DSA Neuroanatomy of Gustation & Olfaction

Question 1

Via _______ _______ neurons, humans can recognize thousands of airborne odors, many at extremely low concentrations. This plays a role in the pleasure associated with eating and helps us recognize environments.

Answer 1

Olfactory receptor

Question 2

The bones of the nasal cavity are very (THICK/THIN). This makes the olfactory receptor neurons very sensitive to facial trauma.

Answer 2

Thin

Question 3

The taste system has a very limited range of sensation. The four basic tastes are…

Answer 3

Sweet
Salty
Sour
Bitter

Question 4

Umami sensation may be important for the identification of…

Answer 4

Amino acids

Question 5

T/F. The combinations of taste qualities are important in acceptance or rejection of foods.

Answer 5

True

Question 6

What can recognize a wider variety of sensations?

A. Tongue
B. Nose
C. They are the same

Answer 6

B. Nose

Question 7

How are we able to recognize different tastes other than the 4 basic ones?

A. There are thousands of types of taste receptors.

B. Few taste receptors in different combinations result in different taste sensations.

C. I have no idea.

Answer 7

B. Few taste receptors in different combinations result in different taste sensations.

Question 8

1.5 yo male presents with a cold. Their parent reports they are completely stopped up. The parent also reports that the child put coffee beans in their mouth and did not spit it up. Why?

A. Young children put stuff in their mouth all the time.
B. The child obviously likes coffee.
C. Olfaction and taste are intimately related.

Answer 8

C. Olfaction and taste are intimately related.

Question 9

This is a critical anatomical structure that helps humans smell. It lies in the cribriform plate of the ethmoid bone.

Answer 9

Olfactory Bulb

Question 10

This helps transmit sensory information from the environment to the brain.

Answer 10

Olfactory Tract

Question 11

The olfactory bulb sits here. This is the rostral end of the olfactory sulcus and the rostral portion of the anterior cranial fossa.

Answer 11

Cribriform Plate

Question 12

These neurons are located on the roof of the nasal cavity. They are located on the inferior surface of the cribriform plate, along the nasal septum, and on the medial wall of the superior turbinate (concha).

Answer 12

Olfactory Receptor Neurons

Question 13

The Olfactory Receptor Neuron is CN 1. It has a single _______ _______ that receives information from the environment. These receptors are found in olfactory mucosa of the superior portion of the nasal cavity.

Answer 13

Dendritic process

Question 14

This is what keeps the nasal cavity moist.

Answer 14

Ducts and glands within the olfactory epithelium

Question 15

Olfactory nerve bodies are surrounded by _________ cells. The dendrites and receptors of these cells will extend into the olfactory epithelium where they will have good exposure to smell molecules.

Answer 15

Supporting

Question 16

The cilia of an Olfactory Receptor Neuron are _________ and contain _________ receptors.

Answer 16

Non-motile

Odorant

Question 17

What type of receptors are odorant receptors?

Answer 17

GPCRs

Question 18

An odorant receptor is activated by a ligand odor molecule binding to its specific GPCR. This causes a signal to be sent from the Olfactory Receptor Neuron to the…

Answer 18

Olfactory Bulb

Question 19

This layer of CT holds lots of immune cells. This is important because the mucosa is directly exposed to the external environment.

Answer 19

Lamina Propria

Question 20

These cells are just superficial to the basement membrane. These act as stem cells for Olfactory Receptor Neurons and supporting cells. They continuously turn over and as a result, most cells in the olfactory mucosa have a life span of 30-60 days.

Answer 20

Basal cells

Question 21

The cell bodies of Olfactory Receptor Neurons lie in one layer, while their single dendrite extends to the ________ layer. The axons travel up to the olfactory bulb through the _______ _______.

Answer 21

Mucus

Lamina Propria

Question 22

These cells offer physical and metabolic support to the surrounding cells in the olfactory mucosa.

Answer 22

Supporting/Sustentacular cells

Question 23

These are ciliated columnar epithelial cells in olfactory mucosa.

