Olfaction and Taste

Question 1

Difference between special senses and general senses

Answer 1

GENERAL
- receptors distributed across large portions of the body
SPECIAL
- receptors located in specific organs

Question 2

division of special and general senses

Answer 2

GENERAL
SOMATIC: located in skin, muscles and joints
- touch
- pressure
- proprioception
- temperature
- pain
VISCERAL: located in internal organs
- pain
- pressure

SPECIAL
- smell
- sight
- taste
- hearing
- balance

Question 3

5 types of specialized sensory receptors

Answer 3

MECHANORECEPTORS
- compression, bending, stretching of cells
- touch, pressure, proprioception, hearing and balance
CHEMORECEPTORS
- chemicals attach to receptors on membrane
- smell and taste
THERMORECEPTORS
- respond to change in temperature
PHOTORECEPTORS
- respond to light
- vision
NOCICEPTORS
- extreme mechanical, chemical or thermal stimuli
- pain

Question 4

Name general components of nasal anatomy

Answer 4

• nasal cavity
  OLFACTORY REGION
• cribriform plate of ethmoid bone
• fibres of olfactory nerve
• olfactory bulb
• olfactory tract (still PNS)

Question 5

Describe how smell signal reaches the olfactory tract

Answer 5

• ODORANT binds to chemoreceptors on OLFACTORY HAIRS of OLFACTORY VESICLE (end of OLFACTORY NEURON)
• oderant must be dissolved in mucous
• causes depolarization of cell (graded potential)
• signal sent to axon, through connective tissue then FORAMINA of CRIBRIFORM PLATE
• synapses with 2nd neuron in OLFACTORY BULB
• signal sent via OLFACTORY TRACT

Question 6

3 cell types of olfactory epithelium

Answer 6

1. Olfactory neurons
   - bipolar
2. Supporting cells
   - help hold olfactory neurons in place
3. Basal cells
   - regenerate olfactory epithelium every 2 months

Question 7

What creates the mucous in the olfactory epithelium?

Answer 7

glands in the connective tissue

Question 8

characteristics of olfactory chemoreceptors

Answer 8

• several different types
• one chemoreceptor can bind multiple different odorants of similar shape

Question 9

7 primary classes of odors

Answer 9

• Camphoraceous (moth balls)
• Musky
• Floral
• Pepperminty
• Ethereal (fruity/sweet)
• Pungent
• Putrid (rotting)

Question 10

Where do olfactory potentials terminate?

Answer 10

1. PRIMARY OLFACTORY
   AREA (olfactory cortex)
   - frontal and temporal lobes
   - conscious perception of smell
2. SECONDARY OLFACTORY AREA
   - near corpus callosum, connects to habenula
   - visceral and emotional reactions to smell

Question 11

How do we adapt to smells? i.e. not smell them anymore

Answer 11

1. Olfactory receptors saturated (not possible for more odorants to bind)
2. Synaptic inhibition (brain blocks further signals from coming through)

Question 12

sense of taste

Answer 12

gustation

Question 13

structure that covers over windpipe when swallowing

Answer 13

epiglottis

Question 14

small epithelial projections that cover surface of tongue

Answer 14

papillae
papilla (singular)

Question 15

4 types of papillae

Answer 15

VALLATE PAPILLAE
- back of tongue
- form V shape
- 8-12 total
- large amount of taste buds (100-300/papillae)
FOLIATE PAPILLAE
- side of tongue
- look like trees, hence foliate
- taste buds deteriorate over time
FUNGIFORM PAPILLAE
- surface of tongue
- irregularly scattered
- ~5 taste buds/papillae
FILIFORM PAPILLAE
- creates rough surface of tongue
- flame shaped
- no taste buds
- most abundant type
- helps manipulate food when eating

Question 16

Anatomy of a taste bud

Answer 16

located on inside of papillae
Epithelium: stratified squamous

3 cell types
1. TASTE CELLS
- GUSTATORY/TASTE HAIR (microvilli) extends out of epithelium via TASTE PORE
- aprx. 50 different taste cells per taste bud
- has no axon
2. SUPPORTING CELLS
3. BASAL CELLS
- regenerate cells every ~10 days

Question 17

differences between sensory receptors for olfaction vs taste

Answer 17

olfaction
- CILIA hold receptors
- axon in olfactory neuron
taste:
- MICROVILI hold receptors
- no axon in gustatory cell

Question 18

how is taste signal sent to brain?

Answer 18

• TASTANTS dissolved in saliva
• bind to chemoreceptor on TASTE HAIRS located on TASTE CELLS
• depolarizes cell, signal sent via neurotrasmittors
• excitatory response sent to brain

Question 19

5 different taste receptor types

Answer 19

Salty
Sour
Sweet
Bitter
Umami

Question 20

How are the different taste receptors activated?

Answer 20

Salty
- Na+ ions
Sour
- H+ ions
Bitter, Sweet Umami
- G protein signalling pathway activated

Question 21

each taste cell only has __ type of chemoreceptor

Answer 21

one

Question 22

taste is differentiated between…

Answer 22

taste buds
not taste cells
This is because buds contain all types of receptors but generally favour one

Question 23

Neural pathway for taste

Answer 23

• gustatory receptor cells
• Cranial nerves VII (facial), IX (glossopharyngeal), X (vagus)
• medulla oblongta
• thalamus
• taste area of INSULA

Question 24

interpretation of taste is based on

Answer 24

number of certain types of receptors activted

Question 25

nerves and regions of taste they govern

Answer 25

XII (facial) - anterior 2/3
IX (glossopharyngeal) - posterior 1/3
X (vagus) - epiglottis