The Special Senses

The Special Senses

the special senses are either complex sensory organs or localized sensory receptors

Unlike general receptors (cold, heat, pain, muscle and tendon stretching) which are widely distributed,

Sight, hearing, equilibrium, smell and taste: eyes, ears, taste buds,

olfactory epithelium.

VisionA. General

characteristics1. 70% of all

sensory receptors in body are in the eye.

2. Requires the most learning.

3. Easily fooled sense (optical illusions)

What we see is conditioned by what we expect to see and the context in which we find it. Which of these is hardest to believe.

• We all argued over this one last week, but the truth of the matter is that you can’t tell whether the silhouette is facing forward or backward.

Who is sitting

comfortably?

What do you see here?

Which center dot is bigger?

Motion?

Color?

Only one guy

We understand shadows

How do these tables compare?

What do you think of these faces?

What do you think now?

Watch the rotating mask.

B. Anatomy

1. Eye is a one-inch sphere. 1/6 is visible.

2. Moved by extrinsic eye muscles.

3. Protections of the eye.

a. Eyebrows

b. Eyelids

c. Eyelashes

3. Protections of the eye continuedd. Meibomian glands. Produce an oily lubricant. When infected cause a cyst.e. Conjunctiva

i. Mucus membrane ii. Lines inner surface of eyelids and covers outer surface of eye iii. Lubricates eyeball.

f. Lacrimal apparatusi. Produces tears

ii. Washes eye. iii. Has antibodies and antibacterial agents iv. Drains tears into nasal passages

Lacrimal apparatus

Which shows the correct order of the flow of tears?

A. Lacrimal gland--Lacrimal canal--lacrimal ducts--nasolacrimal duct--nasal cavity

B. Lacrimal gland--lacrimal duct--lacrimal canals--nasolacrimal duct--nasal cavity

C. Lacrimal duct--lacrimal gland--lacrimal canals--nasolacrimal duct--nasal cavity

Which protection of the eye is formed of a mucus membrane and lubricates

eyeball?A. Conjunctiva

B. Meibomian glands

C. Lacrimal glands

D. Eyelids

Which protection of the eye produces tears?

A. Conjunctiva

B. Meibomian glands

C. Lacrimal glands

D. Eyelids

Which protection of the eye is behind the eyelid and produces an oily

lubricant?A. Conjunctiva

B. Meibomian glands

C. Lacrimal glands

D. Eyelids

Which protection of the eyes includes antibodies and antibacterial agents?

A. Conjunctiva

B. Meibomian glands

C. Lacrimal glands

D. Eyelids

Which extrinsic eye muscles allow you to look to the corner of the room

without moving your head?A. Superior and inferior oblique muscles

B. Superior and inferior rectus mucsles

C. Lateral rectus muscles

Which extrinsic eye muscles allow you to look horizontally to the left or

right?A. Superior and inferior oblique muscles

B. Superior and inferior rectus mucsles

C. Lateral rectus muscles

4. Internal structures of the eye

a. Eye is a hollow sphere surrounded by three layers called tunics.

Tunics of the eyei. Sclera is composed of

a dense white fibrous connective tissue. It’s the white of the eye. Anterior portion of sclera is modified to from transparent cornea, where light enters the eye.

Tunics of the eye

ii. Choroid is a vascular, nutritive layer.• Dark pigment in choroid prevents light from

scattering inside the eye.• Anterior portion is continuous with two structures.• Ciliary body-smooth muscle that controls lens shape.• Iris, made of pigmented smooth muscle. It controls the

size of the central opening of eye (pupil) by dilation and constriction.

Smooth muscle of the iris

Tunics of the eye

iii. Retina is the sensory layer, the innermost layer. It contains the photo- receptors called rods and cones that convert light energy into nerve impulses.

Retina• Rods allow us to see grey

tones.– More sensitive to light than

are cones– Provide peripheral vision– Are excited in dim light

• Cones see color– Need bright light to be

excited– Three types respond either

to red, green or blue light.

Path of light

cone

rod

neurons

Retina: rods, cones, neurons

Retina

• Fovea centralis is a tiny pit in the retina that contains only cones. It lies in the back of the retina in line with the pupil. It is the area of sharpest vision. Anything we want to view critically is viewed on the fovea centralis.

• Blind spot is the optic disk where optic nerve leaves the eye. No rods or cones there.

Fovea and optic disc

Internal chambers and fluidsTwo main chambers divided by

the lensa) Posterior segment is large

chamber behind lens filled with clear gel called vitreous humor. (Vitreous chamber).1) Transmits light

2) Supports back of lens and holds layers of retina in place.

