Sensory Receptors and the Nervous System

Sensory receptors, specialized neurons or associated cells, are the interface between the external world and the nervous system. These receptors convert diverse stimuli into electrical signals the nervous system can interpret, a process called sensory transduction.

Each receptor is tuned to a specific type of stimulus, such as light, sound, pressure, or chemicals. When a stimulus is detected, the receptor cell membrane undergoes a change in permeability, leading to a receptor potential. This potential is a graded potential, meaning its amplitude varies with the intensity of the stimulus. If the receptor potential reaches a threshold, it triggers action potentials in the sensory neuron.

The frequency and pattern of action potentials encode information about the stimulus. For example, a stronger stimulus generates a higher frequency of action potentials. Additionally, some receptors adapt to sustained stimulation, reducing their firing rate over time. This adaptation allows the nervous system to focus on changes in the environment rather than constant background stimuli.

Sensory neurons transmit action potentials along specific pathways to the central nervous system (CNS). The CNS processes this information, integrating it with other sensory inputs and past experiences to create a perception of the world. The type of receptor activated, the frequency of action potentials, and the pathway the signal travels all contribute to how we perceive a stimulus.