September 24 - Cerebral Hemispheres.docx

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Anatomy and Cell Biology
Anatomy and Cell Biology 3319

September 24, 2013 Cerebral Hemispheres Pp. 394-403, 405 - Know the names and locations of the major sulci, fissures; and the name, location and border of the lobes of the cerebral cortex - Know the names, locations and function of the motor, sensory and association areas of the cerebral cortex - Brainpower - Right brain vs. Left brain - Higher order processing - Evolutionary advantage - Sensory processing - Creativity - Understanding - Language The Cerebrum - Made of 2 cerebral hemispheres - 83% of total brain mass - Cover the diencephalon and the rostral brain stem - Cerebral cortex (gray matter) o Superficial layer of cortex containing neuron cell bodies - Cerebral white matter o Deep layer containing fibers which connect cell bodies to each other and other areas o Myelination is responsible for the white color - Deep gray matter o Basal ganglia: deep collection of neuronal cell bodies - Overall Function of cerebrum: o Sensory reception and processing o Motor output and processing o Association areas to process complex interactions between brain areas  Perception and interpretation o Cognitive function including decision making (not fully developed until adolescence) - Fissures separate the major portions of the brain (huge indents) – deep sulci o Transverse cerebral fissure: separates the cerebral hemispheres from the cerebellum o Longitudinal fissure: separates the right and left cerebral hemispheres - Sulci: shallow grooves on the surface of the cerebral hemispheres that separate the lobes (separate gyri) o Central sulcus: separates the frontal lobe from the parietal lobe (uninterrupted line to temporal lobe) o Parieto-occipital sulcus: separates occipital lobe from parietal lobe o Lateral/Sylvian sulcus: separates temporal lobe from parietal and frontal lobes (so deep that it’s actually a fissure) o Precentral sulcus: anterior to precentral gyrus o Postcentral sulcus: posterior to postcentral gyrus - Gyri: twisted ridges (raised parts) o Precentral gyrus (anteriorly – primary motor cortex) and postcentral gyrus (posteriorly – primary sensory cortex) border the central sulcus - Lobes within cerebral hemisphere: o Frontal lobe: cognition and motor control o Parietal lobe: somatosensory processing o Occipital lobe: visual areas o Temporal lobe: auditory areas o Insular lobe: visceral (feeling full) and vestibular sensory areas  Buried deep within lateral sulcus/fissure; covered by parts of frontal, parietal and temporal lobes The Cerebral Cortex - Home of the “conscious mind” - Sensory areas: allow conscious awareness of sensation - Association areas: integrate diverse information to enable purposeful action o Unimodal o Take raw, basic sensory features and ascribe meaning to them o Ex, loud, same pitch, equal timing  AN ALARM - Motor areas: control voluntary motor functions - Primary sensory cortex: sensory area for each major sense o Sensory association areas: area in each primary sensory cortex that processes the sensory information o Multimodal association areas: receives and integrates input from multiple regions of the cerebral cortex o Motor cortex: region that plans and initiates voluntary motor functions - Example: o Sensory information is received by the primary sensory cortex, and the arrival of this information results in awareness of the sensation o The information is relayed to the sensory association area that gives a meaning to the sensory input o The multimodal association areas receive input in parallel from multiple sensory association areas, integrating all of the sensory input to create a complete understanding of the sensory information. These regions also integrate sensory input with past experience and develop a motor response o The motor plan is enacted by the motor cortex Sensory Areas - Conscious awareness of sensation occur in parts of the parietal, temporal and occipital lobes - There is a distinct primary sensory cortex for each of the major senses: o General somatic senses, special senses of vision, hearing, balance, olfaction and taste - Each sense also has an association area adjacent to its primary sensory area 1) Somatosensory areas - Primary somatosensory cortex: primary sensory cortex that receives information from the general somatic senses - Located along the postcentral gyrus of the parietal lobe - Touch, pressure, vibration, pain and temperature from skin and proprioception from muscles and joints - Sensory info. is picked up by sensory receptors in periphery of body and relayed through spinal cord, brain stem and thalamus to primary somatosensory cortex - There, cortical neurons process info. and identify area of the body being stimulated  spatial discrimination - Somatotopy: body mapping; each region of the cortex receives sensory stimuli from a specific area of the body - Sensory homunculus (little man) can be constructed for the postcentral gyrus - Lips and fingertips are our most sensitive body parts - Contralateral projection: the right cerebral hemisphere receives its sensory inp
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