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Contents of the Neurocranium, Part II

Contents of the Neurocranium, Part II. The Brain, its Blood Supply and the Cranial Nerves. Embryology. Central nervous system begins as neural tube Anterior portion of neural tube differentiates into three primary divisions: Hindbrain Midbrain Forebrain. Embryology.

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Contents of the Neurocranium, Part II

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  1. Contents of the Neurocranium, Part II The Brain, its Blood Supplyand the Cranial Nerves

  2. Embryology • Central nervous system begins as neural tube • Anterior portion of neural tube differentiates into three primary divisions: • Hindbrain • Midbrain • Forebrain

  3. Embryology • Lateral walls of the forebrain expand and protrude from both sides of the neural tube • Median portion of forebrain is the diencephalon • Lateral projections form the telencephalon

  4. Embryology Two primary axes of growth in the developing brain 1. Longitudinal flexion of anterior neural tube 2. Inferior spiral rotation of the telencephalon

  5. Ventricles • Lumen of neural tube becomes the CNS ventricular system • Shape of ventricular system reflects developmental deformation of neural tube

  6. Ventricles • Lateral ventricles • Anterior horn • Body • Posterior horn • Inferior horn • Third ventricle • Interventricular foramen (of Monro) • Cerebral aqueduct • Fourth ventricle

  7. HindbrainCerebellum • Motor coordination • Cognitive functions • temporal coordination • planning

  8. HindbrainMedulla Oblongata • Anatomical and physiological junction of brain and spinal cord • Initiates respiration • Regulates heart rate • Origin of cranial nerves IX, X, XI, and XII

  9. HindbrainPons • Bridge between cerebellum and the rest of the brain • Origin of cranial nerves V, VI, VII, and VIII

  10. Midbrain • Least differentiated primary brain division • Contains cerebral aqueduct • Origin of cranial nerves III and IV (from dorsal surface)

  11. MidbrainCorpora Quadrigemina Superior Colliculi • Visual tracking • Coordination of head turning & eye movements • Inferior Colliculi • Sound location • Focusing attention to auditory stimuli

  12. MidbrainSubstantia Nigra • Darkly pigmented (neuro-melanin) nucleus • Produces dopamine • Parkinson’s disease—destruction of the cells of the substantia nigra

  13. MidbrainSubstantia Nigra • In 1982, 6 drug addicts in Santa Clara, CA manifested with Parkinson’s disease (oldest patient was 41 yrs. old) • Each had injected synthetic heroin—MPPP (1-methyl-4-phenyl-4-propionpiperidine), an analog of meperidine (Demerol) • The poorly synthesized designer drug contained a contaminant—MPTP (1-methyl-4-phenyl-1,2,5,6-tetrahydropyridine), which kills the cells of the substantia nigra

  14. MidbrainCerebral Peduncles • Major fiber bundles connecting forebrain to hindbrain • Contain descending axons of upper motor neurons from cortex

  15. DiencephalonThalamus • Potato-shaped structure • Sensory relay for all afferents except olfaction

  16. DiencephalonThalamus • Thalami form walls of 3rd ventricle

  17. Body temperature Hunger Thirst Sexual activity Goal-seeking behavior Endocrine functions Affective behavior Visceral motor system DiencephalonHypothalamus • 4 g neural structure • Connected to pituitary gland • Regulates:

  18. TelencephalonBasal Ganglia • Caudate nucleus • Globus pallidus • Putamen • Modulate and integrate components of motor activity (and cognitive functions) • System depends on dopamine— affected by Parkinson’s disease

  19. TelencephalonAmygdala • Lies at tail of caudate nucleus but is not functionally part of the basal ganglia • Involved in the control of rage, aggression and sexuality

  20. TelencephalonHippocampus • Composed of three-layered cortex (archicortex) • Fornix—major output pathway • Involved in the formation of new episodic memories

  21. TelencephalonCerebrum • Composed of six-layered neocortex and deep white matter • Center of sensory input, motor output, and higher cognitive functions

  22. Cerebrum Primary Fissures • Longitudinal cerebral fissure

  23. Cerebrum Primary Fissures • Lateral fissure • Central sulcus

  24. CerebrumLobes • Frontal • Parietal • Occipital • Temporal

  25. CerebrumLobes • Insula

  26. CerebrumWhite Matter • Corpus callosum—primary connection between left and right cerebral hemispheres

  27. CerebrumWhite Matter • Internal capsule—primary pathway of fibers ascending to cortex from thalamus and descending from cortex to cerebral peduncles

  28. Motor Cortex • Primary motor cortex lies along the precentral gyrus in the frontal lobe • Motor output projects to contralateral side

  29. Motor Output Pathways • Voluntary movement—conducted to lower motor neurons via the pyramidal pathway

  30. Motor Output Pathways • Balance, posture, limb coordination information conducted by numerous extrapyramidal pathways

  31. Somatosensory Cortex • Primary somatosensory cortex lies along the postcentral gyrus in the parietal lobe • Representation of body is from contralateral side

  32. Somatosensory Cortex Somatosensory cortex (like motor cortex) is mapped somatotopically and proportionate to sensitivity, not size

  33. Other Sensory Cortices • Visual cortex—occipital lobe • Auditory cortex—superior portion of temporal lobe • Rhinal (olfactory) cortex—anterior medial temporal lobe • Gustatory (taste) cortex—inferior aspect of postcentral gyrus

  34. Language Areas • Occur only in the left hemisphere of most people (96 % of right-handed individuals, 72% of left-handed individuals) • Broca’s area—motor speech center, in frontal lobe • Wernicke’s area—language interpretation center, in temporal & parietal lobes

  35. Olfactory Optic Occulomotor Trochlear Trigeminal Abucens Facial Vestibulocochlear Glossopharyngeal Vagus Spinal Accessory Hypoglossal Cranial Nerves

  36. I Cribriformplate Cranial NervesExit from Neurocranium

  37. II Optic canal Cranial NervesExit from Neurocranium

  38. Cranial NervesExit from Neurocranium III, IV, VI Superior orbital fissure

  39. Cranial NervesExit from Neurocranium V1 Superior orbital fissue V2 Foramen rotundum V3 Foramen ovale

  40. Cranial NervesExit from Neurocranium VII, VIII Internal auditory meatus

  41. Cranial NervesExit from Neurocranium IX, X, XI Jugular foramen

  42. Cranial NervesExit from Neurocranium XII Hypoglossal Canal

  43. Cranial NervesExit from Neurocranium

  44. Blood Supply • Vertebral arteries • Provide ~30% of blood supply to brain • Internal carotid arteries • Provide ~70% of blood supply to brain

  45. Circle of Willis Vertebral aa.  basilar a.  posterior cerebral aa. Internal carotid a.  middle cerebral aa. anterior cerebral aa. Posterior communicating arteries connect posterior cerebral aa. and internal carotid aa. Anterior communicating ARTERY (sing.) connect anterior cerebral arteries

  46. Blood Supply

  47. Blood Supply

  48. Venous Drainage • Blood from the cortex drains to surface veins that drain into the dural venous sinuses

  49. Venous Drainage • Blood from the deep brain (thalamus, basal ganglia) drains into great cerebral vein (of Galen) before entering the straight sinus • Blood from the lower brainstem drains through the foramen magnum into the vertebral venous plexus

  50. Cerebrovascular Accident (CVA) • Ruptured aneurysm—failure of a localized defect in the elasticity of a vessel • Arterial thrombus—blockage of an artery • Embolism—clot from elsewhere in the body that lodges in a cerebral artery • Hypertensive apoplexy—sudden effusion of blood into cerebral tissue due to rise in blood pressure

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