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16 Pages

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BIOL 4370

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NROB60 Study Package: Week 3 Homira Osman Week 3: Lecture May 20, 2008 Lecture Topics Lecture III Readings: Development of the Nervous System (Pages 187 to 192); Differentiation of the Midbrain; Differentiation of the Hindbrain; Differentiation of the Spinal Cord; Putting the Pieces Together; Classification (Pages 48 to 49); The Prototypical Neuron (Pages 26 to 46) Lecture Summaries [L3] - Differentiation of the Mesencephalic Vesicle: Midbrain - Very little development compared to Forebrain - Dorsal surface becomes the Tectum (roof) - Floor becomes the Tegmentum - CSF-filled space in between constricts into the Cerebral Aqueduct o The aqueduct connects rostrally with the third ventricle of the diencephalon o Because it is small and circular in cross section, the cerebral aqueduct is a good landmark for identifying the midbrain Differentiation of the Midbrain Tectum - Differentiates into superior colliculus and inferior colliculus - Superior colliculus receives direct input from the eye o Controls eye movement o Cranial nerves III and IV NROB60 Study Package: Week 3 Homira Osman - Inferior colliculus receives direct input from the ear - Relay station en route to the thalamus Tegmentum - Most colourful regions - Contains both the substantia nigra (black substance) and the red nucleus o Both are involved in control of voluntary movement - Other cell groups have axons that project widely throughout CNS o Regulate consciousness, mood, pleasure and pain Structure-Function Relationships of the Midbrain - Diverse - Conduit for information passing from the spinal cord to the forebrain and vice versa - Axons descending from cerebral cortex to brain stem and spinal cord (ex: corticospinal tract) - Damage results in loss of movement to opposite side - Contribute to: o Sensory systems, o Control of movement o Several other functions Differentiation of the Rostral Hindbrain - Hindbrain differentiates into three structures: o Cerebellum Develops from rostral part of hindbrain o Pons Develops from rostral part of hindbrain o Medulla oblongata Develops from caudal part of hindbrain Called Medulla - CSF-filled tube becomes the fourth ventricle - Continuous with cerebral aqueduct of the midbrain - The rostral hindbrain differentiates into the cerebellum and pons - The cerebellum is formed by the growth and fusion of the rhombic lips - The CSF-filled space at the core of the hindbrain is the fourth ventricle NROB60 Study Package: Week 3 Homira Osman Differentiation of the Caudal Hindbrain - Ventral and lateral walls swell o Leaves the roof covered by a thin layer of non-neuronal cells o Ventral surface runs a major white matter system o Appear triangular in shape o Called the medullary pyramids - The caudal hindbrain differentiates into the medulla - The medullary pyramids are bundles of axons coursing caudally toward the spinal cord - The CSF-filled space at the core of the medulla is the fourth ventricle Structure-Function Relationships of the Hindbrain - Important conduit for information passing from the spinal cord to the forebrain and vice versa - Contribute to: o Processing of sensory information, o Control of voluntary movement o Regulation of ANS - Cerebellum little brain o Important movement control center o Receives massive axonal inputs from spinal cord and pons Spinal cord: position in space Pons: information regarding goals of intended movement from cerebral cortex NROB60 Study Package: Week 3 Homira Osman o Cerebellum compares these inputs and calculates sequences of movements to reach goals o Damage results in uncoordinated and inaccurate movements - Pons: The Switchboard o > 90% of descending axons that pass through the midbrain from the cerebral cortex synapse on neurons in the pons o Pontine cells relay this information to cerebellum on opposite side - Medulla: o Contains Medullary Pyramids o 10% that do not go through Pons travel caudally and enter the medullary pyramids o Contains neurons that perform many different sensory and motor functions o Synapse sites for auditory axons to the cochlear nuclei o In turn projects axons to many different structures including tectum of midbrain (inferior colliculus) o Contains nuclei for touch and taste o Relay information from spinal cord to thalamus o Relay motor information regarding movement of tongue (CN XII) - The Pyramidal Decussation o Decussation = movement of axons from one side to the other o Pyramidial decussation involves the pyramidal tract crossing from one side of the midline to the other near where the medulla joins with the spinal cord o Explains why cortex from one side of the brain controls movement on the opposite side of the body
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