Portage learning chapter 3

what are the five special senses

vision, smell, taste, hearing, and equilibrium (balance)

what is a special sense

it is a sense that has a specialized organ containing specialized receptor cells, which carry their impulses by way of specialized somatic and visceral afferents. 

which sense does not have specialized organ

touch

what does touch use instead of specialized senses

general receptors composed of modified dendrites of sensory neurons

what is included in touch

pressure, vibration, pain, heat, and the combined information is carried in general somatic afferents and general visceral afferents

how many layers does the eye have

3

what are the three layers of the eye

outer fibrous layer, middle, and inner sensory layer

outer fibrous layer

sclera and cornea

sclera

 posterior portion; also know as white of the eye.

cornea

transparent part of the eye where light enters

Aqueous humor

fills the spaces between the cornea and the lens

what is included in the middle layer

choroid, ciliary body, and iris

choroid

highly vascular and supplies blood to the other layers of the eye

ciliary body

changes the shape of the lens, allowing it to focus

iris

uses its muscle fibers to contract or dilate based on the amount of light in the environment

what does the inner sensory layer include

retina, lens, vitreous body, vitreous fluid

retina

The retina contains containing two types of **photoreceptors,** cells that are sensitive to light

rods

are stimulated in dim light.

cones

operate in bright light, helping to generate sharp color images

lens

 located posterior to the iris and pupil.

 **vitreous body**

The interior of the eye, posterior to the lens

vitreous fluid

helps to hold the retina firmly to the choroid.

what is the pathway of light

cornea, aqueous humor, lens, vitreous humor, retina, optic nerve, optic chiasm, optic tract, and LGN, and optic radiations

where is the optic chiasm located

base of the hypothalamus

where do optic tracts terminate

 in the thalamus in a region called the **lateral geniculate nucleus** (LGN)

when is vision information interpreted

when it reaches the occipital lobe

nasal visual field

closest to the nose

peripheral vision field

 lateral side of each eye

binocular visual field

Overlapping information in the nasal visual fields allows for 3-D vision

what does each eye have

Each eye has a **left visual field** and a **right visual field**

If the right eye saw something which side of the brain would interpret it

left side

which side of the retina is interpreting the left visual field of both eyes

right

what can cross at the optic chiasm

medial fibers

the left side of the brain receives information from

the medial side of the left eye and the lateral side of the right eye (bilateral right visual fields)

what are the six muscles in the eye

medial rectus, inferior rectus, superior rectus, and inferior oblique, superior oblique, lateral rectus

which eyes muscles are controlled by cranial nerve 3

medial rectus, inferior rectus, superior rectus, and inferior oblique

which eyes muscles are controlled by cranial nerve 4

superior oblique

which eyes muscles are controlled by cranial nerve

lateral rectus

medial rectus

turns eye medially

inferior rectus

moves the eye medially and depresses it

superior rectus

moves the eye medially and elevates it

inferior oblique

responsible for eye elevation, lateral movement, and external rotation

superior oblique

responsible for eye depression, lateral movement, and internal rotation

lateral rectus

turns the eye laterally

what are visual impairments

 occur from damage to any part of the vision pathway

cataracts

are lenses that slowly become hardened and cloudy over time. Cataracts make vision look blurry because the light is unable to enter the lens clearly to be refracted onto the retina

what would cause diplopia

Damage to the abducens nerve

\

\

\

what are the major parts of the ear

 external, middle, and inner ears

external ear

consists of the auricle and external acoustic canal (meatus)

auricle

shaped to funnel sound waves into the external acoustic canal so that sounds can be detected; It is composed of elastic cartilage covered with thin skin

external acoustic meatus

tunnel between the auricle and tympanic membrane; composed of elastic cartilage near the auricle and becomes a cylinder through the *temporal bone*.

cerumen

serves to trap foreign materials

tympanic membrane

a thin membrane of connective tissue whose vibration transmits sound energy to the middle ear.

which chamber in the ear is filled with air and has the smallest bones in the body

