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Objectives

Objectives. Define Sensory Nerve Fibre Outline the various types of sensory nerve fibres Describe two clinical aspects in which damage to sensory nerve fibres is prevalent. Sensory Nerve Fibre:

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Objectives

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  1. Objectives • Define Sensory Nerve Fibre • Outline the various types of sensory nerve fibres • Describe two clinical aspects in which damage to sensory nerve fibres is prevalent

  2. Sensory Nerve Fibre: a threadlike process that conveys impulses from the sensory receptors to the Central Nervous System Sensory Nerves and Sensory Nerve Fibres

  3. The Course of Sensory Nerve Fibres

  4. Types of Sensory Nerve Fibres • Different sensory nerve fibres innervate different sensory receptors • A numerical system is used by physiologists to classify sensory nerve fibres • There are five types of sensory nerve fibres: Ia, Ib, II, III and IV

  5. Type Ia Sensory Nerve Fibre • Origin: muscle spindles • Insertion: CNS • Function: Proprioception • Largest and fastest sensory nerve fibre • Diameter: 17 um • Myelinated • Conduction Velocity: 102m/s

  6. Type Ib Sensory Fibre • Origin: Golgi tendon organ • Insertion: CNS • Function: Proprioception • Diameter: 16 um • Myelinated • Conduction Velocity: 96m/s

  7. Type II Sensory Nerve Fibre • Innervates touch and pressure receptors • Origin: muscle spindle • Insertion: CNS • Diameter: 8 um • Myelinated • Conduction Velocity: 48 m/s

  8. Type III Sensory Nerve Fibre • Innervates sharp pain and cold receptors as well as some touch receptors • Origin:Skin • Insertion: CNS • Diameter: 3 um • Myelinated • Conduction Velocity: 18m/s

  9. Type IV Sensory Nerve Fibres • Innervates mainly slow, burning pain and temperature receptors • Origin: Skin • Insertion: CNS • Diameter: 0.5-2 um • Unmyelinated • Conduction Velocity: 0.7-1.4 m/s

  10. Damage To Sensory Nerve Fibres • Causes hyperactivity in neighbouring sensory nerve fibres of the same type • Causes localized loss of sensation

  11. Clinical: Deep Gash • Symptoms: • Sharp burst of pain • Throbbing sensation

  12. Clinical: Deep Gash • Specific Sensory Nerve Fibres Involved: • Impulse from Sensory Nerve Fibre Type III • Impulse from Sensory Nerve Fibre Type IV

  13. Clinical: Diabetic Neuropathy • Diabetes • Definition: Nerve damage caused by diabetes • Cause: High blood glucose levels combined with lack of insulin formation or the inability to use insulin • Symptoms: • Numbness, tingling or pain in the feet, legs arms, hands, fingers • Loss of sensation in one ore more of these areas so that a person will be unable to detect temperature or to notice pain

  14. Clinical: Diabetic Neuropathy • Specific Sensory Nerve Fibres involved: • Increasing damage to Type Ia, Type Ib, Type II, Type III and Type IV Sensory Nerve Fibres • Treatment: • Lower blood glucose levels

  15. Conclusion • Sensory Nerve Fibres transmit sensation in the form of impulses from receptors to the CNS • The Four types of Sensory Nerve Fibres are classified as Ia, Ib, II, III,IV • Initial damage to Sensory Nerve Fibres cause over activation in nearby Sensory Nerve Fibres which in the case of pain receptors cause enhanced pain • Extensive damage to Sensory Nerve Fibres results in a localized loss of sensation

  16. References • Web Sites: • http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1422013Circulation • http://circ.ahajournals.org/cgi/content/full/circulationaha%3B101/14/1665Journal Archive • http://www.journalarchive.jst.go.jp/english/jnlabstract_en.php?cdjournal=aohc1982&cdvol=46&noissue=4&startpage=469Science Direct • http://www.sciencedirect.com/science _ob=ArticleURL&_ud • Books: • Medical Phyiology, Guytons 11th edition - Pg. 312, 313, 585-597, 664-665f

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