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Neurology aNd Special SeNSeS ` neurology—AnAtomy And Physiology Neurology aNd Special SeNSeS ` neurology—AnAtomy And Physiology SecTioN iii 507

Cranial nerve reflexes
reFleX AFFerent eFFerent
Corneal V ophthalmic (nasociliary branch) Bilateral VII (temporal branch—orbicularis
1
oculi)
Lacrimation V (loss of reflex does not preclude emotional VII
1
tears)
Jaw jerk V (sensory—muscle spindle from masseter) V (motor—masseter)
3 3
Pupillary II III
Gag IX X
Cough X X

Mastication muscles 3 muscles close jaw: Masseter, teMporalis, M’s Munch.
Medial pterygoid. 1 opens: Lateral pterygoid. Lateral Lowers (when speaking of pterygoids
All are innervated by trigeminal nerve (V ). with respect to jaw motion).
3
“It takes more muscle to keep your mouth shut.”

Spinal nerves There are 31 pairs of spinal nerves: 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal.
Nerves C1–C7 exit above the corresponding vertebrae (eg, C3 exits above the 3rd cervical vertebra).
C8 spinal nerve exits below C7 and above T1. All other nerves exit below (eg, L2 exits below the
2nd lumbar vertebra).

Spinal cord—lower In adults, spinal cord ends at lower border of Anterior
extent L1–L2 vertebrae. Subarachnoid Space (which longitudinal
ligament
contains the CSF) extends to lower border
of S2 vertebra. Lumbar puncture is usually Q L1 Posterior
longitudinal
performed between L3–L4 or L4–L5 (level of R ligament
cauda equina). Conus
Goal of lumbar puncture is to obtain sample of S medullaris
CSF without damaging spinal cord. To keep T
U
the cord alive, keep the spinal needle between V Cauda
equina
L3 and L5. W
X
Needle passes through: Y
skin Needle
fascia and fat
supraspinous ligament
interspinous ligament S1
ligamentum flavum
epidural space Filum terminale
(epidural anesthesia needle stops here)
dura mater
arachnoid mater
subarachnoid space
(CSF collection occurs here)

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