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NEUROPHYSIOLOGY-Part 1.ppt

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					NEUROPHYSIOLOGY
                Dr Habib ur Rehman
                     Professor
    Department of Physiology & Biochemistry
University of Veterinary & Animal Sciences, Lahore
                     PAKISTAN
          Sensory System
• Revive information from environment in
  periphery and transmit information via
  neurons and synaptic relays to CNS
• It consists of
• Receptors
• Afferent neurons
• Synaptic relays
• CNS
            Afferent Neurons
1st order
2nd order
3rd order
4th order
    SENSORY RECEPTORS
Mechanoreceptors – respond to touch, pressure,
  vibration, stretch, and itch
Thermoreceptors – sensitive to changes in
  temperature
Photoreceptors – respond to light energy (e.g.,
  retina)
Chemoreceptors – respond to chemicals (e.g.,
  smell, taste, changes in blood chemistry)
Nociceptors – sensitive to pain-causing stimuli
         Mechanoreceptors
• Activated by pressure or change of pressure
                 Mechanoreceptors
       Receptor          Location       Adaptation

Pacinian corpuscle        s/c, I/m      Very rapidly

Meissner’s corpuscle   Non-hairy skin     Rapidly

Hair follicles           Hairy skin       Rapidly

Ruffini’s corpuscle      Hairy skin       Slowly

Merkel’s receptors     Non-hairy skin     Slowly

Tactile discs            Hairy skin       Slowly
                 Types of Receptors
      Type            Modality         Receptor                   Location
Mechanoreceptors   Touch            Pacinian corpuscle Skin
                   Audition         Hair cell          Organ of corti
                   Vestibular       Hair cell          Cupula, semilunar canal
Photoreceptors     Vision           Rods & cones         Retina
Chemoreceptors     Olfaction        Olfactory receptor   Olfactory mucosa
                   Taste            Taste buds           Tongue
                   Arterial PO2                          Carotid & aortic bodies
                   pH of CSF                             Medulla
Thermoreceptors    temperature      Cold receptors       Skin
                                    Warm receptors       Skin
Nociceptors (NC)   Extreme pain &   Thermal NC           Skin
                      temperature   Polymodal NC         Skin
          Thermal Receptors
• Cold receptors
quiescent > 36oC
• Warm receptors
  quiescent < 36oC
  > 45oC warm
  receptors don’t
  transmit signals,
  rather nociceptors
           Noceceptors (NC)
• Present in skin
• Response to noxious stimuli & produce damage in skin
• Two types
      1. Thermal/mechanical NC
     Sharp, pricking pain (A-delta afferent fibers)

     2. Polymodal NC
     High intensity mechanical/chemical or thermal
     (un-mylinated C-fiber)

				
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