The sensory system

The sensory system is made up of our sensory organs, sensory receptors, our nervous systems and areas of the brain that receive and interpret information from our environment and our own bodies.

Sensory system

The sensory system

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Sensing can be defined as:

“a physical process by which the sensory systems of the body detect and process information from stimuli, in order to perceive and respond”

Key terms

Here are some key terms that will be used defined for you. It is ok to revisit these definitions as you read the material.

Sense: One system that detects specific types of data from external stimuli, transmits this to the brain, and processes it there, integrating it with previous knowledge, and other sensory systems. For example, the auditory system.

Sensation: The experience of the data from stimuli (hearing)

Perception: The understanding gained through the processing and integration of that data.

The senses

Sensory biology

Sensory biology is made up of the central nervous system (CNS), the peripheral nervous system (PNS), and sensory organs. We have covered the CNS and PNS before, so here we will will gain a basic understanding of the neurobiology of the sensory organs. 

A sensory organ is a group of related sensory cells that respond to a specific type of stimulus. The components of a sensory organ are receptor cells in the peripheral nervous system, transduction axons, and the sensory cortices in the brain. 

Receptor cells come in different types, based on their function, location and ending type. These are seriously cool, so feel free to look up more information on them if this is something you are particularly excited about, or sign up for the nurturing specialism.


Each general type of stimulus, and its corresponding sensory system is known as a sensory modality. There are actually eight well-documented and universally recognised human senses (modalities), even though most people think that there are five. They are:

Modality Sense Brain receives and interprets:
Auditory Hearing Sound
Visual Sight Images, light and darkness.
Olfactory Smell Scent
Gustatory Taste Oral sensation of texture, bitter, sweet, salt and sour.
Tactile Touch Contact with our skin: human or other
Vestibular Movement Trajectory, alignment, balance
Proprioception Coordination Edges of the body, position and placement
Interoception Internal body Physical regulation from body systems

These are often categorised into environmental, or external senses, which are the five traditional senses: hearing, sight, smell, touch and taste, and the personal, or internal senses: movement, external body, internal body and touch again.

“Touch” can be put in both categories because somatosensory receptors can be found both externally and internally, and internally contribute to interception as below. Touch is the most important sensory system in humans. However, whilst we love to categorise things, senses rarely work in isolation from each other and there are relationships between many of them that can be tough to separate.


Each modality has many sub modalities, or elements of information that contribute to the resulting perception. The table below provides many examples but is not an exhaustive list:

Modality Submodality examples
Auditory Location, tonality, tempo, pitch, pace, intensity, clarity, volume, rhythm, multiple-stream sound input.
Visual Association, size, motion, colour, brightness, distance, focus, clarity, depth, shape and frame.
Olfactory Flavour, scent, odor, pheremone, memory, emotion
Gustatory Salt, sweet, salty, bitter, savoury, density, dryness, cohesiveness, viscosity, 
Tactile Light pressure, deep pressure, itch, pain, vibration, temperature, and hair movement
Vestibular Balance, trajectory, alignment, motion, orientation, rotation, acceleration and gravitational force
Proprioceptive Pressure, weight, force, stretch, kinesthesia
Interoceptive Hunger, thirst, pain, oxygen levels, blood sugar, blood pressure, gastrointestinal sensation, heart rate, satiation, fullness.



Humans have complex multimodality senses. This means that our perceptions rarely, if ever, result from one modality providing information. In fact, the vestibular sense does not have a specific brain cortex and inputs are combined with multiple modalities for processing. Research shows that it is possible that this complex relationship can impact the perception of other modalities. It is important to understand how interactive the sensory systems are, because it means that any difficulties or differences in just one sense will impact the others.

Other possible senses

Simply for the purposes of informing you properly, we have included a very brief description of a few other possible senses. These are things that are not currently considered to be human senses. Some for good reasons, and others are more questionable. We simply want you to understand that the science here is ever-evolving, and basic education in society takes a long time to catch up, hence the general belief that there are five senses, and any mention of a sixth sense relates to some kind of potentially mythical or “super” power.


Some sources list our sense of pain in our bodies as a separate modality. It seems obvious to me that although it is clearly one of the things we perceive from our senses, it is something that is interpreted in processing from our tactile and interoceptive senses.


Sometimes questioned is whether our experience of emotion is a sense. It is not. A sense cannot be something that is directly created in the brain. There are no “emotional receptors” outside of the CNS.

Magnetic triangulation

Other species have senses that humans do not, or they have different sub modalities where we share common senses. For instance, some animals have echolocation, can sense the humidity in the air, can see ultraviolet, or infrared in the colour spectrum. One of these senses we find in other species is the sense of the magnetic fields of the earth, used by some birds for triangulation. Recently, research discovered that humans have cells in our brain that could detect data from magnetic stimuli. It is suggested that some humans may be sensitive to this, but scientists are still pretty unsure.

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