Answer 23

Brush Cells

Question 24

This is made and secreted by the glands and ducts in the Olfactory Epithelium.

Answer 24

Mucus

Question 25

What are the layers of the olfactory mucosa?

Answer 25

``` Lamina Propria Basal Cells Olfactory Receptor Neurons (cell bodies) Supporting/Sustentacular cells Brush cells Cilia Mucus ```

Question 26

Describe the process of smell.

Answer 26

At the back of the nasal cavity is olfactory epithelium that has olfactory receptors (GPCRs). We breathe in, and odorant molecules get trapped in mucus and bind to these receptors. This activates the neurons and send a signal through the olfactory bulb, then olfactory tract and into your brain. ***We can distinguish between odors because one odor will bind to certain olfactory receptor neurons, while another odor will bind to different neurons.

Question 27

Smell molecules are transmitted into sensory information when they act as a ligand and interact with the GPCR of an Olfactory Neuron Receptor. Initially, the smell molecule will contact the ________ layer that covers the Olfactory Epithelium. There it will interact with odorant-binding proteins.

Answer 27

Mucus

Question 28

The smell molecule acts as a ligand and binds a GPCR. This activates _______ ______ which results in an increase in _______.

Answer 28

Adenylyl Cyclase | cAMP

Question 29

After smell molecules have lead to the increase in cAMP, cAMP binds ion channels which leads to an increase in _______ and _______ influx into the cell. This causes a depolarization and an action potential. The action potential travels up the Olfactory Receptor Neuron where it synapses with neurons in the ________ ________.

Answer 29

Calcium Sodium Olfactory Bulb

Question 30

Different regions of the Olfactory Epithelium line up with and carry information to specific areas of the ________ _______. This "receptor map" is the initial step for olfactory discrimination.

Answer 30

Olfactory Bulb

Question 31

Odors are encoded by activating several different _________ at varying magnitudes. These are preferentially distributed within the olfactory epithelium.

Answer 31

Receptors

Question 32

The Olfactory Bulb has 5 layers, which are what from deep to superficial (inferior to superior)?

Answer 32

``` Granule cell layer Mitral cell layer External Plexiform layer Glomerular layer Olfactory Nerve layer ``` ***Mnemonic is GRow My EGO

Question 33

These reach the Olfactory Bulb via the Anterior Commissure. Their main job is to help regulate feedback loops.

Answer 33

Centrifugal Fibers

Question 34

What are the components of the Olfactory Tract?

Answer 34

Lateral Olfactory Tract Cells of Anterior Olfactory Nucleus Fibers of the Anterior Limb of the Anterior Commissure

Question 35

Centrifugal fibers have a (POSITIVE/NEGATIVE) effect on Granule cells. The Granule cells have a (POSITIVE/NEGATIVE) effect on Mitral and Tufted cells. Therefore, increasing Centrifugal fiber activity will indirectly (INCREASE/DECREASE) Mitral and Tufted cell activity.

Answer 35

Positive Negative Decrease

Question 36

Olfactory Receptor Neurons upregulate the activity of Mitral/Tufted cells and __________ cells. These cells antagonize the activity of Mitral and Olfactory Receptor Neuron cells, and likely have an important roll in getting used to smells, like when you're in the anatomy lab and the smell "goes away".

Answer 36

Periglomerular

Question 37

As Olfactory Receptor Neurons continue to be active, the __________ cells respond to shut down Mitral and Tufted cells, effectively inhibiting the transmission of information from the environment to the brain.

Answer 37

Periglomerular

Question 38

Afferent projections from Olfactory Receptor Neurons synapse with _______ and _______ cells in the olfactory glomerulus.

Answer 38

Mitral | Tufted

Question 39

The axons of a Olfactory Receptor Neuron only synapses in one _________, however, a single _________ has a large number of Olfactory Receptor Neurons synapsing within it.

