Unit 3_Descending Pathways

Question 1

Where do the descending pathways originate?

Answer 1

Some originate in cerebral cortex and others originate in the brainstem.

Question 2

What pathways are for voluntary activity and modulating brainstem pathways?

Answer 2

Cortical originating pathways

Question 3

What pathways are important for postural control under the influence of cortex and sensory inputs?

Answer 3

Brainstem originating pathways

Question 4

What pathways regulate distal, proximal and postural muscles directly to the spinal cord and/or through brainstem pathways?

Answer 4

Cortical descending pathways

Question 5

What are the two types of the cortical descending pathways?

Answer 5

Ventral Corticospinal Tract
Lateral Corticospinal Tract

Question 6

Where does the crossing occur in the cortical descending pathway?

Answer 6

At the Medulla

Question 7

What pathways are important for postural control and as a group do a lot of bilateral control?

Answer 7

Ventromedial brainstem originating pathways

Question 8

What are the two types of Ventromedial brainstem originating pathways?

Answer 8

Medial brainstem pathway
Lateral brainstem pathway

Question 9

What is bringing center of mass back over base of support?

Answer 9

Postural support

Question 10

What is extending base of support to capture center of mass?

Answer 10

Postural support

Question 11

Responses to postural perturbations are normally what and automatic and involved in brainstem originating pathways?

Answer 11

Adaptable so that they are functional

Question 12

What are the following functions support for?
- Regulate muscle tone: Background muscle activity (stiffness)
- Coordinate balance by utilizing vestibular, visual and proprioceptive inputs

Answer 12

Maintaining postural control

Question 13

What kind of pathways are the following?
Tectospinal (only travels to cervical spine)

Pontine reticulospinal

Medullary reticulospinal

Answer 13

Ventromedial Pathways: Brainstem

Question 14

What pathway includes when neurons in the medullary reticular nuclei send axons bilaterally into the lateral columns of the spinal cord to form the lateral or medullary reticulospinal pathways? These axons affect alpha motor neurons mostly through interneurons. The strongest synaptic connections are on alpha motor neurons (through interneurons) that control proximal muscles.

Answer 14

Medullary Reticulospinal Pathway

Question 15

What pathway includes neurons in the pontine reticular nuclei send axons bilaterally down the pontine reticular tracts in the ventral column of white matter to affect alpha motor neurons (through interneurons) that innervate proximal/axial muscles?

Answer 15

Pontine Reticulospinal Pathway

Question 16

What ventromedial pathway participates in all four of the brainstem motor control functions?

1. It enhances extensor tone.
2. It coordinates movement by influencing the trajectory of movement.
3. Features control of balance with a strong influence on proximal and postural muscles

Answer 16

Lateral Vestibulospinal

Question 17

What ventromedial pathway is for coordinating neck and head righting reactions for balance?

Answer 17

Medial Vestibulospinal

Question 18

What dorsolateral pathway is for coordinating muscle tone in flexor muscles?

Answer 18

Ruprospinal

Question 19

What projections control cranial nerve nuclei?

Answer 19

Corticobulbar (corticonuclear)

Question 20

What are controlled by contralateral motor cortex?

Answer 20

Lower muscles of facial expression (CN VII)

Question 21

What are the differences between a Cranial Nerve injury and a stroke?

Answer 21

Stroke - cortex is able to supply both sides (Right Facial UMN lesion); lower muscles of facial expression affected

Cranial Nerve - complete facial paralysis on side affected

Question 22

What clinical test can be used to take a look at hypoglossal function within the corticobulbar function?

Answer 22

Evaluate genioglossus muscles. Part that is for genioglossus is crossed (CN XII – Hypoglossal)

Question 23

What are the following clinical implications associated with:

Upper Motor Neuron Lesion (syndrome)

Lesion in the primary motor cortex, internal capsule or corticobulbar/corticospinal tract in the brainstem or spinal cord.

Primary motor cortex lesions have potential to produce all UMN signs and symptoms.

Answer 23

Upper Motor Neuron injury

Question 24

What are the following signs and symptoms associated with:
- Weakness (paresis)
- Hyperreflexia and Hypertonia - spasticity (usually)
- No early atrophy (muscles may atrophy months later due to disuse)
- Abnormal synergy movements
- Abnormal reflex activity (Babinski reflex, clonus)

Answer 24

Upper Motor Neuron Disorders

Question 25

The distribution of problems, when one has a lesion causing “UMN” signs and symptoms, is what (i.e. only in that segment or nerve)? Will be contralateral or ipsilateral depending on the lesion site.

Answer 25

Not segmental