Sensation and Structure of the Eye

Study Notes

Sensation is the process of receiving information from our environment through our senses.
Our five senses are sight, hearing, smell, touch, and taste.

Light enters the eye through the cornea, a transparent covering that protects the eye.
The pupil, a small opening in the center of the eye, allows light to pass through.
The iris, the colored part of the eye, controls the amount of light entering by contracting or dilating.
The lens, a transparent structure, focuses light onto the retina.
This process of focusing light is called visual accommodation.
The retina, located at the back of the eye, contains photoreceptor cells that absorb light waves.

Light waves travel from the retina, through the optic nerve, to the occipital lobe of the brain.
The occipital lobe contains the primary visual cortex, which transforms nerve impulses into basic visual sensations.
The primary visual cortex sends impulses to neighboring visual association areas, which add meaning to the sensations.

Sound waves enter the outer ear (pinna).
The waves travel through the auditory canal to the eardrum, causing it to vibrate.
Vibrations are passed to the ossicles, three tiny bones in the middle ear: the hammer, anvil, and stirrup.
The ossicles amplify vibrations and pass them to the oval window, which connects to the cochlea.
The cochlea contains hair cells that perform transduction, transforming vibrations into nerve impulses sent to the brain.

Located in the inner ear, the vestibular sense helps maintain balance and tracks head position.
An infection of the vestibular sense can cause dizziness, nausea, and balance issues.
Motion sickness occurs when there is a mismatch between the vestibular sense (detecting movement) and visual perception (seeing stationary objects).

The kinesthetic sense informs us about our body's position and motion relative to gravity.
Sensory organs send information from body movements through the spinal cord to the brain, coordinating motor movements.

Taste is a chemical sense, meaning the stimuli are chemicals.
The tongue contains taste buds, which are receptors for five tastes: sweet, salty, sour, bitter, and umami.
Taste buds perform transduction, transforming chemical reactions into nerve impulses.