Brain and Cranial Nerves

Brain and Cranial Nerves - Brain & Cranial Nerves...

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Landmarks of the Brain The brain is divided into three major portions cerebrum cerebellum brainstem Gross Anatomy of the Brain Forebrain -(Prosencephalon) telencephalon Cerebral Hemispheres Cerebral Cortex Basal ganglia Basal forebrain nuclei Amygdaloid Nucleus diencephalon Thalamus and Hypothalamus Midbrain -mesencephalon Hindbrain - (Rhombencephalon) metencephalon Pons and Cerebellum mylencephalon Medulla Oblongata Forebrain (Prosencephalon) telencephalon Cerebral Hemispheres Cerebral Cortex Basal ganglia Basal forebrain nuclei Amygdaloid Nucleus diencephalon Thalamus and Hypothalamus Midbrain (mesencephalon) Hindbrain (rhombencephalon) metencephalon Pons and Cerebellum mylencephalon
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Medulla Oblongata Cerebrum Cerebrum Cerebrum prominent sulci divide each hemisphere into five anatomically and functionally distinct lobes frontal central sulcus- posterior boundary parietal parieto-occipital sulcus- caudal boundary occipital temporal lateral sulcus- separate from parietal lobe insula- deep to the lateral sulcus Cerebral Histology Cerebral cortex is a 2-3mm thick layer of tissue covering the cerebrum which contains about 40% of the mass of the brain with about 14-16 billion neurons. Composed of two principal types of neurons Stellate cells- have spherical somas with dendrites projecting for short distances in all directions are concerned with receiving sensory input Pyramidal cells- tall and triangular with an apex that points toward the brain surface and has thick dendrite with many branches and small knobby dendritic spines are the output neurons that transport signals to other parts of the CNS Cerebral Histology About 90% of the cerebral cortex is a six layered tissue called the neocortex because of it recent evolutionary development. The layers are numbered I (outer layer) to VI (most inner layer) and vary from one part of the cerebrum to another in thickness, cellular composition, synaptic connections, size of neurons, and destination of their axons. layer IV is thickest in sensory regions and layer V in motor regions all axons that leave the cortex and enter the white matter arise from layers III, V, and VI. Cerebral Cortex Histology (1) Plexiform layer (molecular layer)- mostly fibers running parallel to surface, neuroglial cells, and a few horizontal cells of Cajal (2) Outer granular cell layer; small pyramidal cells (stellate cells) (3) a layer of medium pyramidal cells (4) Inner granular layer; many small granule cells (stellate cells) (5) Large pyramidal cells (Betz cells) (6) a layer of polymorphic cells- cells with diverse shapes (fusiform cells) Pyramidal cells-
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recognized by their relatively large somata and by their prominent apical dendrites (i.e., the upward "apex" on the "pyramid"). "owl-eye" or "fried-egg" nuclei.
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Brain and Cranial Nerves - Brain & Cranial Nerves...

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