1. Part 6 The Sensory Function of CNS

2. Sensation production Changes of internal and external environment Interoceptor and exteroceptor Sensation conduction pathway Thalamus and cerebral cortex Superficial sensation Corresponding reflex

3. Senses Somatic senses  Mechanoreceptive somatic senses Tactile and position  Thermoreceptive senses  Pain sense Special senses

4. Five basic types of sensory receptors Mechanoreceptors Thermoreceptors Nociceptors (Pain receptors) Electromagnetic receptors Chemoreceptors

5. The somatosensory system includes multiple types of sensation from the body--- light touch, pain, pressure, temperature, joint and muscle position sense (also called proprioception). Sensory pathways: Spinal cord  Brainstem  Thalamus  Cerebral cortex

6. Spinal cord

7. Sensory pathways in spinal cord Two alternative pathways:  The dorsal column-medial lemniscal system Fine touch, two-point discrimination, phasic or position sensation  dorsal column  cross in medulla  medial lemniscal system  thalamus  The anterolateral system Pain, warmth, cold, crude tactile, tickle and itch, sexual sensation  dorsal spinal roots  cross in spinal cord  brain stem and thalamus

8. 1.The dorsal column-medial lemniscal system

9. 2. The anterolateral system

10. Structure of Thalamus

11. A relay station to the cerebrum for all varieties of sensory input except olfaction Function of thalamus

12. 1. Specific sensory relay nuclei Somatosensory  ventral-posterior (VP thalamus)  somatosensory area I Visual signal  lateral geniculate body  visual cortex Auditory signal  medial geniculate body  auditory cortex

13. Nuclei of Thalamus

14. 2. Associated nuclei Association nuclei receive their driving inputs from other cortical areas  Anterior nucleus  ventral-lateral nucleus  Pulvinar nucleus

15. 3. Nonspecific projection nuclei “Nonspecific nuclei" connect to association areas of cortex  Medial nucleus  Nuclei in lamina

16. Specific projection system of thalamus The projecting system of thalamic relay nuclei receives fibers from ascending somatosensory pathways and projects mostly to a localized (discrete) region of the cortex - focal projection

17. Nonspecific projection system of thalamus Nonspecific thalamic nuclei receive afferent fibers from reticular formation and send fibers to very broad regions of cortex - diffuse projection

18. Sensory areas of cerebral cortex Somatic sensory information in venter posterior nucleus are projected onto specific area of cerebral cortex though specific projection system, the area is called the somatic sensory area, mainly including somatosensory area and proprioception area.

19. Sensory Area of Cerebral Cortex 1. Somatosensory area  Primary somatosensory area Located in the postcentral gyrus The sensory projection rules:

20. What is Sensory column?

21.  Second Somatosensory area

22. Sensory Area of Cerebral Cortex 1. Somatic sensory area 2. Proprioception area

23. Somesthesia 1. Touch & Pressure sensation  Two afferent pathways: medial lemniscus and anterior lateral lemniscus. Only wide central damage can block completely the sensation.  Touch and pressure types in two pathways are different:  When pathways damaged 2. Proprioception 3. Temperature sensation 4. Pain sensation

24. Part 7 Control of Motor Function

25. Somatic movement

26. Motor functions of the spinal cord Anterior motor neurons  Anterior horns of the cord gray matter

27. Types of motor neurons  motor neuron  A  motor nerve fiber  large skeletal muscle fibers  Final road of the cord reflex  motor neuron  A  motor nerve fiber  intrafusal fibers β-motor neuron

28. Motor unit A single  nerve fiber + skeletal muscle fibers

29. Spinal shock

30. The spinal cord reflexes Stretch reflex Flexor reflex Crossed extensor reflex

31. Types of stretch reflex 1. Tendon reflex (dynamic stretch reflex)  Rapid stretch  instantaneous, strong reflex contraction  Monosynaptic reflex

32. 2. Muscle tonus (static stretch reflex) Slow stretch  weaker continuous contraction Polysynaptic reflex

