Transcript CNS - Spinal Cord

Spinal Cord
Biology 2121
Chapter 12
Gross Anatomy – Spinal
Cord
1. Embryonic Development
– Neural tube (posterior)
2. Length
– 17 inches
3. Termination
– Conus Medullaris
– L1-L2
4. Filum Terminale
5. Lumbar Enlargements
Lumbar Tap
Spinal Tap
Gross Anatomy – Spinal Cord
Gross Anatomy – Spinal Cord
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(1)
(2)
(3)
(4)
(5)
(6)
intervertebral discs,
vertebral bodies
dura mater
epidural space
spinal cord
subdural space.
Spinal Cord and the Spinal Nerves
(1) Somatic Sensory
Neurons
– ‘Enter’ Dorsal root
ganglion
– Dorsal Horn
(2) Somatic Motor
Neurons
– ‘Exit’ Anterior or Ventral
Horn
Formation of the Spinal Nerves
(1) Ventral and Dorsal
Root form Spinal
Nerve
(2) 1-2 cm in length
• (3) 31 pairs
Spinal Nerves
Visceral vs. Somatic Nerves
(1) Somatic
– ‘body’
– Serving organs with
skeletal muscle
(2) Visceral
– Involuntary organs
– Smooth muscle
Blue – Sensory (Afferent) Somatic
Red – Motor (Efferent) – Somatic
Yellow – Motor – Visceral
Connecting the Spinal Nerves to the
CNS
(1) White Matter
– Cerebrum must
communicate with
spinal cord and
peripheral nerves
– White Columns
(2) Fiber tracts
– Ascending
– Descending
Multi-Synaptic
(1) Neuronal Composition
– First-Order
– Second – Order
– Third – Order
(2) Ascending Pathway send messages up to
the brain and Descending pathways send
messages from the brain to the spinal
cord.
Ascending Pathways
• Nonspecific
– Anteriolateral pathways
– Pain, temperature, course
touch
• Specific
– “medial lemniscal system”
– Precise, straight-through
transmissions
• Spinocerebellar Pathway
Leminiscal Pathway
First – Order : Sensory receptors
through the Dorsal Horns to the
Medulla Oblongata
Second – Order: Medulla
Oblongata to the Thalamus
Third- Order: Thalamus to the
Somatosensory Cortex
Spinothalamic Pathway
First-Order: Receptors to Dorsal
Horn
Second-Order: Dorsal Horn to
Thalamus
Third-Order: Thalamus to
Somatosensory Cortex
Descending Pathways
• Direct
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Pyramidal Tracts
Decussation (medulla)
No synapses
Fast, skilled motor
movements (skeletal muscles)
• Indirect
– all except the pyramidal
pathway
– Multisynaptic
– Axial muscles (balance,
posture); coarse limb
movement; head, neck and
eye movements
Spinal Cord Trauma and Disorders
(1) Polio
(2) Amyotropic
Lateral
Sclerosis
Spina Bifida
Development
(1) Three-weeks
– Ecotderm layer forms neural plate
– Neural Tube develops (4th week)
(2) Formation of the Brain and Spinal Cord
– Anterior (brain)
– Posterior (spinal cord)
Development
(3) Primary brain vesicles give rise to
secondary brain vesicles
– Week 5
– Formation of the cerebrum, midbrain and brain
stem
(4) Week 26
– Continued growth of the cerebrum causes
convolutions to be evident