lost of righting reflex
4. hypotonicity

NOTE: The anterior corticospinal tract has bilateral projections

Question 3

When you talk about the upper motor neurons being lesioned you are usually referring to ________.

Answer 3

stroke.

Question 4

True or False. Rigidity is dependent on velocity.

Answer 4

False.

Rigidity: an increase in extensor/flexor muscle tone characterized by resistance to passive stretch, independent of velocity.

Question 5

What are the two types of rigidity?

Answer 5

a. lead-pipe: resistance constant throughout the range of movement.
b. cogwheel (Parkinson’s Disease) or clasp-knife (pyramidal tract): increase in passive resistance that abruptly decreases, usually at the end of an excursion.

Question 6

Which type of rigidity is seen in Parkinson’s disease?

Answer 6

Cog wheel

Question 7

Spasticity is an increase in muscle tone that is velocity _______ (dependent/ independent).

Answer 7

Dependent

Question 8

Spasticity is greater in _______ of upper limb & __________ of lower limb.

Answer 8

flexors; extensors

Question 9

Spasticity results from damage of _________parts of cortex and disinhibition of reticular and brainstem nuclei.

Answer 9

non-pyramidal

Question 10

What are the major motor efferents from the cortex?

Answer 10

1. Basal ganglia
2. Cerebellum
   * Most projections go here but indirectly through the pons
3. Spinal cord indirectly through

• Red nucleus
• Pontine reticular formation
• Medullary reticular formation
• Vestibular nuclei

Question 11

Rexed lamina IX consist of two distinct groups of motor neurons:

Answer 11

1) medial group-axial musculature
2) lateral group-appendicular musculature

*The intermediate motor system isn’t quite lateral or medial, its not quite the hand and not quite the back. But it controls the muscles that position the hand and feet for proper orientation.

Question 12

The medial motor system (anteromedial funiculus). These axons have a _________projection controlling the medial motor nuclei. It controls muscles that are more proximal. It goes to the medial part of the ventral horn, goes to axial and girdle musculature.

Answer 12

bilateral

Question 13

There is a lateral extension of the medial motor system. This is the intermediate motor system. It’s the medial motor system (anterolateral funiculus). Goes to the intermediate muscles in the ______

Answer 13

ventral horn

*Unilaterl, ipsilateral projections the control proximal limbs

Question 14

Medial pathway: Goes to the medial motor nuclei, activating the __________neurons/ interneurons that control large segments of the back and trunk, innervating proximal musculature, extensors (anti-gravity muscles) as opposed to flexors.

Answer 14

long propriospinal

*Rexed lamina ViII

Question 15

Which muscles are primarily innevated by the medial pathway?

Answer 15

Proximal extensors

Question 16

Which muscles are primarily innevated by the lateral pathway?

Answer 16

Distal Flexors

Question 17

Lateral pathways: Lateral part of the ventral horn, target __________interneurons- neurons that connect different joints so you can move your limbs in coordinated fashion. Targets are muscles in the distal limbs and the output is predominately flexors as opposed to extensors.

Answer 17

short propriospinal

Question 18

Label

Answer 18

Question 19

The tectospinal tract come from the _________ and goes to the neck muscles so you can coordinate head movements.

Answer 19

superior colliculus

Question 20

In the lateral motor system, which of the two pathways is direct and which is indirect?

Answer 20

Direct: Lateral corticospinal tract

Indirect: Rubrospinal tract

Question 21

Label

Answer 21

Question 22

What are the two inputs to the red nucleus from the cerebellum?

Answer 22

• Interposed (magnocellular)
• Dentate (parvocellular)

Question 23

Rubrospinal tract crosses in the___________decussation and overlaps with the lateral corticospinal tract in the lateral funiculus

Answer 23

ventral tegmental

Question 24

Rubrospinal tract innervates proximal musculature of the ____________ (only).

Answer 24

contralateral upper limb

NOTE: It does not control individual digits

Question 25

Rubrospinal firing activity is related to the dynamics of ________ and limb \_\_\_\_\_\_

Answer 25

force; velocity

Question 26

Do the reticulospinal pathways have agonistic or antagonistic functions?

