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 – inner Arachnoid – middle Subarachnoid 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 information Ventral 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