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WSU BIOLOGY 315 - The Brain
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Lecture 13Outline of Last Lecture I. MyelinII. NervesIII. Organization of the CNSIV. Development of the CNSV. Development of the BrainOutline of Current LectureI. Cross-Sections through the braina. Generalb. Myelencephalonc. Metencephalond. Mesencephalone. Diencephalonf. Telencephalon Current LectureI. Cross-Sections through the braina. The general plan and the spinal cordi. the alar and basal plates of cell bodies each become subdivided into somatic and visceral zones 1. these are the 4 sections introduced in the last lectureb. myelencephalon (medulla oblongata)i. lowest part of the brain stemii. the brain stem is involved with the innervation of head, plus other functionsiii. the roof plate over its central cavity expands greatly so that the right and left halves of the medulla are spread apart dorsallyiv. this expanded roof plate is made of non-nervous ependymal cells, and contributes to a structure called the choroid plexus1. the choroid plexus makes the cerebrospinal fluidv. the myelencephalon is the part of the brain that most closely resembles the spinal cordvi. function: the medulla oblongata attaches to many of the nerves that supply the head and pharynx vii. divisions of gray matter that develop into the alar and basal plates:1. alar-plate derivatives in medulla oblongataa. somatic sensory region: the interneurons in this region receive input from sensory neurons carrying somatic sensations from the head b. visceral sensory region: interneurons here receive sensory fibers from visceral structures in the head BIOL_315 1nd Editionc. in both these sensory regions, the interneurons begin the processing the sensory information 2. basal-plate derivatives in medulla oblongataa. visceral motor region: here lie the cell bodies of motor neurons that innervate the pharyngeal-arch musclesi. other motor neurons in this region supply smooth muscle, cardiac muscle, and glands throughout the bodyb. somatic motor region: here are cell bodies of motor neurons that innervate typical skeletal muscles in the head, namely the musclesof the tongue 3. these 4 deep regions of gray matter = nuclei of the cranial nervesviii. in developing brain, interneurons migrate outward from the alar and basal plates into the surrounding white matter  additional brain nucleiix. outwardly migrated gray matter performs complex, information-processing functions that serve the entire body x. the more peripheral brain nuclei include the reticular formation and the inferior olivary nucleic. Metencephaloni. Has an expanded choroid plexus in its roof for making cerebrospinal fluidii. Here the motor and sensory nuclei of the cranial nerves function much the same as in the medulla oblongata iii. Also experiences an outward experiences an outward migration of some gray matter to form nuclei that control complex, whole-body functionsiv. Two extensive groups of neurons have migrated outward from the alar plate: the cells of the cerebellum and the pontine nucleiv. Both the cerebellum and pons help coordinate the complex movements of our bodyvi. Contains a part of the reticular formation (like the myelencphalon)d. Mesencephalon (midbrain)i. Top part of the brain stemii. The 4 basic divisions of the gray matter are less obvious and less distinct because ALL the gray matter in the higher brain performs complex information-processingfunctions1. Alar-plate derivatives in the midbrain: superior colliculus, inferior colliculusa. The colliculi are masses of gray matter that have migrated dorsally from around the ventricles; the interneurons in these colliculi are involved in complex visual and auditory reflexes b. Basal-plate derivatives in the midbrain: the somatic motor neurons contract the skeletal muscles around the eye, while the visceral motor neurons move smooth musculature within the eyeRecall that neither the basal plate nor motor neurons occur any farther rostrally than the midbraine. Diencephaloni. Comes from the alar plate onlyii. 2 subdivisions: thalamus and hypothalamus 1. Thalamus: a relay center for all sensory information on its way up to the cerebral cortex, where it will be consciously perceived 2. Hypothalamus: directly regulates many visceral functions of the bodya. Digestion, body temperature, hunger, thirst, and growth…iii. The stalk is called the infundibulum 1. Hangs down from the floor of the hypothalamus2. Shaft part of the golf-club-shaped pituitary glanda. Lies directly inferior to this part of the brainf. Telencephalon i. From alar plate only ii. Takes 2 cross-sections: one caudal and one rostral 1. Its roof has a choroid plexus for the manufacture of cerebrospinal fluid iii. From the alar plate1. Cerebral cortexa. This cortex is a large sheet of gay matter on the outside of the cerebrumb. Size-wise it is a huge part of the brainc. It is responsible for the conscious feeling and interpretation of sensory stimuli for thought and for willful control of our movements2. Basal ganglia (basal nuclei)a. Belong to the deep gray matter near the ventricles b. Function: help to start, stop, and regulate the intensity of body movements3. Septuma. Forms brain nuclei that control emotions, sexual behavior, and


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WSU BIOLOGY 315 - The Brain

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