Stimuli from different sensory receptors travel as action potentials along different neural pathways.
The brain distinguishes stimuli from different receptors by the area in the brain where the action potentials arrive.
Amplification and Adaptation
Amplification is the strengthening of stimulus energy by cells in sensory pathways.
Sensory adaptation is a decrease in responsiveness to continued stimulation.
Based on energy transduced, sensory receptors fall into five categories:
Mechanoreceptors sense physical deformation caused by stimuli such as pressure, stretch, motion, and sound.
The sense of touch in mammals relies on mechanoreceptors that are dendrites of sensory neurons.
Sensory receptors in human skin
General chemoreceptors transmit information about the total solute concentration of a solution.
Specific chemoreceptors respond to individual kinds of molecules.
When a stimulus molecule binds to a chemoreceptor, the chemoreceptor becomes more or less permeable to ions.
The antennae of the male silkworm moth have very sensitive specific chemoreceptors.
Chemoreceptors in an insect
Electromagnetic receptors detect electromagnetic energy such as light, electricity, and magnetism. Photoreceptors are electromagnetic receptors that detect light.
Some snakes have very sensitive infrared receptors that detect body heat of prey against a colder background.
Many mammals, such as whales, appear to use Earth’s magnetic field lines to orient themselves as they migrate.
Specialized electromagnetic receptors
(a) Rattlesnake – infrared receptors detect body heat of prey
(b) Beluga whales sense Earth’s magnetic field – as they navigate migrations.