_ch_08_special-senses

Special senses

Smell, taste, sight, hearing, equilibrium

Special sense receptors

Large, complex sensory organs that gather unique sensory information

Large complex sensory organs

general receptors for eyes and ears

Localized cluster of receptors

taste buds and olfactory epithelium general receptors

Motor output

The response or action generated by the nervous system based on sensory input

Cerebrum

The specialized area of the brain where each type of sensory information is processed

Eye

Organ responsible for vision

Vision

The ability to see

Eyelids

Structures that protect the eyes and can be opened or closed

Eyelids

Meet at the medial and lateral commissure (canthus)

1 inch in diameter

Adult eye measures about

1/6

Only ____ of the eye’s surface is seen

Eyelashes

Tarsal glands produce oily secretion that lubricates the eye

Eyelashes

where ciliary glands are located between

Palpebral fissure

space between eyelids in an open eye

Tarsal glands

modified sebaceous glands associated with eyelids

Ciliary glands

modified sweat glands that lie between the eyelashes and their ducts open at the eyelash follicle

Conjunctivitis

inflammation of cornea

Pinkeye

infectious form caused by bacteria or viruses which is highly contagious

Conjunctiva

Membrane that lines the eyelids and eyeball

Conjunctiva

Connects with the transparent cornea

Conjunctiva

Secretes mucus to lubricate the eye and keep it moist

Lacrimal apparatus

The lacrimal gland and ducts that produce tears

Lacrimal gland

produces lacrimal fluid (tears); situated on lateral end of each eye

Tears

Fluid secreted by the lacrimal gland that cleanses, protects, moistens, and lubricates the eye

Extrinsic eye muscles

6 Muscles attached to the outer surface of the eye that produce gross eye movements

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

what are the six muscles of extrinsic eye muscle

Lateral rectus

Moves eye laterally

Medial rectus

moves eye medially

Superior rectus

elevates eye and turns it medially

Inferior rectus

depresses eye and turns it medially

inferior oblique

elevates eye and turns it laterally

superior oblique

depresses eye and turns it laterally

VI (abducens)

what controlling cranial nerve is in lateral rectus

III (oculomotor)

what controlling cranial nerve is in medial rectus

III (oculomotor)

what controlling cranial nerve is in superior rectus

III (oculomotor)

what controlling cranial nerve is in inferior rectus

III (oculomotor)

what controlling cranial nerve is in inferior oblique

IV (trochlear)

what controlling cranial nerve is in superior oblique

Dilute salt solution, Mucus, Antibodies, Lysozyme

Tears contains what

Lysozyme

enzyme that destroys bacteria

Eyeball

The structure of the eye consisting of three layers:fibrous layer, vascular layer, and sensory layer

Sclera

white of the eye

Sclera

White connective tissue layer of the eye

Cornea

Transparent, central anterior portion of the eye that allows light to pass through

Cornea

repairs itself and the only human tissue that can be transplanted without fear of rejection

Fibrous (outside), vascular (middle), sensory (inside)

tunics that forms the wall of the Internal Structures: The eyeball

Humors

fluids that fill the interior of the eyeball

the circular muscles contract and the pupil constrict

In close vision and bright light

the radial fibers contract to dilate the pupil

In distant vision and dim light

Lens

divides the eye into two chambers

Fibrous layer

sclera + cornea

Vascular layer

The middle layer of the eyeball, consisting of the choroid, ciliary body, and iris

Choroid

Blood-rich nutritive layer of the eye containing a pigment that prevents light from scattering

Ciliary body

Smooth muscle structure in the anterior part of the choroid that helps regulate the shape of the lens

Iris

Pigmented layer of the eye that regulates the amount of light entering and gives the eye its color

Pupil

Rounded opening in the iris through which light enters the eye

Sensory layer

The inner layer of the eyeball, consisting of the retina

Retina

Two-layered structure in the sensory layer of the eye that contains photoreceptor cells (rods and cones)

Outer pigmented layer and inner neural layer

2 layers of retina

lens

divides the eye into two chamber

Outer pigmented layer

absorbs light and prevents it from scattering

Outer pigmented layer

acts as phagocytes to remove dead cells

Outer pigmented layer

stores Vitamin A

Inner neural layer

contains receptor cells called photoreceptors

Inner neural layer

layer containing rods and cones

Rods

Photoreceptor cells in the retina responsible for vision in dim light and peripheral vision

Cones

Photoreceptor cells in the retina responsible for color vision and visual acuity

Bipolar neurons and ganglion cells

Electrical signals pass from photoreceptors via a two-neuron chain

optic nerve

Signals leave the retina toward the brain through the

Optic nerve

Nerve that carries electrical signals from the retina to the brain for visual processing

Optic disc (blind spot)

The area where the optic nerve leaves the eyeball, resulting in no photoreceptors and the inability to see images focused on the optic disc.

disappears from view and we cannot see it

When a light from the object is focused on the optic disc, the object ______

Rods

They perceive all images in gray tones and are responsible for night vision.

Rods

Most are found toward the edges of the retina

Night Blindness

prolonged Vit A deficiency

Vit A

one of the building blocks of the pigments the photoreceptor cells need to respond to light

Vit A supplements

will restore function if taken before degenerative changes in the neural retina occur

Cones

Photoreceptor cells that allow for detailed color vision and are most densely concentrated in the center of the retina.

Cones

discriminatory receptors that allow us to see the details of our world in color under bright light conditions

Fovea centralis

The area of the retina located lateral to the blind spot, consisting of only cones and providing the sharpest vision.

Fovea centralis

sharpest vision

Cone sensitivity

Each cone type is sensitive to different wavelengths of visible light

blue cones (420 nm),green (530 nm), red (560)

three types of cone

Lens

Flexible, biconvex crystal-like Structure

suspensory ligament (ciliary zonule)

Lens is held in place by ____ attached to ciliary body

Anterior (aqueous segment) and posterior (vitreous segment)

2 chambers in lens

Anterior (aqueous segment)

Anterior to the lens and contains aqueous humor

Aqueous humor

A clear, watery fluid found between the lens and cornea

Aqueous humor

similar to blood plasma and helps maintain intraocular pressure

Aqueous humor

provides nutrients for the lens and cornea

Canal of Schelmm or Scleral venous sinus

Aqueous humor is reabsorbed into venous blood through the

Posterior (vitreous) segment

Posterior to the lens and contains vitreous humor

Vitreous humor

A gel-like substance found in the posterior segment of the eye, behind the lens

vitreous humor

prevents the eye from collapsing and helps maintain intraocular pressure.

Lens

responsible for focusing light onto the retina.

Glaucoma

vision going gray because of increased intraocular pressure due to blockage of aqueous humor. common blindness in elderly and symptoms include halos, headaches, blurred vision

Tonometer

measures the intraocular pressure

eyedrops

treated with ______ that increase the rate of aqueous humor drainage

Ophthalmoscope

An instrument used to illuminate the interior of the eyeball and the posterior wall (fundus) of the retina