first general parts, Gustatory, Olfactory

Special senses are localized

confined to the head region Receptors are distinct receptor cells

Special receptor cells

Are neuronlike epithelial cells or small peripheral neurons

Transfer sensory information to other neurons in afferent pathways

The chemical senses

Taste, Smell

Taste—Gustation occur

Occur in taste buds

Most are found on the surface of the tongue

Located within tongue papillae

Four types of papillae (three contain taste buds)

Fungiform papillae

• Vallate papillae

• Foliate papillae

• Filiform papillae

Filiform papillae

Which tongue papillae has not taste buds

Taste buds has

Collection of approx. 50–100 epithelial cells

• Contain two major cell types

• Gustatory epithelial cells: supporting cells

• Basal epithelial cells: gustatory cells

• Contain long microvilli—extend through a taste pore to the surface of the epithelium

Taste Sensation

Five basic qualities of taste

• Sweet, sour, salty, bitter, and umami

• “Umami” is elicited by glutamate

• All taste modalities can be elicited from all areas containing taste buds

Gustatory Pathway

Taste information reaches the cerebral cortex

• Primarily through the facial (VII) and glossopharyngeal (IX) nerves

• Some taste information through the vagus nerve (X)

• Impulses are transmitted to the thalamus and

ultimately to the gustatory area of the cerebral cortex in the insula

Smell (Olfaction)

Olfactory receptors (olfactory sensory neurons) are part of the olfactory epithelium

• Olfactory cilia act as receptive structures for smell

• Mucus captures and dissolves odor molecules

• Axons of olfactory sensory neurons

• Penetrate the cribriform plate of the ethmoid bone

• Synapse with mitral cells, which transmit impulses to limbic system and cerebral cortex

Olfactory cilia

act as receptive structures for smell

Mucus

captures and dissolves odor molecules

mitral cells

transmit impulses to limbic system and cerebral cortex