THE SPINAL CORD PRE- SUMMARIZED NOTES, Study notes of Nursing

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ANATOMY, PHYSIOLOGY &

PATHOLOGY

NOTES OF THE NERVOUS SYSTEM

AND SPECIAL SENSES

FOURTH EDITION

THE SPINAL CORD PRE- SUMMARIZED NOTES

General Info:

 Extends from Foramen Magnum

 Resides in the vertebral canal

 Bathed in cerebrospinal fluid

 Terminates at the ‘conus medullaris’ (cone of medulla) – approx

L1 in adults.

 Transmits Motor Information Distally from the brain

 Transmits Sensory Information back up to the brain

 Emits spinal nerves at the level of each vertebrae.

Cauda Equina:

 Nerve rootlets of lower-lumbar & sacral regions extend further

down vertebral canal.

Filum Terminale:

 Connective Tissue anchors Cauda Equina to the base of

vertebral canal.

Internal Structure:  Grey Matter: o All neuronal cell bodies o 2 Dorsal Horns  Nerve cells that receive sensory information from body  Via the dorsal root fibres. o 2 Ventral Horns  Contain motor nerve cells  Cell axons leave through ventral root fibres. o Lateral Horns:  Present in thoracic & upper lumbar regions  Autonomic motor nerves from sympathetic nervous system  Exit spinal cord through the ventral roots  White Matter: o Ascending and descending fibre tracts. External Structure:  Spinal Nerves: o Merging of the Dorsal & Ventral root fibres o Carry mixed sensory & motor info to relevant body area  Branches of Spinal Nerves: o Ventral Rami: “ventral branch” o Dorsal Rami: “dorsal branch”  Sympathetic Chain  Sympathetic Ganglia:

Information Pathways: Central → Peripheral

Somatic:  Afferent (Sensory Info) o Receptor cells in periphery o Info conveyed along peripheral axon → Soma (in dorsal root ganglion) o Info conveyed along proximal axon → spinal cord (CNS) o Info → ascending fibres (white matter) → brain for processing  Efferent (Skeletal Muscle) o Neuronal cell bodies in ventral horn of grey matter. o Cell axon leaves spinal cord through ventral root → spinal nerve o Axon flows out of Ventral Rami o Directly innervates muscle @ neuromuscular junction Visceral:  Afferent (Sensory Info) o Receptors in viscera o Info conveyed along peripheral axon → Soma (in dorsal root ganglion) o Info conveyed along proximal axon → spinal cord (CNS) o Info → ascending fibres (white matter) → brain for processing  Efferent (Smooth Muscle) o Neuronal cell bodies in lateral horn of grey matter. o Cell axon leaves spinal cord through ventral root → spinal nerve o Axon flows out of Ventral Rami o Axon synapses with peripheral ganglia o Peripheral ganglia innervates internal viscera:  smooth muscle/glandular tissue/cardiac muscle