1. The sensory function of brain
Nervous system Ⅲ
The sensory function of brain

2. Senses

3. Five basic types of sensory receptors
Mechanoreceptors
Thermoreceptors
Nociceptors(pain receptors): physical or chemical damage
Electromagnetic receptors:light on the retina of the eye
chemoreceptors

4. Sensory receptor A: Free nerve endings (pain, temperature)B C D
A: Free nerve endings (pain, temperature)
B: Pacinian corpuscle (pressure)
C: Meissner’s corpuscle (touch)
D: Muscle spindle (stretch)

5. sensation

6. sensation Somatic senses Mechanoreceptive somatic senses
Stimulated by mechanical compression or stretching of some tissue of the body
Tactile sense
Touch , pressure, vibration , tickle senses
position sense
Static position and rate of movement senses
Thermoreceptive senses
Detect heat and cold
Pain senses

7. sensation Sensory pathway: 1st : enters spinal cord from periphery
2nd : crosses over (decussates), ascends in spinal cord to thalamus
3rd : projects to somatosensory cortex

8. oblongata

10. Sensory pathway Spinothalamic pathway(anterolateral system)
Dorsal column pathway (dorsal column– medial lemniscal system)
Spinocerebellar pathway

11. Spinothalamic pathway
Function
Carries pain, temperature, crude touch and pressure signals (superficial sensations)
Three-order neuron
1st order neuron enters spinal cord through dorsal root
2nd order neuron crosses over in spinal cord; ascends to thalamus
3rd order neuron projects from thalamus to somatosensory cortex

12. spinothalamic
pathway
Pain , temperature, crude touch and pressure signals

13. Spinothalamic Pathway
Primary somatosensory cortex (S1)
Thalamus
Medulla
Small sensory fibres:
Pain, temperature, some touch
Spinothalamic tract
Spinal cord

14. Spinothalamic damage spinothalamic pathway spinal cord injury
Loss of sense of (superficial sensations):
crude Touch
Pain
Warmth/cold
in right leg

15. Dorsal column pathway Function Three-order neuron
Carries fine touch, vibration and conscious proprioception signals
(deep sensations)
Three-order neuron
1st order neuron enters spinal cord through dorsal root; ascends to medulla (brain stem)
2nd order neuron crosses over in medulla; ascends to thalamus
3rd order neuron projects to somatosensory cortex

16. dorsal
cloumn
pathway
fine touch, vibration and conscious proprioception signals

17. Dorsal column pathway Large sensory nerves:
Primary somatosensory cortex (S1) in parietal lobe
Dorsal column
nuclei
Thalamus
Medulla
Medial
lemniscus
Dorsal column
Large sensory nerves:
Fine Touch, vibration, two-point discrimination, proprioception
Spinal cord

18. Dorsal column pathway Function
Sensory nuclei of the trigenimal nerve which subserve the same sensory functions for the head

19. Dorsal column damage dorsal column spinal cord injury pathway
Loss of sense of (deep sensations):
Fine touch
proprioception
vibration
in left leg

20. Central Pathways

21. Differences between the two system
Velocities
The dorsal column–medial lemniscal system: large, myelinated nerve fibers
30 to 110 m/sec,
The anterolateral system :smaller myelinated fibers
a few meters per second up to 40 m/sec.

22. Differences between the two system
spatial orientation : in spinal cord
the dorsal column–medial lemniscal system :high degree of with respect to their origin
the anterolateral system : much less spatial orientation
lower parts of the body---center of the cord
higher parts---lateral layers

23. Spinocerebellar pathway
Function :
receives inputs from golgi tendon organs and muscle stretch receptors. proprioception signals
Receptors : muscles & joints
Three-order neuron
1st order neuron: enters spinal cord through dorsal root
2nd order neuron: ascends to cerebellum
3rd order neuron to cortex
The ventral spinocerebellar tract conveys proprioceptive information from the body to the cerebellum. It is part of the somatosensory system and runs in parallel with the dorsal spinocerebellar tract. Both these tracts involve two neurons. The ventral spinocerebellar tract will cross to the opposite side of the body then cross again to end in the cerebellum (referred to as a "double cross"), as compared to the dorsal spinocerebellar tract, which does not decussate, or cross sides, at all through its path.

24. Spinocerebellar pathway
Division
Peripheral Process of First Order the Neuron
Region of Innervation
dorsal (posterior) spinocerebellar tract
from muscle spindle (primarily) and golgi tendon organs
Ipsilateral Caudal Aspect of the body and legs
ventral (anterior) spinocerebellar tract
from golgi tendon organs
The ventral spinocerebellar tract conveys proprioceptive information from the body to the cerebellum. It is part of the somatosensory system and runs in parallel with the dorsal spinocerebellar tract. Both these tracts involve two neurons. The ventral spinocerebellar tract will cross to the opposite side of the body then cross again to end in the cerebellum (referred to as a "double cross"), as compared to the dorsal spinocerebellar tract, which does not decussate, or cross sides, at all through its path.

