Bats use sonar to detect their prey.
Moths, a common prey for bats, can detect the batís sonar and attempt to flee.
Both organisms have complex sensory systems that facilitate survival.
These systems include diverse mechanisms that sense stimuli and generate appropriate movement.
Can a moth evade a bat in the dark?
Sensory receptors transduce stimulus energy and transmit signals to the CNS, central nervous system
All stimuli represent forms of energy.
Sensation involves converting energy into a change in the membrane potential of sensory receptors.
Sensations are action potentials that reach the brain via sensory neurons.
The brain interprets sensations, giving the perception of stimuli.
Functions of sensory pathways: sensory reception, transduction, transmission, and integration.
For example, stimulation of a stretch receptor in a crayfish is the first step in a sensory pathway.
Sensory Reception and Transduction
Sensations and perceptions begin with sensory reception, detection of stimuli by sensory receptors.
Sensory receptors can detect stimuli outside and inside the body.
Sensory transduction is the conversion of stimulus energy into a change in the membrane potential of a sensory receptor.
This change in membrane potential is called a receptor potential.
Many sensory receptors are very sensitive: they are able to detect the smallest physical unit of stimulus.
For example, most light receptors can detect a photon of light.
After energy has been transduced into a receptor potential, some sensory cells generate the transmission of action potentials to the CNS.
Sensory cells without axons release neurotransmitters at synapses with sensory neurons.
Larger receptor potentials generate more rapid action potentials.
Integration of sensory information begins when information is received.
Some receptor potentials are integrated through summation.
Perceptions are the brainís construction of stimuli.