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Popular in Anatomy
This 9 page Class Notes was uploaded by jj on Tuesday December 8, 2015. The Class Notes belongs to BIOL 2220 at Clemson University taught by John Cummings in Fall 2015. Since its upload, it has received 28 views. For similar materials see Anatomy in Anatomy at Clemson University.
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Date Created: 12/08/15
Chapter 12 The Central Nervous System 0 CNS the brain and spinal cord 0 Introduction of Brain Embryology a Neural Tube contains neural canal Anterior rostral begins to expand and constrictions appear that mark off the three primary brain vesicles Prosencephalon 9 forebrain Mesencephalon 9 midbrain Rhombencephalon 9 hindbrain Posterior caudal becomes the spinal cord b Primary brain vesicles give rise to the secondary brain vesicles Telencephalon 9 endbrain Diencephalon 9 interbrain Metencephalon 9 afterbrain Myelencephalon 9 spinal brain c Each of the five secondary vesicles then develops rapidly to produce the major structures of the adult brain Telencephalon cerebrum cerebral hemispheres cortex White matter basal nuclei Diencephalon thalamus hypothalamus Epithalamus retina Mesencephalon brain stem midbrain Metencephalon brain stem pons cerebellum Myelencephalon brain stem medulla oblongata Posteri0r caudal Spinal cord d Adult Neural Canal Regions Lateral Ventricles Telencephalon Third Ventricles Diencephalon Cerebral Aqueduct Mesencephalon Fourth Ventricle Metencephalon amp Myelencephalon Spinal Cord Central Canal 0 Embryologic Development from Notes In POWERPOINT Ectoderm thickens along midline to form neural plate Neural plate invaginates to form neural grove With neural folds Neural folds fuse to form neural tube Neural crest develops as offshoot of neural folds Primary Brain Vesicles Prosencephalon Mesencephalon Rhombencephalon Secondary Brain Vesicles Telencephalon O O Diencephalon Metencephalon Myelencephalon Adult Brain Structures Cerebrum Hypothalamus Thalamus Epithalamus Midbrain Pons Cerebellum Medulla Oblongata Brain Ventricles Lateral Ventricles Third Ventricle Fourth Ventricle Connecting Channels interventricular foramen amp Cerebral Aquaduct Openings Lateral Apertures amp Median Aperture 0 O Cerebral Hemispheres form the superior part of the brain The most conspicuous part of an intact brain Cerebral Hemispheres 9 covers and obscure the diencephalon and the top of the brain stem Gyri elevated ridges of tissue on outside of brain 9 mountain Sulci separate the gyri by shallow grooves 9 valley Longitudinal Fissure separates the cerebral hemispheres straight down the middle into left and right sides of the brain Transverse Cerebral Fissure separates the cerebral hemisphere from the cerebellum Lobes of the Cerebrum Frontal in front of central sulcus Parietal behind central sulcus and in front of occipital Temporal on the side of the brain under the lateral sulcus and in front of the occipital Occipital back of the brain in front on top of the cerebellum Insula fifth lobe of the cerebral hemisphere buried deep Within the lateral sulcus and forms part of its oor The insula is covered by portions of the temporal parietal and frontal lobes 0 Regions of the Cerebrum Cerebral Cortex gray matter which looks gray in fresh brain tissue White Matter Basal Nuclei islands of gray matter situated deep within the white matter 0 Cerebral Cortex Differing degrees of thickness and structure lined to function Each hemisphere controls opposite side of body Is lateralization of function No area acts alone Modern imaging techniques allow us to see the brain in action 9 PET scans show maximal metabolic activity and functional MRI scans reveal blood ow Contains 3 kinds of functional areas Motor Sensory and Association 0 Functional Areas Motor Areas Control voluntary movement lie in posterior part of frontal lobes 0 Primary Motor Cortex located in the precentral gyrus of the frontal lobe of each hemisphere Pyramidal cells large neurons in these gyri allow us to consciously control the precise or skilled voluntary movements of our skeletal muscles Their long axons project into the spinal cord and form the massive voluntary motor tracts 9 pyramidal tracts O Premotor Cortex anterior to the precentral gyrus in the frontal lobe Helps plan movements This region selects and sequences basic motor movements into more complex tasks like typing or playing a musical instrument It can control voluntary actions that depend on sensory feedback Coordinates the movement of several muscle groups either simultaneously or sequentially by sending activating impulses to the