SENSATION

1
SENSATION

• This is a sensational lecture!

2
Peripheral Sensory Receptors

• SENSATION state of detection and communication
  of external or internal condition of body may be
  unconscious.
• PERCEPTION conscious registration or awareness
  of sensation.

3
Sensation requires four components

• Stimulus energy change in environment initiates
  impulse in receptor/sensory neuron
• Receptor converts stimulus energy to impulse
  (action potential)
• Conduction of impulse over sensory pathway to
  CNS
• Translation region of CNS receives impulse(s)
  integrates information may prepare response.

4
Sensation

• Conduction and translation are functions of
  neurons and CNS.
• Primarily concerned here with Stimuli and
  Receptors

5
Stimulus

• Environmental energy, or energy change, that
  causes a receptor potential in a receptor cell
  sufficient to produce an action potential in a
  sensory neuron.

6
Stimuli and Receptor types

• Light photoreceptor
• Heat thermoreceptor
• Chemicals chemoreceptor
• Pain nociceptor
• Mechanical force mechanoreceptor
• touch light, deep
• pressure (including gravity)
• vibration
• stretch

7
Locations of Receptors

• Exteroceptors
• at or near body surface
• react to external stimuli
• Visceroceptors or interoceptors
• deep
• react to internal body condition
• Proprioceptors
• muscles, tendons, ligaments
• react to muscle tone, tension, stretch

8
Senses

• Sight, vision
• Hearing
• Taste
• Smell
• Touch
• 5, according to Aristotle

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Special Senses and Sensors

• Vision - photoreceptors (retina)
• Hearing - phonoreceptors (hair cells in cochlea)
• Balance, equilibrium - mechanoreceptors (hair
  cells in vestibules semicircular ducts)
• Olfactory receptors - chemoreceptors (nasal
  mucosa)
• Gustatory receptors - chemoreceptors (taste buds)

10
General Senses and Sensors

• Light touch - Merkel discs, Meissner's corpuscles
• Deep pressure - Pacinian corpuscles, Ruffini's
  corpuscles
• Hair deflection - hair root plexuses
• Temperature change - free dendritic endings
• Muscle stretch - muscle spindles
• Tendon stretch - Golgi tendon organs
• Ligament joint capsule stretch - joint
  kinesthetic receptors
• Pain - free dendritic endings
• Itch - free dendritic endings

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How many senses?

• Five ??
• 12-14 (above)