25. Dorsal column damage Sensory ataxia (loss of coordination)
Patient staggers; cannot perceive position or movement of legs
partially compensated by visual surveillance
ataxia [英] [ə‘tæksiə] 共济失调

26. Spinocerebellar tract damage
Cerebellar ataxia
a failure of the fine coordination of muscle movements
Clumsy movements
Incoordination of the limbs (intention tremor)
Wide-based, reeling gait (ataxia)
Alcoholic intoxication produces similar effects
reeling gait 步态蹒跚

27. "inner chamber” in Greek
thalamus
anterolateral view
"inner chamber” in Greek

29. Compositions of thalamus
Geniculate [英] [dʒiˈnikjulit]
ventral posterior thalamus
pulinar

30. Lateral-lower part of body Medial –upper part

32. thalamus 2 Associated nuclei Receive their driving inputs from
Other cortical areas
ventral-lateral nucleus
cerebullum ,globus pallidus—motor
Pulvinar nucleus
Medial ,lateral geniculate--sensors
ventral lateral
pulvinar nucleus

33. thalamus 3 nonspecific projection nucleus
“nonspecific nuclei”connect to association areas of cortex and/or limbic structure.
Anterior nuclei
Medial nuclei
Intralaminar and reticular nuclei
limbic structure
intralaminar reticular
nonspecific projection nuclei: Dispersion in projection

35. Projection system of thalamus
Discrete fenlide

36. Projection system of thalamus
Reticular formation

37. Projection system of thalamus
Function
Specific projection system of thalamus
Specific senses: visual or auditory cortex (except olfaction)
Non-specific projection system of thalamus
Maintain and alter the excitatory situation of cortex

39. Sensory areas of cerebral cortex postcentral gyrus

40. Somatosensory cortex
Located in the post-central gyrus of the human cerebral cortex Ⅰ
gyrus [英] [ˈdʒaiərəs]
coronal section
Sagittal section
From side

41. Somatotopic map of the somato-sensory cortex

42. Somatosensory cortex Cross projection
Each side of the cortex receives sensory information exclusively from the opposite side of the body (the exception: the sensor information from face is bilateral projection).
exclusively

43. Somatosensory cortex
The finer the sense, the larger the somato-sensory cortex area
The lips, face and thumb are represented by large areas in the somatic cortex, whereas the trunk and lower part of the body, relatively small area.
exclusively

44. Somatosensory cortex Inversely projection “Up is down and down is up ”
The head in the most lateral portion, and the lower body is presented medially.
exclusively

45. Proprioception sensory area

46. Visual cortex
Primary visual cortex
Secondary visual areas

47. bitamporal
nasal side
chiasma [英] [kaiˈæzmə] bitamporal

49. Pain
: Easily localized, occur first
: occur second

52. Pain Impulses transmitted to spinal cord by
Myelinated Aδ nerves: fast pain (80 m/s)
Unmyelinated C nerves: slow pain (0.4 m/s)
spinothalamic
pathway
to reticular
formation
Aδ nerve
C nerve
nociceptor
nociceptor

53. Impulses ascend to somatosensory cortex via:
thalamus
spinothalamic
pathway
reticular
formation
Impulses ascend to somatosensory cortex via:
Spinothalamic pathway (fast pain)
Reticular formation (slow pain)---cingulate gyrus

54. Viseral sensation:
Pain ?
without proprioceptor
few thermoceptor

55. Spasm of a hollow viscus

57. Visceral pain Poorly localized; may be “referred” Slow pain
Mostly caused by distension of hollow organs or ischemia (localized mechanical trauma may be painless)

58. Visceral pain
Agina:
due to ischemia of the heart muscle, generally due to obstruction or spasm of the coronary arteries.

59. Refered pain
is pain perceived at a location other than the site of the painful stimulus
Site of pain may be distant from organ
umbilicus

60. Visceral pain myocardial infarction :
 (heart attack), where pain is often felt in the neck, shoulders, and back rather than in the chest, the site of the injury. 

61. Mechanism of refered pain
Convergence theory
The primary afferent axons of skin and viscera converged on the same interneurons in the pain pathways.

62. Mechanism of refered pain
Convergence theory
This theory explains why referred pain is believed to be segmented in much the same way as the spinal cord.
 Fail to explain why there is a delay between the onset of referred pain after local pain stimulation.
 Threshold for the local pain stimulation and the referred pain stimulation are different, but according to this model they should both be the same.

63. Mechanism of referred pain
Facilitated theory
The primary afferent axons of skin and viscera closed to each other

64. Mechanism of referred pain
Facilitated theory
to explain why there is a delay between the onset of referred pain after local pain stimulation.

65. Summary Spinothalamic pathway Dorsal column pathway
Specific projection system
Non-specific projection system
Sensory area of cerebral cortex
Referred pain