2007 Sensory Physiology

General Principles & Somatosensation Objectives

At the end of these lectures, you should be able to:


  1. Distinguish among the processes of transduction, transmission and perception as related to information processing in sensory systems.  In particular, be able to define transduction.
  2. Compare and contrast the properties of a receptor potential and an action potential.
  3. Define the terms sensory unit and receptive field.
  4. List 3 major categories of stimulus energy, and be able to give an example of each.
  5. Identify the 2 core principles underlying the specificity of receptors that led to the definition of an adequate stimulus.  Identify six major special senses and their corresponding adequate stimuli, and be able to list several examples of "non-special" senses.
  6. Compare and contrast the labelled line and pattern theories.  Be able to give an example of a sensory system that uses each of these types of processing.
  7. Contrast the principles of frequency vs. population coding of stimulus intensity.
  8. Define adaptation, and describe the different forms adaptation can take.
  9. Define acuity, and outline how receptor density and receptive field size determine the acuity of a sensory system.
  10. Define lateral inhibition, and be able to diagram a neuronal circuit that enables lateral inhibition to occur.  Explain how lateral inhibition resolves the paradox between the encoding of the location and of the amplitude of a stimulus.
  11. Outline a generic sensory pathway.  List 3 mechanisms by which sensory processing deviates from a series (“labelled line”) model.  Be able to give an example of a sensory system that exhibits each mechanism.
  12. Outline the difference between sensation and perception.  List factors that affect awareness, and be able to give an example of each type of factor.


  1. Define somatosensation, distinguish it from proprioception and list subtypes.
  2. Compare and contrast the characteristics of thermo-, mechano- and noci-ceptors (esp. stimuli, receptor types, location, receptive field size, adaptation), including what is known about the gating of the channels involved.  Describe the nature of the currents that flow through TRP channels.
  3. Compare and contrast the transmission of touch and nociceptive information (pathways and conduction velocities).  Especially, be able to explain how the the humunculus is established.
  4. Explain the perception of temperature
  5. Contrast the two types of pain.  Define referred pain, and explain why it is perceived. 
  6. Diagram the gate theory of pain, and explain how it accounts for the success of TENS.
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