Answer 26

Anatagonistic

Question 27

The pontine reticulospinal tract is \_\_\_\_\_\_\_\_\_\_, while the medullary reticulospinal tract are \_\_\_\_\_\_\_\_\_.

Answer 27

medial; lateral

Question 28

Which vestibular nuclei give rise to the vestibulospinal tract?

Answer 28

Medial and lateral

Question 29

Label

Answer 29

Question 30

In slide, how do you know that you are at the pontomedullary junction?

Answer 30

Presence of dorsal and ventral cochlear nuclei

Question 31

**The medial vestibulospinal tract** ## Footnote Originates from the \_\_\_\_\_\_\_\_\_\_ Terminates medially in the ventral horn of \_\_\_\_\_\_\_\_regions Affects axial musculature of \_\_\_\_\_\_\_ Adjustments to \_\_\_\_\_\_\_\_\_\_\_

Answer 31

medial vestibular nucleus cervical NECK angular acceleration of head

Question 32

**The lateral vestibulospinal tract** ## Footnote Originates from the _______________ ipsilaterally Terminates in the _________ ventral horn group proximal limb muscles…balance

Answer 32

lateral vestibular nucleus (Deiter’s) intermediate

Question 33

True or false. The lateral vestibulospinal tract does not cross over.

Answer 33

True

Question 34

The lateral vestibular system gets a lot of information from the \_\_\_\_\_\_\_\_

Answer 34

utricle

Question 35

It receives inhibitory input directly from Purkinje cells of the cerebellum, so the lateral vestibular nucleus will be modulated by the \_\_\_\_\_\_\_\_\_\_.

Answer 35

cerebellum.

Question 36

The lateral vestibulospinal tract receives **tonically** inhibitory inputs from the \_\_\_\_\_\_\_\_\_\_\_.

Answer 36

Cortex

Question 37

What is the pathway of the tectospinal tract?

Answer 37

1. Originates from the deep layers of **superior colliculus** 2. Decussates in the **dorsal tegmentum** 3. Terminates medially in the ventral horn of **cervical** cord coordinates neck & eye movements

Question 38

The _____________ tract decussates in the dorsal tegmentum, which the __________ tract decussates in the ventral tegmentum.

Answer 38

Tectospinal; rubrospinal

Question 39

The cortex and red nucleus have a facilitatory influence on _______ tone.

Answer 39

flexor \*And inhibitory influence over extensors

Question 40

It’s the loss of the inhibitory influences of cortex on these pontine reticular spinal neurons that gives you the \_\_\_\_\_\_\_\_\_\_\_- hyperextension in the neck.

Answer 40

**opisthotonos**

Question 41

The systems that try to maintain muscle tone of the flexors are \_\_\_\_\_\_\_\_\_\_\_, \_\_\_\_\_\_\_\_\_\_, and \_\_\_\_\_\_\_\_\_\_\_.

Answer 41

corticospinal, rubrospinal, and medullary reticulospinal.

Question 42

Antagonists to flexors will be the ___________ and \_\_\_\_\_\_\_\_\_\_\_.

Answer 42

medial/lateral vestibulospinal systems and the pontine reticulospinal systems.

Question 43

Which motor neuron si problematc in decrebrate animals?

Answer 43

gamma \*because gamma system that adjusts the muscle tone, is increased.

Question 44

If you stimulate the anterior lobe of the cerebellum, you will reduce rigidity. Why is this?

Answer 44

The cerebellum has inhibitory input to the vestibular system. If you stimulate the cerebellum you increase the amount of inhibition of the vestibular spinal tract therefore rigidity is reduced

Question 45

Why do you get flexion of the upper limb in decorticating but in decerebrate you get extension?

Answer 45

Decorticate rigidity is when you have damage to the **cerebral cortex or to the internal capsule**

Question 46

The lesion for \_\_\_\_\_\_\_\_is above the red nucleus where as for \_\_\_\_\_\_\_\_\_\_\_it is below the red nucleus.

Answer 46

decorticate; decerebrate

Question 47

A lesion of what places will cause decorticate symptoms?

Answer 47

**Above the red nucleus** * Cortex * Internal Capsule * Thalamus