Taste and olfaction video

Question 1

What is Olfaction and Gustation?

Answer 1

• Taste and smell
• Their chemoreceptors respond to chemicals in aqueous solution

Question 2

What is Olfaction?

Answer 2

• Sense of smell
• Volatile molecules, odorants, dissolved in nasal cavity mucous
• Sample environment for information about food, people, etc.
• Less developed in humans than many other animals
• Can distinguish one odor among thousands

Question 3

Structure of olfactory

Answer 3

Olfactory organs
- Organs of smell
Olfactory epithelium
* lines superior region of nasal cavity
composed of:
- olfactory receptor cells detecting odors
- supporting cells sustaining receptors
- basal cells replacing olfactory receptor cells every 40 to 60 days

Question 4

What is lamina propia?

Answer 4

• areolar connective tissue layer internal to olfactory epithelium
• houses blood vessels and nerves

Question 5

What are Olfactory glands?

Answer 5

• housed in lamina propria
• help form mucous with supporting cells
• covers exposed surface of olfactory epithelium

Question 6

What are Olfactory receptor cells?

Answer 6

• Primary neuron in sensory pathway for smell
• Bipolar with single dendrite and unmyelinated axon

Question 7

What are Olfactory hairs?

Answer 7

• unmyelinated extensions projecting from dendrites
• house receptor proteins for detecting specific odorant molecule

Question 8

What are olfactory nerves?

Answer 8

• formed from bundles of axons of olfactory cells
• project through cribiform plate of ethmoid bone enter olfactory bulbs

Question 9

What are olfactory bulbs?

Answer 9

• terminal ends of olfactory tracts
• inferior to the frontal lobes of the brain
• axons of olfactory nerves synapsing here
• synapse with mitral cells and tufted cells
• together form olfactory glomeruli
• convergence of multiple cells

Question 10

What are olfactory tracts?

Answer 10

• axon bundles of mitral and tufted cells
• project posteriorly along inferior frontal lobe surface
• project directly to primary olfactory cortex in temporal lobe
• projects to hypothalamus, amygdala, and other regions
• do not project to thalamus unlike other sensory information

Question 11

How do you detect smell?

Answer 11

Deep breathing
* helps facilitate mixing of air in superior nasal cavity
* helps diffusion of odor molecules into mucus layer
Odorant-binding proteins
* soluble proteins within mucus
* display an affinity for variety of odorants
* assist in concentration of odorants to olfactory hair receptors

Question 12

Describe Physiology of Smell

Answer 12

• Dissolved odorants bind to receptor proteins in the olfactory cilium membranes
• A G protein mechanism is activated, which produces
  CAMP as a second messenger
• CAMP opens Nat and Ca2+ channels, causing
  depolarization of the receptor membrane that then triggers an action potential

Question 13

Describe olfactory pathway

Answer 13

• Olfactory receptor cells synapse with mitral cells in glomeruli of the olfactory bulbs
• Mitral cells amplify, refine, and relay signals along the olfactory tracts to the:
• Olfactory cortex
• Hypothalamus (visceral effects), amygdala, and limbic system (emotional effects)

Question 14

What is smell adaptation?

Answer 14

• Smell adaptation
• ion channels altered once receptors stimulated
• interferes with subsequent receptor potentials
• adaptation to odors occurring rapidly

Question 15

Name some areas of the brain where the olfactory nerves project and give their purposes.

Answer 15

The cerebral cortex allows conscious perception of smell.

The hypothalamus controls visceral reactions to smell.

The amygdala recognizes odors and ties those odors to particular emotions.

Question 16

What is gustation?

Answer 16

• Sense of taste
• From molecules we eat and drink
• Gustatory cells
• taste receptors housed in specialized organs, taste buds
• Involves mechanoreceptors and thermoreceptors
• provide information about texture and temperature

Question 17

Describe taste buds

Answer 17

• Receptor organs are taste buds
• Found on the tongue
• On the tops of fungiform papillae
• On the side walls of foliate papillae and circumvallate (vallate)
  papillae

Question 18

What is structure of taste bud?

Answer 18

• Flask shaped
• 50-100 epithelial cells:
• Basal cells-dynamic stem cells
• Gustatory cells-taste cells
• Microvilli (gustatory hairs) project through a taste pore to the surface of the epithelium

Question 19

Describe Physiology of Taste

Answer 19

** In order to be tasted, a chemical:**
- Must be dissolved in saliva
- Must contact gustatory hairs
Binding of the food chemical (tastant)
- Depolarizes the taste cell membrane, causing release of neurotransmitter
- Initiates a generator potential that elicits an action potential

Question 20

Describe taste transduction?

Answer 20

• The stimulus energy of taste causes gustatory cell depolarization by:
• Nat influx in salty tastes (directly causes depolarization)
• Ht in sour tastes (by opening cation channels)
• G protein gustducin in sweet, bitter, and umami tastes (leads to release of Cal+ from intracellular stores, which causes opening of cation channels in the plasma membrane)

Question 21

Five basic taste sensations

Answer 21

• Sweet
• produced by organic compounds, e.g., sugar or artificial sweeteners
• Salt
• produced by metal ions, e.g., Nat and K+
• Sour
• associated with acids, e.g., vinegar
• Bitter
• produced by alkaloids, e.g., unsweetened chocolate
• Umami
• taste related to amino acids to produce meaty flavor