The chemical senses: Smell and taste

chapter 53

Dr. Z Akbari

Sense of tastePrimary sensation of taste:

- 13 possible chemical receptor in taste cell13 possible chemical receptor in taste cell

Sour taste

S l Salty taste

Sweet taste

Bitter taste

Umami

Threshold for taste

Taste blindnessTaste blindness

Dr. Z Akbari

Function of Taste bud

L ti f t t b dLocation of taste bud :

Circumvallate papillae

Fungiform papillae

Foliate papillaeFoliate papillae

Specificity of taste buds

* Chemoreceptor cells live only * Chemoreceptor cells live only about about 10 10 daysdays

Dr. Z Akbari

Dr. Z Akbari

Mechanism of taste bud stimulation

Dr. Z Akbari

Mechanism of taste bud stimulation

Dr. Z Akbari

Dr. Z Akbari

Dr. Z Akbari

Transmission of

taste signals into

the CNS

Dr. Z Akbari

• Taste reflex integrated in the brain stem (sup & inf salivatory n)

• Adaptation of taste T f d i• Taste preference and aversion

Dr. Z Akbari

SmellOlf t bOlfactory membrane

Olfactory cells (Olfactory sensory neurons)Th lf iTh lf i f h i i lf h i i lThe olfactory mucosa contains The olfactory mucosa contains somatosensorysomatosensory receptors of the trigeminal receptors of the trigeminal nerve. Activation of these receptors with noxious or thermal stimuli. nerve. Activation of these receptors with noxious or thermal stimuli.

Dr. Z Akbari

Dr. Z Akbari

• Membrane potentials and AP in the olfactory cells• Mechanism of excitation of olfactory cells• Mechanism of excitation of olfactory cells• Adaptation: role of inhibitory granule cells

Th h ld f ll• Threshold for smell

Dr. Z Akbari

Olfactory Olfactory glumerolglumerol contains three main cell types:contains three main cell types:

mitral cells, tufted cells,mitral cells, tufted cells, and and interneuronsinterneurons (granule cells)(granule cells)

The olfactory glomeruli demonstrates lateral inhibition mediated byThe olfactory glomeruli demonstrates lateral inhibition mediated byThe olfactory glomeruli demonstrates lateral inhibition mediated by The olfactory glomeruli demonstrates lateral inhibition mediated by periglomerular cells and granule cells. This sharpens and focuses olfactory periglomerular cells and granule cells. This sharpens and focuses olfactory signalssignals

Dr. Z Akbari

Central olfactory pathwaysCentral olfactory pathwaysTh f i l ll lf• The axons of mitral cells olfactory tracts.

• Anterior olfactory nucleus (Within the olfactory tracts) receivesinput from and projects to the contralateral olfactory bulb through thep p j y ganterior commissure.

• At the base of the brain, OT splits into the lateral and medialolfactory striaeolfactory striae.

• Lateral olfactory stria primary olfactory cortex(prepiriformcortex.

• Medial olfactory stria amygdala Basal forebrainLimbic system

Dr. Z Akbari

Neo cortex: Conscious discrimination of odors.Neo cortex: Conscious discrimination of odors.Limbic projection: Affective nature of smellOdors can effectively call up memoriesOdors can effectively call up memories

The endThe end

Odors can effectively call up memories. Odors can effectively call up memories. Dr. Z Akbari

Most people walk in and Most people walk in and out of your life,out of your life,butbutonly friends leave only friends leave yyfootprints in your heart.footprints in your heart.

Dr. Z Akbari

Neo cortex: Conscious discrimination of odorsNeo cortex: Conscious discrimination of odors

Limbic projection (amygdala & hypothalamus): Affective nature of smellDr. Z Akbari

Dr. Z Akbari