How Do the Five Principal Sensory Systems Detect and Process Different Stimuli?
- Before we talk about how senses become experiences, start with the basics: you have five main senses, each with its own specialized receptors (as covered previously).
- These senses give your brain different types of information so you can understand and respond to the world.
Definition
Sense
A way the body gathers information through receptors and sends it to the brain for interpretation.
Hint
- You never experience the world “directly.”
- You experience the signals your brain creates from the information your senses collect.
How Do Senses Translate Signals Into Experiences?
Each sense uses the same basic idea: detect → convert → send → interpret.
| Sense | Main Receptors | What They Detect | Where Signals Go |
|---|---|---|---|
| Vision | Photoreceptors | Light | Visual cortex |
| Hearing | Mechanoreceptors | Vibrations | Auditory cortex |
| Taste | Chemoreceptors | Dissolved chemicals | Gustatory cortex |
| Smell | Chemoreceptors | Airborne chemicals | Olfactory cortex |
| Touch | Mechanoreceptors, thermoreceptors, nociceptors | Pressure, temp, pain | Somatosensory cortex |
Analogy
- If receptors are messengers, your senses are the ones to collect the parcel.
- Perception is therefore the step where your brain opens that parcel and decides what the information actually means.
Vision: How Do We Turn Light Into Images?
Definition
Photoreceptors
Light-sensitive cells that convert light into electrical signals.
- Light enters your eye, passes through the lens, and lands on the retina at the back.
- The retina contains two specialized receptors:
- Rods: detects dim light, helps you see at night
- Cones: detects bright light and color, helps you see sharpness, detail, and color.
Note
You see with your brain, using information your eyes collect.
Hearing: How Do Vibrations Become Sound?
Definition
Mechanoreceptors
Receptors that bend when sound vibrations move through the inner ear.
- Sound is just vibrating air that travels down your ear canal and makes the eardrum vibrate.
- These vibrations pass into the cochlea, where fluid movement bends tiny hair cells.
- These hair cells convert the vibrations into electrical signals for the auditory cortex.
- Your brain then identifies pitch, volume, and direction.
Note
Because different hair cells detect different frequencies, damage to one frequency range affects how you hear certain sounds.
Taste: How Do Chemicals Become Flavours?
Definition
Taste receptor
A cluster of chemoreceptors that detect dissolved chemicals in food.
- When you eat, chemicals dissolve in your saliva and activate taste buds.
- Taste buds detect five main flavours: sweet, sour, salty, bitter, and umami.
- These signals go to the gustatory cortex where your brain identifies flavour.
Tip
Most of what you think is “taste” is actually smell working together with taste receptors.
Smell: How Do Airborne Chemicals Become Odours?
Definition
Olfactory receptor
A chemoreceptor in the nose that detects airborne chemicals.
- Scents are airborne molecules that enter your nose and bind to receptors high in your nasal cavity.
- These receptors send signals straight to the brain, faster than any other sense.
- Smell is strongly linked to memory and emotion, which is why scents can trigger strong reactions.
Hint
Taste and smell combine to create flavor, which is why food tastes different when you’re sick.
Touch: How Do We Detect Pressure, Pain, and Temperature?
Definition
Somatosensory receptors
Receptors in the skin that detect physical changes like pressure, heat, and pain.
- Your skin contains multiple receptor types:
- Mechanoreceptors → pressure, stretch
- Thermoreceptors → temperature
- Nociceptors → pain
- Different body areas have different receptor densities, which is why:
- Fingertips are extremely sensitive
- Your back is less sensitive
- Signals travel to the somatosensory cortex, which maps your entire body.
Why Do Different People Perceive the Same Stimulus Differently?
- People have different numbers of receptors (e.g., color vision differences).
- The brain interprets sensory information based on past experiences.
- Emotion and attention change how signals are perceived.
- Cultural background influences how tastes and smells are interpreted.
- Neurodivergent individuals may experience sensory sensitivity or sensory overload, which changes perception further.
Self review
- What are the five main senses, and what does each detect?
- How do senses turn receptor signals into actual experiences?
- How do rods and cones differ in function?
- What structure in the ear converts vibrations into signals?
- Why is taste strongly linked with smell?
- Why do different people perceive the same stimulus differently?
