[A&P 1] Chapter 16: Special Senses

vision, taste, smell, hearing, equilibrium

what are the special senses of the body?

special sensory receptors

what type of receptors do special senses use?

smell

what sense am I?

• has olfactory epithelium that

- supports cells

- basal (stem) cells

- olfactory sensory neurons

olfaction

term for the sense of smell

olfactory pathway

what does the following pathway describe?

olfactory epithelia → olfactory bulbs (CN I) → olfactory tract → temporal lobe and limbic system

anosmia

define the diagnosis:

the inability to smell

• caused from trauma, infections, and neurologic disorders (e.g. Alzheimer's, Brain tumors, Parkinson's)

taste

what sense am I?

contains taste buds, tongue papillae, taste pore, chemo- receptors.

gustation

term for the sense of taste

gustatory pathway

what does the following pathway describe?

gustatory receptors → CN VII & CN IX → medulla → thalamus

facial (CN VII) and glossopharyngeal (CN IX)

what nerves are involved in the gustatory pathway?

insula

where is the primary gustatory cortex located?

ageusia

define the diagnosis:

the loss of taste

• caused by common cold, COVID, sinusitis, dry mouth

80%

what percentage of taste comes from smell?

superior palpebra

what is the term for upper eyelid?

inferior palpebra

what is the term for lower eyelid?

medial commissure

what is the medial angle of the eye?

lateral commissure

what is the lateral angle of the eye?

extrinsic eye muscles

what are the muscles attached to the outside of the eyeball and enable the eyes to move in all directions of sight?

lateral rectus

what is the extrinsic eye muscle LR₆?

lateral rectus

what extrinsic eye muscle moves the eye laterally?

abducens (CN VI)

what is the controlling cranial nerve of the extrinsic eye muscle LR₆?

oculomotor (CN III)

what is the controlling cranial nerve of the extrinsic eye muscles: medial rectus, superior rectus, inferior rectus and inferior oblique?

medial rectus

what extrinsic eye muscle moves the eye medially?

superior rectus

what extrinsic eye muscle elevates the eye and moves it medially?

(i.e.: moves eyeball up and medially)

inferior rectus

what extrinsic eye muscle depresses the eye and turns it medially?

(i.e.: moves eyeball down and medially)

inferior oblique

what extrinsic eye muscle elevates the eye and turns it laterally?

(i.e.: moves eyeball up and out)

superior oblique

what is the extrinsic eye muscle

(SO₄)₃?

superior oblique

what extrinsic eye muscle depresses the eye and turns it laterally?

(i.e.: moves eyeball down and out)

trochlear (CN IV)

what is the controlling cranial nerve of the extrinsic eye muscle (SO₄)₃?

fibrous layer

define the structure of the eyeball

the outermost layer made of dense avascular connective tissue

• has two regions: sclera and cornea

sclera

define the region in the fibrous layer of the eyeball:

• white of the eye

• opaque, posterior region that protects & shapes eyeball

• anchors extrinsic eye muscles

sclera

what part of the fibrous layer of the eyeball supports & maintains the shape of the eye and provides attachment to the extrinsic eye muscles?

cornea

define the region in the fibrous layer of the eyeball:

• the transparent outer covering of the eye

• forms a clear window that lets light enter and bends light as it enters the eye

• has numerous pain receptors that contribute to blinking and tearing reflexes

cornea

what part of the fibrous layer of the eyeball mediates light refraction and allows light entry?

vascular layer

define the structure of the eyeball

the pigmented layer of eye, also called uvea

• has three regions: choroid, ciliary body, and iris

choroid

define the region in the vascular layer of the eyeball:

• the posterior portion of uvea

• supplies blood to all layers of eyeball

• brown pigment absorbs light to prevent scattering of light, which would cause visual confusion

choroid

what part of the vascular layer of the eye has blood vessels and a brown pigment, which eventually becomes the ciliary body?

ciliary body

define the region in the vascular layer of the eyeball:

• the thickened ring of tissue surrounding lens

• consists of smooth muscle bundles, ciliary muscles, that control the shape of the lens

ciliary zonule (suspensory ligament)

what component of the ciliary body extends from ciliary processes to the lens and holds lens in position

ciliary zonule (suspensory ligament)

what connects the lens to the ciliary body?

iris

define the structure of the eyeball

the colored part of the eye that lies between the cornea and the lens,

• continuous with ciliary body

pupil

what is the central opening that regulates amount of light entering eye in the iris?

sphincter pupillae

fill in the blank

close vision and bright light cause __________________________ (circular muscles) to contract and pupils to constrict;

sphincter pupillae

if an eye sees a close, bright object, what type of pupillae will contract to prevent the eye from getting damaged?

parasympathetic control

what type of ANS control occurs when sphincter pupillae contract and the pupils constrict?

dilator pupillae

fill in the blank

distant vision and dim light cause _____________________ (radial muscles) to contract and pupils to dilate

dilator pupillae

if an eye sees a dim object that has been pushed farther away, what type of pupillae will contract?

sympathetic control

what type of ANS control occurs when dilator pupillae contract and the pupils dilates?

retina

define the structure of the eyeball

light-sensitive region of the eye; contains rods and cones

• contains: millions of photoreceptor cells, neurons, and glial cells

photoreceptor cells

what type of cells are rod and cones that transduce light energy to convert it into electrical signals?

inner layer of retina

define the layer of the retina

• pigmented layer of the retina

• single-cell-thick lining next to the choroid

• extends anteriorly, covering the ciliary body and iris

inner layer of retina

what layer of the retina has the following functions?

