Physiology of Gustation/ Olfaction

Question 1

What is Olfaction?

Answer 1

The sense of smell, allows you to detect small amounts of many substances from a great distance

Question 2

What is Gustation?

Answer 2

The sense of taste, allows you to detect large amounts of a few substances

Question 3

What is the function of the olfactory bulb?

Answer 3

It processes odours in the brain

Question 4

What is the olfactory recess?

Answer 4

A labyrinth of thin bones covered in epithelium

Question 5

What is the lamina transversa?

Answer 5

Bone separates the main airway and olfactory recess traps odours even after air is exhaled

Question 6

What is the point of having lateral slits?

Answer 6

direct the airflow laterally to prevent interference with incoming smells

Question 7

What is the lamina transversa?

Answer 7

a bone that separates the olfactory recess from the main airway and traps scent molecules to enhance detection

Question 8

What are turbinates?

Answer 8

long thin bones covered in nasal tissue that can expand

Question 9

What are olfactory receptors?

Answer 9

detect air-borne odour molecules

Question 10

What is an adaptation of olfactory receptors to be able to detect odour molecules?

Answer 10

They have cilia that can project into the mucous to detect odour molecules

Question 11

What are mitral cells?

Answer 11

Neurones that are part of the olfactory system

Question 12

Where are mitral cells found?

Answer 12

Found in the olfactory bulb

Question 13

What is olfactory epithelium?

Answer 13

A type of pseudostratified columnar epithelium that lines the turbinate’s in the caudal cavity involved in sensing smell

Question 14

What are the three turbinates that airflow can be directed through?

Answer 14

Ventral, Middle and Dorsal

Question 15

What is the ventral meatus?

Answer 15

Widest and shortest meatus, goes directly to the nasopharynx

Question 16

What is the Middle meatus?

Answer 16

leads air through the heat exchanger and to the caudal part of the olfactory epithelium before it reaches the nasopharynx

Question 17

What is the dorsal meatus?

Answer 17

leads air above the heat exchanger and to the olfactory epithelium before reaching the nasopharynx

Question 18

Where does exhalation usually occur?

Answer 18

occurs mainly through the ventral meatus

Question 19

Where does breathing at rest usually occur?

Answer 19

air flows mainly through the two more ventral meatuses

Question 20

What kind of receptor are olfactory receptors?

Answer 20

G-protein coupled

Question 21

What enzyme do G-Protein receptors activate?

Answer 21

adenylyl cyclase

Question 22

How are olfactory receptors stimulated?

Answer 22

Vibrational theory, each odour molecule has a specific vibrational energy that a receptor detects

Question 23

What is the olfactory threshold?

Answer 23

The lowest concentration of an odour that can be detected when it is in contact with the olfactory epithelium

Question 24

What is olfactory adaptation mediated by?

Answer 24

Ca2+ ions// action potentials

Question 25

Which nerve stimulates pain in the nose e.g by irritating substances

Answer 25

The Trigeminal nerve

Question 26

What is Anosmia?

Answer 26

absence of the sense of smell

Question 27

What is Hyposmia?

Answer 27

diminished olfactory sensitivity

Question 28

What is Dysosmia?

Answer 28

distorted sense of smell

Question 29

What is the vomeronasal organ?

Answer 29

Sensory organ located in the rostral palatine bone that is sensitive to odour molecules suspended in liquids

Question 30

What are the 5 categories of taste?

Answer 30

Sweet, Salty, Sour, Bitter and Umani

Question 31

What is Umani?

Answer 31

detection of amino acids

Question 32

What is bitter taste?

Answer 32

detection of toxins

Question 33

What are the three different types of taste cells?

Answer 33

Type 1, Type 2 and Type 3

Question 34

What type of receptor cells detect sweet, umami and bitter taste?

Answer 34

Type II cells

Question 35

What type of receptor cells detect sour taste?

Answer 35

Type III detector cells

Question 36

What are some of the functions of olfaction?

Answer 36

Detection of food Detection of enemies Navigate the terrain

Question 37

Where do sensory receptors in the vomeronasal organ synapse?

Answer 37

They synapse with mitral cells in the olfcatory bulb

Question 38

What animals lack an olfactory bulb?

Answer 38

Birds

Question 39

How does the sense of smell travel?

Answer 39

Mucous glands secrete mucus that traps the odour molecules olfactory receptor cells can then detect these odour molecules The axons of the olfactory cells then synapse with the mitral cells in the olfactory bulb | axons of the olfactory nerve travel through the cribiform plate ## Footnote synapses are called glomeruli

Question 40

How does the sense of smell travel?

Answer 40

Mucous glands secrete mucus that traps the odour molecules olfactory receptor cells can then detect these odour molecules The axons of the olfactory cells then synapse with the mitral cells in the olfactory bulb | axons of the olfactory nerve travel through the cribiform plate ## Footnote synapses are called glomeruli

Question 41

Where do nerve fibres extending from the mitral cells end up?

Answer 41

The cerebral olfactory cortex

Question 42

How is the olfactory cortex responsible for odours illiciting strong emotions?

Answer 42

Olfactory cortex is related to the limbic system

Question 43

What are the three branches of the trigeminal nerve that cause pain fibres in the nasal cavity?

Answer 43

* Mandibular branch * Maxillary branch * Ocular branch

Question 44

What are the three branches of the trigeminal nerve that cause pain fibres in the nasal cavity?

Answer 44

* Mandibular branch * Maxillary branch * Ocular branch

Question 45

What are the nasal pain branches responsible for?

Answer 45

initiating sneezing and lacrimation/ other reflex responses

Question 46

What is the purpose of olfactory cells secreting mucus?

Answer 46

allows odour molecules to become trapped

Question 47

What is the purpose of the Flehmenn response?

Answer 47

Draws fluid/smalls into the vomeronasal organ

Question 48

What occurs when ATP is released due to the detection on sweet, umani or bitter compounds are released?

Answer 48

ATP binds to purinergic receptors to have excitatory effect on own receptor cell (autocrine), nearby receptors (paracrine), presynaptic cells and sensory nerve endings » Serotonin released directly when low pH detected (sour, acidic compounds) or indirectly from ATP stimulation » Serotonin has excitatory effect on sensory nerve endings but inhibitory paracrine effect on receptor cells » GABA also released from stimulated presynaptic cells which has inhibitory paracrine effect on receptor cells » Stimulated nerve endings release glutamate that has an excitatory effect on presynaptic cells

Question 49

What ion mediates the increase in the olfactory threshold over time?

Answer 49

calcium ions

Question 50

What does stimulation of the vomeronasal organ lead to?

Answer 50

Increased secretion of GnRH