Question

D. Light Ray You are a ray of light that is getting ready to enter the eye where you will be converted into a nerve impulse and then travel to the brain for interpretation. In the space provided below, describe all of the structures you encounter on your way to the brain. Also describe what function each structure is performing in the eye. Each of the following structures should be included in your discussion: a. Lacrimal apparatus b. Conjunctiva oybed c. Sclera d. Iris and pupil e. Anterior cavity f. Lens and suspensory ligaments g. Ciliary muscle h. Posterior cavity i. Retina j. Macula lutea k. Rods and cones 1. Optic nerve m. Optic chiasma n. Thalamus o. Occipital lobe

Answer 1

D.Pathway of light :-

1. Light bounces off an object and into your eye. It first enters the cornea, where the light is refracted slightly.

2.The light then passes through a clear liquid called the aqueous humor.

3. It travels through the pupil which is surrounded by the colored part of the eye called the iris, which controls the amount of light entering the eye.

4.The light then passed through the lens where it is refracted even more.

5. It travels through the vitreous humor until it reaches the retina.

6. Photoreceptors within the retina (rods and cones) are excited by the light stimuli and generate a nerve impulse.

7. The nerve impulse travels down the optic nerve to the area of the brain which processes sight (the occipital lobe.)

8. The brain processes and interprets the information. It flips the information and superimposes the images from both eyes.

#. Functions of different structures of eye :-

SCLERA

maintains shape of eye; protects internal structures; provides muscle attachment point; continuous with cornea; "white of eye"

CHOROID

thin membrane that provides oxygen and nourishment to outer retina

RETINA

contains light sensitive neurons (rods and cones)

CONJUNCTIVA

thin, transparent mucous membrane; covers inner eyelid and anterior part of eye

CORNEA

with lens and humors, focuses light onto the retina

CILIARY BODY/MUSCLES

contraction of muscles controls shape of lens

SUSPENSORY LIGAMENTS

attach ciliary body to lens

IRIS

contractile structure, controls light entering pupil, regulates amount of light entering the eye

FOVEA CENTRALIS (MACULA LUTEA)

portion of retina that where light is most focused when eye is looking directly at an object; the area of highest visual acuity; contains only cone cells

OPTIC DISC

"blind spot," where optic nerve and central retinal artery and vein enter eye

H. Pathway of sound :-

Pinna (Auricle)--> External auditory meatus--> Tympanic membrane--> Malleous (Hammer)--> Incus (Anvil)--> Stapes (Stirrup)--> Oval Window--> Perilymph--> Vestibular membrane--> Endolymph--> Tectorial membrane--> Hair cells bent--> Neurotransmitters are released--> Impulse crosses basilar membrane--> Cochlear nerve--> Merge w/vestibular nerves--> Auditory nerve--> Medulla oblongata--> Thalamus--> Temporal lobe ----> HEARING

#. Functions of different structures of ear :-

- pinna (auricle)

visible part of the outer ear, collects sound and directs it into the outer ear canal

- outer ear canal

the tube through which sound travels to the eardrum

- eardrum (tympanic membrane)

; a thin membrane that vibrates when sound waves reach it

- hammer (malleus)

a tiny bone that passes vibrations from the eardrum to the anvil

- anvil (incus)

a tiny bone that passes vibrations from the hammer(malleus) to the stirrup (stapes)

- stirrup (stapes)

a tiny U shaped bone that passes vibrations from the stirrup (stapes) to the cochlea . this is the smallest bone in the human body

- cochlea

a spiral shaped fluid filled inner ear structure; it is lined with cilia (tiny hairs) that move when vibrated and cause a nerve impulse to form

- semicircular canals

three loops of fluid filled tubes that are attached to the cochlea in the inner ear. they help us to maintain our sense of balance.

- oval window

small thin membranes situated between the middle ear and the inner ear that receives vibrations from the tympanic membrane via the ossicles

- ear ossicles

made up of three main bones in the middle ear known at the malleus (hammer), incus (anvil) and stapes (stirrup)