UBC NSCI 311 Lecture 3 (Spinal cord and Spinal nerves)

Advanced Neuroanatomy, Midterm 1 Content

spinal cord’s general function

all the pathways between the brainstem (and rest of brain) and the body

motor tracts go…

down (descending tracts)

sensory tracts go…

up (ascending tracts)

locomotion as a function of the spinal cord

central pattern generators, not sending the same signal all the way each time (eg. walking)

spinal cord reflex examples

• stretch/myotatic (safety net muscle contraction)

• flexor withdrawal (stepping on lego, touching something hot)

• reciprocal inhibition

how are the spinal cord segments named

• C1-C7 are named after the inferior vertebra

• T1-T12 , L1-L5, S1-S5 and Co are named after the superior vertebra

Why are cervical spinal segments named differently

because there are 8 cervical spinal segments, but only 7 cervical vertebrae

where do the spinal nerves exit the spine

intervertebral foramen

brachial plexus

cervical enlargement, innervates upper limbs

lumbar plexus

lumbosacral enlargement, innervates lower limbs

where is the brachial plexus

~C5-T1

where is the lumbar plexus

~L1-S2/S3

when does the spine start growing faster than the spinal cord

3 months of fetal development

how is the spinal cord anchored to the spinal column

extension of pia mater called the filum terminale, anchored to sacrum

where does a fully developed spinal cord end in the vertebral column

the conus medullaris at the L1/L2 vertebral level

lumbar cistern

subarachnoid space below the conus medullaris in the verterbral column, filled with cerebrospinal fluid

cauda equina

remaining spinal roots and nerves in the lumbar cistern

spinal dura and arachnoid mater

surround spinal cord and roots, separating them from the vertebrae

space between dura mater and vertebrae

epidural space (real)

space between arachnoid and pia mater

subarachnoid space (real, holds CSF and vasculature)

space between dura mater and arachnoid mater

subdural space (potential)

denticulate ligaments

pia mater surrounding the spinal cord that extend between spinal nerves (triangles)

where do anterior and posterior spinal arteries branch off from

vertebral arteries just after they enter the skull

spinal cord blood supply comes from…?

two sets of arteries (anterior and posterior spinal arteries)

segmental spinal artery gives rise to

• radicular arteries

• segmental medullary arteries

what do radicular arteries do

supply spinal roots/rootlets

where are radicular arteries

enter vertebral column at every level

what do segmental medullary arteries do

reinforce anterior and posterior spinal arteries

where are segmental medullary arteries

enter at some levels of the vertebral column, the largest being the great medullary artery

what do posterior spinal arteries supply

1/3 of spinal cord (dorsal horns and stuff between them)

what does anterior spinal artery supply

2/3 of spinal cord (everything lateral and ventral of the dorsal horns)

regional landmarks of cervical spinal cord

• oval shape

• more gray matter

• 2 fasciculi

regional landmarks of thoracic spinal cord

• lateral horns

• 2 fasciculi

• round shape

regional landmarks of lumbar spinal cord

• lots of gray matter

• 1 fasciculus

• round shape

regional landmarks of sacral spinal cord

• very round shape

• small but lots of gray matter relative to white matter

what does lateral motor system control

appendicular muscles (eg. in limbs)

what does medial motor system control

axial muscles (eg. posture and balance)

what does dorsal column control

discriminative touch, vibration and conscious proprioception

what does anterolateral system control

pain and temperature and non-conscious proprioception

what do spinocerebellar tracts control

pain and temperature and non-conscious proprioception

how many thoracic nerves

12

how many thoracic vertebrae

12

how many cervical nerves

8

how many cervical vertebrae

7

how many lumbar nerves

5

how many lumbar vertebrae

5

how many sacral nerves

5

how many sacral vertebrae

1 (5 vertebrae fused)

how many coccygeal nerves

1

how many vertebrae fuse to form coccyx

1-4