Dermatomes overlap Skin Peripheral nerve Dorsal root Ventral

Dermatomes overlap Skin Peripheral nerve Dorsal root Ventral root

Dermatomes overlap Skin Peripheral nerve Dorsal root Ventral root

Dorsal column Dorsal root ganglion Lateral column “Anterolateral” column Ventral column Dorsal root Spinal nerve Dorsal horn Intermediate zone Ventral horn Ventral root

Anterolateral system Dorsal columnmedial lemniscal system Meissner’s corpuscle Bare nerve ending Merkel’s receptor Pacinian corpuscle

Reminder: Rexed’s laminae

Somatotopic organization of the dorsal columns Rostral Demyelination Caudal

Lamina 5

Lamina 5

Spinal Hemisection Ipsilateral loss of touch… Contralateral loss of pain… (2 -3 segments caudal to injury) Mechanoreceptor Nociceptor

Syringomyelia Site of lesion • Bilateral loss of pain & thermal senses • Preservation of mechanosensations

Somatotopy of spinal paths

Anterolateral system Postcentral gyrus / Insular/ Cingulate cortex Also: • Reticular formation • Superior colliculus (mesencephalon) Spinal commissure Dorsal columnmedial lemniscal system Postcentral gyrus / 1° SScx Internal Pain, arcuate thermal, fibers itch Dorsal horn Dorsal column nuclei Mechano…

Somatic Sensory Thalamus Medial dorsal Ventral posterior medial-VPM (trigem) Ventral posterior lateral-VPL (spinal) Touch Ventral posterior (VMpo) Pain

Leg area Arm area Face area Internal capsule Ventral posterior nucleus