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Unformatted text preview: Chapter 12 Central Nervous System I Brain II Higher Mental Functions III Protection of the Brain IV Spinal Cord V Diagnostic Procedures for Assessing CNS Dysfunction VI Developmental Aspects Brain A. General Info a. Cephalization elaboration of anterior (rostral) portion of CNS i. Increase in number of neurons in the head b. Brain size = average mass is 3 - 4 pounds B. Embryonic Development a. Development of neural tube from embryonic ectoderm ( fig 12.1 ) i. Neural plate ectoderm (dorsal surface) thickens along dorsal midline axis of embryo at about 3 weeks ii. Neural folds plate invaginates to form neural groove iii. Neural crest groups of folds give rise to neurons in ganglia iv. Neural tube groove deepens, superior edges of folds fuse 1. Will separate from ectoderm and sinks lower v. Steps in brain development ( fig 12.2 ) 1. Immediately 3 primary brain vesicles form from neural tube by expansion of anterior end & constrictions to mark off areas a. Prosencephalon (forebrain) b. Mesencephalon (midbrain) c. Rhombencephalon (hindbrain) 2. 5 weeks Secondary brain vesicles a. Telencephalon endbrain from forebrain i. Forms mouse ears on sides = celebral hemispheres of cerebrum b. Diencephalon interbrain from forebrain i. Forms hypothalamus, thalamus & epithalamus c. Mesencephalon stays the same i. Brain stem, midbrain d. Metencephalon afterbrain from hindbrain i. Brain stem, pons and cerebellum e. Myelencephalon spinal brain from hindbrain i. Brain stem, medulla oblongata vi. Tube stays full of fluid and becomes ventricles of brain b. Effects of space restriction on brain development ( fig 12.3 ) i. Brain grows faster than skull ii. 2 major flexures: midbrain & cervical flexures 1. Bend toward forebrain toward the brain stem 2. Restricted space makes cerebral hemispheres grow in horseshoe shape (posteriorly & laterally) 3. Grow over diencephalon and midbrain 4. More folds and creases to fills space (convolutions) to increase surface area, more neurons in space C. Regions and Organization ( fig 12.3 ) a. 4 main parts i. Cerebral Hemispheres ii. Diencephalon iii. Brain stem midbrain, pons and medulla iv. Cerebellum b. Basic Pattern ( fig 12.4 ) i. Central cavity surrounded by gray matter core external white (myelinated) cavity ii. Brain has additional regions of gray matter not in spinal cord iii. Cortex- outer layer (bark) surrounds cerebellum and cerebral hemispheres D. Ventricles ( fig 12.5 ) a. Arise from expansion of lumen of embryonic neural tube b. Lined with ependymal cells and cerebropspinal fluid c. Lateral ventricles i. Large C-shaped chamber, 1 in each hemisphere d. Septum pellucidum i. Thin membrane that separates lateral ventricles e. Third ventricle narrow, in diencephalon i. Communications with lateral via interventricular foramen f. Fourth ventricle i. Connected via cerebral aqueduct ii. Lies hindbrain, dorsal to pons and superior medulla iii. Continuous with central canal of spinal cord inferiorly...
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This note was uploaded on 07/10/2011 for the course BIO 2113 taught by Professor Gantt during the Spring '11 term at Chatt Tech.
- Spring '11