1. The CNS Part II pg

2. Protection of the Brain
Objectives
Describe how the meninges, cerebrospinal fluid, and the blood brain barrier protect the CNS.
Explain how Cerebrospinal fluid is formed, and describe its circulatory pathway

3. Meninges Cover and protect the CNS
Protect blood vessels and enclose venous sinuses
Contain Cerebrospinal fluid
Form partitions in the skull
Superficial to Deep: Dura Mater, Arachnoid Mater, Pia Mater

4. Dura Mater (tough mother)
Strongest Meninx
Fibrous bilayer:
Periosteal layer (absent in spinal cord)
Deeper meningeal layer
Fused together except in dural venous sinuses
Dural Septa
Falx Cerebri, Falx Cerebelli, Tentorium Cerebelli

5. Arachnoid Mater Middle Meninx Loose covering Does not dip into sulci
Subdural Space
Subarachnoid space
arachnoid villi

6. Pia Mater (gentle mother)
delicate highly vascularized tissue
only meninx that clings to brain tissue
Pia Mater (gentle mother)

7. Cerebrospinal fluid (CSF)
Suspends CNS
Reduces brain weight be 97%
Protects CNS from trauma
Similar to blood plasma, but less protein and different ion concentrations
Choroid plexuses

8. CSF circulation

9. Blood Brain Barrier Maintains stable environment for brain
bloodborne substances must pass through three layers to reach the fragile neurons
endothelium of capillary wall
thick basal lamina surrounding each capillary
bulbous feet of the astrocytes
missing in places
underdeveloped in newborns and younger

10. Traumatic Brain Injuries
Leading cause of accidental death in north america
coup, countrecoup
Concussion
Contusion
Subdural/Subarachnoid hemorrhage
cerebral edema

11. Cerebrovascular Accidents
3rd leading cause of death in N.A.
Most common Nervous system disorder
Ischemic strokes
Hemorrhagic strokes
TIA’s

12. Degenerative Brain Disorders
Alzheimer’s Disease
Parkinson’s Disease
Huntington’s Disease

13. Check Your Understanding
pg 464

14. The Spinal Cord
Describe the gross and microscopic structure of the spinal cord.
list the major spinal cord tracts, and classify each as a motor or sensory tract

15. Gross Anatomy and Protection
Foramen Magnum to L1-L2 Vertebrae level
Major Reflex Center
Composed of Ascending and Descending tracts
Protected by bone, meninges, and CSF
Epidural space, meninges extend to S2.
Conus Medullaris, Cuada Equina, Filum terminale, denticulate ligaments.
31 Spinal nerves
Cervical and Lumbar Enlargements

16. Cross Sectional Anatomy

17. Gray Matter and Spinal Roots
Mirror image lateral gray masses
gray commissure
posterior horns
anterior horns
lateral horns
Ventral roots
Dorsal roots
Dorsal root ganglion
4 zones
somatic sensory, visceral sensory, visceral motor, somatic motor

18. Spinal Cord White Matter
Ascending
Descending
Transverse

19. Neuronal Pathways
All spinal tracts are part of multineuron pathways that connect the brain to the body’s periphery
4 key generalizations
Decussation
Relay
Somatotopy
Symmetry

20. Ascending Pathways to the Brain
First order neurons
Second order neurons
Third order neurons

21. Ascending Pathways to the Brain
Dorsal Column Medial Lemniscal pathways
Spinothalamic pathways
Spinocerebellar pathways

22. Descending Pathways
Upper Motor Neurons
Lower Motor Neurons

23. Descending Pathways Direct (Pyramidal) Pathways
Originate from neurons in the pre central gyro
impulses are sent through the brain stem via large pyramidal (corticospinal) tracts
No synapse until ventral horn motor neurons

24. Descending Pathways Indirect Pathways all other motor pathways
complex, multi synaptic
control axial muscles, coarse limb movements, head, neck, and eye movements
reticulospinal and vestibulospinal tracts maintain balance, rubrospinal tracts control flexor muscles, tectospinal/superior colliculi mediate head movements in response to visual stimuli

25. Spinal cord disorders Spinal cord trauma Poliomyelitis
Flaccid Paralysis
Spastic Paralysis
Poliomyelitis
Amyotrophic Lateral Sclerosis

26. Study Guide
AandPonline.com

27. Check your understanding
page 473