Ch. 17: Special Senses

Threshold for taste

(lowest to highest) Bitter > sour > sweet = salty

structures of the inner ear

-Contains semicircular canals and cochlea. -The spiral organ or Corti contains supporting cells including approximately 16,000 hair cells, which are the receptors for hearing.

olfactory pathway to the brain

-olfactory receptors -olfactory nerve -olfactory bulb -olfactory tract -olfactory cortex of temporal lobe

When viewing an object close to your eyes, which of the following are required for proper image formation on the retina? 1. increased curvature of the lens 2. contraction of the ciliary muscle 3. divergence of the eyeballs 4. refraction of light at the anterior and posterior surfaces on the cornea 5. constriction of the pupil by contraction of the extrinsic eye muscle

1, 2, 4

Which of the following are true? 1. The sites of olfactory transduction are the olfactory hairs. 2. The olfactory bulbs transmit impulses to the temporal lobe of the cerebral cortex. 3. The axons of olfactory receptors pass through the olfactory foramina in the cribriform plate of the ethmoid bone. 4. The olfactory nerves are bundles of axons that terminate in the olfactory tracts. 5. Within the olfactory bulbs, the first-order neuron synapses with the second-order neurons.

1, 3, 5

How many odors can humans recognize?

10,000

gustatory pathway to the brain

4nerve impulses propagate along these cranial nerves to the gustatory nucleus in the medulla oblongata. From the medulla, some axons carrying taste signals project to the limbic system and the hypo- thalamus; others project to the thalamus. Taste signals that project from the thalamus to the primary gustatory area in the parietal lobe of the cerebral cortex

-A degenerative disorder of the retina in persons 50 years of age or older. -Abnormalities occur in the region of the macula lutea, which is ordinarily the most acute area of vision. -Victims retain their vision but lose the ability to look straight ahead. -Leading cause of blindness

AMD (Age-related macular disease)

a decrease in sensitivity. It occurs rapidly. 50% of the decrease occurs within the first second or so and then very slowly after that.

Adaptation

structures of the middle ear

Auditory ossicles: -Malleus attaches to the internal surface of the tympanic membrane. -Incus articulates with the head of the stapes -Stapes fits into the oval window which is enclosed by a secondary tympanic membrane. Eustachian (pharyngotympanic) tube: -connects the middle ear to the nasopharynx. -it helps to equalize pressure in the middle ear

-Found in the connective tissue that supports the epithelium. -They produce mucous which moistens the epithelial surface and dissolves the odorants.

Bowman's glands

Innervation of the olfactory glands

Branches of the facial nerve (CN VII) -This nerve also stimulates lacrimal gland to produce tears from scents of pepper and ammonia

Place in order the structures involved in the visual pathway. a. optic tract b. ganglion cells c. cornea d. lens e. bipolar cells f. optic nerve g. visual cortex h. vitreous body i. optic chiasm j. aqueous humor k. pupil l. photoreceptors m. thalamus

C. Cornea J. aqueous humor K. pupil D. lens H. vitreous body L. photoreceptors E. bipolar cells B. ganglion cells F. optic nerve I. optic chiasm A. optic tract M. thalamus G. visual cortex

Innervation of extrinsic eye muscles

CN III - Oculomotor: Superior rectus, inferior rectus, medial rectus, inferior oblique CN IV - Trochlear: Superior oblique CN VI - Abducens Lateral rectus

Infection of the Meibomian glands that produces a cyst

Chalazion

a sensory receptor that transduces a chemical signal into an action potential. Detects change in environment

Chemosensor/chemoreceptor

Passes from the eyelids to the surface of the eyeball and covers the sclera ("white" of the eye). Is vascular. Irritation or infection cause bloodshot eyes.

Conjuctiva

narrowing of the pupil

Constriction

Refraction abnormalities

Emmetropic eye - normal eye - can sufficiently refract light rays from objects 6 m (20 ft) away so that a clear image is focused on the retina. Myopia - nearsightedness - can see close objects clearly, but not distant objects. Hyperopia (hypermetropia) - farsightedness - can see distant objects clearly, but not close ones. Astigmatism - either the cornea or the lens has an irregular curvature. Parts of the image are out of focus.

