Sensation and Perception Review

Sensation: The process of detecting physical energy from the environment and encoding it as neural signals.

Wavelength: The distance between successive peaks of a wave, crucial for determining color.
Hue (color): The specific color we perceive, determined by wavelength.
Intensity: The amount of energy in light waves, perceived as brightness, related to wave amplitude.
White light: Light that contains all visible wavelengths.
Prism: An optical element that refracts light into its constituent colors.
Wavelength Measurements:
- 400-700 nm: Visible spectrum where humans perceive light
- 400 nm (violet) - 700 nm (red)

Wavelength Range: Illustrated from very short (gamma rays) to very long (radio waves).
Nanometer Scale: Measurements ranging from $10^{-5}$ to $10^{17}$ nanometers.
- Visible light is found between 400 nm and 700 nm.

Physical Properties:
- Short wavelength = high frequency (perceived as bluish);
- Long wavelength = low frequency (perceived as reddish).
- Amplitude indicates brightness: Great amplitude = bright colors, Small amplitude = dull colors.

Cornea: The outer covering of the eye, providing most of the eye's optical power.
Pupil: The adjustable opening at the center of the eye, controlling light entry.
Iris: Colored muscle around the pupil; adjusts the pupil's size in response to light.
Lens: Transparent structure that focuses light onto the retina; accommodates to focus on near or far objects.
Retina: Light-sensitive layer at the back of the eye containing rods and cones for photoreception.

Rods and Cones: Types of photoreceptors in the retina.
- Rods: 120 million, sensitive to dim light, located in the periphery of the retina, low color sensitivity.
- Cones: 6 million, high sensitivity to color and detail, concentrated in the fovea (center of retina).

Photochemical Reaction: Light entering the eye triggers this reaction in the rods and cones.
Activation of Bipolar Cells: The chemical reaction in photoreceptors activates bipolar cells.
Activation of Ganglion Cells: Bipolar cells trigger ganglion cells, forming the optic nerve that transmits signals to the visual cortex of the brain via the thalamus.
Blind Spot: The area where the optic nerve exits the eye, lacking receptor cells.
Fovea: The area of sharpest vision where cones are most densely packed.

Pathway: Visual information travels from retina to optic nerve, to the thalamus, and finally to the visual cortex.
Feature Detection: Nerve cells in the brain respond to specific features of stimuli such as edges, angles, and movements.
Parallel Processing: The simultaneous processing of various aspects of vision (motion, form, depth, color).

Young-Helmholtz Trichromatic Theory: States that there are three types of cones sensitive to red, green, and blue light.
Opponent-Process Theory: Suggests that color perception depends on opposing neural processes (e.g., red-green, blue-yellow).

Sound Waves: Vibrations in the air that enter the ear.
- Amplitude: The height of sound waves related to perceived loudness.
- Frequency: The number of wave cycles per second, related to pitch.

Outer Ear: Includes the auditory canal and eardrum.
Middle Ear: Contains three bones - the hammer, anvil, and stirrup which amplify sound.
Inner Ear: Contains the cochlea, where sound waves trigger nerve impulses.

Motion of fluid in the cochlea stimulates hair cells, transforming vibrations into neural signals sent to the auditory cortex via the auditory nerve.

Conduction Hearing Loss: Results from damage to the mechanical system conducting sound to the cochlea.
Sensorineural Hearing Loss: Results from damage to the cochlea’s receptor cells or the auditory nerves.

Place Theory: Different portions of the cochlea are activated by different sound frequencies.
Frequency Theory: The rate of impulse matches the frequency of the tone to perceive pitch.

Biopsychosocial Model: Acknowledges biological, psychological, and socio-cultural influences on pain perception.

Taste: Basic tastes include sweet, sour, salty, bitter, and umami, which serve important survival functions.
Smell (Olfaction): Processed through olfactory receptors in the nose, influencing taste and memories.

Kinesthesis: Ability to sense position and movement of individual body parts.
Vestibular Sense: Awareness of body movement and positioning, including balance.

Sensory System	Source	Receptors
Vision	Light waves striking the eye	Rods and cones in the retina
Hearing	Sound waves striking the ear	Cochlear hair cells in the inner ear
Touch	Pressure, warmth, cold, pain	Skin receptors
Taste	Chemical molecules in the mouth	Basic tongue receptors
Smell	Chemical molecules breathed in through the nose	Olfactory receptors
Kinesthesia	Changes in body position	Kinesthetic sensors throughout the body
Vestibular Sense	Movement of fluids in the inner ear	Hairlike receptors in semicircular canals and vestibular sacs

Different senses interact and influence each other to form a comprehensive perception of stimuli.
Understanding sensation leads to insights into human perception and interaction with the environment.