Lecture 16: Senses- The eye

What does it mean when the brain becomes aware of a sensory impulse?

sensation

What does it mean when the brain interprets the sensory impulse?

perception

T/F sensory info enters the brain in the same way

true

sensory info results depend on what?

which area of the brain receives info

What is the brains ability to ignore unimportant stimuli known as?

sensory adaptation

What does sensory adaptation result from?

receptors becoming unresponsive or inhibition of nerve impulse

What are the types of sensory receptors?

1. chemoreceptors

2. pain receptors

3. thermoreceptors

4. mechanoreceptors

5. photoreceptors

What type of receptors is stimulated by chemical concentration (smell, taste)?

chemoreceptors

What type of receptors is stimulated by tissue damage (all senses)?

pain receptors

What type of receptors is stimulated by temperature change (skin)?

thermoreceptors

What type of receptors is stimulated by pressure or movement (skin, ears)?

mechanoreceptors

What type of receptors is stimulated by light energy (eye)?

photoreceptors

What are the two basic types of sensory categories?

1. somatic senses

2. special senses

Receptors of skin, muscles, joints and visceral organs (sense of touch, temp, pressure) fall under what?

somatic senses

What falls under special senses?

nose, tongue, ear, eye

What are the visual accessory organs?

eyelids, lacrimal apparatus, and extrinsic eye muscles

What are eyelids moved by?

orbicularis oculi

What is a thin, translucent membrane that covers the sclera (white), cornea and lines the under surface? Where is it located?

• conjuctiva

• eyelids

Lacrimal apparatus contains what?

• lacrimal duct

• lacrimal gland

What secretes tears… moistens, lubricates, and contains antibacterial agent?

lacrimal glands

What connects to nose to drain tears?

lacrimal duct

What is the function of extrinsic eye muscles?

move eyeball

The wall of the eye has ______ tunics (layers)

three

What is part of the fibrous (outer) tunic of the eye?

• cornea

• sclera

• optic nerve

What structure is a transparent dome; helps to focus entering light rays?

cornea

What structure is known as the whites of the eye; continuous with the cornea; muscle attachment?

sclera

What structure transmits electrical impulses from the retina to the brain?

optic nerve

What is part of the vascular (middle) tunic?

• iris

• pupil

• lens

• choroid coat

• ciliary body

• aqueous humor

What structure is a diaphragm regulating amount of light entering the pupil; associated with eye color?

iris

What structure is a circular opening in the center of the iris where light enters; black?

pupil

What structure is located behind the iris/pupil; it focuses light onto the retina?

lens

What is the term for when the lens changes shape to adjust for close or distance vision?

accommodation

What connects lens to ciliary muscles (smooth)… contraction/relax causes accomodation?

suspensory ligaments

What is it called when the cornea and lens bend light waves to focus an image on the retina?

light refraction

What two structures of the eye cause light refraction?

cornea and lens

What is the accommodation mechanism for distance (far)?

thin lens; ciliary muscles relax

What is the accommodation mechanism for close (short distance)?

thick lens; ciliary muscles contract

Figure A is a demonstration of what?

normal refraction and accommodation

Why does hyperopia and myopia occur?

due to shape of eye or cornea

Why does presbyopia occur?

due to age

Figure B is a demonstration of what?

hyperopia

Figure C is a demonstration of what?

myopia

What is hyperopia?

can’t see near (farsighted)

What is myopia?

Can’t see far (nearsighted)

What is the general effect of presbyopia?

reading glasses

What structure lines internal surface of sclera?

choroid coat

vascular

nourished retina

choroid coat has a dark pigment that

absorbs excess light

What structure produces aqueous humor fluid; houses certain muscles?

ciliary body

What structures are part of the nervous (inner) tunic?

• retina

• fovea centralis

• optic disc

• vitreous humor

What structure is a multi-layered sensory tissue that lines the back of the eye and captures light rays?

Retina

Photoreceptors are?

rods and cones

What provides colorless vision and vision in dim light; more sensitive to light?

rods

What provides color vision; sharper image?

cones

What is the color blindness test?

Ishihara test

What is the region of the retina that produces the sharpest vision; densely packed with cones?

fovea centralis

What is the area on the retina where the optic nerve attaches; absence of photoreceptors causing a blind spot?

optic disc

Where is the anterior segment located?

between cornea and lens

What is a watery, fluid that gives shape, nourishes the lens and cornea; maintains intraocular pressure?

aqueous humor

The anterior segment contains what kind of humor?

aqueous humor

Where is the posterior cavity?

between lens and retina

What is a jelly like fluid; holds retina in place; maintain intraocular pressure?

vitreous humor

What kind of humor does the posterior cavity have?

vitreous humor

In order, list the structures in which light passes through the eye.

cornea → aqueous humor → pupil/iris → lens → vitreous humor → retina → optic disc → optic nerve → brain

What are the layers (tunics) of the eye?

1. fibrous (outer) tunic

2. vascular (middle) tunic

3. nervous (inner) tunic