Special Senses (chapter 15) Flashcards
Occurs when a physical or chemical stimulus is converted into a neural signal that can be interpreted by the brain.
Transduction
Sense of smell
Olfaction
A small patch of specialized epithelium located in the superior region of the nasal cavity
Olfactory epithelium
Modified bipolar neurons that detect the chemical substances we perceive as odors
Olfactory neurons
Chemical substances in the air that can be transduced into signals the brain can interpret
Odorants
A sensory receptor that responds to a change in the concentration of a specific chemical in the air or the body fluids
Chemoreceptors
A structure located in the brain just superior to the ethmoid bone and inferior to the frontal lobe of the brain
Olfactory bulb
Carries olfactory information to further parts of the brain for analysis
Olfactory tract
Stem cells that develop into olfactory neurons; lifespan 10-14 days
Basal cells
Columnar cells that support and surround the olfactory neurons; have no role in taste sensation
Supporting cells
Responsible for the awareness and identification of an odor; the only sensory pathway that has no synapse in the thalamus
Primary olfactory cortex
Lack of olfaction (smell)
Anosmia
Reduce olfactory sensitivity
Hyposmia
Sense of taste
Gustation
Clusters of receptor cells and supporting cells on the tongue that detect taste sensations
Taste buds
Round projections that covers the tongue
Papillae
The largest and most dome-shaped; each contains hundreds of taste buds
Vallate (circumvallate) papillae
Mushroom-shaped and contain only a few taste buds
Fungiform papillae
Ridges on the sides of the tongue and contain taste buds only in childhood
Foliate papillae
Long, thin cylinders scattered across the tongue; they do not contain taste buds but have sensory nerve endings that detect texture and temperature of food
Filiform papillae
Specialized epithelial cells with microvilli that contain receptors that detect different tastes
Gustatory (taste) cells
Small pocket on the surface of the papilla
Taste pore
Simple sugars such as glucose and fructose
Sweet tastes
Produced by hydrogen ions, found in the citric acid of lemon juice
Sour tastes
this taste is due to the presence of metal ions such as sodium and potassium ions
Salty tastes
Flavors are imparted by many nitrogen-containing compounds and are often found in rancid or poisonous substances
Bitter taste
A taste often associated with meat or broth, is produced by glutamate or other amino acids
Umami taste (savory)
Pathway:
*facial, glossopharyngeal, vagus nerves carry taste to the CNS
- axons of the 3 nerves terminate in the solitary nucleus in the medulla by synapsing onto central sensory neurons
- axons from the nucleus synapses on neurons in the thalamus, which then send the taste signals to the primary gustatory cortex in the parietal lobe
The Gustatory Pathway
Two thin folds that cover the anterior part of the orbit, prevents objects from entering the eye, and distribute tears across the eye when blinking
Eyelids (Palpebrae)
A thin piece of dense regular collagenous connective tissue that the eyelid is stiffened by
Tarsal plate
Modified sebaceous glands that are located in the tarsal plate and secrete oil to prevent the eyelids from sticking together
Tarsal glands
A fleshy structure found at the medial commissure that contains sebaceous glands that secrete a whitish lubricating substance
Lacrimal caruncle
Hairs along the ridge of the brow that serve as a protective function
Eyebrows
Stiff hairs located in the edges of the upper and lower eyelids
Eyelashes
A thin epithelial membrane that lines the posterior surfaces of the eyelids
Conjunctiva (palpebral)
Covers the anterior surface of the white part of the eye
Conjunctiva (ocular or bulbar)
Tiny holes in the medial edge of each eyelid, where tears first enter
Lacrimal puncta
Small ducts that empty into the lacrimal sac
Lacrimal canliculi
Small depression in the lacrimal bone and drains into the nasolacrimal duct
Lacrimal sac
Superior rectus Inferior rectus Lateral rectus Medial rectus Superior oblique Inferior oblique
The Six Extrinsic Muscles
When the eyes cannot move together, they send different images to the brain, which is interpreted as blurred or double vision
Diplopia (lazy eye or strabismus)