Internal chambers and fluids

b) Anterior segment is smaller chamber between lens and cornea filled with aqueous humor. (Aqueous chamber)

1) Nourishes lens and cornea

2) Secreted by choroid

b) Lens1) Focuses incoming light on retina

2) Held in place by suspensory ligaments attached to ciliary body.

The path of light through the eye

Go to Internal Structures Activity

Go to internal structures of the mammalian eye video.

Visual tracts

Visual Pathways

Eyesight

• Myopia

• Hyperopia

• Astigmatism

• Presbyopia

Myopia: nearsightedness

Hyperopia: farsightedness

Astigmatism

Presbyopia (elder eyes): can’t see close-up

• Video clip on focusing Scroll down to link to video.

• Add CPS questions

When the ciliary muscle is relaxed, the choroid acts like a spring pulling on the lens via the zonule fibers causing the

lens to become flat. When the ciliary muscle contracts, it stretches the choroid,

releasing the tension on the lens and the lens becomes thicker.

The aqueous humor appears

A. Liquid

B. Gel-like

C. Creamy

D. Tough and fibrous

The vitreous humor is

A. Liquid

B. Gel-like

C. Creamy

D. Tough and fibrous

The technical name for the blind spot is

A. Optic chiasma

B. Optic disk

C. Optic nerve

D. Optic plate

Which sequence best describes the route light takes as it enters the eye?

A. vitreous humor, lens, aqueous humor, cornea

B. cornea, aqueous humor, lens, vitreous humor

C. cornea, vitreous humor, lens, aqueous humor

D. lens, aqueous humor, cornea, vitreous humor

Which of the following lists the tunics of the eyeball in the correct order from

outermost to innermost layer?

A. Choroid, sclera, retina

B. Sclera, retina, choroid

C. Retina, choroid, sclera

D. Sclera, choroid, retina

Blockage of the canal of Schlemm might result in…

A. Sty

B. Conjunctivitis

C. Glaucoma

D. Cataract

Which sequence of reactions occurs when a person is reading?

A. pupils constrict, eyes converge, lenses become more convex

B. pupils dilate, eyes converge, lenses becomes more convex

C. pupils dilate, eyes remain fixed, lenses become less convex

D. pupils constrict, eyes remain fixed, lenses become more convex

A function of the rods is

A. depth perception

B. color vision

C. vision in dim light

D. refraction

E. accommodation for near vision

The fovea centralis is

A. also known as the blind spot

B. an area that contains a high concentration of rods

C. a vascular tunic

D. an area that contains a high concentration of cones

Presbyopia is usually due to

A. loss of elasticity of the lens

B. unequal curvature of refracting surfaces

C. an eyeball that is too long

D. a flattened cornea

Hearing and

Equilibrium

A. Anatomy of ear

1. External eara. Auricle (pinna)-shell-shaped outer structure

collects and directs sound waves. The pinna is very important in many animals.

b. External auditory canal is about 1” long and 1/4” wide.

c. Tympanic membrane (eardrum) is at the end of the auditory canal. 1) Separates outer ear from middle ear2) Sound waves cause membrane to vibrate and pass

vibrations to middle ear.

Tympanic Membrane

2. Middle ear (tympanic cavity) is a small air-filled cavity within the temporal bone.

a. Contains three small bones called ossicles.

1) Hammer: malleus

2) Anvil: incus

3) Stirrup: stapes

2. Middle ear continued

b. Vibrations from eardrum pass on to and through ossicles. The last ossicle connects to the oval window, which then passes the vibration on to the fluids in the inner ear.

Path of sound

2. Middle ear continued

• c. Eustachian tube connects middle ear to throat. Is usually flattened, but will open to equalize pressure in cavity with that of atmosphere.

Why do children get more ear infections?

3. Inner ear is called a bony labyrinth: a maze of chambers and canals filled with fluid.

a. Cochlea involved in hearing

b. Vestibule involved in static balance

c. Semicircular canals involved in dynamic balance.

Inner ear

What forms the boundary between the outer and middle

ear?A. Tympanic membrane

B. Pinna

C. Auricle

D. External auditory canal

Which allows for pressure equilazation in the middle ear?

A. Tympanic membrane

B. Eustachian tube

C. External auditory canal

D. Ossicles

Which ossicle touches the tympanic membrane?

