1. Where is the location of the olfactory organs?
A. Nasal cavity on either side of the nasal septum.
2. Why is the olfactory epithelium lined with mucus? Why is this important?
A. The mucus dissolves the chemical compounds that are present in the air. The dissolving of
these chemicals into the mucus is important because there are olfactory nerve fibers present in
them. When the nerve fibers get stimulated an action potential will occur, sending information
to the olfactory bulb and then to the brain via the olfactory nerve this allows you to recognize
3. What are the structures that cause the air current in the nasal cavity?
A. Nasal conchae.
4. What structure lies on the ethmoids cribiform plate?
A. Olfactory bulb.
5. What is different about the olfactory synaptic path to the brain relative to all other senses?
A. It is the only sense that does not first synapse at the thalamus. Instead the olfactory action
potentials first synapse at the olfactory bulb. This electrical information (i.e., the information
that the brain understands the language of action potentials) will then travel to the olfactory
cortex, hypothalamus, and the limbic system.
1. Where is the location of the gustatory receptors?
A. On the dorsal surface of the tongue, clustered within individual taste buds.
2. Where is the gustatory cortex?
A. Found superior to the temporal lobe in the mediolateral parietal lobe (there is one on each
3. Do the action potentials, caused by the taste buds, travel to the same side (ipsilarteral) or to the
opposite side (contralateral) of the brain as the side of the taste buds? For instance, if the right side of
the tongue sends action potentials to the brain, will the right or the left brain be stimulated?
A. Contralateral if the right side of the tongue is stimulated, then the left side of the brain will
1 Special Senses
1. What structure(s) make up the outer ear and what is the function?
A. The visible portion of the ear, which collects and directs sound waves to the middle ear.
2. What structure(s) make up the middle ear (be specific) and what is the function?
A. The chamber containing the auditory ossicles (malleus, incus, stapes), which amplify the sound
waves and transmit them to the inner ear.
3. What structure(s) make up the inner ear?
A. The sensory organs for hearing (cochlea) and also for equilibrium (semi-circular canals and
4. What cranial nerve innervates the inner ear? Does this nerve split? If so, what part of the nerve
innervates what part of the inner ear?
A. Vestibulocochlear nerve. This nerve splits into the vestibular branch and the cochlear branch.
The vestibular branch innervates the vestibule and semi-circular canals, while the cochlear
branch innervates the cochlea.
5. Tell me about the path of the sound waves from the external ear and stop at the structure of the inner
ear. Remember: MISO
A. The outer ear will direct sounds from the surrounding environment into the external acoustic
(auditory) canal. Sound waves cause the tympanic membrane (eardrum) to vibrate. This
vibration causes the auditory ossicles - malleus, incus, and stapes - to move, passing these
vibrations on to the cochlea, via the oval window.
6. Tell me about the path of the sound waves, and the structures involved, from the oval window through
A. The oval window is covered with a thin membrane. The vibrations cause this thin membrane to
vibrate, which in turn creates waves in the fluid (perilymph) inside the cochlea (like ripples in
water). The cochlea is a snail shaped, fluid-filled (fluid = perilymph) structure in the inner ear.
These waves will propagate (travel) from the oval window to the round window. From the oval
window to the apex of the cochlea (center of the snail), the sound waves will travel through
the vestibular duct. From the apex of the cochlea to the round window, the sound waves will
travel through the tympanic duct.
7. How do we know what we are hearing? Basically, how do we convert fluid vibrations or waves (which
the brain does not understand) into electrical impulses (which the brain does understand)? Be Specific.
A. Since the brain only speaks in action potentials (i.e., electrical nerve impulses), we need to
convert fluid vibrations into action potentials. Inside the cochlear duct is a structure called the
Organ of Corti. On the basilar membrane of this organ, there are hair cells. The cilia (look like
the hair of the cell) of the hair cells make contact with another membrane called the tectorial
membrane. When the sound waves travel down the perilymph of the vestibular duct they
2 Special Senses
create vibrations in the fluid of the cochlear duct. When the hair cells (in the Organ of Corti)
are excited by the vibrations in the fluid, the nerve (which is attached to the hair cell)
depolarizes, creating an action potential (nerve impulse). These impulses allow for the
conversion of fluid vibrations to electrical nerve impulses) - which is the language that the
brain understands. This nerve impulse will travel down the cochlear branch of the
vestibulocochlear nerve, join up with the vestibulocochlear nerve, and travel to the brain.
8. How can you differentiate between high pitched sounds and low pitched sounds?
A. Low pitched sound waves will peak farthest from the oval window, while high pitched sound
waves will peak closest to the oval window.
9. What is the name of the structure immediately downstream from the tympanic membrane?
10. What is the name of the structure immediately upstream from the round window?
A. Tympanic duct.
11. What is the name of the structure immediately upstream from the auditory tube (which empties the
sound into the nasopharynx)?
A. Round window.
12. What is the name of the structure located in the cochlear duct that moves and depresses hair cell cilia
in response to fluid vibrations?
A. Tectorial membrane.
13. What is the name of the structure/ layer located in the cochlear duct that the hair cells are anchored
A. Basilar membrane.
14. What is the functional unit of the cochlea? Where can it be found?
A. Organ of Corti; found in the cochlear duct (located in between the vestibular and tympanic
1. Equilibrium is part of what kinesthetic sense?
A. Vestibular system.
2. What is the primary function of the vestibular system?
A. Tells us where our body is in space.
3 Special Senses
3. What is the name of the structure of the inner ear that is responsible for equilibrium?
A. Semicircular canals.
4. What is the name of the structure that is at the base of the semicircular canals? HINT: They reside in
5. Where would you find the ampullae?
A. In the swellings at the base of the semicircular canals.
6. What are and where would you find the structures responsible for detecting rotational or turning
movements of the head and body?
A. Ampullae, found in the swellings at the base of the semicircular canals.
7. What is the function of the ampullae? HINT: They are your Magic Bullets.
A. They detect rotational or turning movements of the head and body.
8. Where would the hair cell that has kinocilia be located?
9. What is the name of the structure of the inner ear that has kinocilia?
10. What is the function of the structure of the inner ear that has the kinocilia?
A. Detects rotational or turning movements of the head and body.
11. Why do we have three semicircular canals?
A. One for each dimension of movement that we can move in.
12. What is the function of the semicircular canals?
A. There are three semicircular canals, one for each plane of movement (since we move in 3-
dimensions). Depending on the plane of movement, the fluid (endolymph) within the
semicircular canals stimulates the appropriate movement hair cells in the ampullae (singular:
ampulla). The semicircular canals are especially good at maintaining balance and sending fluid
wave information to the ampullae which detect turning (rotational) movements.
13. What is the name of the structure in the inner ear that maintains balance and aids in the detection of
A. Semicircular canals.
14. What is the name of the structures that detect movement of the head up/down (i.e., gravitational
effects) and linear acceleration of the body?