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Part 6

Sensory analysis function of the nervous system. Section 1: Analysis of CNS to somatic sensation Section 2: Analysis of CNS to visceral sensation Section 3: Analysis of CNS to special sensation. Part 6. Section 1: Analysis of CNS to somatic sensation. 1.Afferent pathway of somatic sensation.

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Part 6

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  1. Sensory analysis function of the nervous system Section 1: Analysis of CNS to somatic sensationSection 2: Analysis of CNS to visceral sensation Section 3: Analysis of CNS to special sensation Part 6

  2. Section 1: Analysis of CNS to somatic sensation 1.Afferent pathway of somatic sensation Changes of internal and external environment Interoceptor and exteroceptor Sensory Afferent pathways Thalamus and cerebral cortex Superficial sensation Corresponding reflex

  3. Sensory afferent pathways

  4. The afferent system of anterior thalamus • Two alternative pathways: • The dorsal column-medial lemniscal system • Fine touch, two-point discrimination, 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  brainstem and thalamus

  5. The dorsal column-medial lemniscal system

  6. The anterolateral system

  7. Trigeminal nerve - trigeminal lemniscus

  8. Gate control theory of posterior horn of spinal cord gate control theory suggests that the spinal cord contains a neurological "gate" that blocks pain signals or allows them to continue on to the brain. Pain signals traveling via small nerve fibers are allowed to pass through, while signals sent by large nerve fibers are blocked. Gate control theory is often used to explain chronic pain.

  9. Anatomical characteristics of sensation pathways and its performance when damaged

  10. The nucleus of the thalamus

  11. Function of thalamus Specific sensory relay nucleus Somatic sensory ventral posterior nucleus  somatic sensory area    Visual signal lateral geniculate nucleusvisual cortex Auditory signal medial geniculate nucleus auditory cortex

  12. Associated nucleus • Anterior nucleus • ventral-lateral nucleus • Pulvinar nucleus Anterior nucleus receive the fibers from hypothalamic mamillary body , send fibers to project the cingulate gyrus of cerebral cortex, involved in regulation of visceral activities. Ventral-lateral nucleus mainly receive the fibers from cerebellum, globus pallidus and ventral posterior nucleus, then send fibers to project the motor cortex, involved in the movement regulation; Pulvinar nucleus receive the fibers from medial and lateral geniculate nucleus, then send fibers to project the association area of cortex, involved in a variety of sensory contact function.

  13. Nonspecific projection nucleus • Medial nucleus • Nucleus in lamina Various structure near the midline, is mainly the internal laminar nucleus group, including central nucleus, parafascicular nucleus, lateral central nucleus. cell groups are projected onto the cortex, its function is to keep and change the cerebral cortex excitatory state. Parafascicular nucleus may be related to pain, stimulus to the area can aggravate pain, and damage to the area can reduce pain.

  14. Specific projection system of thalamus Sensory projection system • Receive fibers from ascending somatic sensory pathways and projects mostly to a localized (discrete) region of the cortex - focal projection

  15. Nonspecific projection system of thalamus Sensory projection system • receive afferent fibers from reticular formation and send fibers to very broad regions of cortex - diffuse projection

  16. Sensory projection system

  17. 2.Sensory areas of cerebral cortex

  18. Somatic sensory area • Primary area Located in the postcentral gyrus The sensory projection rules:

  19. Functional unit of the sensory cortex: Sensory column Sensory column :The cells in postcentral gyrus cortex are longitudinal column arrangement.

  20. Second area

  21. Proprioception area

  22. 3.Somatic sensation 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

  23. Pain sensation • Superficial pain • Deep pain

  24. 1. Afferent pathway of visceral sensation Autonomic nerves

  25. 2. Visceral sensation Characteristics of visceral pain • Poorly localized • Occurs slowly, long duration(usually slow pain) • Receptors on hollow viscera (such as stomach, intestine, gallbladder and bile duct) is very sensitive to expanding and pulling stimulus, is not sensitive to cutting and burning stimulus • Secondary autonomic symptoms (sweating, vomit, nausea) and unpleasant emotional activity

  26. 2. Visceral sensation Parietal pain Visceral disease can stimulate the adjacent parietes or skeletal muscle spasm to produce the pain. For example, peritonitis can cause parietal pain.

  27. Referred pain

  28. Mechanism of referred pain • Convergence theory • Facilitation theory

  29. 1.Visual sensation Afferent pathway

  30. Visual cortex  Include：primary visual cortex (17 area) secondary visual cortex (18 area) Advanced visual cortex (19 area) cortex association area of occipital or parietal lobe  Area that is related with these cortex: Controlling eye movement area in brainstem Cortical language center Contact the other side of the brain via the corpus callosum

  31.  Visual cortex structure

  32.  Orientation column

  33. Analysis of CNS to vision Projection rule of visual fibers

  34. The visual pathway from the retina to the visual cortex. Lesions in the visual pathway (a-g) produce defects of the visual fields as indicated at the right.

  35. 2. Auditory sensation Afferent pathway

  36. Auditory cortex 3. Equilibrium sensation

  37. Control of Posture and Motor Function Section 1: Final common pathway of motor efferent Section 2: Central regulation to postureSection 3: Central regulation to somatic movement Part 7

  38. Section 1: Final common pathway of motor efferent 1. Motor neuron in spinal cord and brainstem •  motor neuron • A  motor nerve fiber large skeletal muscle fibers • Final common pathway for somatic motor reflex Cause voluntary motor Regulate posture Coordinate the activities of different muscle groups

  39. β-motor neuron it control both extrafusal muscle and intrafusal muscle. But its function is not very clear. •  motor neuron • A  motor nerve fiber intrafusal fibers

  40. 2. Motor unit • A single  nerve fiber + skeletal muscle fibers

  41. Section 2: Central regulation to posture 1. Regulation function of spinal cord Spinal shock  Spinal shock:.  Spinal animal:

  42. (2) Regulation of spinal cord to posture 1) Crossed extensor reflex

  43. (2) Regulation of spinal cord to posture 2) Stretch reflex Tendon reflex: Rapid stretchinstantaneous, strong reflex contraction Monosynaptic reflex: knee reflex, achilles tendon reflex and elbow reflex

  44. Muscle tonus: Slow stretch weaker continuous contraction Polysynaptic reflex:

  45. Reflex arc of stretch reflex Sensory receptors • Muscle spindle • Intrafusal fibers • Nuclear bag muscle fiber • Nuclear chain fiber • Stimulation: • Muscle length or change rate of length

  46. Intrafusal fibers

  47. Relationship of Ia afferent fibers and α-motor neuron When the muscle is in resting state: Ia afferent can send a certain frequency impulse,which play a role in the α-motor neuron activity When the muscle is shortened: because of intrafusal muscle relaxation, Ia afferent impulse reduce, so the excitatory function to alpha motor neurons also reduce. When the muscle is stretched: because of intrafusal muscle tension, Ia afferent impulse increase, so the excitatory function to alpha motor neurons also increase. When γ-efferent impulse increase: because of intrafusal muscle tension, Ia afferent impulse increase, so the excitatory function to alpha motor neurons also increase.

  48. Golgi tendon organ • Stimulation: Tendon tension or change rate of tension • Provide a negative feedback

  49. Comparison of muscle spindle and tendon organ

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