primary motor cortex 0 Broca s Area lies anterior to the inferior region of the premotor area Present in one hemisphere only usually left and a special motor speech area that directs the muscles involved in speech production Imaging studies indicate that it also becomes active as we prepare to speak and even as we think about plan many voluntary motor activities 0 The Frontal Eye Field located partially in and anterior to the premotor cortex and superior to Broca s area Controls voluntary movement of eyes Sensory Areas Conscious awareness of sensation occur in the parietal insular temporal and occipital lobes 0 Primary Somatosensory Cortex in the postcentral gyrus of the parietal lobe just posterior to the primary motor cortex Neurons in this gyrus receive information from the general somatic sensory receptors in the skin and from proprioceptors in skeletal muscles joints and tendons The neurons then identify the body region being stimulated Amount of sensory cortex devoted to a particular body region is related to that regions sensitivity of receptors NOT its size In humans the face especially lips and the fingertips are the most sensitive body areas Somatosensory Association Center major function of this area is to integrate sensory inputs temperature pressure etc relayed to it via the primary somatosensory cortex to produce an understanding of an object being felt its size texture and relationship of its parts Visual Areas 1 Primary Visual striate Cortex largest cortical sensory area the primary visual cortex receives visual information that originates on the retina of the eye There is a contralateral map of visual space on the primary visual cortex analogous to the body map of the somatosensory cortex 2 Visual Association Area communicating with the primary visual cortex the visual association area uses past visual experiences to interpret visual stimuli color form and movement enabling us to recognize a ower or a person s face and to appreciate what we are seeing O Auditory Areas 0 O 1 Primary Auditory Cortex sound energy exciting the hearing receptors of the inner ear causes impulses to be transmitted to the primary auditory cortex where they are interpreted as pitch loudness and location 2 Auditory Association Area permits the perception of the sound stimulus which we hear as speech as scream music thunder etc Memories of sounds heard in the past can be stored here for reference Olfactory Cortex conscious awareness of different odors Gustatory Cortex a region involved in perceiving taste stimuli is located in the insula just deep to the temporal lobe Vestibular Cortex responsible for conscious awareness of balance Association Areas 0 O Prefrontal Cortex involved with intellect complex learning abilities recall and personality It contains working memory with is necessary for abstract ideas judgement reasoning persistence and planning Language Areas General Interpretation Area Visceral Association Area White Matter Fibers Commissures allow the two hemispheres to function as a coordinated Whole The largest commissure is the corpus callosum Association Fibers connects different parts of the same hemisphere Short association fibers connect adjacent gyri Long association fibers are bundled into tracts and connect different cortical lobes Projection Fibers run vertically They tie the cortex to the rest of the nervous system and to the body s receptors and effectors Basal Nuclei Thalamus Caudate Nucleus Putamen Globus Pallidus Amygdala Contains several nuclei each With a specialty function Connect to specific regions of the cortex All sensory input sorted here and then sent to cortex Also all nonsensory inputs Hypothalamus Regulates ANS activity Controls emotional responses Regulates body temperature Controls food intake Regulates water balance Controls sleep cycle Regulates hormone release Epithalamus Secretes Melatonin Therefore functions in sleepwake cycle Produces cerebrospinal uid Brain Stem Midbrain Deep gray matter Surrounded by White matter Also gray matter embedded in White matter Provide programmed automatic behaviors needed for survival Contains motor tract that connects to spinal cord Also tracts that connect to cerebellum Functions in pain suppression Serves as link between amygdala and ANS Contain visual re ex center Functions as auditory relay 0 Pons Chie y Composed of Conduction tracts Complete pathway between higher brain centers and spinal cord Relay information between motor cortex and cerebellum O 0 Medulla Oblongata Major Autonomous Re ex Center Controls heart rate and blood vessel diameter Controls rate and depth of breathing Regulates