Answer 39

Glomerulus | Glomerulus

Question 40

The glomerulus actually receives axons from all the Olfactory Receptor Neurons expressing the same odor molecule specific receptor. This suggest that a single glomerulus will receive input from only one type of ________.

Answer 40

GPCR

Question 41

Activity in the glomerulus is regulated by...

Answer 41

``` Periglomerular cells Olfactory Neuron Receptors Mitral cells Tufted cells Centrifugal Fibers ```

Question 42

Which cell type carries afferent information from the olfactory bulb to the brain? A. Olfactory Receptor Neurons B. Tufted cells C. Granule cells D. Periglomerular cells

Answer 42

B. Tufted cells

Question 43

Which cell type carries efferent information from the brain to the olfactory bulb? A. Mitral cells B. Periglomerular cells C. Centrifugal Fibers D. Olfactory Receptor Neurons

Answer 43

C. Centrifugal Fibers

Question 44

Certain cells in the olfactory bulb have inhibitor effects on others. What neurotransmitter is responsible for this action? ``` A. cAMP B. Serotonin C. Dopamine D. GABA E. ACh F. Norepinephrine ```

Answer 44

D. GABA

Question 45

The olfactory bulb projects information to other regions of the brain. The information is carried from the olfactory bulb to the olfactory cortex via the ________ ________ ________. The cells carrying information are the _______ and _______ cells.

Answer 45

Lateral Olfactory Tract Mitral Tufted ***Olfactory projections go directly to the olfactory cortex, they DO NOT have to pass through the relay center (thalamus).

Question 46

The olfactory epithelium has zones that corresponded with zones in the olfactory bulbs (depending on smell type). The zones of the olfactory bulb DO NOT have a similar projection pattern on the _______ _______. This means that information from the different zones of the olfactory bulb can go to any region of the _______ _______.

Answer 46

Olfactory Cortex | Olfactory Cortex

Question 47

Smells are often associated with memory. This long-term processing occurs because of secondary projections of the Olfactory Cortex to the...

Answer 47

Hippocampus

Question 48

Smell is a primitive sense. Smell can help an organism recognize danger and fear. In humans, projection to the ________ helps this process occur.

Answer 48

Amygdala

Question 49

Afferent projections from the Olfactory Bulb go to several areas of the Olfactory Cortex FIRST. Then certain areas may send information to the thalamus, specifically the _______ _______ _______, for further processing. This is a SECONDARY projection.

Answer 49

Dorsomedial Thalamic Nucleus ***Remember, smell is a primitive sense. It does NOT have to go to the thalamus for initial processing.

Question 50

After reaching information from the Lateral Olfactory Tract, the Olfactory Cortex (specifically the ________ _______ ________) sends information back to the Olfactory Bulb.

Answer 50

Anterior Olfactory Nucleus

Question 51

This tract is where the Mitral and Tufted cells are sending their axons to the Olfactory Cortex (afferent).

Answer 51

Lateral Olfactory Tract

Question 52

If information is directed from the Olfactory Cortex to the _______ _______ the body responds with appropriate feeding behavior. For example, an individual smells warm bread, they salivate and become hungry.

Answer 52

Lateral Hypothalamus

Question 53

If information is directed from the Olfactory Cortex to the _________ then the input is linked to learning and behavior. For example, I have smelled bad body odor all day no matter where I go. It must be me, I smell. I will take a shower later.

Answer 53

Hippocampus

Question 54

The Paleocortex (primitive cortex) sends projections to other areas of the brain like the hippocampus and dorsomedial thalamic nucleus. These areas are part of the _________, which helps discriminate and identify odors. An example of how it processes -- "this drink smells like coffee, if I drink this it will help me stay awake."

Answer 54

Neocortex

Question 55

This helps integrate olfaction, taste, and other food cues to help humans experience flavors and enjoy food.

