Carl D. Hopkins
Lecture 21. Sensory Transduction
occurs when some form of external energy such as chemical,
mechanical, or light is converted into a neuro-electric event that can be used for neural
signaling. In this lecture we will attempt to unify the diverse sensory transduction
mechanisms into three basic types: G-protein coupled receptors, ion-channel receptors,
and mechanically-linked ion channels. Sensory transduction thus is considered from the
point of view of molecular machinery at the level of membranes. The objective is for
students to understand how different sensory systems each employ variants on these three
basic themes, while each achieves neuronal activation in response to an external energy.
Purves et al. 4
ed (2007) pp. 234 (box); 264-269; 327-330; 346-7 (box); 372-378; 387-
389. The reading material for this lecture is dispersed among the various chapters on
pain reception, vision, hearing, olfaction, and taste. Please read the assigned pages
looking to integrate the topics according to the learning objectives listed above.
Students should be able to:
1) Identify the precise anatomical location of sensory transduction in the following types
of sensations: hearing, touch on the hand, pain, light, taste. Where are the sensory
transduction molecules located? Is transduction taking place in a specialized “receptor
cell” or in a nerve ending of a sensory nerve fiber?
2) Make a list of all of the sensory modalities listed above and be able to define the
molecular transducers in each case.
3) For vision and for smell, define the
sequence of biochemical steps that lead
from transduction to opening or closing
an ion channel.
4) What are some of the sensory
transducers for which the transduction
mechanism is unknown?
Neurons are normally activated in two
ways, either by synaptic inputs from
other neurons, which we have already
discussed extensively, or by sensory
receptor activation. These six lectures
focus on sensory mechanisms,
highlighting vision, hearing, and
Animals are sensitive to a wide range of
Fig. 1. Different types of sensory receptor cells found in
vertebrates. Sensory stimuli act at sites indicated by the small
arrows. Stippling indicates ares were transduction/synaptic
transmission takes place. Large arrows indicate the site of
impulse initiation (From: Shepherd, G. M. 1983. Neurobiology.
Oxford Univ. Press, Oxford, Fig. 11.1, p 191.) (Shepherd, 1983)