Central Nervous System

1. Central Nervous System Chapter 12

2. 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

3. Embryonic Brain Development Secondary vesicle system Adult brain structures Ventricle system Primary vesicle system Lateral ventricles 3rd ventricle Cerebral aqueduct 4th ventricle

4. 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

5. 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

6. 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

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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

15. 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

16. 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

17. 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

18. 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

19. 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

20. 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

21. 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