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CENTRAL NERVOUS SYSTEM, SPINAL
NERVES, AND CRANIAL NERVES
CHAPTER 10
SPINAL CORD STRUCTURE:
PROTECTION AND COVERINGS
• Meninges – 3 layers of
con tissue around spinal
cord and brain
– Dura mater – extends to
2nd sacral disc
– Arachnoid mater
– Pia mater
– Subarachnoid space –
where cerebrospinal
fluid circulates
Gross anatomy of the spinal cord
•
•
Lower part of brain to 2nd lumbar
vertebrae
Cauda equina
– Nerves of lumbar, sacral, coccygeal
regions of the spinal cord
•
Cervical enlargement
– Nerves supply upper limbs
•
Lumbar enlargement
– Lower limbs
•
•
Each of 31 spinal segments give rise
to a pair of spinal nerves
Anterior median fissure and posterior
median sulcus divide the spinal cord
into right and left halves
– White matters surrounds H shaped gray
matter
– Central canal – contains cerebrospinal
fluid
Internal structure of the spinal
cord
• Gray matter –cell bodies,
dendrites, unmyelinated
axons, axon terminals,
neuroglia
– Anterior horns – cell
bodies Somatic motor
neurons
– Posterior gray horns –
somatic and autonomic
sensory neurons
– Lateral gray horns – only in
upper lumbar, sacral,
thoracic segments; cell
bodies of autonomic motor
neurons
Continued
• White matter:
myelinated axons
– Columns – 1 or more
tracts with bundles of
axons
• Sensory (ascending) tract
• Motor (descending) tract
• Name of tract indicates
position in white matter,
where it begins and ends,
direction of impulse
• Ex: anterior spinothalamic
tract
Spinal nerves
• Roots – connect each spinal nerve to a section
of the cord
– Posterior root – contains only sensory axons
• posterior root ganglion cell bodies sensory neurons
– Anterior root – axons of somatic motor neurons
and autonomic motor neurons
– sensory and motor axon = mixed nerve
• 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1
coccygeal
Spinal nerve coverings
• Endoneurium –
individual axon
• Fascicles – groups of
axons wrapped in
perneurium
• Epineurium – covering
over entire nerve fuses
with dura mater of
spinal meninges
Plexuses
• passes through it intervertebral
foramen it divides into branches
• form networks by joining with
adjacent nerves = plexuses
– From here nerves bearing names of
the region they supply or course
they take
• Cervical – skin, muscles of
posterior head, upper shoulder,
diaphragm
• Brachial – upper limbs, several
neck and shoulder muscles
• Lumbar – abdominal wall,
external genitalia, parts of lower
limbs
• Sacral – buttocks, perineum,
lower limbs
Intercoastal nerves
• T2-T11 do not form
plexuses
• extend directly to what
they supply;
– muscles between ribs,
abdominal muscles, skin
of chest and back
Spinal cord functions
• White matter
– Highway for nerve impulse
• Gray matter
– Receives, integrates incoming and outgoing info
– Spinal Reflexes
• Inborn
• Learned
Reflex arc: patellar reflex
Major parts and protective coverings
of brain
•
•
•
•
•
Brain stem
Diencephalon
Cerebrum
Cerebellum
Protected by cranium
and cranial meninges
Brian blood supply and the bloodbrain barrier
• Needs 20% body’s oxygen supply
• Neurons with 0 oxygen for 4min or more
permanently damaged
• BBB
– Protects brain cells from harmful substances,
pathogens by preventing passage from blood to
brain tissue
– Consists Of:
• Tightly sealed blood capillaries
Cerebrospinal fluid (CSF)
• clear
• Carries O2, glucose, other need chemicals from
blood – neurons, neuroglia and removes wastes,
toxics
• moves trough subarachnoid space and ventricles
– 2 lateral, 3rd, 4th
• Made by choroid plexuses
• Reabsorbed into blood by arachanoid villi
• Drains into superior sagittal sinus
Meninges and ventricles
Brain stem
• Medulla oblongata
– Wm: sensory and motor tracts between spinal
cord and other parts of brain
– Nuclei (gm)
•
•
•
•
•
Cardiovascular center
Medullary rhythmicity area
Touch and vibration
Reflexes
5 pairs of cranial nerves
Pons
• Wm
– Connects parts of the brain to each other
• Nuclei (GM)
– Signal for volunatary movements that originate in
the cerebral cortex are relayed to the cerebellum
– Help control breathing
– Association with cranial nerves 5-8
Inferior aspect of the brain
Midbrain
• Connects pons to the diencephalon
• Wm
– Cerebral peduncles
• MN from cerebrum – spinal cord, medulla, pons
• SN medulla – thalamus
– Nuclei (GM)
• Substantia nigra
• Right/left red nuclei – axons from cerebrum and cerebellum
synapse
• Association CN 3-4
• Superior colliculi
• Inferior colliculli
Midbrain
Reticular formation
• Small clusters of gray matter mixed with white
matter
• RAS
– Sensory info upward to cerebral cortex =
consciousness
– Motor – regulating muscle tone