In most sensory systems, cells at all levels of the nervous system - from the surface sheet of receptors to the cerebral cortex - are arranged in an orderly, map-like manner. With bilateral receptor systems - the two ears or the two nostrils for example - the relative time of arrival of the stimulus at the two receptors is directly related to the stimulus.  

Hierarchy of Sensory Systems

Sensory receptors are specialized neurons that are uniquely responsive to specific types of stimuli from the environment. Their function is to detect sensory information, such as light, sound, or pressure, and initiate the process of sensation.

Sensory Receptors

Sensory receptor organs act as filters of the environment by responding to certain stimuli (ie. eyes for vision, ears for hearing). These organs, often times body parts, are particularly sensitive to some forms of energy.
- Receptor cells
- Hierarchy of Sensory Systems

Johns Hopkins University

Sensory receptors such as eyes or taste buds develop differently in different species. Sensory processing refers to the ways the brain integrates information received from sensory receptors in order to process appropriate behavioral or cognitive response. 

- Sensory organs
- Stimuli
- Receptor Cells
- Touch and the skin
- Pain
- Sensory processing disorder
- Synesthesia

Sensory processing, touch and pain

Breedlove, S. & Watson, N. (2017). Behavioral neuroscience, eighth edition. Oxford University Press.

Behavioral Neuroscience 8th Edition

Sensory Organs

A stimulus (plural: stimuli) is an event that affects the sensory organ. Stimuli can be sound waves, light entering the eye, or food touching the tongue.
- Adequate stimulus
- Labeled Lines
- Stimulus localization
- Selection and analysis along sensory pathways
- Selectivity and Range of Response to Stimuli

Stimuli

A condition in which a stimulus in one modality can trigger experiences in another or multiple other modalities. For example, to someone with this condition (a synesthete), the letter could be seen as green, or a particular musical tone could evoke a particular taste sensation. 
For the colored letters and numbers, some studies have pointed to this association with popular toys that depict these figures in the same colors. 

Synesthesia

A large part of our somatosensory system is responsible for our perception of touch.
- Sensory Organ: Skin
- Dorsal Column System
- Primary Sensory Cortex
- Secondary Sensory Cortex
- Skin sensory receptors

Somatosensory System: Touch

The somatosensory system is partly responsible for detecting painful stimuli. Pain is defined as an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.
- Importance of Pain
- Congenital Insensitivity to Pain
- Classifying Pain
- Biological Basis of Pain

Somatosensory System: Pain

Sensory processing, touch and pain references

A condition where the brain has trouble receiving and responding to sensory input. May affect one or multiple senses. Symptoms could include over-sensitivity to certain stimuli, difficulties with coordination, or failure to respond to outside stimuli. This disorder is often seen in individuals on the Autism spectrum. It is not currently recognized as a distinct medical diagnosis.

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