Answer 55

Orbitofrontal Cortex

Question 56

These are sensory organs that can perceive experiences of sweet, salty, sour, bitter, and umami.

Answer 56

Taste buds

Question 57

Taste buds can be found throughout the _________ cavity. They are most obvious on the tongue.

Answer 57

Oropharyngeal

Question 58

This innervates the Fungiform Papillae and anterior Foliate Papillae on the anterior 2/3 of the tongue.

Answer 58

Chorda Tympani ***Part of CN VII

Question 59

The taste buds on the soft palate are innervated by the...

Answer 59

Greater Superficial Petrosal N. ***Part of CN VII

Question 60

This is where afferent fibers of the Facial N. carrying taste sensory information enter the brainstem.

Answer 60

Pontomedullary Junction

Question 61

This is where sensory fiber cell bodies of the Facial N. are located. These fibers of CN VII carry taste sensation to the Rostral Solitary Nucleus (aka Gustatory Nucleus).

Answer 61

Geniculate Ganglia

Question 62

Sensory fibers of the Facial N. synapse in the Solitary Tract and information is then transmitted to the Solitary Nucleus and carried to the part called the ________ ________ (aka the Rostral portion of the Solitary Nucleus).

Answer 62

Gustatory Nucleus

Question 63

Taste reception is initiated when soluble chemicals (from food) diffuse through a taste pore. The chemical then bind to receptors on apical ________ of taste cells and cause hyperpolarization or depolarization. If depolarization of cells is sufficient, an action potential in the taste cell is relayed to afferent fibers.

Answer 63

Microvilli

Question 64

This nerve innervates taste buds in the Vallate Papillae and posterior Foliate Papillae.

Answer 64

Glossopharyngeal N.

Question 65

This nerve innervates taste buds of the epiglottis and esophagus.

Answer 65

Vagus N.

Question 66

What is the pathway for taste reception?

Answer 66

Taste bud afferents (from Geniculate Ganglia) --- Synapse in Solitary Nucleus (specifically rostral or Gustatory Nucleus) --- 2nd order neurons travel via ipsilateral Central Tegmental Tract --- Central Tegmental Tract take neurons to synapse in VPMpc (parvicellular ventral posteromedial nucleus) --- 2nd order neurons synapse with 3rd order neurons in VPMpc --- Gustatory information now traveling on ipsilateral Posterior Limb of Internal Capsule --- Taken to Frontal Operculum and Anterior Insular Cortex, specifically the Rostral area of Brodmann area 3b (in post central gyrus)

Question 67

This region of the brain receive input from the primary taste cortex (Brodmann area 3b). It takes information and integrates it with visional and olfactory senses associated with food ingestion.

Answer 67

Lateral Posterior Orbitofrontal Cortex

Question 68

This is the loss of smell.

Answer 68

Anosmia

Question 69

This is decreased sensitivity to odorants. An example that causes this is nasal polyps (noncancerous growths in the nasal cavity or sinuses).

Answer 69

Hyposmia (aka Olfactory Hypesthesia)

Question 70

This is a complete loss of taste. It is rare because many nerves carry gustatory sensory information (CN VII, IX, X).

Answer 70

Ageusia

Question 71

This is decreased taste sensitivity.

Answer 71

Hypogeusia

Question 72

This is when perception of taste is altered. Commonly due to drug use (prescription or recreational).

Answer 72

Parageusia/Dysgeusia

Question 73

Lesions of CN VII can be caused by tumors in the Internal Auditory Meatus (called a Vestibular Schwannoma) because it may bump the Chorda Tympani. This results in loss of taste in the anterior 2/3 of tongue on the (CONTRALATERAL/IPSILATERAL) side. It will also manifest as (CONTRALATERAL/IPSILATERAL) facial paralysis, hearing loss (due to paralysis of Stapedius M.), impaired secretion of nasal, lacrimal, submandibular, and sublingual glands.

Answer 73

Ipsilateral | Ipsilateral

Question 74

This is the first ganglion where the Facial N. fibers carrying taste information from the tongue synapse. If there is damage here, taste may or may not be lost but IPSILATERAL facial paralysis will be seen.

Answer 74

Distal Geniculate Ganglion