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The brain and cranial nerves Ch. 15

The brain and cranial nerves Ch. 15. Development of the brain. Major parts of the brain. Brain stem Medulla oblongaga, pons, midbrain Cerebellum Diencephalon Thalmus, hypothalamus, and associated structures Cerebrum Largest and most distinctive part of brain.

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The brain and cranial nerves Ch. 15

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  1. The brain and cranial nervesCh. 15

  2. Development of the brain

  3. Major parts of the brain • Brain stem • Medulla oblongaga, pons, midbrain • Cerebellum • Diencephalon • Thalmus, hypothalamus, and associated structures • Cerebrum • Largest and most distinctive part of brain

  4. Protective structures of brain • Skull • Meninges • Division of brain into hemispheres • Blood-brain barrier • Ventricles

  5. Meninges • Dura mater • Sinuses contain fluid and blood vessels • Arachnoid mater • Covers cranial blood vessels • Pia mater • Attached to surface of brain

  6. Meninges help separate the brain into compartments • Falx cerebri (cerebral hemispheres) • Tentorium cerebelli- separates cerebellum from cerebrum • Falx cerebelli- divides cerebellum into hemipsheres • Diaphragma sellae- lines sella turcica

  7. Distribution of cerebrospinal fluid (CSF) • Ventricles and subarachnoid space • Shock absorber • Chemical balance (electrolytes) • Circulation of nutrients and wastes • Formed in choroid plexuses • Reabsorbed through arachnoid villi

  8. Ventricles • 4 ventricles • CSF circulates between ventricles and spinal canal • 4th ventricle is continuous with spinal cord

  9. Blood supply to brain • No oxygen or energy stores • Internal carotid and vertebral arteries supply oxygenated blood • Drained by internal jugulars

  10. The brain stem: medulla oblongata • White matter: ascending and descending tracts • Pyramids formed by motor tracts; neurons cross from one side to the other • Gray matter (nuclei); cardiovascular, rhythmicity area, various reflexes; cranial nerves

  11. What about the cranial nerves? • 12 pairs • Part of peripheral nervous system (PNS) • Numbered I through XII, in order of anterior to posterior emergence from the brain • Nose- I; eyes- II; inner ear (VIII); brain stem (III-XII); spinal cord (XI) • I and II are sensory; others are mixed • Sensory cell bodies are in ganglia; motor cell bodies are in brain • Motor function is somatic (skeletal) or autonomic

  12. Cranial nerves • I-olfactory • II-optic • III- oculomotor • IV-trochlear • V-trigeminal-opthalmic, maxillary, mandibular • VI-abducens • VII- facial

  13. Eye function is complex • III- eyeball movement as well as intrinsic muscles • IV-superior oblique eye muscle • V-eyelids • VI-lateral movements of eye

  14. Medulla oblongata and associated cranial nerves (inferior view) • Vestibulocochlear (VIII)-hearing • Glossopharyngeal (IX)- taste, chewing, salivation • Vagus (X)-multiple (digestive, heart rate, sensation) • Accessory (XI)-swallowing, head and neck movement • Hypoglossal (XII)-tongue movements during speech

  15. Pons is directly superior to medulla • Nuclei and tracts that connect one part of the brain with another • Pneumotaxic (limits inhalation) and apneustic (prolongs inhalation) centers • Associated with cranial nerves: • Trigeminal (V) chewing • Abducens (VI) movement of eyeballs • Facial (VII)- facial expression; secretion of saliva and tears • Vestibulcochlear (VIII) –balance, equilibrium, hearing

  16. The pons

  17. Reflexes and tracts characterize the midbrain (mesencephalon) • Superior and inferior colliculi • Superior- eye reflexes • Inferior- auditory reflexes • substantia nigra • dopaminergic; motor coordination • Red nuclei • Tracts (cerebral peduncles) • Association with cranial nerves: • Oculomotor (III)- movement of eyeball, puil and lens • Trochlear (IV)- movement of eyeball

  18. What does the midbrain look like? Transverse view Posterior view

  19. Reticular formation • Network of cell bodies and myelinated axons • Extends from spinal cord to diencephalon • Helps maintain muscle tone • RAS (reticular activating system) extends to cerebral cortex; helps maintain wakefulness

  20. The cerebellum • Each hemisphere divided into lobes • Anterior, posterior- subconsccious skeletal movement • Flocculonodular- equilibrium • Peduncles organize transmission between cerebellum and rest of brain • Skilled movements • Posture and balance

  21. Functions of cerebellum • Adjusting posture (involuntarily) • Memory of learned movements • Regulates (inhibits) activity in cerebral cortex, basal nuclei, and motor pathways

  22. Diencephalon: thalamus and associated structures • Thalamus is major relay station of sensory information to cerebrum (basal nuclei and cortex) • Anterior (limbic) • Medial • Ventral group • Anterior and lateral (motor) • Posterior (sensory) • Integration of sensory information, perception, emotional state, learning, memory

  23. Hypothalamus • Control of ANS • Hormone production • Regulation of behavior (with limbic system) • Satiety and thirst • Thermoregulation • Epithalamus- pineal gland • Subthalamus-coordination

  24. Cerebrum- most recognizable part of the brain • Left and right hemispheres • Corpus callosum • Lobes formed by sulci and fissures • Insula is deep to the superficial lobes

  25. Basal ganglia • Globus pallidus, putamen, caudate nucleus • (motor) input from cerebral cortex and each other • Control of movement • Damage causes tremor, rigidity, involuntary movements • May intersect limbic system

  26. Limbic system, the emotional brain • Major components: • Amygdala • Hippocampus • Various nuclei and tracts • Olfactory bulbs

  27. Organization of the cerebral cortex • Sensory areas • Generally in parietal or temporal lobe • Primary somatosensory area (postcentral gyrus) • Primary visual area, auditory, gustatory, olfactory • Motor areas • Primary motor area- precentral gyrus • Broca’s area

  28. Association areas • Association areas • Somatosensory-identify sensory input; memory • Visual- recognition, recall • Auditory- what do you hear? • Wernicke’s- what are you saying? • Common integrative area-full integration of sensory input • Premotor- learned motor skills • Frontal eye field area- taking in visual information

  29. Hemispheric lateralization • Each hemisphere controls the opposite side of the body • Corpus callosum connects hemispheres • People tend to concentrate activities in one hemisphere • Left- speech, reasoning, numerical skills • Right- spatial awareness, pattern recognition, musical and artistic sensibility

  30. Summary • Brain grows rapidly during fetal and juvenile development; loses mass with aging • Organization of brain and functional areas is sophisticated with a considerable amount of overlap

  31. Summary • “Higher order” functions in cerebrum • Diencephalon is processing center. Hypothalamus integrates emotions, autonomic, hormone function • Midbrain- visual, auditory, somatic motor • Pons-motor control • Cerebellum-”fine-tunes” • Medulla oblongata- regulates autonomic function

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