Spinal

Question 1

What is the white and grey matter of the spinal cord composed of?

Answer 1

white matter (outside) - myelinated neurons separated into tracts

grey matter (inside):

• anterior (ventral) horns - contain cell bodies of motor neurons
• posterior (dorsal) horns - contain cell bodies of sensory neurons

Question 2

What are the descending spinal tracts

Answer 2

• pyramidal
  
  • corticospinal/bulbar
• non-pyramidal
  
  • rubrospinal (decussates)
  • tectospinal (decussates)
  • reticulospinal
  • vestibulospinal

Question 3

what is the function and course of the corticospinal tract?

Answer 3

• controls voluntary motor actions
• course
  
  • begins in cerebral cortex, through internal capsule, crus cerebri, pons (ventral) to pyramids of medulla
  • 85% of fibres decussate at medulla - lateral corticospinal tract
  • Remaining fibres remain on ipsilateral side but cross over at level of their innervation (ant. white commisure) - anterior corticospinal tract

Question 4

What is the function of the rubrospinal tract?

Answer 4

• fine control of hand movements
• originates from red nucleus in midbrain, fibres decussate and descend into spinal cord

Question 5

What is the function of the tectospinal tract?

Answer 5

• coordinates head movement in relation to visual stimuli
• originates in superior colliculi of midbrain (input from optic nerve)
• neurons decussate and terminate at C-levels of spinal cord

Question 6

What is the function of the medial/lateral reticulospinal tracts?

Answer 6

• medial reticulospinal tract
  
  • facilitates voluntary movements (increases muscle tone)
  • arises from pons
• lateral reticulospinal tract
  
  • inhibits voluntary movements (decreases muscle tone)
  • arises from medulla

Question 7

What is the function of the vestibulospinal tract?

Answer 7

• control balance and posture - innervates anti-gravity muscles (e.g. arm + leg) via LMNs
• arises from vestibular nucleus, recieving input from organs of balance
• remains ipsilateral

Question 8

What are the ascending spinal tracts?

Answer 8

• Dorsal column-medial lemniscal pathway (DCML)
• anterolateral system (anterior + lateral spinothalamic)
• anterior + posterior spinocerebellar
• spinotectal

Question 9

What sensations does the DCML pathway convey?

Answer 9

Fine touch, vibration, proprioception

from peripheral nerves to primary sensory cortex via thalamus & internal capsule

Question 10

What is the course for first order neurons in the lower/upper limb in the DCML pathway?

Answer 10

• signals from upper limb (>T5) travel in fasciculus cuneatus (lateral of dorsal column), synapsing in nucleus cuneatus of medulla
• signals from lower limb (

Question 11

What is the function of the anterolateral system and of what does it consist?

Answer 11

• anterior spinothalamic tract - carries modalities of crude touch + pressure
• lateral spinothalamic tract - carries modalities of pain + temperature

Question 12

What is the course of the anterolateral (spinothalamic) tract?

Answer 12

• 1 neurons areise from sensory receptors, ascend 1-2 levels before entering spinal cord, synapsing at substantia gelatinosa
• 2 neurons immediately decussate in spinal cord forming lateral/anterior tracts
• 3 carry signals from thalamus to ipsilateral sensory cortex

Question 13

What is the function of the spinocerebellar tract(s)?

Answer 13

• unconcious sesnsation - proprioceptive info from lower and upper limbs to cerebellum
• anterior spinocerebellar tract decussates twice

Question 14

What will occur in brown-sequard syndrome?

Answer 14

• damage to all neurons on one side
• LMN no longer recieving signals from UMN - paralysis on same side below injury (spastic paralysis)
• Muscles at that level recieve no input at all - flaccid paralysis
• loss of sensation on contralateral side 1-2 segments below
• loss of sensation to ipsilateral side at level