MYP Biology 4.7 Senses Notes

How Do the Five Principal Sensory Systems Detect and Process Different Stimuli?

1. 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).
2. These senses give your brain different types of information so you can understand and respond to the world.

How Do Senses Translate Signals Into Experiences?

Each sense uses the same basic idea: detect → convert → send → interpret.

Vision: How Do We Turn Light Into Images?

1. Light enters your eye, passes through the lens, and lands on the retina at the back.
2. The retina contains two specialized receptors:
   1. Rods: detects dim light, helps you see at night
   2. Cones: detects bright light and color, helps you see sharpness, detail, and color.

Hearing: How Do Vibrations Become Sound?

1. Sound is just vibrating air that travels down your ear canal and makes the eardrum vibrate.
2. These vibrations pass into the cochlea, where fluid movement bends tiny hair cells.
3. These hair cells convert the vibrations into electrical signals for the auditory cortex.
4. Your brain then identifies pitch, volume, and direction.

Taste: How Do Chemicals Become Flavours?

1. When you eat, chemicals dissolve in your saliva and activate taste buds.
2. Taste buds detect five main flavours: sweet, sour, salty, bitter, and umami.
3. These signals go to the gustatory cortex where your brain identifies flavour.

Smell: How Do Airborne Chemicals Become Odours?

1. Scents are airborne molecules that enter your nose and bind to receptors high in your nasal cavity.
2. These receptors send signals straight to the brain, faster than any other sense.
3. Smell is strongly linked to memory and emotion, which is why scents can trigger strong reactions.

Touch: How Do We Detect Pressure, Pain, and Temperature?

1. Your skin contains multiple receptor types:
   1. Mechanoreceptors → pressure, stretch
   2. Thermoreceptors → temperature
   3. Nociceptors → pain
2. Different body areas have different receptor densities, which is why:
   1. Fingertips are extremely sensitive
   2. Your back is less sensitive
3. Signals travel to the somatosensory cortex, which maps your entire body.

Why Do Different People Perceive the Same Stimulus Differently?

1. People have different numbers of receptors (e.g., color vision differences).
2. The brain interprets sensory information based on past experiences.
3. Emotion and attention change how signals are perceived.
4. Cultural background influences how tastes and smells are interpreted.
5. Neurodivergent individuals may experience sensory sensitivity or sensory overload, which changes perception further.