Unit 2: Olfactory System

Question 1

The sense of olfaction is also called the ______ sense

Answer 1

osmatic

Question 2

Components of the Olfactory System:

Answer 2

1. olfactory mucosa
2. olfactory nerves
3. olfactory bulbs
4. olfactory tracts
5. olfactory cortex

Question 3

Humans are considered _______ because our sense of smell is less important than sensations of vision or audition.

Answer 3

Microsmatic

Question 4

Where is olfactory mucosa located?

Answer 4

located in superior aspect of each nasal fossa (sphenoethmoid recess) and extends onto the median nasal septum and lateral wall

Question 5

What epithelial type is found in the olfactory mucosa?

Answer 5

Pseudostratified columnar epithelium

Question 6

What kind of glands are found beneath epithelium and secrete fluid onto surface of mucosa to dissolve odorant
chemicals?

Answer 6

olfactory glands = Bowman’s glands

Question 7

What are olfactory cells?

Answer 7

bipolar neurons that are modified to serve as olfactory receptor cells and conduct impulses

Question 8

Olfactory cells have a limited functional life. What is this called and how long is it?

Answer 8

Olfactory cell turnover every 3 months or so

Question 9

Describe the axons of olfactory cells?

Answer 9

axons are unmyelinated and form filaments of CN I

Question 10

Specialized “dendrites” from olfactory cells on the mucosal surface and includes _______ receptors

Answer 10

odorant

Question 11

bundles of axons (filaments of CN I) enter the cranial cavity through the ________ of the ethmoid bone

Answer 11

• foramina of the cribriform plate

Question 12

What are glomeruli?

Answer 12

clusters of synaptic endings where axons (filaments of CN I) entering the olfactory bulb terminate

Question 13

The end portion of an extension of the brain that is along the ventral
surface of the frontal lobe and associated with the olfactory system.

Answer 13

olfactory bulbs

Question 14

What helps increase olfactory sensitivity?

Answer 14

Convergence where one mitral cell communicates with several olfactory cells

Question 15

Dendrites of ________ arborize within the glomeruli with olfactory cell axons

Answer 15

principal neuron = mitral cell

Question 16

Another type of neuron found within the olfactory bulbs? The axons of these cells travel through the olfactory tracts.

Answer 16

tufted cells

Question 17

What comprises most of the fibers of the olfactory tract and project centrally in the brain?

Answer 17

mitral cell axons

Question 18

association neurons of the olfactory bulb include:

Answer 18

periglomerular cells, granule cells and others

Question 19

association neurons of the olfactory bulb serve to:

Answer 19

modify olfactory information before reaching the cerebral olfactory areas

Question 20

most fibers of the olfactory tract are from ______, some from ________.

Answer 20

mitral cells, tufted cells

Question 21

Fibers of the olfactory tract lead to the ________ at base of brain, which splits into a lateral and medial.

Answer 21

• olfactory trigone

- olfactory stria

Question 22

Which stria of the olfactory tract do most of the fibers traverse?

Answer 22

lateral olfactory stria

Question 23

Where do the fibers of that traverse the lateral olfactory stria travel to?

Answer 23

lateral olfactory area of the cerebrum

Question 24

Some fibers of the olfactory tract make up an intermediate olfactory stria and terminate where?

Answer 24

in the anterior perforated substance

Question 25

although often observed as a ridge of tissue, what does not include olfactory tract fibers to the septal area as originally thought?

Answer 25

the “medial olfactory stria”

Question 26

What cerebral olfactory area receives input from the olfactory bulbs through fibers of the lateral olfactory stria?

Answer 26

Lateral Olfactory Area

Question 27

Areas of the Lateral Olfactory Area includes:

Answer 27

(1) uncus (anterior part of the parahippocampal gyrus) (2) limen insula (cortex of the ventral part of insula) (3) part of the amygdala

Question 28

The areas of the lateral olfactory area comprise the ____________, which is largely in the temporal bone.

Answer 28

Primary Olfactory Area

Question 29

What is the Primary Olfactory Area responsible for?

Answer 29

responsible for subjective appreciation (awareness) | of an olfactory stimulus

Question 30

Where is the olfactory association area located?

Answer 30

cortical areas adjacent to the primary olfactory cortex: • lateral portion of the orbital surface of the frontal lobe Note: permits the identification of the qualities of odors and also the significance

Question 31

The hippocampus and amygdala are part of the limbic system. What areas of the olfactory system are also part of it?

Answer 31

Lateral olfactory areas

Question 32

How do the circuits of the limbic system allow odor to affect us?

Answer 32

odors to influence | memories, emotions, and visceral responses

Question 33

What receives olfactory input from intermediate olfactory stria?

Answer 33

Anterior Perforated Substance

Question 34

Where is the Anterior Perforated Substance | postitioned?

Answer 34

between the lateral and ‘medial’ olfactory stria

Question 35

What area forms the intermediate olfactory area: plays no role in conscious olfaction

Answer 35

Anterior perforated substance

Question 36

Neurons in the Anterior Perforated Substance play no role in conscious olfaction but instead mostly connect to structures in which system? It therefore appears to be involved in odors influencing what?

Answer 36

- Important structures of the limbic system | - memories, emotions, and visceral function

Question 37

connections to the septal area and the hypothalamus permit olfactory sensations to influence _________.

Answer 37

autonomic activity (GI motility, salivation, or vomiting)

Question 38

structures and pathways of the lateral and intermediate olfactory areas, directly and indirectly, connect to what 3 areas?

Answer 38

- cerebral cortex - limbic structures - reticular system.

Question 39

protocols to test olfactory sensations should consider the following:

Answer 39

a. each nostril should be tested separately b. the substance should have an odor recognizable to the subject c. substance should be volatile (aromatic): so that it can reach olfactory mucosa d. substance must be non-irritative so you are not inadvertently testing nociception

Question 40

Why do individuals who lose sensibility of smell often complain that food “doesn’t taste right” or “tastes bland”?

Answer 40

it is difficult to distinguish between qualities of smell and of taste

Question 41

What is anosmia?

Answer 41

loss of smell

Question 42

What are some destructive lesions that cause interruption of the pathway?

Answer 42

a. fractures of the ethmoid bone: leading to damage of CN I | b. meningioma in the floor of the anterior cranial fossa: which can interrupt an olfactory bulb or tract

Question 43

What causes olfactory hallucinations?

Answer 43

irritative lesions of the lateral olfactory cortex

Question 44

What are features of olfactory hallucinations?

Answer 44

a. inappropriate olfactory sensations b. often unfamiliar to patient c. usually extremely disagreeable

Question 45

specific condition that affects the lateral olfactory area where patients experience disagreeable olfactory hallucinations and sometimes display convulsive, involuntary movements of the tongue and lips?

Answer 45

uncinate seizures

Question 46

uncinate seizures are often associated with problems of what lobe?

Answer 46

Temporal

Question 47

Following an uncinate seizure, patients experience a period of _______.

Answer 47

Confusion