Main regions of the ear

External ear - collects sound waves and channels them inward. Middle ear - conveys sound vibrations to the oval window. Internal ear - houses the receptors for hearing and equilibrium.

accessory structures of the eye

Eyelids (palpebrae): -Shade the eyes during sleep, protect the eyes from excessive light and foreign objects, and spread lubricating secretions over the eyeballs. -The upper eyelid contains the levator palpebrae superioris muscle and is more moveable than the lower. -The lacrimal caruncle is a small, reddish elevation on the medial border and contains sebaceous (oil) and sudoriferous (sweat) glands. Eyelashes & Eyebrows: help protect the eyeballs from foreign objects, perspiration, and the direct rays of the sun. Lacrimal apparatus: -a group of structures that produces and drains lacrimal fluid or tears. -The lacrimal ducts empty tears onto the surface of the conjunctiva of the upper lid. Extrinsic eye muscles: -Superior rectus, inferior rectus, medial rectus, inferior oblique, superior oblique, lateral rectus -Conduct smooth, precise, and rapid movements of the eye.

T or F: The ability to change the curvature of the lens for near vision is convergence.

False

Three layers of the eyeball

Fibrous tunic Vascular tunic Retina

the sites of taste transduction, projects through the taste pore.

Gustatory hairs

Why do the chemical senses form emotional responses and memories?

Impulses from these senses propagate to the limbic system and higher cortical areas.

flow of tears

Lacrimal gland -- lacrimal ducts -- superior or inferior lacrimal canal -- lacrimal sac -- nasolacrimal duct -- nasal cavity

What can impair receptors leading to hyposmia?

Neurological changes impair the receptors. Head injury, Alzheimer's, Parkinson's, COVID/viruses Medications impair receptors. Antihistamines, analgesics, steroids.

What are the three cells present in olfactory receptors?

Olfactory receptors 1st order neurons - bipolar Olfactory hairs - cilia that project from the dendrite - respond to chemicals called odorants Supporting cells Columnar epithelium of mucous membrane Support, nourish, detoxify chemicals Basal cells Stem cells - produce new olfactory cells (live approx. 1 month)

What is the survival function of olfaction?

Our sense of smell serves a survival function to help us select non-poisonous foods.

specialized cells that begin the process by which light rays are converted to nerve impulses.

Photoreceptor

-When light rays pass from one substance (air) to another substance with a different density (water), they bend at the junction between the two substances -Light is bended at both the cornea and the lens so that it comes into exact focus on the retina

Refraction

infection of sebaceous ciliary glands

Sty

What are the 3 kinds of epithelial cells in the taste bud?

Supporting cells: surround approximately 50 gustatory receptor cells in a taste bud. Gustatory receptor cells: synapse with 1st order neurons. 1st order neurons contact many gustatory receptor cells. basal cells: stem cells at the periphery of the taste bud. They produce supporting cells which will develop into gustatory cells.

The kinds of epithelial cells with each taste bud

The Supporting Cells: -surround approximately 50 gustatory receptor cells in a taste bud. The Gustatory Receptor Cells: -synapse with 1st order neurons. 1st order neurons contact many gustatory receptor cells. The Gustatory Hair (microvillus): -projects through the taste pore. The Basal Cells: -Stem cells at the periphery of the taste bud. They produce supporting cells which will develop into gustatory cells.

-the level of stimulation required to trigger a neural impulse. - The amount of molecules of certain substances that need be present in air to be perceived as an odor.

Threshold

T or F: Of all the special senses, only smell and taste sensations project both to higher cortical areas and to the limbic system.

