Sensory Adaptation vs Sensory Amplification

Sensory Adaptation

• Definition: Change over time in the responsiveness of a sensory receptor to a constant stimulus.
• Mechanism: Downregulation of a sensory receptor due to a lack of change in the stimulus.
  • Example:
    • Placing a hand on a table
    • Initial contact activates pressure receptors in the fingers and palm.
    • Receptors send signals to the brain.
    • After a few seconds, receptors stop firing, even if the hand is still on the table.
• Explanation:
  • Pressure causes the receptor cell to fire an action potential which reaches the brain.
  • If the pressure remains constant, the receptor stops sending signals.
  • Pressing down harder resets the cycle temporarily.
• Importance:
  • Prevents the brain from being overloaded with constant, unchanging information.
  • Prevents overexcitation and potential damage to the cell.

Sensory Amplification

• Definition: Upregulation or increase in the response to a stimulus.
  • Example:
    • A ray of light hitting a photoreceptor in the eye.
    • Activates a molecular cascade, amplifying the signal.
    • One light ray can cause multiple molecules to activate, each of which can further amplify the signal.
    • By the time the signal reaches the brain, it has been significantly amplified.
• Mechanism:
  • Light activates molecules which trigger more molecules in a cascading fashion.
  • Amplified signals result in stronger responses.

Why Adaptation is Important

• Protects cells from overexcitement and potential death.
• Capsaicin as example of overexcitement:
  • Can cause pain receptors to be excessively activated.
  • Downregulation prevents excessive signal that could harm the cell.
• Ensures the brain is not overwhelmed by constant stimuli.