The Central Nervous System

1. The CentralNervous System PART 1

2. Central Nervous System • Brain • Spinal Cord

3. Directional Terms of the Central Nervous System • Directional terms unique to the CNS • Rostral – toward the nose (anterior) • Caudal – toward the tail (posterior) • Dorsal – superior • Ventral - inferior

4. Four Main Regions of the Brain • Cerebral hemispheres • Diencephalon • Brain stem: • midbrain • Pons • medulla • Cerebellum

5. Basic Organization of Gray and White Matter in the CNS Figure 13.5

6. Ventricles of the Brain • Filled with cerebrospinal fluid • Lined with ependymal cells • Continuous with each other • Continuous with the central canal of the spinal cord

7. Lateral Ventricles • Lateral ventricles – located in cerebral hemispheres • Horseshoe-shaped Figure 13.6a, b

8. Third Ventricle • Third ventricle – lies in diencephalon • Connected with lateral ventricles by interventricular foramen Figure 13.6a, b

9. Fourth Ventricle • Fourth ventricle – lies in hindbrain • Connects to the central canal of the spinal cord Figure 13.6a, b

10. Ventricles of the Brain • Cerebral aqueduct – connects 3rd and 4th ventricles Figure 13.6a, b

11. The Cerebral Hemispheres • Account for 83% of brain mass • Landmarks • Lateral fissure • Longitudinal fissure • Sulci (sulcus) – grooves • Gyri (gyrus) – ridges • Central sulcus

12. The Cerebral Hemispheres: Fissures • Fissures – deep grooves – separate major regions of the brain • Transverse fissure – separates cerebrum and cerebellum • Longitudinal fissure – separates cerebral hemispheres

13. The Cerebral Hemispheres: Sulci and Gyri • Sulci – grooves on the surface of the cerebral hemispheres • Gyri – twisted ridges between sulci • Prominent gyri and sulci are similar in all people

14. The Cerebral Lobes • Deeper sulci divide cerebrum into lobes • Lobes are named for the skull bones overlying them

15. Frontal Lobe • Anterior/rostral to central sulcus • Superior to transverse/lateral fissure

16. Parietal Lobe • Posterior to central sulcus • Superior to lateral fissure • Anterior to parieto-occipital sulcus

17. Temporal Lobe • Inferior to lateral fissure (sulcus) • Anterior to occipital lobe

18. Occipital Lobe • Posterior & inferior to parieto-occipital sulcus • Posterior to temporal lobe

19. Top View of the Cerebral Hemispheres Figure 13.7b, c

20. Insula

21. Gray and White Matter in the CNS • Frontal section through forebrain • Cerebral cortex • Cerebral white matter • Deep gray matter of the cerebrum (basal ganglia)

22. Frontal Section of Forebrain Figure 13.8

23. The Cerebral Cortex • Composed of gray matter 2 – 4 mm thick • Neuronal cell bodies, dendrites, and short axons • Folds in cortex – triples its size • Approximately 40% of brain’s mass • Brodmann areas – 52 structurally distinct areas (we will not cover these by number, only name)

24. Functional and Structural Areas of the Cerebral Cortex Figure 13.11a

25. Functional and Structural Areas of the Cerebral Cortex Figure 13.11b

26. The Cerebral Cortex • Three kinds of functional areas • Motor areas • Sensory areas • Association areas

27. Motor Areas – Primary Motor Cortex • Controls motor functions • Primary motor cortex (somatic motor area) • Located in precentral gyrus • Pyramidal cells – large neurons of primary motor cortex

28. Motor Areas – Corticospinal Tract (Pyramidal Tract) • Corticospinal tracts descend through brainstem and spinal cord • Axons signal motor neurons to control fine skilled movements • Contralateral – pyramidal axons cross over to opposite side of the brain

29. Corticospinal Tract

30. Primary Motor Cortex Organization • Specific pyramidal cells control specific areas of the body • Face and hand muscles – controlled by many pyramidal cells for fine control • Motor homunculus – body map of the motor cortex • Somatotopy – body is represented spatially in many parts of the CNS

31. Motor Homunculus Figure 13.10

32. Motor Areas – Premotor Cortex • Located anterior to the precentral gyrus • Controls more complex movements • Involved in the planning of movements

33. Motor Areas – Frontal Eye Field • Lies anterior to the premotor cortex • Controls voluntary movement of the eyes • Especially when moving eyes to follow a moving target

34. Motor Areas – Broca’s Area • Located in left cerebral hemisphere • Manages speech production • Corresponding region in the right cerebral hemisphere • Controls emotional overtones to spoken words

35. Sensory Areas • Cortical areas involved in conscious awareness of sensation • Distinct area for each of the major senses

36. Sensory Areas – Primary Somatosensory Cortex • Located along the postcentral gyrus or parietal lobe • Involved with conscious awareness of general somatic senses

37. Sensory Areas – Primary Somatosensory Cortex • Projection is contralateral • Cerebral hemispheres • Receive sensory input from the opposite side of the body • Sensory homunculus – a body map of the sensory cortex

38. Sensory Areas – Sensory Homunculus Figure 13.10

39. Sensory Areas – Somatosensory Association Area • Lies posterior to the primary somatosensory cortex • Integrates different sensory inputs • Touch, pressure, and others • Draws upon stored memories of past sensory experiences

40. Sensory Areas – Primary Visual Cortex • Primary visual cortex • Located deep within the calcarine sulcus • On the posterior and medial part of the occipital lobe • Receives visual information that originates on the retina • First of a series of areas that interprets visual input

41. Sensory Areas – Visual Association Areas • Visual association area • Surrounds the primary visual area • Continues the processing of visual information • Complex visual processing extends into: • Temporal and parietal lobes

42. Visual Association Areas continued • Approximately 30 cortical areas have been identified • Visual information proceeds in two streams

43. Sensory Areas – Ventral and Dorsal Streams • Ventral stream – into inferior part of the temporal lobe • Responsible for recognizing objects, words, and faces = “What” • Dorsal stream – extends to the postcentral gyrus • Perceives spatial relationships = “Where”

44. Sensory Areas – Primary Auditory Cortex • Primary auditory cortex • Function – conscious awareness of sound • Location – superior edge of the temporal lobe

45. Sensory Areas – Auditory Association Areas • Auditory association area • Lies posterior to the primary auditory cortex • Permits evaluation of different sounds

46. Sensory Areas – Gustatory Cortex • Involved in the conscious awareness of taste stimuli • Located on the “roof” of the lateral sulcus

47. Sensory Areas – Vestibular Cortex • Located in the posterior part of the insula • Deep to the lateral sulcus

48. Sensory Areas – Olfactory Cortex • Lies on the medial aspect of the cerebrum • Located in a region called the piriform lobe • Olfactory nerves transmit impulses to the olfactory cortex • Provides conscious awareness of smells

49. Sensory Areas – Olfactory Cortex • Connects the brain to the limbic system • Explains why smells trigger emotions • Orbitofrontal cortex • Involved with consciously identifying and recalling specific smells

50. Association Areas • Make associations between different types of sensory information • Associate new sensory input with memories of past experiences • New name for association areas – higher order processing areas