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Chapter 11 Nervous System II Meninges • membranes surrounding CNS • protect CNS • three layers • dura mater – outer, tough • arachnoid mater weblike • pia mater – inner, delicate 11-2 Ventricles • interconnected cavities • within cerebral hemispheres and brain stem • continuous with central canal of spinal cord • filled with cerebrospinal fluid (csf) • lateral ventricles • third ventricle • fourth ventricle • cerebral aqueduct 11-4 Cerebrospinal Fluid • secreted by choroid plexus • circulates in ventricles, central canal of spinal cord, and subarachnoid space • completely surrounds brain and spinal cord • clear liquid • nutritive and protective • helps maintain stable ion concentrations in CNS 11-5 Spinal Cord Structure • extends foramen magnum to 2nd lumbar vertebra 11-6 Cross Section of Spinal Cord 11-7 Spinal Cord Functions • center for spinal reflexes • conduit for nerve impulses to and from the brain 11-8 Reflex Arcs Reflexes – automatic, subconscious responses to stimuli 11-9 Tracts of the Spinal Cord • Ascending tracts conduct sensory impulses to the brain • Descending tracts conduct motor impulses from the brain to motor neurons reaching muscles and glands 11-13 Brain Functions Major Parts • interprets sensations • cerebrum • two cerebellar hemispheres • determines perception • diencephalon • stores memory • brain stem • reasoning • cerebellum • makes decisions • coordinates muscular movements • regulates visceral activities • determines personality 11-16 Brain Development Three Major Vesicles 1. Forebrain 2. Midbrain 3. Hindbrain Forebrain (prosencephalon) • anterior portion (telencephalon) • cerebrum • basal ganglia • posterior portion (diencephalon) • thalamus • hypothalamus • posterior pituitary • pineal gland 11-17 Brain Development Midbrain (mesencephalon) • midbrain Hindbrain (rhombencephalon) • anterior portion (metencephalon) • cerebellum • pons • posterior portion (myelencephalon) • medulla oblongata 11-18 Structure of Cerebrum • corpus callosum • connects hemispheres • convolutions • bumps or gyri • sulci • grooves • longitudinal fissure • separates hemispheres • transverse fissure • separates cerebrum from cerebellum 11-19 Lobes of Cerebrum • Frontal • Parietal • Temporal • Occipital • Insula 11-20 Functions of Cerebrum • interpretation • initiating voluntary movements • storing memory • retrieving memory • reasoning • center for intelligence and personality 11-21 Functional Regions of Cerebral Cortex Cerebral Cortex – thin layer of gray matter that constitutes the outermost portion of cerebrum; contains 75% of all neurons in nervous system 11-22 Motor Areas • Primary Motor Areas • frontal lobes • control voluntary muscles • Broca’s Area • anterior to primary motor cortex • usually in one hemisphere • controls muscles needed for speech • Frontal Eye Field • above Broca’s area • controls voluntary movements of eyes and eyelids 11-23 Motor Areas 11-24 Sensory Areas • Cutaneous Sensory Area • parietal lobe • interprets sensations on skin • Visual Area • occipital lobe • interprets vision • Auditory Area • temporal lobe • interprets hearing 11-25 Sensory Areas 11-26 Association Areas • regions of cortex that are not primary motor or primary sensory areas • widespread throughout the cerebral cortex • analyze and interpret sensory experiences • provide memory, reasoning, verbalization, judgment, emotions 11-27 Association Areas Frontal Lobe Association Areas • concentrating • planning • problem solving • judging Temporal Lobe Association Areas • remember visual scenes • remember music • remember complex patterns Parietal Lobe Association Areas • understanding speech • using words to express thought Occipital Lobe Association Areas • combine visual images with other sensory experiences 11-28 Hemisphere Dominance • In over 90% of population, left hemisphere is dominant • Dominant hemisphere controls • speech • writing • reading • verbal skills • analytical skills • computational skills • Nondominant hemisphere controls • nonverbal tasks • motor tasks • understanding and interpreting musical and visual patterns • provides emotional and intuitive thought processes 11-29 Memory Short Term • working memory • closed circuit • circuit is stimulated over and over • when impulse flow stops, memory disappears Long Term • changes structure and function of neurons • enhanced synaptic transmission 11-30 Basal Nuclei • masses of gray matter • deep within cerebral hemispheres • caudate nucleus, putamen, globus pallidus • produce dopamine • control certain muscular activities 11-31 Diencephalon • between cerebral hemispheres and brainstem • surrounds third ventricle • thalamus • hypothalamus • optic tracts • optic chiasm • infundibulum • posterior pituitary • mammillary bodies • pineal gland 11-32 Brain Stem Three Parts 1. Midbrain 2. Pons 3. Medulla Oblongata 11-35 Midbrain •contains bundles of fibers that join lower parts of brainstem and spinal cord with higher part of brain 11-36 Pons • rounded bulge on underside of brainstem • between medulla oblongata and midbrain • helps regulate rate and depth of breathing • relays nerve impulses to and from medulla oblongata and cerebellum 11-37 Medulla Oblongata • enlarged continuation of spinal cord • conducts ascending and descending impulses between brain and spinal cord • contains cardiac, vasomotor, and respiratory control centers • contains various nonvital reflex control centers (coughing, sneezing, vomiting) 11-38