Spinal Cord

Question 1

What is the function of the Corticospinal tract

Answer 1

conveys axial and limb motor control

controls voluntary movement of muscle

Question 2

Describe the corticospinal tract

Answer 2

Begins in the precentral gyrus (primary motor cortex)
>internal capsule>cerebral peduncle>pons>pyramids>Lateral/Anterior Corticospinal tract
80% decussate in pyramids

• *80% decussate at pyramids so they just synapse with neuron on anterior horn (limb)- Lateral corticospinal tract
• *20% decussate same side on anterior white commissure then synapse in anterior horn of grey matter -Anterior corticospinal tract

any lesion here is UMN lesion

Question 3

What are the 2 neurons involved in the Corticospinal tract

Answer 3

1. Upper motor neuron (from cerebral cortex to ventral horn)

2. Lower motor neuron
from ventral horn to skeletal muscle

Question 4

Describe the
Reticulospinal tract
-function
pathway

Answer 4

Posture and locomotion

• form reticular formation(pons) to spinal cord
• regulates ventral horn motor activity/reflexes
• facilitates and inhibits lower motor neurons

Question 5

Amyotrophic lateral sclerosis

Answer 5

• Genetic (SOD1 gene)
• Affects LMN and UMN selectively
• progressive weakness and atrophy of muscles but mind intact
• spasticity when UMN affected
• symptoms usually in limbs or bulbar signs
• short life span due to resp failure

Question 6

Spinocerebellar tract

• function
• pathway

Answer 6

ipsilateral, 2 neurons
unconscious muscle proprioception 
Posterior Tract: above L3
1st order- synapse at dorsal horn
2nd order- ascend in lateral column to cerebellum (terminate ipsilaterally in cerebellar cortex after entering through inferior cerebellar peduncle)

Question 7

Spinothalamic Tract

Answer 7

First Order Neurons 
-enter dorsal horn 
-form tract of Lissauer 
-Synapse in substantia gelatinosa 
2nd Order Neurons 
- cross in dorsal horn at each level 
-ascend in anterolateral column to thalamus

Question 8

how does UMN lesion occur?

-cause?

Answer 8

damage to corticospinal tract

e.g following a stroke

Question 9

UMN disease

-symptoms

Answer 9

• Spastic paralysis (increased muscle tone)
• Overactive tendon reflexes
• No significant muscle atrophy

Above pyramids: Opposite side
Below pyramids: Same side

Question 10

how can a LMN lesion occur?

Answer 10

Degeneration of lower motor neurons in ventral horn
E.g. Spinal muscular atrophy
- caused by defects in the SMN1 gene

Question 11

LMN disease

-symptoms

Answer 11

• Flaccid paralysis (no muscle tone)
• No tendon reflexes
• Muscle atrophy