Ch 7.3/4 Gustation and Olfactory Perception

• Stimulated by chemicals in mucus or saliva

• Both senses complement each other and respond to many of the same stimuli.

• Taste and smell are most acute at birth and decrease sensitivity after age 40 as the number of olfactory and gustatory receptors decreases.

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Chemoreceptors

• Chemosensory integration

  • odor perception is a combing effect of both the olfactory bulb and the gustatory pathway

• ​Taste is significantly impacted by the ability to perceive odors

• Olfactory Epithelium

  • ​Olfactory neurons embedded between support cells

    • ​long cilia

  • ​Bowman's gland

    • ​produces mucus

• ​Chemicals must be dissolved in mucus for detection.

• ​Olfactory Neurons synapse at the glomeruli with mitral cells

• ​Mitral cell axons form the olfactory tract to the brain.

• ​Limbic system

  • rhinencephalon, or "smell-brain because it reacts primarily to signals of odor

  • Hypothalamus, emotion, and memory retrieval

• Thalamus

  • connected through it to other parts of the brain​​

• olfactory is connected through nerve endings called common chemical sense

• Primary locations:

  Eyes, Nose, Mouth, throat

• These are used to detect noxious or irritating chemicals

Anosmia- lack of smell (usually temporary)

Dysomnia- ​distorted smell

Hyperosmia-overly acute sense of smell

Hyposmia- decreased sense of smell​

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​Smell Disorders

The Tongue

• Gustatory Papillae

  • ​Papillae

    • ​Small projections on the surface of the tongue

  • Taste "buds" are taste pores

    • Most are on the tongue, soft palate, and cheeks

    • Possess gustatory hairs (long microvilli)

      • Hairs are stimulated by chemicals dissolved in saliva

• ​5 different sensory cells

  • ​Umami- Protein, amino acids

  • ​Sweet - carbohydrates

  • ​Salty- Na⁺ concentration or metal ions

  • ​Sour- concentration of H⁺

  • ​Bitter- 550 compounds

    • alkaloids

• Multisensory

  • smell, texture, temperature

  • ​Cranial Nerves

    • ​7, 8, 9 10

    • ​transmit and integrate a sense of taste

• ​Brain

  • ​Medulla

  • ​thalamus

  • ​gustatory cortex in the temporal lobe

• ​Phantogeusia

  • ​lingering unpleasant taste

• ​hypogeusia

  • ​loss or reduced ability to perceive one type of taste sensory cell

• ​ageusia

  • ​usually temporary loss of all taste sensation

• ​Hairy tongue

  • ​extra long papillae due to lack of shedding, altering taste perception