A. Stirrup

B. Anvil

C. Hammer

Which lists the ossicles in the order they transmit the motion of

sound waves?A. Stirrup, hammer, anvil

B. Hammer, anvil, stirrup

C. Anvil, stirrup, hammer

Which answer correctly matches the English names with the Latin

terms?A. Hammer, malleus; Stirrup, stapes;

Anvil, incus

B. Hammer, stapes; Stirrup, malleus; Anvil, incus

B. Mechanism of Hearing

• 1. Stirrup vibrates oval windowcauses cochlear fluids to start moving stimulates organ of corti in the central canal of cochlea (the cochlear duct.)

2. Organ of corti has three parts involved in translating nerve impulsesa. upper membrane called tectoral membrane is moved by fluidsb. tectoral membrane bends and pulls “hairs”c. Hairs connect to receptor cells in basilar membrane

3. Nerve impulses travel from cochlea to brain: basilar membranecochlear nervemedulla oblongatamidbrain auditory cortex of temporal lobe.

Hyperlink to hearing animation

http://www.lakemichigancollege.edu/

dept/Arts-Sciences/bio/anat/sense.html

C. Equilibrium1. Semicircular canals contain dynamic

equilibrium receptors. a. Three loops arranged in semicircular planes

respond to changes in angular motion.

b. Moving fluid in these canals disturbs the crista ampullaris at the entrance of each canal. They send information to the cerebellum via the vestibulocochlear nerve (VIII)

c. Detects primarily rotational motion.

C. Equilibrium continued

2. Vestibule (between cochlea and semi-circular canals) contains static equilibrium receptors called maculae.a. Receptors report on the position of the head with respect to gravity. Also respond to linear acceleration. There are two, one vertical and one horizontal.

b. Messages are sent to cerebellum via the vestibulocochlear nerve (VIII).

The two maculae, the utricle and saccule, are oriented in the horizontal and vertical planes and tell us how we are aligned relative to gravity.

C. Equilibrium continued

3. Information from these apparati are integrated with sight and information from proprioceptors to control balance.

Equilibrium

• Semi-circular canals• Crista ampullaris• Rotational motion

• Vestibule• Maculae (saccule

and otricle)• Static equilibrium

The bone(s) that encase(s) the middle ear is/are

A. Ossicles

B. Parietal

C. Occipital

D. Temporal

This tube connects the middle ear to the throat….

A. Eustachian Tube

B. Esophagus Tube

C. Trachea Tube

D. Sinuses

Patients with equilibrium problems primarily complain of:

A. Loss of hearing

B. Dizziness

C. Loss of vision

D. Fatigue

Inflammation of the middle ear, commonly seen in children, is

called…

A. Otosclerosis

B. Anosmia

C. Otitis Media

D. Presbycusis

Your friend convinces you to ride a carnival ride that spins around. When you get off the ride, it feels as though your head is still spinning. What could be causing this experience?

A. Overstimulation of the maculae of the vestibule

B. Puncture of the tympanic membrane

C. Overstimulation of the crista ampullaris in the semicircular canals

D. Overproduction of cerumen by the ceruminous glands

III. Smell (Olfaction)A. Olfactory Receptors are

receptors for smell. Located in olfactory epithelium, a 5 cm square at the top of the nose.

1. Neurons equipped with olfactory hairs that extend into mucus which covers olfactory epithelium.

2. These receptors are stimulated by chemicals that are volatile and water soluble.

A. Olfactory receptors continued

3. Receptors transmit impulses to the olfactory nerve.

4. Olfactory nerve sends info via two pathways:a. Olfactory nervethalamusolfactory areas of temporal lobe cortex and frontal lobe just below orbitsconscious interpretation and identification.b. Olfactory nervehypothalamus amygdala and other parts of the limbic systememotional response to smells

B. Adaptation--olfactory nerves adapt to an unchanging smell, which is why you don’t smell your perfume all day.

C. Anosmias--olfactory disorder caused by a head injury, nasal cavity inflammation, or age.

IV. Taste (Gustatory sense)

A. Taste Buds1. Specific

receptors for the sense of taste

2. 10,000 taste buds, mostly located on tongue

IV. Taste (continued)

B. Dorsal tongue surface

1. Covered with papillae, which contain taste buds

2. Gustatory cells are epithelial cells that respond to chemicals dissolved in saliva

3. Cranial nerves carry taste impulses from the various taste buds to the gustatory complex: Facial nerve (VII) glassopharyngeal nerve (IX) vagus nerve (X) Medulla oblongata thalamus gustatory cortex in parietal lobes.

Taste Buds

IV. Taste continued

C. Four basic taste sensations

1. Sweet receptors—sugar, saccharine, alcohols, amino acids, Pb salts

2. Sour receptors—acids

3. Bitter receptors—alkaloids, nicotine, caffeine, morphine, aspirin

4. Salty receptors—metal ions—Na+ & Mg++

What do you think?