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Understanding Sensation and Perception

Nov 13, 2024

Sensation and Perception

Definition

  • Sensation
    • Awareness of changes in internal and external environment.
    • Occurs in the peripheral nervous system (sensory division).
  • Perception
    • Conscious interpretation of stimuli.
    • Occurs in the central nervous system, specifically the brain.

Importance

  • Survival depends on the ability to sense and perceive.

Levels of Sensory Perception

  1. Feature Abstraction
    • Understanding of specific textures or shapes.
  2. Quality Discrimination
    • Understanding sub-modalities of a sensation.
  3. Pattern Recognition
    • Highest level of perception, recognizing patterns in stimuli.

Classification of Sensory Receptors

Based on Stimulus Type

  • Mechanoreceptors
    • Detect touch, vibration, stretch.
    • Found in inner ear and skin.
  • Thermoreceptors
  • Photoreceptors
  • Chemoreceptors
  • Nociceptors

Based on Location

  • Exteroceptors
    • Detect external stimuli.
  • Visceroceptors (Interoceptors)
    • Detect internal body conditions, e.g., blood.
  • Proprioceptors (Sixth Sense)
    • Awareness of body position in space.

Based on Structural Complexity

  • Complex Structures
    • Sense organs like eyes, retina, nasal epithelium.
  • Simple Structures
    • Dendritic nerve endings of sensory neurons.
    • More numerous.

Example: Hair Cells

  • Mechanoreceptors
    • Respond to pressure/vibrations in ear.
  • Exteroceptors
    • Respond to external stimuli.
  • Simple
    • As individual cells, but part of a complex organ (organ of Corti).

Somatic Sensation

Types

  • Touch, pressure, temperature.

Receptors

  • Encapsulated Receptors
    • Mostly mechanoreceptors.
    • Varied distribution around the body.
    • Examples:
      • Meissner's corpuscles (Tactile corpuscles)
      • Pacinian corpuscles (Lamellar corpuscles)
      • Muscle spindles
      • Golgi tendon organs
      • Ruffini's corpuscles
      • Joint kinesthetic receptors
  • Unencapsulated Receptors
    • Found in epithelium and connective tissues.
    • Examples:
      • Free dendritic nerve endings (detect temperature and pain)
      • Tactile discs (deepest layer of epidermis)
      • Hair follicle receptors (very sensitive to light touch)

Adaptation (Habituation/Desensitization)

  • Some sensory receptors become less responsive over time.
  • Phasic Receptors: Rapid habituation.
  • Some receptors do not habituate at all.
  • Examples to be discussed further in class.

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