**middle ear** (or tympanic cavity

name the smallest bones in the body

malleus, incus, and stapes

which bone in the ear receives vibrations from the eardrum and transfers them along through the incus, then finally the stapes, which conveys them to the inner ear

malleus

the inner ear is composed of what

bony and membranous labyrinths filled with fluid

what are the 3 sections in the bony labyrinth

the vestibule, semicircular canals, and cochlea

what connects to the semicircular canals

the vestibule

semicircular canals

house receptors to provide the body's **vestibular** (equilibrium and balance) system and are also filled with fluid

what causes action potentials in the semicircular canals

equilibrium receptors

where are action potentials in the ear sent

vestibular portion of CN VIII

what does the facial nerve do in the ear

innervates the stapedius, which is attached to the stapes

what does the stapedius control

the amount of tension on the bone, allowing for increased or decreased vibration to help control the intensity of sounds

I am a spiral, bony chamber containing the membranous endolymph-filled cochlear duct, who am I?

cochlea

the cochlea houses

the organ of corti

cochlea stops where

at the cochlear nerve

I am the sense organ for the auditory system and I contain the tectorial membrane and tiny hairs called **stereocilia**

organ of corti

what happens when the fluid within the cochlear duct receives vibrations

the **tectorial membrane** moves and bends the attached stereocilia

when the stereocilia is moved

it initiates an action potential in neurons that is transmitted through the cochlear nerve portion of CN VIII

what is the pathway of sound

1. sound waves are funneled into the external auditory canal causing the eardrum to vibrate
2. vibrations transmit to the ossicles, which push against fluid inside the cochlear duct
3. The movement of the fluid causes movement of the stereocilia in the organ of Corti
4. The movement of the stereocilia then stimulates the neurons to send impulses through the cochlear nerve to the primary auditory cortex of the temporal lobe

why is sound interpreted equally in each ear

because the ascending pathways cross in addition to sending signals to the same side of the brain

deafness is always total, true or false

false

conduction deafness

occurs from damage to the outer or middle ear structures

Nerve deafness

 occurs from damage to the nerve pathway

which kind of deafness is never complete

conduction deafness

I am a sense that is activated by chemical substances dissolving in the fluid of the nasal mucous membranes

olfaction

olfactory nerves have what kind of cells

bipolar receptor cells

bipolar cells are found

on the roof of the nasal cavity

pathway of olfactory nerve

1. olfactory nerves travel through the *ethmoid bone* in a location called the *cribriform plate*
2. dendrites extend from the cell body to the surface of the epithelium where it terminates in the **olfactory bulbs,** which are paired masses of gray matter 
3. In the olfactory bulbs, olfactory nerve axons synapse with other cell bodies of the olfactory pathway.
4. The axons then travel together from the olfactory bulbs to form the **olfactory tracts**, which carry information to the temporal lobes. Here, the signals are interpreted in the primary olfaction area as smell

what are the seven primary odors

floral (roses), ethereal (dry-cleaning fluid), camphorates (mothballs), musky (perfumes), peppermint (mint gum), pungent (vinegar) and putrid (rotten eggs)

which system is responsible for special sense of taste

gustatory system

I am responsible for gripping food and repositioning it between the teeth, forming it into a compact mass called a **bolus**

tongue

what is the front and back of the mouth called

apex and base

frenulum

inferior surface of the tongue along the midline

I’m a raised bump on the tongue

papillae

three types of papillae

circumvallate, fungiform, and filiform

which papillae contain taste buds

circumvallate, fungiform

what are taste buds

they contain chemical receptors that are stimulated by the chemical composition of food

are found primarily on the tongue as well as on the surface of the mouth and wall of the pharynx.

taste buds

taste buds are formed

from gustatory cells and supporting cells

what are chemoreceptor cells inside the taste buds

gustatory cells

gustatory hair

projects into the saliva to detect dissolved chemicals

what are supporting cells

 form the bulk of the taste bud and separate the taste receptors cells from one another

serve as stem cells, which divide and differentiate into new supporting cells that then form new gustatory cells

basal cells

taste pathway

1. begins as food chemicals contact the gustatory hairs, which generate an action potential in dendrites that are wrapped around the gustatory cells.
2. The nerve impulse is carried by afferent fibers through two cranial nerve pairs, the *facial* nerves, and the *glossopharyngeal* nerves
3. transmit the impulse to the thalamus and ultimately to the parietal lobe to be interpreted as taste.
4. The facial nerve carries information from the anterior two-thirds of the tongue, while the glossopharyngeal nerve carries information from the posterior one-third of the tongue