Lecture 20 - Olfaction and taste

Visceral senses + location

Internal organs
Pain and pressure

Somatic senses + location

Skin, muscles, joints (Distributed over a large part of body)
Touch, pressure, proprioception, temperature, pain

Special senses + location

Localized within specific organs
Smell, taste, sight, hearing, balance

proprioception

body's awareness of the position and movement of its muscles and joints without relying on vision.

Which senses use mechanoreceptors + how they work

Touch, pressure, proprioception, hearing, balance
Compression, bending, stretching of cells

Which senses use chemoreceptors + how they work

Smell and taste
Chemicals attach to receptors

What do thermoreceptors do

Respond to changes in temperature

Sense + what it does for photoreceptors

Responds to light
vision

Nociceptors receptor + when is it activated

Pain
Extreme mechanical chemical or thermal stimuli
Very large stimulus

Hard palete

Separates nasal and oral cavity
Thick bone under nasal cavity

ethmoid bone

Roof of nasal cavity

cribiform plate

thin area on the ethmoid bone

nasal conchae

Ridges in nasal cavity
Helps swirl air around to increase binding

Olfactory epithelium

3 different cell types found here
Layer of cells in upper nasal cavity

What are the 3 cells of olfactory epithelium

Olfactory neurons - bipolar cells
Supporting cells - Help hold olfactory neuron in place
Basal cells - Help regenerate epithelium layer (Abt every 2 months)

Olfactory vesicle

Contains olfactory hairs (cilia) (Chemoreceptor location)
Extends out into nasal cavity from dendrite of olfactory neuron

Odorants

chemicals being detected by chemoreceptors

Mucus layer

Covers olfactory hairs
Dissolves odorants
Created by connective tissue

foramina

little holes in cribriform plate

Where does olfactory neurons synapse

olfactory bulb

What are the 7 primary classes of odors

Camphoraceous - Medicine smell
Musky - Smells animals give off to mate, earthy and strong
Floral - Flower smell
Pepperminty - Peppermint smell
Ethereal - Fruit, sugar smell
Pungent - Strong smell
Putrid - Stinky smell

How are odorants classified

Classified on their shape
Similar shape chemicals will bind to similar chemoreceptors - puts the smells together
Patterns also tell brain what is being smelled

Primary olfactory area (aka olfactory cortex)

Conscious perception of smell
Frontal and temporal lobes

Secondary olfactory area

Visceral and emotional reactions to smell
Connects to epithalamus

synaptic inhibition

Sends a signal to olfactory bulb to stop taking in signals

Papillae

Epithelial projections on the tongue
Folds into itself to form pockets
Pockets are where tastebuds are

4 main types of papillae

Vallate papillae
Foliate papillae
Fungiform papillae
Filiform papillae

Vallate papilla

Largest of papillae
Makes a V shape in posterior part of tongue, borders posterior and anterior
8-12 total papillae
Largest amount of tastebuds in each papillae

Foliate papillae

Folds on the sides of tongue
Tastebuds degenerate as we age
Most sensitive tastebuds

Fungiform papillae

Largest number of papillae
Small amounts of tastebuds in each but lots of papillae
Main surface of tongue

Filliform papillae

No taste buds
Most abundant
Creates rough surface on tongue

Taste bud

3 different cell types
Has gustatory/taste hair that contains receptors, has no axon
Food dissolves in saliva to bind to gustatory hair
Where depolarization occurs

3 different cell types for taste buds

Taste cells - Does the tasting
Supporting cells
Basal cells - replace cells every 10 days

Tastants

dissolved foods that act as chemicals to bind to chemoreceptors in taste hair

5 different tastes for taste buds

Salt, sour, bitter, sweet, umami (meaty taste)

Salt and sour taste path

Ions that are part of these tastes
Salt - Na Sour - H
Ions can move through ion channels to cause depolarization

Bitter, sweet, umami taste path

G protein signaling pathway to open ion channel

How many receptors in 1 taste buds

All, but usually focused on a specific type

Where does taste info go in the brain

Insula region