Unit 1: Sensation

Sensation

The process by which sensory receptors and the nervous system receive stimulus energy.

Transduction

The conversion of physical energy into neural impulses that the brain can process.

Absolute Threshold

The minimum stimulation needed to detect a stimulus 50% of the time.

Just-Noticeable Difference (JND)

The smallest detectable change in a stimulus.

Weber’s Law

The principle that the perceived difference in a stimulus is proportional to its original intensity.

Sensory Adaptation

Diminished sensitivity to constant, unchanging stimulation.

Synesthesia

A condition where stimulation of one sensory pathway leads to involuntary experiences in another.

Anatomy of Vision

Light enters through the cornea, passes through the pupil (controlled by the iris), and is focused by the lens onto the retina.

Rods

Photoreceptors highly sensitive to light; responsible for low‑light vision and motion detection.

Cones

Photoreceptors responsible for color vision and fine detail; concentrated in the fovea.

Blind Spot

The point on the retina where the optic nerve exits; contains no photoreceptors.

Trichromatic Theory

The theory that color vision is based on three types of cones (red, green, blue).

Opponent-Process Theory

The theory that color vision is based on opposing color pairs (red‑green, blue‑yellow, black‑white), explaining afterimages.

Dichromatism

A visual deficiency where only two types of cones function.

Monochromatism

A visual deficiency where one or no cone types function, severely limiting color vision.

Blindsight

The ability to respond to visual stimuli without conscious awareness due to brain damage.

Prosopagnosia

A neurological condition involving the inability to recognize familiar faces.

Wavelength

A property of sound determining pitch (shorter wavelengths = higher pitch).

Amplitude

A property of sound determining loudness (higher amplitude = louder sound).

Place Theory

The theory that pitch is determined by which region of the cochlea is stimulated.

Frequency Theory

The theory that pitch corresponds to the rate of auditory nerve firing.

Volley Theory

The idea that groups of neurons fire in rapid succession to encode high‑frequency sounds.

Conduction Deafness

Hearing loss caused by damage to the outer or middle ear structures.

Sensorineural Deafness

Hearing loss caused by damage to the inner ear or auditory nerve.

Sound Localization

The brain’s ability to determine sound source location based on timing and intensity differences between ears.

Sensory Interaction

The principle that one sense influences another (e.g., smell affecting taste).

Olfactory System

The sensory system in which receptors in the nasal cavity detect chemical compounds, processed via the olfactory bulb and thalamus.

Gustation (Taste)

The sense of taste; detects sweet, sour, salty, bitter, umami, and oleogustus.

Vestibular Sense

The sense of balance and body orientation, regulated by the semicircular canals in the inner ear.

Kinesthesis

The sense of body position and movement of individual body parts.

Pain & Gate Control Theory

The idea that pain perception can be modulated by a “gate” in the spinal cord that can be closed by competing sensory input.

Phantom Limb

The perception of sensation in a missing limb due to neural plasticity in the somatosensory cortex.