Protection of the Central Nervous System Slide 7.44a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Bone Membranes (meninges) Cerebrospinal fluid Blood brain barrier Figure 7.16a

1. Meninges A. Dura mater: outermost layer double-layered: periosteal layer attached to skull (outer) and menigeal layer covers brain and continues to spinal cord

b. Arachnoid Mater Slide 7.45b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Middle layer  Web-like  subarachnoid space attaches to pia mater  space is filled with cerebrospinal fluid

c. Pia mater  Internal layer (delicate)  Clings to the surface of the brain

2. Cerebrospinal Fluid Slide 7.46 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Similar to blood plasma composition  Formed by the choroid plexus  Forms a watery cushion to protect the brain and spinal cord  Circulated in arachnoid space, ventricles, and central canal of the spinal cord

Ventricles and Location of the Cerebrospinal Fluid Slide 7.47a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 7.17a

Ventricles and Location of the Cerebrospinal Fluid Slide 7.47b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 7.17b

3. Blood Brain Barrier Must remain constant Composed of least permeable capillaries Bound by tight junctions Only H 2 O, glucose, and amino acids pass through capillaries Excludes many potentially harmful substances (urea, most drugs)  Useless against some substances: fats and fat soluble molecules, respiratory gases, alcohol, nicotine and anesthesia

Traumatic Brain Injuries Slide 7.49 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Concussion  Slight brain injury  No permanent brain damage  Contusion  Nervous tissue destruction occurs  Nervous tissue does not regenerate  Cerebral edema  Swelling from the inflammatory response  May compress and kill brain tissue