Sense of Smell

Olfactory Organs

  • Location: Upper part of a nasal cavity, superior nasal conchea, and nasal septum.

Major Structures

  • Chemoreceptors

  • Odorant molecules enter the nasal cavity as a gas, which also must be partially dissolved in the nasal fluids or receptors won’t detect them.

  • Bipolar neurons that have hair like cilia attached to dendrites.

  • Cilia project into the nasal cavity and have 500 receptor proteins on their surface.

Olfactory Bulb

  • Group of neurons that analyzes impulses.

  • Location: Crista galli of the ethmoid.

Olfactory Nerve Pathway

  1. Stimulated olfactory receptors send impulses along their axons.

  2. Axons synapses with neurons located in the olfactory bulbs.

  3. Olfactory bulbs analyzes impulses and send additional impulses along olfactory tracts to the limbic system.

  4. Impulses are interpreted within the temporal and frontal lobes.

Olfactory Stimulation

  • Uncertain how odors stimulate receptors.

  • One hypothesis suggest a lock and key.

  • Olfactory receptors are easily adaptable.

Sense of Taste

Major Structures

  • Taste Buds: Tongue (papillae), roof of mouth, and walls of throat.

  • Contain: Taste cells, taste pae, taste hair, and supporting epithelial tissue.

Taste Cells

  • AKA gustatory cells.

  • Functions as receptor cells.

  • Each taste bud has 50 to 150 receptor cells.

  • Sensitive to a specific type of chemical stimulus.

Taste Hair

  • Stick out from the taste buds.

  • Most sensitive part of the taste cells.

Taste Sensations

  • Four types: Sweet, sour, bitter, and salty.

  • Flavor is a combination of one or more of the taste sensations,

  • Flavor is multisensory experience: Taste, smell, and touch (texture and temperature).

Taste Distributions on the Tongue

  • All the taste cells can interpret all four sensations.

  • Tongue sensitivity varies from individual to individual.

Taste Nerve Pathways

  • Impulse travels from taste receptors along the facial, glossopharyngeal, and vague nerves into the medulla oblongata.

  • Impulses then ascend to the thalamus which directs them to the parietal lobe.