Spinal Cord Flashcards
Conus Medullaris
most caudal end of the spinal cord
located at L1-2 vertebral column levels in adults
Filum Terminale
an inferior extension of the pia mater beyond the conus medullaris
anchors spinal cord to the coccyx (bone) at the very bottom of the vertebral canal
Cauda Equina
nerve fibers coming from spinal cord segments lumbar 5 to coccygeal 1 which exit the vertebral column below the conus medullaris
occupies the lumbar cistern
Lumbar Cistern
subarachnoid space inferior to the conus medullaris
spinal taps done here
Tethered Spinal Cord Syndrome
neurological disorder caused by tissue attachments that limit the movement of the spinal cord within the spinal column, resulting in low lying conus medullaris
Sulcus Limitans
longitudinal groove that extends the width of the spinal cord, dividing it into dorsal and ventral segments and separating the alar and basal plates
Spinal Cord beginning and end
begins at foramen magnum at the interface with the medulla oblongata
ends at the L1-2 vertebral level at the conus medullaris
31 spinal cord segments
Cervical Enlargement
supplies nerves to upper extremity
Lumbar Enlargement
supplies nerves to lower extremity
Spinal Cord Segment nerves
Dorsal roots - ganglia neurons are a part of PNS and send sensory info into CNS
Ventral roots - are in the CNS (don’t have ganglia) and send motor info from brain to PNS
Spinal Cord Segments
8 - cervical spinal cord segments 12 - thoracic spinal cord segments 5 - lumbar spinal cord segments 5 - sacral spinal cord segments 1 - coccygeal spinal cord segment
Segment Orientation
Dorsal - receives sensory input –> afferent
Ventral - motor output –> efferent
Posterior Horn
contains sensory interneurons of the ascending sensory tracts
Intermediate Gray Matter
contains neurons that are primarily involved with activity of the autonomic nervous system (unconscious control of body’s systems)
Anterior Horn
contains neurons that supply motor signals to skeletal muscles
Lissauer’s tract
in posterior horn
made up of both myelinated and unmyelinated axon fibers
convey pain, temperature and crude (light) touch info
Marginal Zone
located at the tip of the dorsal horn
relays info about pain, temp
Substantia Gelatinosa
located at the top of the dorsal horn
relays info about pain and temp
receives input from Lissauer’s tract
Nucleus Proprius
located in the ‘neck’ of the dorsal horn
relays info about proprioception (body position) and crude (light) touch
Light/crude touch
poorly localised eg pressure, tickle, itch
Fine touch
discriminative touch –> 2 point discrimination
Dorsal Nucleus of Clarke
Clarke’s nucleus
located medially at very bottom of dorsal horn
corresponds to medial part of Rexed lamina VII
relays unconscious sensory info about proprioception
only found in thoracic to lumbar spinal segments T1-L2
Interomediolateral Nucleus
located in lateral horn within Rexed lamina VII
relays motor info from the organs to and from brain, contains autonomic neurons that give rise to the sympathetic nervous system
T1-L3
Lateral Motor Neurons
located in ventral horn
relays motor info from brain to viscera and skeletal muscles of limbs
Medial Motor Neurons
located in ventral horn
relays motor info from brain to viscera and skeletal muscles of the trunk and neck
Rexed Laminae
system of ten layers of grey matter
neurons towards dorsal end involved in relaying sense info
neurons towards ventral end involved in executing movement
Lamina I
overlaps with marginal zone nucleus
sends info about pain and temp input
Lamina II
corresponds to substantia gelatinosa nucleus
relay both pai and non-noxious sensation info to brain
modulate sensory input to help determine if incoming signals are painful or not
Lamina III and IV
contain the nucleus proprius
relays proprioceptive and light touch sense info
Lamina V
contains neurons that relay both noxious (pain) and visceral sensory (organ) stimuli
Lamina VI
deepest layer of the dorsal horn
relays proprioceptive signals from joints, muscle, and skin
Lamina VII
contains cells of Clarke’s nucleus, intermediolateral nucleus, and large portion of neurons of the lateral and ventral horns
relay proprioception (body position) and motor information
to from brain –> viscera
found in T1-S4
Laminae VIII and IX
represent motor neuron groups in ventral gray horn
medial portion: contains motor neurons that innervate muscles of the trunk and neck
lateral portion: contain lateral motor nucleus that innervate distal muscles of arms and legs
Lamina X
small neurons around central canal
relay motor info from one side of the spinal cord - axons decussate (cross over) here in the gray commissure
Ascending Tracts
carry sensory info up the spinal cord to areas of the brain (terminating in cerebrum/cerebellum)
Descending Tracts
carry motor info from brain down to specific levels of spinal cord (terminating on skeletal muscles)
Reflex Arc
- receptor organ
- sensory (peripheral) neuron
- spinal cord interneuron
- spinal cord motor neuron
- effector organ (muscle)
Monosynaptic Reflex Arc
reflex arc involving only one synapse
Central Pattern Generators
functional units of neurons in the spinal cord built from groups of the more simple spinal reflexes, that produce rhythmic patterned outputs without sensory feedback
eg walking, breathing
Primary Injury
- Loss of Neurons/Axons
2. Demyelination
Secondary Injury
- Loss of Neurons/Axons
- Demyelination
- Inflammation
- Reactive Oxidative Damage and the Astrocytiic Glial Scar
- Cyst Formation
