Eye Anatomy Quiz

Nervous System III: Senses and Autonomic Nervous System

• The nervous system has three sections for the ear: outer, middle, and inner.
• The outer and middle ear conduct sound to the inner ear.
• The inner ear is the sense organ for hearing and equilibrium.
• The outer ear begins with the auricle, supported by elastic cartilage.
• The outer ear directs sound into the auditory canal, which is protected by guard hairs and cerumen.
• The middle ear begins with the tympanic membrane.
• The middle ear has three ear bones (malleus, incus, and stapes), which are connected to the oval window. These bones transmit vibrations to the inner ear.
• The inner ear is housed in a bony labyrinth of the cranium.
• The inner ear has a membranous labyrinth within the bony labyrinth, forming a tube-in-tube structure.
• The inner ear begins at the oval window and leads to the vestibule, semicircular canals, and cochlea.
• The spiral organ is located in the cochlear duct and is the sensory organ for hearing.
• The cochlear duct is above the vestibular membrane and scala vestibule and below the basilar membrane and scala tympani.
• The spiral organ has hair cells (stereocilia) that generate auditory signals.
• Inner hair cells supply 90-95% of sensory fibers.
• Outer hair cells are in three rows and adjust the response to different frequencies.
• The stereocilia are covered by the tectorial membrane.
• Sound waves vibrate the tympanic membrane, followed by the auditory ossicles transferring the vibrations through fluid in the inner ear.
• The basilar membrane vibrates, causing hair cells to move, which generates nerve signals.
• The saccule and utricle are sense organs for static equilibrium and linear acceleration.
• The macula is a patch of hair cells and supporting cells on the saccule and utricle.
• The macula sacculi is vertical, and the macula utriculi is horizontal.
• Stereocilia embed in the otolithic membrane (calcium carbonate and protein), and are moved by head movement.
• Stereocilia bending generates nerve signals interpreted to determine head orientation.
• The semicircular ducts sense angular acceleration.
• The ampulla is a dilated sac inside each semicircular duct.
• Hair cells in the ampulla have stereocilia embedded in the cupula (gelatin-like structure).
• Head turns cause endolymph to lag behind and stimulate hair cells which generate nerve signals to the cranial nerves.

Chemical Senses: Taste and Smell

• Chemical senses detect environmental chemicals.
• Gustation (taste) responds to chemicals in food and drinks.
• Olfaction (smell) responds to chemicals in the air.
• Lingual papillae are visible bumps on the tongue.
• Taste buds are clustered in the lingual papillae and found on the tongue, cheeks, and pharynx.
• Taste cells cluster in taste buds and respond to chemicals.
• Five primary tastes are sweet, salty, sour, bitter, and umami.
• All primary tastes can be detected throughout the tongue.
• Flavor is the result of combinations of primary tastes, smell, food texture, temperature, and appearance.
• Cranial nerves are involved in gustation: CN VII for anterior 2/3 and CN IX for posterior 1/3 of the tongue.
• CN X transmits taste from the taste buds for the palate, pharynx, and epiglottis.
• Sensory signals travel through the medulla to the hypothalamus and amygdala for autonomic reflexes and through the thalamus and insula for taste interpretation.
• Receptor cells in the olfactory mucosa detect airborne chemicals.
• Receptor cells are the only neurons directly exposed to the external environment that have a lifespan of about 60 days.
• Receptor cells have cilia (olfactory hairs) with olfactory receptors for odor molecules.
• CN I collects axons for receptor cells.
• Receptor cells respond to a particular odor, sending axons to a structure called a glomerulus.
• They synapse with other neurons: mitral and tufted cells which send signals through the olfactory tract to the brain.
• Olfactory tract sends signals to the primary olfactory cortex directly, not through the thalamus. Signals from the cortex travel to the insula and limbic system (amygdala and hippocampus).
• Smell can trigger emotions directly.

Eye and Vision

• The orbit is a bony socket that houses the eyeball.
• Eyebrows, eyelashes, and eyelids protect the eye from foreign objects, persperation, and glare.
• The conjunctiva is a transparent mucous membrane that lines the eyelids and covers the anterior portion of the eyeball.
• The lacrimal apparatus produces and drains tears into the nasal cavity. Tears are produced by the lacrimal gland and flow through the conjunctiva, lacrimal punctum, canaliculus, sac, and nasolacrimal duct to the nasal cavity.
• Extrinsic eye muscles move the eyeballs in four directions (Superior, Inferior, Lateral, and Medial rectus) and rotate the eyeballs (Superior and Inferior Obliques).
• The eyeball has three layers (tunics): the outer fibrous layer (sclera and cornea), the middle vascular layer (choroid, ciliary body, and iris), and the inner layer (retina).
• The optical components (cornea, aqueous humor, lens, and vitreous body) admit and focus light.
• The cornea is transparent and admits light.
• The aqueous humor is a serous fluid secreted by ciliary processes.
• The lens is suspended by suspensory ligaments and focuses the image.
• The vitreous body is a transparent jelly-like substance that maintains intraocular pressure.
• The retina is the inner layer containing photoreceptors (rods and cones).
• Rods are responsible for night vision (monochromatic).
• Cones are responsible for day vision (trichromatic).
• Pigment epithelium absorbs stray light.
• Neural components (retina and optic nerve) produce and transduce neural signals.
• Bipolar cells transmit signals from photoreceptors to ganglion cells (axons form the optic nerve).
• Ganglion cells axons form the optic nerve and transmit signals to the brain.

Autonomic Nervous System

• The autonomic nervous system (ANS) regulates fundamental life processes unconsciously (blood pressure, heart rate, digestion).
• Visceral reflexes involve receptors, interneurons, and effectors, responding to stimuli like stretch, tissue damage, or blood chemicals, with a slower response than somatic reflexes.
• Examples include high blood pressure activating visceral baroreflexes.
• The ANS is traditionally divided into sympathetic (fight-or-flight) and parasympathetic (rest-and-digest) divisions.
• Sympathetic pathways have relatively short preganglionic fibers and long postganglionic fibers, often extending to target organs.
• Parasympathetic pathways have long preganglionic fibers and short postganglionic fibers, often ending in or near target organs.

Test your knowledge on the anatomy of the eye with this engaging quiz. Explore the functions of different eye components, including the iris, ciliary body, and the role of aqueous humor. Perfect for students studying biology or anatomy.