Sensation is the process by which sensory receptors and the nervous system detect and receive physical energy from the environment, such as light, sound waves, pressure, or chemicals. It is the first step in perceiving the world and is distinct from perception, which is the interpretation of those sensory signals.

Each sense has specialised receptor cells: rods and cones in the retina detect light, hair cells in the cochlea detect sound, thermoreceptors and mechanoreceptors in the skin detect temperature and pressure, and chemoreceptors in the nose and tongue detect odours and tastes. Sensory signals travel to the brain, where they are processed and integrated.

Key points

• Sensation is detection; perception is interpretation
• Receptors are specialised for specific stimuli
• Signals travel via the thalamus to the cortex
• Thresholds and adaptation shape what we detect