Descending Pathways

Question 1

Descending tracts from the cerebral cortex?

Answer 1

1. Corticospinal tract
   - axons destined for spinal cord nuclei
2. Corticobulbar or corticonuclear tract
   - axons destined for brainstem motor nuclei
   >pyramidal tracts

Question 2

Descending tracts from the brain stem?

Answer 2

1. Tectospinal tract
2. Rubrospinal tract
3. Vestibulospinal tract
4. Reticulospinal tact
   - extrapyramidal tracts

Question 3

Describe the lateral corticospinal tract?

Answer 3

voluntary, discrete, skilled movements

> Cortex 321 (40%), 4 (31%), 6 (29%)
Corona radiata
Internal capsule (posterior Ilmb)
Mid-brain (crus)
Pons (pyramidal eminence)
Medulla Oblongata (Pyramids)
Pyramidal decussation
Lateral funiculus (Lateral corticospinal tract)
Lamina 7,8,9
Ventral root

Question 4

Describe anterior corticospinal tract?

Answer 4

voluntary, discrete, skilled movements

> Cortex 321 (40%), 4 (31%), 6 (29%)
Corona radiata
Internal capsule (posterior Ilmb)
Mid-brain (crus)
Pons (pyramidal eminence)
Medulla Oblongata (Pyramids)
Pyramidal decussation
anterior funiculus (anterior corticospinal tract)
Lamina 7,8,9
Ventral root

Question 5

Consequences of lesions of the corticospinal tract?

Answer 5

1. Babinski sign is present (extensor plantar)
2. Superficial abdominal reflex loss
3. Loss of fine skilled voluntary movements

Question 6

Describe the tectospinal tract?

Answer 6

Mediates reflex postural movements in response to visual and auditory stimuli

> Superior colliculus (mid brain)
Dorsal tegmental decussation
Anterior funiculus
Lamina 7,8,9
Ventral root

Question 7

Describe the vestibulospinal tract?

Answer 7

Controls extensor muscles of trunk and extremities (helps maintain balance)

> Vestibular nuclei
Anterior funiculus
Lamina 7,8,9
Ventral root

Question 8

Describe the rubrospinal tract?

Answer 8

Controls flexor muscles

> Red nucleus (mid brain)
Ventral tegmental decussation
Lateral funiculus
Lamina 7,8,9
Ventral root

Question 9

Functions of reticulospinal tract?

Answer 9

1. Facilitates or inhibits voluntary movements
2. Effects on respiration
3. Effects on circulatory system
4. Influences muscle tone
5. Facilitates or inhibits transmission of sensory impulse

Question 10

Describe the reticulospinal tracts?

Answer 10

1. Pontine reticulospinal
   - mostly uncrossed
   - excite antigravity muscles
2. Medullary reticulospinal tract
   - mix of crossed and uncrossed fibers
   - inhibit antigravity muscles
   Note: originate from reticular formation of pons and medulla

Question 11

Descending autonomic pathways?

Answer 11

> Cortex, Hypothalamus, Amygdala, Reticular formation
Reticulospinal tract
Sympathetic (T1-L2)
&
Parasympathetic (cranial nerves 3,7,9 & 10 and S2, S3 & S4)

Question 12

Consequences of lesion of posterior funiculus?

Answer 12

Touch, Pressure, Proprioception, Vibration, Two point discrimination, loss on the ipsilateral side below the lesion

Question 13

Consequences of lesion of lateral funiculus?

Answer 13

pain and thermal sense on the contralateral side below the lesion

Question 14

Consequences of lesions of anterior white commissure?

Answer 14

pain and thermal sense, light touch and pressure? Loss at T8 level

Question 15

Consequences of lesion of dorsal root?

Answer 15

All sensory loss at T10