True

Taste buds and their locations

Vallate (Circumvallate) Papillae: -About 12 very large circular vallate papillae form an inverted V-shaped row at the back of the tongue. -Each of these papillae contains approximately 100-300 taste buds. Fungiform Papillae: -mushroom shaped elevations scattered over the entire surface of the tongue with 5 taste buds each. Foliate Papillae: -In small trenches on the lateral margins of the tongue, but most of their taste buds degenerate in early childhood. Filiform Papillae: -On the entire surface of the tongue. -Are pointed, threadlike structures that contain tactile receptors but no taste buds. -They increase friction between the tongue and the food

visual pathway from eye to brain

Visual signals from the retina exit the eyeball as the optic nerve (CN II) and proceed to the brain. Retina -> Bipolar Cells -> Ganglion Cells -> Optic Nerve -> Thalamus -> Cortex of Brain

Which of the following statements is incorrect? a. Olfactory receptors respond to the chemical stimulation of an odorant molecule by producing a receptor potential. b. Basal stem cells continually produce olfactory receptors. c. Adaptation to odors is rapid and occurs in both olfactory receptors and the CNS. d. Production of nasal mucus by olfactory glands serves to moisten the olfactory epithelium and dissolve odorants. e. The orbitofrontal area is an important region for odor identification and discrimination.

a. Olfactory receptors respond to the chemical stimulation of an odorant molecule by producing a receptor potential.

The change in shape of the lens

accommodation

swollen enlargement in semicircular canals; contains structures involved in dynamic equilibrium

ampulla

watery fluid in the anterior cavity that helps nourish the lens and cornea; helps maintain the shape of the eyeball

aqueous humor

the pressure equalization tube that connects the middle ear to nasopharynx

auditory or eustachian tube

the flap of elastic cartilage covered by skin that captures sound waves; the pinna

auricle

Structures of the external ear

auricle (pinna) and external acoustic meatus (auditory canal), and eardrum

Which of the following are mismatched? a. fungiform papillae: scattered over the entire tongue's surface b. filiform papillae: contain taste buds in early childhood c. vallate papillae: each houses 100-300 taste buds d. foliate papillae: located in trenches on the lateral margins of the tongue e. fungiform papillae: each houses about five taste buds

b. filiform papillae: contain taste buds in early childhood

Which of the following statements is incorrect? a. Retinal is the light-absorbing portion of all visual photopigments. b. The only photopigment in rods is rhodopsin, but three different cone photopigments are present in the retina. c. Retinal is a derivative of vitamin C. d. Color vision results from different colors of light selectively activating different cone photopigments. e. Bleaching and regeneration of the photopigments account for much but not all of the sensitivity changes during light and dark adaptation.

c. Retinal is a derivative of vitamin C.

circular band of smooth muscle that alters the shape of the lens for near or far vision

ciliary muscle

contains the spiral organ

cochlea

surface that curves inward, this type of lens refracts incoming light rays away from each other.

concave

-Stimulated in brighter light. -Produce color vision. -Located @ outer segment of retina: the distal end next to the pigmented layer. -The outer segments are tapered

cones

a thin, protective mucous membrane that lines the inner aspect of the eyelids onto the surface of the eyeball, where it covers the sclera

conjunctiva

the medial movement of the two eyeballs so that both are pointed towards the object.

convergence

surface that curves outward, this type of lens will refract incoming light rays towards one another.

convex

Which of the following statements is incorrect? a. Taste is a chemical sense. b. The receptors for taste sensations are found in taste buds located on the tongue, the soft palate, the pharynx, and the epiglottis. c. Gustatory hairs are the sites of taste transduction. d. The threshold for bitter substances is the highest. e. Complete adaptation to taste can occur in 1 to 5 minutes.

d. The threshold for bitter substances is the highest.

When you enter a darkened room, your sensitivity increases slowly over several minutes

dark adaptation

energy in the form of waves that radiate from the sun. Types: -Gamma rays, X-rays, UV rays -Visible light -Infrared radiation, Microwaves, Radio waves

electromagnetic radiation

fluid found within the membranous labyrinth; pressure waves in this fluid cause vibration of the basilar membrane

endolymph

What is the correct sequence for the auditory pathway? (a) external auditory canal, tympanic membrane, auditory ossicles, oval window, cochlea and spiral organ (b) tympanic membrane, external auditory canal, auditory ossicles, cochlea and spiral organ, round window (c) auditory ossicles, tympanic membrane, cochlea and spiral organ, round window, oval window, external auditory canal (d) auricle, tympanic membrane, round window, cochlea and spiral organ, oval window (e) external auditory canal, tympanic membrane, auditory ossicles, internal auditory canal, spiral organ, oval window

