Spinal Cord Flashcards
Conus Medullaris
End tip of the spinal cord
Level of conus medullaris in newborns and adults
Newborns: L3/L4 Adults: L1/L2
Areas of the spinal cord that are enlarged
Cervical (5-T1) , Lumbosacral (L1-L3) : limbs need more innervation
Ventral median fissure
Wide groove on the anterior midline
Dorsal median sulcus
Narrow groove on the posterior midline
Order of nerves from medial to lateral
Spinal cord, rootlet, root, spinal nerve, rami
White matter: 3 tracts
Dorsal, spinothalamic, Lateral corticopinal (pyramid) tracts
Dorsal column of white matter
- Primary ascending fibers
- Transmits ipsilateral fine touch/proprioception
- Subsets: Fasciculus gracilis/cuneatus
- Synapses w/ 2º fibers within the nuclei of medulla, then decussates
Ascending fibers
Sensory fibers
Fasciculus gracilis
Subset of dorsal column that carries lower body info
Fasciculus cuneatus
- Subset of dorsal column, carries upper body information
- Only found in the upper body
Decussation
Crossing over the midline
Spinothalamic tract
- in both lateral and ventral columns
- 2º ascending fibers (synpasing in dorsal gray horn)
- Lateral tract transmits Contralateral pain/temp
- Anterior tract transmits crude touch/pressure
- synapse with 3º in thalamus
Clinical: unilateral lesions of spinothalamic tract cause what?
Contralateral anesthesia, 1-2 segments below lesion
Lateral Corticospinal (pyramidal tract)
- Lateral column of white matter
- Formed by descending upper motor neurons
- Synapse with lower motor neurons in ventral gray horn for distribution to keletal muscle for voluntary motor control
Descending neurons
Motor neurons
Upper motor neurons
- Originate in the motor cortices of the Cerebrum
- decussate in medulla at the pyramids
- Run contralaterally in spinal cord
- Contralateral motor control
Lower motor neurons
- Synapse with UMN in ventral gray horn
- Connect UMN with muscles for voluntary muscle control
Clinical: what happens if there is a lesion in the lateral cortiocospinal tract?
Paralysis below the level of damage
Gray matter: neurons and portions
- Primarily formed by neural cell bodies, axon terminal branches, dendrites
- Ventral, lateral, dorsal, horns and gray commissure
Ventral horns of gray matter
- Found in all levels of the spinal cord
- Contains Somatic motor neurons
Somatic
voluntary, skeletal muscle
Efferent
Going away (exiting) the CNS to motor neurons
General Somatic efferents
- aka Lower motor neurons
- Innervate skeletal muscles
Dorsal Horns of gray matter
- Found in all levels of spinal cord
- contains central processes of sensory neuron axons and interneurons
General Somatic Afferents
- aks sensory neuron axons
- Take sensory info to the brain
Interneurons
- aka Ia
- Integrate various sensory and motor neurons
Lateral horns of gray matter
- Found only in spinal cord segments T1 to L2
- Contains preganglionic sympathetic neuron cell bodies
General Visceral Efferents
- Relays information for the preganglionic (autonomic nervous system) sympathetic (excitement neurons) neuron bodies
- Goes to the involuntary muscles
Gray Commissure
- Found at all levels of the spinal cord
- Connects the left and righ gray columns
- Area of decussation
Central Canal
- Continuous with the 4th ventrical of the brain
- Contains cerebrospinal fluid
- May be occluded in aged or diseased spinal cord