Lecture 12: Special Senses

IV. Classification of Special Senses

A. Olfaction (smell)

1. olfactory cells - bipolar neurons in epithelium

2. olfactory glands - secrete mucus to clean epithelium

3. olfactory nerve (I) - axons of olfactory cells

4. olfactory bulbs - brain region where (I) synapses

5. olfactory tract - axons from bulbs to cortex

B. Gustation (taste)

1. gustatory cells - neuron with hairlike extension

2. taste buds - location of gustatory cells

3. facial nerve (VII) - anterior 2/3 of tongue

4. glossopharyngeal nerve (IX) - posterior 1/3

5. vagus nerve (X) - throat and epiglottis

6. -> medulla -> thalamus -> cortex

C. Vision

1. Accessory Structures of the Eye

a. eyebrows

b. eyelids (palpebrae)

i. levator palpebrae superioris muscle

ii. palpebral fissure

iii. lateral commissure

iv. medial commissure

v. lacrimal caruncle (lacrimal gland) crying

c. tarsal plate - inner wall of eyelid

d. tarsal glands - secrete oil

e. conjunctiva - mucous membrane of eyelid

f. eyelashes

g. lacrimal gland - for tear secretion

i. lacrimal ducts

ii. lacrimal puncta

iii. lacrimal sac

iv. nasolacrimal duct

2. The Structure of the Eyeball

a. fibrous tunic - outer coat of the eyeball

i. sclera - posterior portion

ii. cornea - anterior portion

b. vascular tunic (uvea) - middle layer

i. choroid - posterior, pigment/vasculature

ii. ciliary body - muscle shapes lens

iii. iris - colored part, with pupil (hole)

c. nervous tunic (retina) - posterior surface

i. photoreceptors (rods & cones)

ii. bipolar cells

iii. ganglion cells

d. lens - just behind pupil and iris

3. Pathway of Light to the Brain

a. photoreceptors pick up the light

b. ganglion cells converge signals -> optic nerve

c. optic nerve -> lateral geniculate of thalamus

d. lateral geniculate -> occipital cortex

D. Hearing & Equilibrium

1. external ear

a. pinna (auricle) - Ross Perot

b. helix - rim of the pinna

c. lobule - your mate's favorite part

d. external auditory canal

e. ceruminous glands - love that earwax!

f. tympanic membrane (eardrum)

2. middle ear

a. tympanic antrum - chamber to air cells

b. auditory (Eustachian) tube - to nasopharynx

c. auditory ossicles - bones of middle ear

i. malleus - attached to tympanic membrane

ii. incus - intermediate bone

iii. stapes - stirrup

d. tensor tympani muscles - to malleus (protect)

e. stapedius muscle - to stapes (protect)

f. oval and round windows - to inner ear

3. inner ear (labyrinth)

a. bony labyrinth - has fluid called perilymph

i. vestibule

ii. cochlea

iii. semicircular canals

b. membranous labyrinth - has endolymph

c. vestibule - oval central portion body labyr.

i. utricle & saccule - two sacs

d. cochlea - sound organ, sounds are sensed here

e. semicircular canals - equilibrium in 3-D

4. Neural Pathway for Sound/Equilibrium Sensation

a. cochlea/vestibular -> vestibulocochlear (VIII)

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