The Central Nervous System: Part A

1. 12 The Central Nervous System: Part A

2. Central Nervous System (CNS) • CNS consists of the brain and spinal cord

3. Embryonic Development • Neural plate forms from ectoderm • Neural plate invaginates to form a neural groove and neural folds

4. Embryonic Development • Neural groove fuses dorsally to form the neural tube • Neural tube gives rise to the brain and spinal cord

5. Neural crest 3 Neural fold cells migrate to form the neural crest,which will form much of the PNS and many otherstructures. Figure 12.1, step 3

6. (e) Adultneural canalregions (c) Secondary brainvesicles (d) Adult brainstructures Cerebrum: cerebral hemispheres (cortex, white matter, basal nuclei) Lateral ventricles Telencephalon Diencephalon (thalamus, hypothalamus, epithalamus), retina Third ventricle Diencephalon Cerebral aqueduct Brain stem: midbrain Mesencephalon Metencephalon Brain stem: pons Fourth ventricle Cerebellum Brain stem: medulla oblongata Myelencephalon Central canal Spinal cord Figure 12.2c-e

7. Regions and Organization of the CNS • Adult brain regions • Cerebral hemispheres • Diencephalon • Brain stem (midbrain, pons, and medulla) • Cerebellum

8. Cerebral hemisphere Diencephalon Cerebellum Brain stem • Midbrain • Pons • Medullaoblongata (d) Birth Figure 12.3d

9. Regions and Organization of the CNS • Spinal cord • Central cavity surrounded by a gray matter core • External white matter composed of myelinated fiber tracts

10. Lateral ventricle Septum pellucidum Anterior horn Posterior horn Inferior horn Interventricular foramen Lateral aperture Median aperture Third ventricle Inferior horn Lateral aperture Cerebral aqueduct Fourth ventricle Central canal (a) Anterior view (b) Left lateral view Figure 12.5

11. Cerebral Hemispheres • Surface markings • Ridges (gyri), shallow grooves (sulci), and deep grooves (fissures) • Five lobes • Frontal • Parietal • Temporal • Occipital • Insula

12. Cerebral Hemispheres • Longitudinal fissure • Separates the two hemispheres • Transverse cerebral fissure • Separates the cerebrum and the cerebellum PLAY Animation: Rotating brain

13. Precentral gyrus Central sulcus Postcentral gyrus Frontal lobe Parietal lobe Parieto-occipital sulcus (on medial surface of hemisphere) Lateral sulcus Occipital lobe Temporal lobe Transverse cerebral fissure Cerebellum Pons Medulla oblongata Fissure Spinal cord (a deep sulcus) Gyrus Cortex (gray matter) Sulcus White matter (a) Figure 12.6a

14. Central sulcus Frontal lobe Gyri of insula Temporal lobe (pulled down) (b) Figure 12.6b

15. Left cerebral hemisphere Transverse cerebral fissure Brain stem Cerebellum (d) Figure 12.6d

16. Cerebral Cortex • Thin (2–4 mm) superficial layer of gray matter • Site of conscious mind: awareness, sensory perception, voluntary motor initiation, communication, memory storage, understanding • Each hemisphere connects to contralateral side of the body • There is lateralization of cortical function in the hemispheres

17. Functional Areas of the Cerebral Cortex • The three types of functional areas are: • Motor areas—control voluntary movement • Sensory areas—conscious awareness of sensation • Association areas—integrate diverse information • Conscious behavior involves the entire cortex

18. Motor Areas • Primary (somatic) motor cortex • Premotor cortex • Broca’s area • Frontal eye field

19. Motor areas Sensory areas and related association areas Central sulcus Primary motor cortex Primary somatosensory cortex Premotor cortex Somatic sensation Frontal eye field Somatosensory association cortex Broca’s area (outlined by dashes) Gustatory cortex (in insula) Taste Prefrontal cortex Wernicke’s area (outlined by dashes) Working memory for spatial tasks Executive area for task management Primary visual cortex Working memory for object-recall tasks Vision Visual association area Solving complex, multitask problems Auditory association area Hearing Primary auditory cortex (a) Lateral view, left cerebral hemisphere Motor association cortex Primary sensory cortex Primary motor cortex Sensory association cortex Multimodal association cortex Figure 12.8a

20. Primary Motor Cortex • Located in the precentral gyri • Allows conscious control of precise, skilled, voluntary movements

21. Motor homunculi: upside-down caricatures representing the motor innervation of body regions Posterior Motor Anterior Motor map in precentral gyrus Toes Jaw Primary motor cortex (precentral gyrus) Tongue Swallowing Figure 12.9

22. Premotor Cortex • Anterior to the precentral gyrus • Controls learned, repetitious, or patterned motor skills

23. Broca’s Area • Present in one hemisphere (usually the left) • A motor speech area that directs muscles of the tongue

24. Frontal Eye Field • Controls voluntary eye movements

25. Primary somatosensory cortex Somatosensory association cortex Visual areas Auditory areas Olfactory cortex Gustatory cortex Visceral sensory area Vestibular cortex Sensory Areas

26. Motor areas Sensory areas and related association areas Central sulcus Primary motor cortex Primary somatosensory cortex Premotor cortex Somatic sensation Frontal eye field Somatosensory association cortex Broca’s area (outlined by dashes) Gustatory cortex (in insula) Taste Prefrontal cortex Wernicke’s area (outlined by dashes) Working memory for spatial tasks Executive area for task management Primary visual cortex Working memory for object-recall tasks Vision Visual association area Solving complex, multitask problems Auditory association area Hearing Primary auditory cortex (a) Lateral view, left cerebral hemisphere Motor association cortex Primary sensory cortex Primary motor cortex Sensory association cortex Multimodal association cortex Figure 12.8a

27. Primary Somatosensory Cortex • In the postcentral gyri • Receives sensory information from the skin, skeletal muscles, and joints • Capable of spatial discrimination: identification of body region being stimulated

28. Posterior Sensory Anterior Sensory map in postcentral gyrus Genitals Primary somato- sensory cortex (postcentral gyrus) Intra- abdominal Figure 12.9

29. Somatosensory Association Cortex • Posterior to the primary somatosensory cortex • Integrates sensory input from primary somatosensory cortex • Determines size, texture, and relationship of parts of objects being felt

30. Visual Areas • Primary visual (striate) cortex • Extreme posterior tip of the occipital lobe • Receives visual information from the retinas

31. Visual Areas • Visual association area • Surrounds the primary visual cortex • Uses past visual experiences to interpret visual stimuli (e.g., color, form, and movement)

32. Auditory Areas • Primary auditory cortex • Superior margin of the temporal lobes • Interprets information from inner ear as pitch, loudness, and location • Auditory association area • Stores memories of sounds and permits perception of sounds

33. OIfactory Cortex • Medial aspect of temporal lobes • is also part of the limbic system) • Region of conscious awareness of odors

34. Gustatory Cortex • In the insula • Involved in the perception of taste

35. Visceral Sensory Area • Posterior to gustatory cortex • Conscious perception of visceral sensations, e.g., upset stomach or full bladder

36. Vestibular Cortex • Posterior part of the insula Responsible for conscious awareness of balance (position of the head in space)

37. Multimodal Association Areas • Receive inputs from multiple sensory areas • Send outputs to multiple areas, including the premotor cortex • Allow us to give meaning to information received, store it as memory, compare it to previous experience, and decide on action to take

38. Multimodal Association Areas • Anterior association area (prefrontal cortex) • Contains working memory needed for judgment, reasoning, persistence, and conscience

39. Limbic Association Area • Part of the limbic system • Provides emotional impact that helps establish memories