33. Reflex arc of stretch reflex 1. Sensory receptors  Muscle spindle Intrafusal fibers  Nuclear bag muscle fiber  Nuclear chain fiber Stimulation:  Muscle length or rate of change of its length

34. Intrafusal fibers:

35.  Golgi tendon organ Stimulation: Tendon tension or rate of change of tension Providing a negative feedback

36. 2. Afferent fibers of stretch reflex Muscle spindle  Ia fiber  II fiber (flower-spray ending) Golgi tendon organ  Ib fiber

37. 3. Neural center: anterior motor neurons 4. Efferent fibers: large  motor nerve fibers or small  motor nerve fibers 5. Effector: extrafusal skeletal muscle fibers

38. Summary of stretch reflex 1) When the stretch receptors fire, the a-motor neuron is excited, and the muscle contracts 2) When the Golgi tendon organ fires, the a-motor neuron is inhibited (via an inhibitory interneuron), and the muscle relaxes

39. Flexor reflex  Nociceptive reflex, withdrawal reflex or pain reflex  A spinal reflex intended to protect the body from damaging stimulus, and is polysynaptic

40. Crossed extensor reflex

41. Brain stem control of motor function Brain stem  Medulla, pons, and mesencephalon Reticular system  Facilitatory and inhibitory area  Regulation of muscle tonus

42.  Facilitatory & inhibitory area

43. Decerebrate rigidity Sectioned below the midlevel of the mesencephalon Antigravity muscles  Neck, trunk and extensors of the legs

44. Decorticate rigidity (A, B, C) A: supine position. head pose is normal, upper limbs is half flexion; B and C: the upper limb posture in rotating the head ; Decerebrate rigidity (D) Both upper and lower limbs are stiff. Decorticate rigidity

45.  Mechanism of decerebrate rigidity  Alpha rigidity: alpha rigidity is caused by the descending function of high center to increase alpha motor neuron activity. Alpha rigidity is mainly realized through the vestibulospinal tract.  Gamma rigidity: gamma rigidity is caused by the descending function of high center to firstly increase gamma motor neuron activity then alpha motor neuron activity. Gamma rigidity is mainly realized through the reticulospinal tract.

46. Brain stem regulation to posture  Attitudinal reflex  Tonic neck reflex:  Tonic labyrinthine reflex:  Righting reflex

47. 1. Production of voluntary movement CNS Regulation to Somatic Motor 2. Cortical motor area  Primary motor area

48. Its function characteristics  Primary motor area

49.  Other motor area

50. 3. Efferent Pathway of Cerebral Cortex  Corticospinal tract Including corticospinal tract and corticonuclear tract  Cortex lateral funiculus of spinal cord :  Cortex anterior funiculus of spinal cord:  Corticonuclear tract  Efferent pathway injury

51.  Babinski sign

52. 4. Motion Regulatory Function of Basal Ganglia  Structure of Basal Ganglia

53.  Connection between basal ganglia and cerebral cortex

54. Direct pathway and indirect pathway DA: dopamine GABA: gamma- aminobutyric acid GLu: glutamate (+): excitatory effect (-): inhibitory effect

55.  Nigrostriatal dopaminergic projection system

56. Parkinson’s disease

58. Huntington disease What is Huntington's Disease? Symptoms: Pathological mechanism :

59. 5. Motion Regulatory Function of Cerebellum

60.  Structure of Cerebellum

61.  Vestibulocerebellum

62.  Spinocerebellum

63.  Corticocerebellum

64. The central analysis to visceral sensation Afferent Pathway and Cortical Area

65. Visceral sensation 1. Characteristics of visceral pain: 2. Parietal pain 3. Referred pain

66. Mechanism of referred pain

67. The central analysis to special sensation Vision 1. Afferent pathway

68. 2. Visual cortex Vision

69.  Visual cortex structure 

70.  Orientation column

71. Auditory sensation 1. Afferent pathway

72. Auditory sensation 2. Auditory cortex