Chapter 9a The Central Nervous System 2013 Pearson Education Inc About This Chapter Emergent properties of neural networks Evolution of nervous system Anatomy of the central nervous system The spinal cord The brain Brain function 2013 Pearson Education Inc Emergent Properties of Neural Networks Affective behaviors are related to feeling and emotion Cognitive behaviors link to thinking 2013 Pearson Education Inc Figure 9 1a 1 of 6 Nerve net of jellyfish Nerve net Figure 9 1b 2 of 6 The flatworm nervous system has a primitive brain Primitive brain Nerve cords Figure 9 1c 3 of 6 The earthworm nervous system has a simple brain and ganglia along a nerve cord Esophagus Primitive brain Mouth Subpharyngeal ganglion Ventral nerve cord with ganglia Figure 9 1d 4 of 6 The fish forebrain is small compared to remainder of brain Forebrain Figure 9 1e 5 of 6 The goose forebrain is larger Forebrain Cerebellum Figure 9 1f 6 of 6 The human forebrain dominates the brain Forebrain Cerebellum Figure 9 2a ESSENTIALS Development of the Human Nervous System Day 20 In the 20 day embryo dorsal view neural plate cells purple migrate toward the midline Neural crest cells migrate with the neural plate cells Neural crest Neural plate Figure 9 2b ESSENTIALS Development of the Human Nervous System Day 23 By day 23 of embryonic development neural tube formation is almost complete Anterior opening of neural tube Neural crest becomes peripheral nervous system Dorsal body surface Posterior opening of neural tube Neural tube becomes CNS Figure 9 2c ESSENTIALS Development of the Human Nervous System 4 Weeks A 4 week human embryo showing the anterior end of the neural tube which has specialized into three brain regions Forebrain Midbrain Hindbrain Spinal cord Lumen of neural tube Figure 9 2d ESSENTIALS Development of the Human Nervous System 6 Weeks At 6 weeks the neural tube has differentiated into the brain regions present at birth The central cavity lumen shown in the cross section will become the ventricles of the brain see Fig 9 4 Hindbrain Medulla oblongata Cerebellum and Pons Midbrain Forebrain Diencephalon Cerebrum Diencephalon Cerebrum Medulla oblongata Spinal cord Eye Midbrain Figure 9 2e ESSENTIALS Development of the Human Nervous System 11 Weeks By 11 weeks of embryonic development the growth of the cerebrum is noticeably more rapid than that of the other divisions of the brain Cerebrum Diencephalon Midbrain Cerebellum Pons Medulla oblongata Spinal cord Figure 9 2f ESSENTIALS Development of the Human Nervous System 40 Weeks At birth the cerebrum has covered most of the other brain regions Its rapid growth within the rigid confines of the cranium forces it to develop a convoluted furrowed surface Cranial nerves Cerebrum Pons Cerebellum Medulla oblongata Spinal cord Figure 9 2g ESSENTIALS Development of the Human Nervous System Child The directions dorsal and ventral are different in the brain because of flexion in the neural tube during development Dorsal superior Rostral Caudal Rostral Ventral inferior Ventral anterior Dorsal posterior Caudal Figure 9 3 ANATOMY SUMMARY The Central Nervous System ANATOMY SUMMARY CNS Gray and White Matter Gray matter Unmyelinated nerve cell bodies Clusters of cell bodies in the CNS are nuclei Dendrites Axon terminals White matter Myelinated axons Axon bundles connecting CNS regions are tracts Contains very few cell bodies 2013 Pearson Education Inc Figure 9 3c ANATOMY SUMMARY The Central Nervous System Posterior View of Spinal Cord and Vertebra ANATOMY SUMMARY Central canal Gray matter White matter Spinal nerve Spinal cord Body of vertebra Pia mater Arachnoid membrane Meninges Dura mater Autonomic ganglion Spinal nerve CNS Bone and Connective Tissue Brain is encased in bony skull or cranium Spinal cord runs through vertebral column Meninges lie between bone and tissues to stabilize neural tissue and protect from bruising Dura mater hard dura Arachnoid membrane Subarachnoid space contains cerebrospinal fluid secreted by choroid plexus Pia mater tender pia 2013 Pearson Education Inc Figure 9 3 1 ANATOMY SUMMARY The Central Nervous System Posterior View of the Central Nervous System Sectional View of the Meninges of the Brain showing how they cushion and protect delicate neural tissue Cranium Cerebral hemispheres Cerebellum Cervical spinal nerves Subdural Subarachnoid space space Cranium Duramater Venous sinus Arachnoid membrane Pia mater Brain FIGURE QUESTION Moving from the cranium in name the meninges that form the boundaries of the venous sinus and the subdural and subarachnoid spaces Figure 9 3b ANATOMY SUMMARY The Central Nervous System ANATOMY SUMMARY Sectional View of the Meninges of the Brain showing how they cushion and protect delicate neural tissue Cranium Duramater Venous sinus Arachnoid membrane Pia mater Brain Subdural space Subarachnoid space Figure 9 4a ANATOMY SUMMARY Cerebrospinal Fluid The Ventricles of the Brain The lateral ventricles consist of the first and second ventricles The third and fourth ventricles extend through the brain stem and connect to the central canal that runs through the spinal cord Compare the frontal view to the cross section in Fig 9 10a Lateral ventricles Third ventricle Fourth ventricle Cerebellum Central canal Spinal cord Lateral view Frontal view Figure 9 4b d ANATOMY SUMMARY Cerebrospinal Fluid Cerebrospinal Fluid Secretion Cerebrospinal fluid is secreted into the ventricles and flows throughout the subarachnoid space where it cushions the central nervous system ANATOMY SUMMARY Cerebrospinal Fluid Reabsorption Cerebrospinal fluid is reabsorbed into the blood at fingerlike projections of the arachnoid membrane called villi Cerebrospinal fluid Arachnoid villi Choroid plexus of third ventricle Pia mater Arachnoid membrane Bone of skull Dura mater Endothelial lining Blood in venous sinus Fluid movement Arachnoid villus Dura mater inner layer Subdural space Cerebral cortex Pia mater Subarachnoid space Arachnoid membrane FIGURE QUESTIONS 1 Physicians may extract a sample of cerebrospinal fluid when they suspect an infection in the brain Where is the least risky and least difficult place for them to insert a needle through the meninges See Fig 9 4b 2 The aqueduct of Sylvius is the narrow passageway between the third and fourth ventricles What happens to CSF flow if the aqueduct becomes blocked by infection or tumor a condition known as aqueductal stenosis stenos narrow On a three dimensional imaging study of the brain how would you