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Central Nervous System. 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 (3 rd week)
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Central Nervous System 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 Secondary vesicle system Adult brain structures Ventricle system Primary vesicle 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 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.fizyka.umk.pl/~duch/ref/01/01-plastic/motorsomato.gif http://www.pc.rhul.ac.uk/staff/J.Zanker/PS1061/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 gyrior different lobes • Projection • Enter or leave cerebral cortex • Connect cortex to rest of NS, receptors, & effectors • E.ginternal 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 • PD and HD • Corpus striatum • Caudate nucleus • Lentiform nucleus • Putamen • Globuspallidus • Associated with subthalamic nuclei and substantianigra http://www.iupucanatomy.com/images/Picture%20943a.jpg 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 • 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 http://academic.kellogg.cc.mi.us/herbrandsonc/bio201_McKinley/f15-15_diencephalon_c.jpg
Brain Stem • Brain stem organized like spinal cord • Survival responses and cranial nerves (10 of 12) • Midbrain • Cerebral peduncles: pyramidal motor tracts • Corpora quadrigemina • Substantianigra: 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 • Cingulategyrus • 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) • Falxcerebri: longitudinal fissure (superior sagital sinus) • Falxcerebelli: vermis • Tentoriumcerebelli: transverse fissure (transverse sinus) • Arachnoid mater • Doesn’t follow convolutions • Serous fluid in subdural space above • CSF in subarachnoid space below (arachnoidvilli) • 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