• absorbs light and prevents its scattering

• phagocytizes photoreceptor cell fragments

• stores vitamin A

inner layer of retina

define the layer of the retina

• neural layer of the retina

• composed of 3 main types of neurons: photoreceptors, bipolar cells, ganglion

inner layer of retina

what layer of the retina contains optic discs

optic disc

what region in the inner layer of the retina has the following description:

• is the site where optic nerves leave the eye

• lacks photoreceptors; referred to as blind spot

optic disc

what is the blind spot of that eye that lacks photoreceptors?

rods and cones

what are the two types of photoreceptors in the retina?

rods

what is the type of photoreceptor based on the characteristics?

• dim light, peripheral vision receptors

• has low acuity (many converge into one ganglion cell)

rods

what type of retinal receptor is more numerous?

rods

what type of retinal receptor is more sensitive to light?

rods

what type of retinal receptor responds to dim light?

cones

what is the type of photoreceptor based on the characteristics?

• vision receptors for bright light

• high-resolution color vision

• has high acuity (one per ganglia cell in fovea)

cones

what type of retinal receptor responds to bright light and colors?

cones

what type of retinal receptor has high visual acuity?

pigment

the ______________ in the eyes are meant to absorb the light and avoid light scattering

pigment

what component in the retinal layer stores vitamin A and has phagocytes that remove cellular fragments?

macula lutea

what is the area at posterior pole lateral to blind spot in the retina and contains mostly cones?

fovea centralis

what is the tiny pit in the center of the macula lutea that contains all cones, so it's the region with the best visual acuity?

internal chambers and fluids

define the structure of the eyeball

the lens and ciliary zonule separate the anterior and posterior segments into…

posterior segment

which segment of the eyeball is behind the lens and contains vitreous humor?

vitreous humor

what type is the fluid that...

• allows light transmission in the eye and supports the posterior surface of lens

• holds neural layer of the retina firmly against pigmented layer

• contributes to intraocular pressure

vitreous humor

what type of fluid supports the posterior part of the lens?

anterior segment

which segment of the eyeball contains aqueous humor?

anterior segment

which segment of the eyeball contains anterior and posterior chambers?

anterior chamber

what chamber of the anterior segment in the retina is between the cornea and iris

posterior chamber

what chamber of the anterior segment in the retina is between the iris and lens

aqueous humor

what type is the fluid has the following characteristics:

• a plasma-like fluid continuously formed by capillaries of ciliary processes

• drains via scleral venous sinus (canal of Schlemm) at sclera- cornea junction

• supplies nutrients and oxygen mainly to lens and cornea but also to retina, and removes wastes

aqueous humor

what type of fluid provides nutrition the lens & cornea and removes waste?

aqueous humor

increasing what type of humor causes the intraocular pressure to increase, and could lead to glaucoma if not treated?

scleral venous sinus

what is the component that drains extra aqueous humor?

lens

define the structure of the eyeball

biconvex, transparent, flexible, and avascular

• changes shape to precisely focus light on retina

contractions

fill in the blank

ciliary muscle __________________ (contraction/relaxation) loosens the ciliary zonules

loosens

when ciliary muscles contract, the ciliary zonules _____________ (loosens/tightens)

relaxation

fill in the blank

ciliary muscle __________________ (contraction/relaxation) tightens the ciliary zonules

tightens

when ciliary muscles relax, the ciliary zonules _____________ (loosens/tightens)

bulges

fill in the blank

the lens _______________ (bulges/flattens) for close vision

parasympathetic input

what type of input contractions the ciliary muscle

this action loosens the ciliary zonule and allows the lens to bulge

flattens

fill in the blank

the lens _______________ (bulges/flattens) for distant vision

sympathetic input

what type of input relaxes the ciliary muscle

this action tightens the ciliary zonule and allows the lens to flatten

distant vision

what type of vision are the eyes best adapted for?

far point of vision

what is the distance beyond which no change in lens shape is needed for focusing?

pupillary reflex

what type of reflex involves the constriction of pupils to prevent most divergent light rays from entering eye?

convergence of the eyeballs

what is the medial rotation of the eyeballs toward the object being viewed?

myopia

define the diagnosis:

nearsightedness

• eyeball is too long, so focal point is in front of the retina

• corrected with a concave lens

concave lens

what type of lens corrects myopia (nearsightedness)?

hyperopia

define the diagnosis:

farsightedness

• eyeball is too short, so focal point is in the retina

• corrected with a convex lens

convex lens

what type of lens corrects hyperopia (farsightedness)?

astigmatism

define the diagnosis:

unequal curvatures in different parts of cornea or lens

• corrected with cylindrically ground lenses or laser procedures

epithelial cells

photoreceptors (rods and cones) are modified neurons that resemble what upside down cell?

cell body, synaptic terminal, and outer & inner segments

what are the components of photoreceptors?