Spinal Cord

Location Function

Meninges (for CNS)

Meninx Primitiva – protective covering in fish

Leptomeninx, - thin inner membrane in higher vertebrates

Dura Mater – outer thick membrane in higher vertebrates

Meninges

Leptomeninx splits in mammals only, into:Pia mater – innerArachnoid – middleSubarachnoid space contains Cerebrospinal

fluid

Key Points

Why is meningitis a life-threatening disease?

Spinal cord

Gray matter contains nuclei, nonmyelinated neurons, at center of spinal cord

White matter contains myelinated ascending and descending tracts, at peripheral spinal cord

Spinal Nerves

Show metamerism & carry information to & from spinal cord

Cauda equina – caudal-most set of spinal nerves resembling a horse’s tail

Spinal Nerves

Occipitospinal nerves– In anamniotes– Innervate hypobranchial muscles– Motor only

Spinal Nerves

Spinal nerves are mixed nerves with:Dorsal root carrying sensory informationVentral root carrying motor information

Key Points

Are spinal nerves CNS or PNS?

Spinal Nerves

Spinal nerves branch into dorsal branch supplying epaxial muscles called Dorsal Ramus

And ventral branch supplying hypaxial muscles called Ventral Ramus

Spinal Nerves

Adjacent spinal nerves for networks or plexuses when supplying limbs