Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings 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)

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Protection of the Central Nervous System (P. 249) Figure 7.17a

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings 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 skull  Meningeal layer — outer covering of brain  Folds inward in several areas

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Meninges  Arachnoid mater  Middle layer  Web-like  Pia mater  Internal layer  Clings to the surface of the brain

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Meninges Figure 7.17b

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Meningitis  Inflammation of meninges  Threat to brain because bacteria/viruses may spread into CNS tissue  Encephalitis = brain inflammation

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings 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

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Hydrocephalus in a Newborn Figure 7.19

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings 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 brain & spinal cord  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

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Figure 7.18a–b Ventricles and Location of the Cerebrospinal Fluid

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Ventricles and Location of the Cerebrospinal Fluid (P. 250) Figure 7.18c

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings 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)

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Blood-Brain Barrier Continued...  CanNOT pass through:  Metabolic Wastes (urea, toxins, proteins, most drugs)  Nonessential Amino Acids  Potassium Ions

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings 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

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings 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  Transient Ischemic Attack (TIA)  Temporary (5 – 50 minutes) brain ischemia (restriction of blood flow)  “Incomplete Stroke”

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings 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

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings 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

Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings 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