بسم الله الرحمن الرحيم

1. بسم الله الرحمن الرحيم ﴿و ما أوتيتم من العلم إلا قليلا﴾ صدق الله العظيم الاسراء اية 58

2. Sensory System By Dr. Abdel Aziz M. Hussein Assist. Prof. of Medical Physiology Member of American Society of Physiology

3. Headache

4. Headache Def: • Pain felt in the head region • It is an example of referred pain from deep structures of head Pain sensitive structures in the head • Extracranial structures • All structures in the scalp , covering skull including skin, fasciae, ms, arteries and nerves • Eyes • Paranasal sinuses • Teeth

5. Headache Pain sensitive structures in the head B) Intracranial structures • Brain is insensitive to pain • Some structures are sensitive to pain e.g. • Arteries e.g. middle meninegial arteries • Venous sinuses • Parts of dura covering skull base • Cranial nerves carrying pain V,IX, X

6. Headache Site of referral of intracranial headache : A) Frontal headache: • Due to stimulation of pain receptors above tentorium (referred by trigeminal nerve) B) Occipital headache: • Due to stimulation of pain receptors below tentorium (referred by 2nd cervical nerve)

9. Headache Mechanism: • Irritation of pain sensitive structures e.g. in case of meningitis • Pressure or traction on pain sensitive structures e.g. in brain tumors • Dilatation of pain sensitive structures e.g. arterial dilatation and brain tumors • Spasm of ms e.g. spasm of neck and head ms

10. Headache Causes of Extracranial headache: • Due to stimulation of pain receptors in extracranial structures by; • Spasm of head and neck ms due to emotional tension (psychogenic headache). • Sinusitis: inflammation of nasal sinuses • Eye diseases: • Glaucoma →increased intraocular pressure • Errors of refraction e.g. astigmatism and myopia 4. Oral causes: e.g. teeth caries.

11. Headache Causes of Intracranial headache: • Meningeal irritation e.g. meningitis, trauma, alcoholics and constipation (absorption of toxins from rectum which cause meningeal irritation) • Brain tumours cause pressure, traction, or dilatation of intracranial pain sensitive structures. • Changes in CSF pressure: a) ↓ CSF pressure → compensatory dilatation of blood vessels

12. Headache Causes of intracranial headache: 3) Changes in CSF pressure: b) ↑ CSF pressure → pressure and traction on pain sensitive structures e.g. in hydrocephalus 4) Dilatation of intracranial arteries : • Pulsation of arteries and severe headache as in migraine (due to release of histamine) • Characterized by sudden or paroxysmal attacks of throbbing pain with blurring of vision even nausea and vomiting. b. Hypertension also leads to dilatation of cerebral vessels and headache

14. Somatic Sensory Cortex

15. Somatic Sensory Pathways

16. Somatic Sensory Cortex

17. Somatic Sensory Cortex Def. • It is the part of cerebral cortex that is concerned with perception and interpretation of somatic sensations Types: A) Somatic sensory areas: • 1ry somatic sensory area I (area 3,1,2) • 2ry somatic sensory area II (area 40) B) Somatic sensory association areas (area 5,7)

18. Area 3,1,2 Area 5,7 Area 40

19. Somatic Sensory Area I (Area 3, 1, 2) 1) Site: • Post central gyrus of the parietal lobe

20. Somatic Sensory Area I 2) Structure : • Consists of 6 layers from the surface to inside

21. Somatic Sensory Area I 3) Body representation: Locality representation Modality representation Contralateral (crossed) Inverted or upside down Definite somatotopic organization Proportionate with sensory function of organ or number of receptors • Its neurons arranged into columns , each column respond to specific modality • Pain and temp. have no specific columns but few scattered neurons ( ) mechanoceptive columns

22. Locality representation Crossed or contralateral i.e. receives impulses from opposite side of body

23. Locality representation b) Inverted upside down (except face) : head represented in lower part while leg represented in upper part

24. Locality representation

25. Sensory Homunculus c) Definite somatotopic map or organization i.e. each part of the body has a specific region in SMI

26. Sensory Homunculus Homunculus

27. Locality representation d) Related to functions: size of the represented part is proportionate with its functionnot its size e.g. fingers, lips and face represented by large, while the trunk represented by small areas. • The peripheral parts of the body are widely represented due to; • great number of receptors • greater number of the afferents • little convergence

29. Modality representation

30. Modality representation Deep Pressure Touch sensation Proprioceptive sensations

31. Somatic Sensory Area I 3) Functions: receives nearly all somatic sensations • Fast pain • Fine touch • Fine grades of temperature • Deep sensations pressure, tension, vibration, position, movements • It is concerned with the perception or discrimination of the intensity, locality and fine grades of the sensory stimuli without disclosing their meanings.

32. Somatic Sensory Area I 4) Damage : • Inability to localize accurately the site of different stimuli. • Inability to perceive minute differences in the intensity of sensory stimuli. • Astereognosis i.e. inability to recognize the shapes or forms or texture of materials. • Loss of fine touch and orientation of different parts of body to each other.

33. Somatic Sensory Area II (Area 40) • Site: • Parietal lobe posterior and inferior to lower end of area I 2) Representation: • less sharp than area I • Face represented anterior and legs represented posterior • Receives direct input from VPN of thalamus and from the primary somatic sensory cortex

36. Somatic Sensory Area II (Area 40) 3) Functions: • Start the meaning of somatic sensations 4) Damage: • Defect in learning based on tactile discrimination

37. Somatic Sensory Association Area (Area 5,7) 1) Site: • Parietal lobe behind area I and above area II

38. Somatic Sensory Association Area 2) Connections: Area 3,1,2 Area 5,7 Non specific thalamic nuclei PVNT Visual area Auditory area

39. Somatic Sensory Association Area 3) Functions : • Give the meaning of all types of sensations received from primary sensory areas • Transmit the pre-analyzed kinesthetic sensory information to brain motor centers that helps in control and coordination of movements.

40. Somatic Sensory Association Area 4) Lesion : • Astereognosis (loss of ability to recognize the complex objects). • The sensory information from the opposite side of the body are ignored and neglected and even the brain forgets the other ½ of the body and often forgets to use the contralateral side of his body (Parietal lobe neglect).

43. Sensory Disturbances

44. Syringomyelia Def. • Cystic dilatation of central canal of spinal cord Site: • Lower cervical and upper thoracic segments Effect : • Damage of crossing fibers → loss of pain, temp and crude touch only (dissociated) on both sides of body which have jacket distribution

47. Pain • Temp. • Crude touch Ventral and lateral spinothalamic tracts

50. Tabes Dorsalis Def. • Chronic degenerative disease of dorsal root of spinal central to DRG Cause: • Syphilis of CNS Site: • Usually lumbosacral region and cervicothoracic regions Mechanism: • Syphilis causes inflammation leading to irritation followed by compression and degeneration.