The white fibrous layer of the eyeball that covers approximately five-sixths of its surface, maintains shape of the eyeball and lubricates it
Sclera
The translucent (clear) part of the eyeball that admit light into eye and focus it
Cornea
Vascular layer of the eyeball that contain many blood vessels called capillaries as well as pigment to reduce the scattering of light
Choroid
Continuous with the choroid, contains a ring of smooth muscle that surrounds and control the shape of the lens
Ciliary body
Connect the ciliary body to the lens
Suspensory ligaments
The colored portion of the eye, responsible for controlling the diameter and size of the pupil and the amount of light entering the eye
Iris
The hole located in the middle of the iris, allows light to strike the retina
Pupil
Muscle contracts following parasympathetic stimulation and constricts the pupil to reduce the amount of light entering the eye
Pupillary sphincter
Muscle contracts following sympathetic stimulation and enlarged the pupil to permit the entrance of more light into the eye (dilate the pupil)
Pupillary Dialator
The innermost layer of the eyeball that contains photoreceptors
Retina
Specialized to detect the presence of light and produce a neural signal
Photoreceptor cells
An area in the retina that contain a high density of photoreceptors (cones)
Fovea centralis
The yellowish region where the fovea is located that also contains a high density of photoreceptors
Macula lutea
Portion of the retina that does not contain photoreceptors, axons of the optic nerve gather here
Optics disc (blind spot)
Flattened sphere located posterior to the iris and pupil and focuses light on the retina from objects near the eye
Lens
Posterior to the lens, filled with gelatinous material called vitreous humor
Posterior cavity
Presses the retina against the choroid and helps maintain the shape of the eyeball
Vitreous humor
The area anterior the the lens and ciliary body that contains the the anterior and posterior chambers that are filled with aqueous humor
Anterior cavity
Secreted by the ciliary body
Aqueous humor
Blood vessels that circles the anterior edge of the iris that prevent the build up of aqueous humor by draining at the same rate as the anterior chamber
Scleral venous sinus
A clouded lens that light cannot pass through even if there are functional photoreceptors
Cataracts
Aqueous humor cannot drain and fluid builds up in the anterior and posterior chambers
Glaucoma
The range of wavelengths that we can detect with our eyes, and we perceive segments of that range as particular colors
Visible light
When the eye is relaxed and focusing on a distant object
Emmetropic
The lens increases its total refraction by changing its shape from flattened to round
Accommodation
The closest point at which we can focus on an object
Near point accommodation
A condition in which the lens stiffens with age and cannot focus on near objects
Presbyopia
The length of the eyeball is normal in the anterior-posterior direction and the lens can focus light on the retina
Emmetropia
The eyeball is too short or the cornea is too flat and the lens cannot round up enough, and the image focuses behind the retina causing blurry images when viewing objects up close
Hyperopia (farsightedness)
The distance between the cornea and the retina is too long, or the cornea curves too much and the lens cannot flatten enough, which focuses the light in front of the retina and blurs the image when viewing distant objects
Myopia (nearsightedness)
Neurons that synapses with photoreceptors and communicate with retinal ganglion cells
Bipolar cells
The most anterior cells in the retina
Retinal ganglion cells
Contain pigments that allow us to perceive color and they function best in bright light
Cones
Cannot detect color, but they are very sensitive and capable of responding in dim light (white and black)
Rods
The pigment in rods
Rhodopsin
Pigment in cones
Iodopsin
When a person lacks a functional gene for one or more cone pigments (red, green, blue)
Color blindness
An X-shaped structure formed by the meeting of the optic nerves at the midline, location were some of the axons of the optic nerve cross to the other side of the brain
Optic chiasma
Forms after the axons leaves the optic chiasma
Optic tracts
Where most of the axons end in the thalamus
Lateral geniculate nucleus