Chapter 9 The Senses

Question 1

Eyelashes & eyelids

Answer 1

Keep dust out of eye; lids sweep tears across the anterior surface of the eyeball

Question 2

Lacrimal glands

Answer 2

Produce tears at the upper outer corner of eyeball; tears wash eye and contain lysozyme to inhibit growth of bacteria

Question 3

Extrinsic muscles

Answer 3

6 voluntary muscles; 4 rectus and 2 oblique; move eyeball up, down, side to side; nerves are the 3rd, 4th, 6th cranial nerves

Question 4

Sclera

Answer 4

Outer layer of eyeball; white of eye, made of thick fibrous connective tissue; the most anterior portion is transparent cornea

Question 5

Cornea

Answer 5

Transparent front of sclera in front of iris; first structure to refract light rays

Question 6

Conjunctiva

Answer 6

Mucous membrane that lines eyelids & covers white of eye

Question 7

Choroid layer

Answer 7

Middle layer of eyeball; has dark blue pigment to absorb light & prevent glare inside eyeball

Question 8

Iris

Answer 8

Anterior portion of choroid; disc with an opening in center, the pupil; 2 sets of smooth muscle fibers change diameter of pupil to regulate how much light strikes retina

Question 9

Ciliary body (muscle)

Answer 9

Anterior portion of choroid; circular smooth muscle that with its suspensory ligaments changes shape of lens for focusing at different distances

Question 10

Lens

Answer 10

Transparent & elastic protein disc behind iris; refracts light rays & is adjustable for different distances

Question 11

Aqueous humor

Answer 11

Tissue fluid of anterior cavity of the eye; made by capillaries in the ciliary body; nourishes lens & cornea, which have no capillaries

Question 12

Canal of Schlemm

Answer 12

Small veins at edge of iris; site of reabsorption of aqueous humor back to blood

Question 13

Vitreous humor

Answer 13

Semisolid gel that fills the posterior cavity of the eye; between back of lens & the retina; keeps retina in place

Question 14

Retina & optic disc

Answer 14

Inner layer of eyeball, made of several layers of neurons, including photoreceptor rods and cones; optic disc is site of passage of optic nerve through eyeball and has no rods or cones

Question 15

Rods

Answer 15

Photoreceptors that detect presence of light; most numerous toward the periphery of retina

Question 16

Cones

Answer 16

Photoreceptors that detect wavelengths of colors; red: absorbing, blue: absorbing, green: absorbing; most numerous toward center of retina

Question 17

Macula lutea, fovea centralis

Answer 17

Area of retina directly behind center of lens on visual axis; fovea contains only cones & is the area for best color vision as long as ambient light is not too dim

Question 18

Ganglion neurons

Answer 18

Receive impulses generated by the rods and cones; their axons form the optic nerve

Question 19

Optic nerves

Answer 19

2nd cranial nerves, each extends posteriorly from retina to the optic chiasma

Question 20

Optic chiasma

Answer 20

Crossing of medial fibers of 2 optic nerves just in front of pituitary gland; this crossing is important for binocular vision

Question 21

Optic tracts

Answer 21

Continuation of optic nerves with branches to midbrain & thalamus, and then to occipital lobes

Question 22

Visual areas

Answer 22

Areas in occipital lobes where impulses from retina are “seen” and interpreted

Question 23

Auricle or pinna

Answer 23

External ear, made of cartilage covered with skin

Question 24

External auditory meatus

Answer 24

Ear canal, tunnel into temporal bone that ends at eardrum

Question 25

Tympanic membrane

Answer 25

Eardrum, first structure to vibrate when sounds waves enter ear canal

Question 26

Malleus, incus, & stapes

Answer 26

Bones of middle ear cavity (filled with air), which transmit vibrations from eardrum to oval window and cochlea of inner ear

Question 27

Eustachian tube

Answer 27

Extends from middle ear cavity to the nasopharynx, permits air to enter or leave to equalize pressure and allow eardrum to vibrate properly

Question 28

Bony & membranous labyrinths

Answer 28

Inner ear cavities in temporal bone, filled with fluid; vestibule contains utricle and saccule; adjacent are the 3 semicircular canals

Question 29

Cochlea

Answer 29

Shaped like a snail shell, receives vibrations from the stapes at the oval window; vibrations continue to round window, which bulges to equalize pressure; contains spiral organ of Corti

Question 30

Organ of Corti

Answer 30

Contains hair cells that bend with vibrations (from sound waves) in the fluid of the cochlea and generate impulses to the 8th cranial nerve

Question 31

Utricle & Saccule

Answer 31

Membranous sacs that contain otoliths (CaCO3 crystals) that are pulled by gravity and bend hair cells when the head tilts; impulses from hair cells are carried by the 8th cranial nerve

Question 32

Semicircular canals

Answer 32

3 membranous loops, each containing a tuft of hair cells (crista) that are bent by movement of the head or body as a whole; impulses from hair cells are carried by the 8th cranial nerve

Question 33

8th cranial nerve (auditory or vestibulocochlear)

Answer 33

Transmits impulses from all of inner ear receptors to the brain: temporal lobes for hearing; cerebellum, midbrain and cerebrum for equilibrium