WEEK 5-Spinal Cord, Spinal Nerves, and Spinal Injuries

Flashcards for spinal cord anatomy, spinal nerves, and spinal injuries, including spinal cord segments, meninges, and ascending/descending pathways.

Function of Spinal Cord

Carries nerve impulses to and from the brain and acts as a major reflex center.

Location of Spinal Cord

Extends from brainstem, passes through foramen magnum, ends at conus medullaris (L1 or L2).

Protection of Spinal Cord

Vertebrae, meninges, and cerebrospinal fluid (CSF).

Cauda Equina

Collection of lumbar and sacral nerve roots angling downwards below the conus medullaris.

Filum Terminale

Anchors the spinal cord to the coccyx.

Dura Mater (Spinal Cord)

Tough outer covering of the spinal cord, separated from the vertebrae by the epidural space.

Arachnoid Mater

Loose middle layer of the spinal cord meninges, separated from the dura mater by the subdural space.

Pia Mater

Delicate connective tissue clinging to the spinal cord, rich in blood vessels; contains denticulate ligaments.

Subarachnoid Space

Space between the arachnoid and pia mater, filled with CSF and blood vessels.

Number of Spinal Cord Segments

8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal.

Spinal Nerves

31 pairs; arise from fusion of dorsal and ventral roots; mixed nerves.

Dorsal Roots

Contain axons of sensory neurons, relaying sensory input; cell bodies in dorsal root ganglion.

Ventral Roots

Contain axons of motor neurons relaying motor commands.

Rami (Branches) of Spinal Nerves

Dorsal rami supply posterior trunk; ventral rami supply rest of trunk and limbs (form plexuses).

Grooves of Spinal Cord

Ventral median fissure and dorsal median fissure.

Grey Matter of Spinal Cord

Butterfly/H-shaped core consisting of cell bodies and unmyelinated axons.

Dorsal (Posterior) Horns

Receive afferent sensory input; consist entirely of interneurons.

Ventral (Anterior) Horns

Mainly cell bodies of somatic motor neurons sending axons to skeletal muscles.

Lateral Horns

Cell bodies of autonomic motor neurons innervating internal organs (thoracic and superior lumbar segments).

Grey Commissure

Connects two grey matter masses; surrounds central canal.

White Matter of Spinal Cord

Surrounds grey matter; divided into dorsal, lateral, and ventral funiculi.

Funiculi (Columns)

Dorsal, Lateral, and Ventral.

Fiber Directions in White Matter

Ascending (sensory), descending (motor), and transverse.

Decussation

Most pathways cross from one side of the CNS to the other.

Relay (Neural Pathways)

Most pathways involve a relay of two or three neurons.

Somatotopy

Nervous system is precisely mapped, fibres from specific body parts travel together.

Symmetry (Neural Pathways)

All pathways are paired symmetrically.

First-order Neurons

From receptors to spinal cord/brainstem, synapsing with second-order neurons.

Second-order Neurons

Transmit impulses to thalamus or cerebellum, where they synapse.

Third-order Neurons

Relay impulses from thalamus to somatosensory cortex (none in cerebellum).

Dorsal Column-Medial Lemniscal Pathway

Transmits impulses for fine touch, vibration, pressure, and conscious proprioception; crosses in medulla.

Spinothalamic Pathway

Primarily transmits pain and temperature impulses, also coarse touch/pressure; crosses in spinal cord.

Spinocerebellar Pathway

Conveys information about muscle/tendon stretch to cerebellum; does not cross over.

Direct (Pyramidal) Pathways

Originate in primary motor cortex; regulate fast and fine movements; decussate in medulla.

Indirect Pathways (Descending Motor)

Include brain stem motor nuclei; regulate axial muscles, coarse limb movements, head/neck/eye movements.

Reticulospinal Tract

Controls muscle tone and visceral motor functions.

Vestibulospinal Tract

Maintains balance by varying postural muscle tone.

Rubrospinal Tract

Possibly contributes to tone of distal limb flexor muscles.

Tectospinal Tract

Mediates head movements in response to visual stimuli.

Causes of Spinal Cord Injuries (SCI)

Motor vehicle crashes, falls, vascular dysfunction, infections, tumors.

Damage to Lower Motor Neurons (SCI)

Flaccid paralysis in affected muscles.

Damage to Primary Motor Cortex or Upper Motor Neuron Tracts (SCI)

Spastic paralysis below the lesion.