ANALAB SEC Q SPECIAL SENSES

Smell taste hearing sight equilibrium

Special senses include:

Special Sens Receptors

Large, complex sensory organs

Localized clusters of receptors

70,

- percent of all sensory receptors are in the

eyes

1

Each eye has over -million nerve fibers carrying

information to the brain

Accessory structures

include the:

 Extrinsic eye muscles

 Eyelids

 Conjunctiva

 Lacrimal apparatus

Eyelids

Meet at the medial and lateral commissure (canthus)

Eyelashes, tarsal glands

-produce an oily secretion that lubricates the eye

Ciliary glands

-are located between the eyelashes

Conjuctiva

Membrane that lines the eyelids and eyeball

Transparent cornea, conjuctiva

Connects with the -

Conjuctiva

Secretes mucus to lubricate the eye and keep it moist

Lacrimal gland

—produces lacrimal fluid (tears);

situated on lateral end of each eye

Teaes, lacrimal canaliculi,, lacrimal sac, nasolacrimal duct, nasa cavity

- drain across the eye into the -

then the -, and into the -

which empties into the+

Lysozyme

Tears contain:

 Dilute salt solution

 Mucus

 Antibodies

 - (enzyme that destroys bacteria)

Extrinsic eye muslces

Six muscles attach to the outer surface of the eye

Extrinsic eye muscles

Produce gross eye movements

Lateral rectus, VI abducens

Moves eye laterally

Medial rectus, III oculomotor

Moves eye medially

Superior rectus, III Oculomotor

Elevates eye and turns in medially

Inferior rectus, iii

Decrease eye and turns it medially

Inferior oblique III oculomotor

Elevates eye and turns it laterally

Superior oblique IV trochlear

Depresses eye and turns it laterallt

Fibrous

Vascular

Sensory layer

Three layers, or tunics, form the wall of the

eyeball

Fibrous layer

outside layer

Vascular layer

middle layer

Sensory layer

inside layer

Humors

are fluids that fill the interior of the

eyeball

Lens

divides the eye into two chambers

Sclera + Cornea

Fibrous layer =

Sclera

White connective tissue layer

Sclera

Seen anteriorly as the ―white of the eye‖

Cornea

Transparent, central anterior portion

Cornea

Allows for light to pass through

Cornea

Repairs itself easily

Cornea

The only human tissue that can be transplanted without

fear of rejection

1. Choroid

2. Ciliary body

3. Iris

4. Pupil

Vascular layer

Choroid

is a blood-rich nutritive layer that contains a

pigment (prevents light from scattering)

Iris

Regulates amount of light entering eye

Iris

Pigmented layer that gives eye color

Pipil

rounded opening in the iris

1. Retina

2. Rods

3. Cones

Sensory layers

Outer pigmented layer

Inner neural layer

 Retina contains two layers

Outer pigmenter layer, retina

absorbs light and prevents it

from scatterin

Inner neural layer

Rods cones

contains receptor cells

(photoreceptors)

Electrical signals,

Bipolar neurons

Ganglion cells

signals pass from photoreceptors via a two-

neuron chain

Optic nerve

Signals leave the retina toward the brain through the -

Optic disc (blind spot)

is where the optic nerve leaves

the eyeball

Optic disc

Cannot see images focused on the

Rods

Most are found toward the edges of the retina

Rods

Allow vision in dim light and peripheral vision

Rods

All perception is in gray tones

Cones

Allow for detailed color vision

Cones

Densest in the center of the retina

Fovea centralis, cones

Lateral to blind spot

Fovea centralis

Area of the retina with only cones

Fovea centralis

Visual acuity (sharpest vision) is here

Photoreceptors cells

No - are at the optic disc, or blind

spot

Core sensitivity

Three types of cones

Cone sensitivity

Each cone type is

sensitive to different

wavelengths of

visible light

Lens

Flexible, biconvex crystal-like structure

Lens, suspensory ligament

Held in place by a - attached to the

ciliary body

1. Anterior (aqueous) segment

2. Posterior (vitreous) segment

Lens divides the eye into two chamber

Anterior (aqueous) segment

Anterior to the lens

 Contains aqueous humor, a clear, watery fluid

Posterior (vitreous segment)

Posterior to the lens

 Contains vitreous humor, a gel-like substance

Aqueous humor

Watery fluid found between lens and cornea

Aqueous humor

Similar to blood plasma

Aqueous humor

Helps maintain intraocular pressure

Aqueous humor

Provides nutrients for the lens and cornea

Canal of Schlemm, aqueous humor

Reabsorbed into venous blood through the scleral

venous sinus, or -

Vitreous humor

Gel-like substance posterior to the lens

Vitreous humor

Prevents the eye from collapsing

Vitreous humor

Helps maintain intraocular pressure

Opthtalmoscope

Instrument used to illuminate the interior of the eyeball

and fundus (posterior wall)

Opthtalmoscope

Can detect diabetes, arteriosclerosis, degeneration of

the optic nerve and retina

Light, point, retina

- must be focused to a - on the - for

optimal vision

Light, bent, refracted,

- is -, or -, by the cornea, aqueous

humor, lens, and vitreous humor

20

The eye is set for distant vision (over - feet away)

Accommodation, lens, 20

-the - must change shape to

focus on closer objects (less than - feet away)

Real image

Image formed on the retina is a

Reversed from left to right

Upside down

Smaller than the object

Real images are:

1. Optic nerve

2. Optic chiasma

3. Optic tract

4. Thalamus

5. Optic radiation

6. Optic cortex in occipital lobe of brain

Summary of the pathway

of impulses from the

retina to the point of

visual interpretation

Emmetropia

eye focuses images correctly on

the retina

Myopia

Distant objects appear blurry

Myopia

Light from those objects fails to reach the retina and

are focused in front of it

Myopia

Results from an eyeball that is too long

Hyperopia

Near objects are blurry, whereas distant objects are

clear

Hyperopia

Distant objects are focused behind the retina

Hyperopia

Results from an eyeball that is too short or from a ―lazy

lenns

Astigmatism

Images are blurry

 Results from light focusing as lines, not points, on the

retina because of unequal curvatures of the cornea or

lens

Convergence

reflexive movement of the eyes medially

when we focus on a close object

Photopupilarry reflex

bright light causes pupils to

constrict

Accomodations pupillary reflex

close objects

causes pupils to constrict

Hearing

Equilibrium balance

Ear houses two senses

Mechanoreceptors

Receptors are -

Receptors

Different organs house - for each sense

1. External

2. Middle

3. Inner ear

The ear is divided into three areas

External acoustic meatus (auditory canal)

Narrow chamber in the temporal bone

External acoustic meatus (auditory canal)

Ceruminous glands

Lined with skin and -

External acoustic meatus auditory canal

Tympanc membrane

Ends at the -

External ears

Is involved only in collecting sound waves