external auditory canal, tympanic membrane, auditory ossicles, oval window, cochlea and spiral organ

move the eyeball medially, laterally, superiorly, or inferiorly

extrinsic eye muscles

arch transversely above the eyeballs and help protect the eyeballs from foreign objects, perspiration, and the direct rays of the sun

eyebrows

project from the border of each eyelid; help protect the eyeballs from foreign objects, perspiration, and direct rays of the sun

eyelashes

avascular superficial layer of eyeball; includes cornea and sclera

fibrous tunic

-pressure in the eye produced by aqueous humor -It helps to maintain the shape of the eyeball and prevent it from collapsing.

intraocular pressure

colored portion of the eyeball; regulates the amount of light entering the posterior part of the eyeball

iris

produces and drains tears

lacrimal apparatus

biconvex transparent structure that fine tunes focusing of light rays for clear vision

lens

When you emerge from dark surroundings into the light, your visual system adjusts within seconds to the brighter surroundings

light adaptation

receptor for static equilibrium; also contributes to some aspects of dynamic equilibrium; consists of hair cells and supporting cells

macula

what are the three bones of the auditory ossicles?

malleus, incus, stapes

the minimum distance from the eye that an object can be clearly focused with the maximum accommodation.

near point of vision

chemicals that stimulate olfactory receptors

olfactants

Adaptation of olfaction and taste

olfaction: taste: complete adaptation in 1-5 minutes

opening between the middle and inner ear; receives base of stapes

oval window

upper and lower eyelids; shade the eyes during sleep, spread lubricating secretions over the eyeball

palpebrae

fluid found inside bony labyrinth; bulging of the oval window causes pressure waves in this fluid

perilymph

the hole in the center of the iris

pupil

Hyposmia

reduced ability to smell

innermost layer of the eyeball; beginning of the visual pathway; contains rods and cones

retina

-Allow us to see in dim light. -Do not provide color vision. -Located @ outer segment of retina: the distal end next to the pigmented layer. -The outer segments are cylindrical

rods

opening between the middle ear and internal ear; is enclosed by a membrane called the secondary tympanic membrane

round window

white of the eye; gives shape to the eyeball, makes it more rigid, protects its inner parts

sclera

Located at the base of the hair follicles of the eyelashes. The release a lubricating fluid into the follicles.

sebaceous ciliary glands

auditory pathway to brain

spiral ganglion --> cochlear nucleus --> superior olive --> inferior colliculus --> Medial Geniculate Nucleus thalamus --> primary auditory area

contain hair cells which are the receptors for hearing

spiral organ

_______ equilibrium refers to the maintenance of the position of the body relative to the force of gravity; _______ equilibrium refers to the maintenance of body position in response to rotational acceleration and deceleration.

static dynamic

What tastants do not enter gustatory receptor cells but instead bind to receptors on the plasma membrane and trigger second messengers in the cell?

sweet bitter and umami

What are the five primary taste sensations?

sweet, sour, salty, bitter and umami

modified sebaceous glands; secretion helps keep eyelids from adhering to one another

tarsal or Meibomian glands

a thick fold of connective tissue that gives form and support to the eyelids

tarsal plate

Chemicals that stimulate gustatory receptor cells; Different types stimulate the gustatory receptors in different ways to generate the receptor potential. tastants

tastants

What are the two chemical senses?

taste and smell

a learned avoidance of a particular food

taste aversion

color vision results from?

the stimulation of various combinations of these three types of cones (red cones, green cones, blue cones)

partition between external auditory canal and middle ear

tympanic membrane

a thin, semitransparent partition between the external auditory canal and the middle ear. Tearing of this structure is called perforated eardrum

typanic membrane

middle, vascularized layer of the eyeball; includes choroid, ciliary body and iris

vascular tunic

receptor organs for equilibrium; the saccule, utricle and semicircular canals

vestibular apparatus

oval central portion of the bony labyrinth; contains utricle and saccule

vestibule

Occasionally, collections of debris may cast a shadow on the retina and create the appearance of specks that dart in and out of the field of vision

vitreous floaters