2200Topic2.ppt

Forebrain Neocortex (cerebral cortex) Has expanded the most during evolution Comprises 80% of the human brain 2500 square centimeters, thickness of 1.5-3.0 millimeters Six layers Two cerebral hemispheres, four lobes Fissures, Sulci, and Gyri Fissure A cleft in the cortex that is deep enough to indent the ventricles Sulci A shallow cleft in the cortex Gyri A ridge in the cortex Organization of the Cortex in Relation to its Inputs and Outputs Projection Map Map of the location of the inputs and outputs to the cortex Primary Areas Frontal lobe - Motor functions Parietal lobe - Body senses Temporal lobe - Auditory functions Occipital lobe - Visual functions Organization of the Cortex in Relation to its Inputs and Outputs Secondary Areas Adjacent to primary areas Receive input from the primary areas Engaged in interpreting sensory input or organizing movements Tertiary Areas (Association Cortex) Located between secondary areas Mediate complex activities Cellular Organization of the Cortex Six Layers of Cortex Layers V and VI Send axons to other brain areas Particularly large and distinctive in the motor cortex Layer IV Receives axons from sensory systems Small densely packed cells Layers I, II, III Receive input from layer IV Cellular Organization of the Cortex Cytoarchitectonic Map Map based on the organization, structure, and distribution of cortical cells Brodmann’s Map Most widely used cytoarchitectonic map Connections Between Cortical Areas Neocortical regions are connected by four types of axon projections Long connections between one lobe and another Relatively short connections between one part of a lobe and another Interhemispheric connections Homotopic points Contralateral points that correspond to each other Connections through the thalamus The Crossed Brain Brain has contralateral organization Each symmetrical half responds to sensory stimulation from the contralateral side or controls musculature on the contralateral side Decussations Crossings of sensory