The Chemical Senses

Gustatory

All have Chemoreceptors

In order for a sensation to be registered by the individual … the chemical (aroma or taste sensation) must be dissolved in solution.

•Mucus

•Saliva

Gustatory Pathway

Most all taste receptors are located on the tongue in raised structures called Papillae

Gustatory Pathway

There are a few receptors in the lining of the cheek and soft pallet

Gustatory Pathway

Epithelial supporting cells forming the taste bud have microvilli called Gustatory Hairs connected directly to dendrites

Gustatory cells are shed and replaced every 7 to 10 days

Gustatory Pathway

The act of tasting evokes reflexes in the digestive system.• Increase of saliva production

• Increase of gastric juices release

Gustatory Pathway

The digestive process begins in the mouth

?

Gustatory Pathway

Taste is approximately 80% Olfactory

Gustatory Pathway

The Hot sensation of peppers excite pain receptors

Gustatory Pathway

Thermo receptors, mechanoreceptors, and nociceptors stimulation of these receptor cites may enhance or detract from the quality of the sensation

Gustatory Pathway

There are three major types of papillae:1. Filiform: no taste buds found

Gustatory Pathway

2. Fungiform: Mushroom shaped

All over the tongue

Highest concentration found at the tip and sides

Taste buds are found on the top of the the

papillae

Gustatory Pathway

3. Circumvallates:

Largest and least numerous (7-12) form a “V” at the back of the tongue

The taste buds are located on the sides of these papillae

Taste

Many substances produce several sensations, thus exciting many different taste buds. Many of the taste buds will respond to each of the following qualities.

Taste

Bitter:• Produced by alkaloids (hydroxide ions)

generally found on the back of the tongue

Taste

Salt:

• Metal ions

• Appears to be evenly distributed

Taste

Sour

• Produced by hydrogen ions

• Generally found on the sides of the tongue

Taste

Sweet:

• Sugars and some amino acids

• Generally found on the tip of the tongue

Gustatory Pathway

Damage to:• Glossopharyngeal nerve – bitter taste

diminished (Cranial Nerve Number?)

• Facial nerve – sweet, sour, salty taste diminished (Cranial Nerve Number?)

The Chemical Senses

OlfactoryOlfactory

Olfactory Pathway

Receptors are found on the roof of the nasal cavity - bilaterally• There are approximately 5 million olfactory

receptor cells

Olfactory Pathway

Collectively, these receptors are referred to as :

Olfactory epithelium

Olfactory Pathway

Regulation of air flow:

• To reduce the stimulation of receptors:

•Inhale slowly through your nose

•Or inhale through your mouth

•What bone structures allow for the air being channeled?

Olfactory Pathway

Regulation of air flow:

• To heighten the stimulation of receptors:

•Inhale quickly through your nose with your mouth closed

Olfactory Pathway

The sensation of an Aroma is stimulated by the excitation of olfactory hairs protruding from the olfactory epithelium in a field of mucosa manufactured by glands in the lamina propria

Olfactory Pathway

In order for an aroma to be detected, it must be volatile

•1. the aroma must be in

a gaseous state

•2. the aroma must be water soluble• Why can we not smell natural gas?

Olfactory Pathway

Acclamation

• A process where the sense of olfaction adapts quickly

• CNS response is not a diminished response from the receptor group

Olfactory Pathway

Olfactory neurons are quite different from other neurons:

they are replaced approximately every 60 days by a process called basal cell basal cell differentiationdifferentiation in the olfactory epithelium

Compare:

Gustatory paths separates four distinct chemical sensations

Olfactory paths distinguish tens of thousands of different sensations with only 15 to 30 different types of receptors

Compare:

The sensation of smell requires the stimulation of ALL receptors in the nasal concha prior to detection

The sense of taste?• Each taste is independent of the other and

does not require the other receptors to be stimulated

Compare:

The irritating response of strong aromas such as ammonia stimulates pain receptors

What is the response and why is it important?

Pain receptor stimulation in the mouth provides us with the sensation of “hot” (spicy). How do you deal with food that is too

spicy?