1. Protection of the Central Nervous System
Enclosing it in bone
Skull & vertebral column
Enclosing it in membranes
Meninges = connective tissue membranes that cover & protect CNS structures
Watery cushion
Cerebrospinal fluid (CSF)

2. Protection of the Central Nervous System (P. 249)
Figure 7.17a

3. Meninges
From most superficial to deepest: dura mater, arachnoid mater, pia mater
Dura mater
Double-layered external covering
Periosteal layer—attached to inner surface of the skull
Meningeal layer—outer covering of the brain
Folds inward in several areas

4. Meninges Arachnoid mater Middle layer Web-like Pia mater
Internal layer
Clings to the surface of the brain

5. Meninges
Figure 7.17b

6. The subarachnoid space is filled with CSF;
And arachnoid villi= specialized projections

7. Meningitis Inflammation of meninges
Threat to brain because bacteria/viruses may spread into CNS tissue
Encephalitis = brain inflammation

8. Hydrocephalus “Water on the Brain”
CSF accumulates & exerts pressure on brain because something obstructs its drainage
In babies, brain size increases
In adults, brain damage may occur because nervous tissue is crushed

9. Hydrocephalus in a Newborn
Figure 7.19

10. Cerebrospinal Fluid (CSF)
Similar to blood plasma composition (make-up)
Different because contains less protein, more vitamin C, & ion composition differs
Formed by the choroid plexus continually
Forms a watery cushion to protect the brain
Circulated in arachnoid space, ventricles, and central canal of the spinal cord
Drains at a constant rate to maintain pressure & volume
Lumbar spinal tap is used to get a sample of CSF

11. Some of this fluid continues down the spinal cord.
Cerebral Spinal Fluid
Circluates from the 2 lateral ventricles into the third ventricle, then through the cerebral aqueduct of the mid brain and into the fourth ventricle.
Some of this fluid continues down the spinal cord.
Ordinarily it forms and drains at a constant rate to maintain pressure and volume.

12. Ventricles and Location of the Cerebrospinal Fluid
Figure 7.18a–b

13. Ventricles and Location of the Cerebrospinal Fluid (P. 250)
Figure 7.18c

14. Blood-Brain Barrier Keeps neurons separated from bloodborne substances
Includes the least permeable capillaries of the body
Can pass through:
Water
Glucose
Essential Amino Acids
Fats
Respiratory Gases
Fat-Soluble Molecules (alcohol, nicotine, anesthesia)

15. Blood-Brain Barrier Continued . . .
CanNOT pass through:
Metabolic Wastes (urea, toxins, proteins, most drugs)
Nonessential Amino Acids
Potassium Ions

16. Traumatic Brain Injuries
Concussion
Slight brain injury but no permanent brain damage
Contusion
Nervous tissue destruction occurs & tissue does not regenerate
Intracranial Hemorrhage
Bleeding from ruptured vessels in the brain
Cerebral Edema
Swelling of brain due to inflammatory response
May compress and kill brain tissue

17. Cerebrovascular Accident (CVA)
Commonly called a stroke
Blood circulation to brain area is blocked by blood clot or ruptured blood vessel
Brain tissue supplied with oxygen from that blood source dies
Loss of some functions or death may result

18. Transient Ischemic Attack (TIA)
Temporary (5 – 50 minutes) brain ischemia (restriction of blood flow)
“incomplete stroke”

19. Alzheimer’s Disease
Progressive degenerative brain disease that results in dementia
Memory loss, short attention span, language loss
Caused by shortage of ACh & structural changes in the brain
Drugs ease symptoms by inhibiting ACh breakdown

21. Parkinson’s Disease
Basal nuclei problem caused by degeneration of dopamine-releasing neurons
As a result, basal nuclei become overactive, causing tremors
Drug L-dopa helps alleviate symptoms
Drug deprenyl slows deterioration

22. Huntington’s Disease Genetic
Massive degeneration of basal nuclei & later the cerebral cortex
Wild, jerky, flapping movements called chorea
Treated with drugs that block dopamine’s effects