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Chapter 12 Embryonic Nervous System Development Ectoderm dorsal to the notocord thickens to form the neural plate Invagination forms the neural groove Fusing of neural folds completes the neural tube as it lengthens (3rd week) Anterior seals and expands = brain Posterior = spinal cord Spina bifida variations due to Neural crest cells migrate to become PNS ganglia and glia; also pigment cells Embryonic Brain Development Primary vesicle system Secondary vesicle system Adult brain structures Ventricle system Lateral ventricles 3rd ventricle Cerebral aqueduct 4th ventricle Ventricles Interconnected tubular system Filled with CSF (ependymal cells) Apertures in 4th ventricle connect to subarachnoid space Need to know: • Lateral ventricles • Septum pellucidum • Interventricular foramen • 3rd ventricle • Cerebral aqueduct • 4th ventricle • Central canal Cerebral Hemispheres Gyri Pre- & postcentral Sulci Central, pareito-occipital, & lateral Fissures Longitudinal & transverse Lobes Frontal, parietal (2), temporal (2), occipital, & insula Basic regions Cotex, white matter, & basal nuclei Cerebral Cortex Gray matter composed of interneurons 3 Functional areas Motor areas Frontal eye field Sensory areas Olfactory cortex Association areas Posterior association Limbic association Demonstrates lateralization Left: math, speech, concrete processing, logic Right: creativity, facial and pattern recognition Contralateral control Homunculus Entire body mapped within the http://www.fizyka.umk.pl/~duch/ref/01/01-plastic/motorsomato.gif brain = somatotopy Most neurons to areas w/ most precise control or sensitivity Somatosensory version receives message from sensors Spatial discrimination Motor version sends message to muscles Areas are adjacently mapped Contralateral control http://www.pc.rhul.ac.uk/staff/J.Zanker/P S1061/L6/homuncul.gif Cerebral Cortex Damage Primary motor cortex Paralyzes voluntary muscles; reflexes intact Contralateral effects Premotor cortex Loss of motor skills; strength and ability unaffected Practice rewires Visual cortex Primary: functional blindness Association: can see, but not comprehend Language areas Broca’s: speech production Wernike’s: speech comprehension Cerebral White Matter Communication between cerebral areas and lower CNS Directional myelinated fibers Commissural fibers Connect hemispheres E.g. corpus callosum Association Connect parts of same hemisphere Adjacent gyri or different lobes Projection Enter or leave cerebral cortex Connect cortex to rest of NS, receptors, & effectors E.g internal capsule & corona radiata Basal Nuclei Input from all of cortex Project to premotor & prefrontal areas via the thalamus Inhibits motor systems Release = muscle mov’ts (action selection) Start, stop, & monitor to limit excessive mov’ts; multitasking http://www.iupucanatomy.com/images/Picture%20943a.jpg PD and HD Corpus striatum Caudate nucleus Lentiform nucleus Putamen Globus pallidus Associated with subthalamic nuclei and substantia nigra http://www.colorado.edu/intphys/Class/IPHY3730/image/figure5-31.jpg Diencephalon Thalamus Gray matter masses joined by the intermediate mass Regionally named specialty nuclei http://academic.kellogg.cc.mi.us/herbrandsonc/bio201_McKinley/f15-15_diencephalon_c.jpg All afferents ‘relay’ through sorts and edits Mediates sensation, motor activities, arousal, learning and memory Hypothalamus Walls form infundibulum which attaches to pituitary gland Homeostatic control ANS (visceral activities), emotion, body temp., food intake, water balance/thirst, sleep, and endocrine control (releasing hormones) Epithalamus Pineal gland produces melatonin to regulate sleep-wake cycle Brain Stem Brain stem organized like spinal cord Survival responses and cranial nerves (10 of 12) Midbrain Cerebral peduncles: pyramidal motor tracts Corpora quadrigemina Substantia nigra: melanin; voluntary initiation of mov’t Red nucleus: hemoglobin; coordinates motor mov’ts Pons Bridges cerebrum and cerebellum Respiratory centers assist breathing Medulla oblongata Decussation of pyramids Olives: sensory info about muscle and joint stretch to cerebellum Cardiovascular and respiratory centers; emesis, hiccupping, sneezing, and coughing Cerebellum Anterior & posterior lobes Vermis connects 2 hemispheres of posterior Coordination, balance, & proprioception Ipsilateral input/output Learning patterned sequences Cerebellar processing Interprets intent of mov’t from cortex & proprioception from sensors Determines best means of mov’t execution Sends plans to motor cortex to coordinate Damage results in clumsy, misguided mov’ts Limbic System Emotional center Interactions with prefrontal lobes Coordinates sensory input with emotions Hippocampus Learning and memory Amygdala Fear and aggression Assess danger and elicits response to emotional stimuli Cingulate gyrus Associating memories to smells and pain Expression of emotions through gestures Focusing attention on emotionally significant events http://universe-review.ca/I10-41-limbic.jpg Reticular Formation Arousal and alertness due to constant stimulation Studying w/ background noise Filters repetitive, familiar, and weak stimuli 99% sensory stimuli ignored LSD interrupts = overload stimuli Coarse skeletal mov’t Inhibited by sleep centers Depressed by alcohol & tranquilizers http://www.daviddarling.info/images/reticular_formation.jpg Meninges Covers and protects CNS 3 layers (superficial to deep) Dura mater Periosteal layer attaches to skull Meningeal layer form septa to anchor brain (sinuses too) Falx cerebri: longitudinal fissure (superior sagital sinus) Falx cerebelli: vermis Tentorium cerebelli: transverse fissure (transverse sinus) Arachnoid mater Doesn’t follow convolutions Serous fluid in subdural space above CSF in subarachnoid space below (arachnoid villi) Pia mater Connected to brain, follows all convolutions Meningitis General disease term Bacteria/virus invades CSF and inflames Cerebrospinal Fluid Surrounds the brain & spinal cord Buoyancy Supply for nutrients & chemical signals Secreted by choroid plexus In all ventricles Lined with ependymal cells Selective barrier to ions and removes wastes CSF pathway Blood Brain Barrier Maintains stable environment for brain Allows selective permeability Nutrients in Wastes and toxins/dugs out Ineffective against fats, O2, and CO2 Absent at 3rd and 4th ventricle Alcohol and other poisonings Metabolic activity monitoring Spinal Cord Protection Within the vertebral foramen End L1/L2 Lumbar puncture L3/L4 or L4/L5 Epidural space Padding of veins and fat Dura mater Meningeal layer only Subdural space – histology only Arachnoid Subarachnoid space Extends beyond spinal cord (S2) Pia mater Denticulate ligaments External Anatomy Cervical and lumbar enlargements Increased gray matter Conus medularis, cauda equina, & filum terminale 31 spinal nerve pairs Dorsal roots: sensory w/ganglia Ventral roots: motor Shingles attacks dorsal root ganglia and cranial nerves Internal Anatomy Anterior median fissure Posterior median sulcus Gray commissure Central canal Gray and white matter Anterior, posterior, and lateral horns Ascending (sensory) and descending (motor) tracts