vomiting hiccupping swallowing coughing and sneezing O O 0 Cerebellum Refines skeletal muscle contractions Plays role in cognition language and problem solving Activity occurs subconsciously Composition like cerebrum Gray cortex internal white mater with gray matter masses 0 Cerebellar Processing Motor association area of cerebral cortex sends signals to cerebellum of its intent to initiate voluntary muscle contraction Cerebellum receives info from visual receptors equilibrium receptors and proprioceptors throughout body Cerebellar cortex calculates best way to coordinate force of contraction Cerebellum dispatches message to cerebral cortex Signal is sent to muscle 0 Functional Brain Systems Networks of neurons that work together but span relatively large distances in the brain Cannot be localized to specific brain regions 0 Limbic System Emotional Brain Closely linked with rhinencephalon Output relayed through hypothalamus Strong link between feelings and thoughts 0 Reticular Formation Loosely clustered neurons in center of medulla pons and midbrain Governs arousal of brain as a whole RAS filters sensory input Brain Waves Pattern of neuronal electrical activity Recorded in electroencephalogram Consciousness Awareness of sensations and control of movement Is a continuum Sleep State of partial unconsciousness Memory Storage and retrieval of information Protection of the Brain Bone Membranes Fluid Meninges Cover and protect CNS Protect blood vessels Contain cerebrospinal uid Dura Mater Twolayered sheet of fibrous connective tissue Strongest and most superficial covering Arachnoid Mater Middle MeninX Creates subarachnoid space Filled With uid and larger blood vessels Pia Mater Deepest meninx immediately covering brain Cerebrospinal Fluid Liquid cushion around brain and spinal cord Reduces brain weight by 97 Protects CNS from physical trauma Helps nourish brain and carries chemical signals Formed by choroid plexuses in each ventricle BloodBrain Barrier Protective mechanism for brain that helps maintain a stable environment Substances in brain capillaries are separated from brain by O Capillary endothelium Thick basal lamina on capillaries Astrocytes Is a selective barrier Are select regions Where barrier is absent Vomiting center Hypothalamus O O CNS Spinal Cord Develops from neural tube Forms two distinct clusters of neuroblasts Alar Plate Basal Plate Gross Anatomy Extends from foramen magnum to first lumbar vertebra Terminus called conus medullaris Covered With meninges Single layer dura With epidural space Meninges extend beyond conus Anchored to coccyx by filum terminale Also secured to dura mater by denticulate ligaments Cauda equine extends sacral and lumbar nerves beyond conus O O O CrossSectional Anatomy Marked by grooves that run length of cord and divide it into right and left halves Anterior median fissure Posterior median sulcus Gray matter looks like letter H Anterior posterior and lateral horns connected by gray commissure O Neuronal MakeUp Gray matter consists of multipolar neurons Posterior horns interneurons Anterior horns mostly cell bodies of somatic motor neurons I Axons extend via ventral roots Lateral Horns autonomic sympathetic motor neurons 0 0 Division of Labor Both sensory and motor information conveyed thru spinal cord White Matter Divided into three white columns Columns contain collections of fibers that run as multineuron tracts Spinal Cord Tracts Most pathways cross from one side of CNS to other Most exhibit somatotropy All pathways are paired Most consist of a chain of two or three neurons that contribute to successive tracts X Order Neurons First Order Neurons Cell bodies in ganglion Conduct impulses from sensory receptors and proprioceptors SecondOrder Neurons Cell bodies is dorsal horn of spinal cord or medulla Transmit impulses to thalamus or cerebellum ThirdOrder Neurons Located in thalamus Conduct impulses to somatosensory cortex of cerebrum Ascending Pathways Nonspecific ascending pathway Specific ascending pathway Spinocerebellar Tracts Transmits proprioceptive information only to the cerebellum and so is subconscious Descending Pathways Direct pyramidal System Axons descend without synapsing from the pyramidal cells to the spinal cord There they synapse either with intemeurons or with ventral horn motor neurons Regulates fast and fine skilled movements such as doing needle work and writing Indirect extrapyramidal System Axial muscles that maintain balance and posture Muscles controlling coarse limb movements Head neck and eye movement that follow object in the visual field
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