Special Senses and Vision Quiz

Senses are general capabilities to detect stimuli, categorized into general and special senses.
Special senses utilize specific organs for complex processing of vision, hearing, balance/equilibrium, taste, and smell.
Sensory receptors are microscopic detectors that translate stimuli into signals for the nervous system.

Eyelashes: hairs preventing foreign matter from entering the eyes.
Eyelids (palpebrae): the continuation of skin; they close to protect the eye.
- Blinking: cleans and lubricates the surface of the eye.
- Medial angle of the eye
- Lateral angle of the eye
- Palpebral fissure: gap between upper and lower eyelids
Lacrimal caruncle
Eyelids, or palpebrae
Palpebral fissure
Medial angle of the eye
Conjunctiva: mucous membrane lining the eyelids and covering the anterior aspect of the eye.
- Palpebral conjunctiva
- Bulbar conjunctiva
- Fornix
- Conjunctivitis (pinkeye): inflammation of the conjunctiva, often related to blood vessel dilation.
Eye muscles: move the eyeball.

Lacrimal gland: produces tears to lubricate, nourish, and oxygenate the cornea. Tears also contain lysozyme and antibodies.
Tear duct: delivers tears from the lacrimal gland.
Lacrimal puncta: small openings at the medial corners of the upper and lower eyelids.
Lacrimal canaliculi: connect lacrimal puncta to the lacrimal sac.
Lacrimal sac: reservoir for tears, located in the lacrimal fossa of the medial orbital wall.
Nasolacrimal duct: delivers tears to the nasal cavity; empties into the inferior meatus.

Fibrous tunic (outermost layer):
- Cornea: transparent structure covering the iris and pupil; allows light to enter and focus.
- Sclera: firm, white outer part; maintains eye shape, protects internal structures, and connects with the cornea at the corneoscleral junction.
Vascular tunic (middle layer):
- Choroid: vascular layer underlying the sclera.
- Ciliary body: holds the lens in place.
- Iris: colored part surrounding the pupil; regulates the amount of light entering the eye.
  - Pupil: opening in the center of the iris; constricts or dilates to regulate light.
- Lens: flexible disk focusing light onto the retina.
Nervous tunic (innermost layer):
- Retina: most inner layer; the outer pigmented layer absorbs light, while the inner sensory/neural layer has photoreceptors (rods and cones).
  - Rods: sensitive to low light; low visual acuity
  - Cones: require bright light; high visual acuity.
- Posterior region: Contains macula, fovea centralis, and optic disc.
- Macula: surrounds the fovea centralis for central vision.
  - Fovea centralis: sharpest visual and fine details; located in the center of the macula.
- Optic disc: white spot medial to the macula; no photoreceptors.

Anterior cavity: separated by lens/ciliary body.
- Anterior chamber: between the cornea and the iris.
- Posterior chamber: between the iris and the lens.
Posterior cavity: filled with vitreous body.
- Vitreous humor: fluid part of the vitreous body.

Auricle (pinna): collects and directs sound waves toward the middle ear.
External auditory meatus (auditory canal): directs sound waves down toward the middle ear.

Tympanic cavity: air-filled chamber containing the auditory ossicles.
Auditory ossicles: transmit vibrations from the tympanic membrane to the inner ear (malleus, incus, stapes).
Oval window
Eustachian or auditory tube

Bony labyrinth: shell of dense bone surrounding/protecting the membranous labyrinth.
Filled with perilymph.
Membranous labyrinth: inside bony labyrinth.
- Cochlea
- Vestibule
- Semicircular canals
- houses receptors for hearing and equilibrium.
- contains endolymph.
Cochlea: snail-shell structure; has three channels- Scala vestibuli (vestibular duct), Scala tympani (tympanic duct), Cochlear duct (scala media)
Scala vestibuli (vestibular duct): Filled with perilymph
Scala tympani (tympanic duct): filled with perilymph
Cochlear duct (scala media): filled with endolymph
Spiral organ(organ of Corti): contains hair cells
Tectorial membrane: vibrates against hair cells

Equilibrium: ability to maintain balance, stability, and orientation.
- Static equilibrium: maintains balance when stationary.
- Dynamic equilibrium: maintains balance during motion.

Semicircular canals: detect rotational or angular movements of the head. Consists of three canals - anterior, posterior, and lateral.
Each canal has crista ampullaris at its base, containing hair cells for receptor function.
Otolith organs: detect linear movements and gravitational pull. Located in the vestibule and include the utricle and saccule.
Otoliths: crystalline structures present in the otolith membrane, influencing hair cell bending.
Maculae: structures containing hair cells and sensory receptor cells, influenced by head position.

Olfactory epithelium: Specialized olfactory receptor cells detecting odors; supported by supporting cells and nourished by basal cells.
Olfactory bulb: receives signals from olfactory receptor cells and processes them.
Olfactory tract: transmits processed signals from olfactory bulb to the brain, mostly olfactory cortex, amygdala, and hippocampus.

Taste buds: found within papillae on the tongue; vary in the tongue's region.
Types of papillae (on the tongue): Fungiform, Circumvallate, Foliate and Filiform.
Gustatory cells: specialized receptor cells within taste buds; possess microvilli projecting into the taste pore to detect substances.

Taste detection
Signal generation
Signal Transmission (Cranial nerves)
Facial Nerve; Glossopharyngeal Nerve (Posterior one-third of tongue), and Vagus nerve (taste from the pharynx and epiglottis)
Brainstem processing (medulla oblongata)
Thalamic relay (ventral posteromedial (VPM) nucleus)
Perception in the Gustatory cortex