Physiology of special senses: Taste and Smell Flashcards
What is the olfactory epithelium?
a pseudostratified epithelium, located in the roof of the nasal cavity.
Afferent fibers carrying taste information are found primarily in which two cranial nerve pairs?
Facial nerve
Glossopharyngeal
What is the role of the facial nerve in the neural pathway of taste/gustatory?
transmits impulses from taste receptors in the anterior two-third of the tongue
What is the role of the glossopharyngeal nerve in the neural pathway of taste/gustatory?
services the posterior 1/3 & pharynx just behind
Taste impulses from the few taste buds in the epiglottis and the lower pharynx are conducted by the
vagus nerve
The impulses received in the gustatory pathway travel to the thalamus, and from there fibers branch to the:
- Gustatory cortex (taste)
- Hypothalamus and limbic system (appreciation of taste)
How does a chemical bind during the activation of taste receptors?
- Depolarizes the taste cell membrane, releasing NT onto the sensory neuron
- Initiates a depolarizing GP that causes NT release.
- Binding of the NT to the sensory dendrites triggers AP in these fibers.
- Then is carried back to the brainstem
what are the Three different mechanisms that underlie how we taste?
- Salty taste is due to Na+ influx through Na+ channels, which directly depolarizes gustatory epithelial cells
- Sour is mediated by H+ (by directly entering the cell, by opening cation channels, or by blockade of K+ channels), which acts intracellularly to open channels that allow other cations to enter
- Bitter, sweet, and umami Activation leads to the release of Ca2+ from intracellular stores, which causes cation channels in the plasma membrane to open, thereby depolarizing the cell and releasing the neurotransmitter ATP.
How is smell transmitted?
- The axons of the olfactory receptor cell ascend up through the nasal cavity via the cribriform plate of the ethmoid bone into the cranial cavity
- They reach the olfactory bulbs and synapse with nmitral cells
Taste reception depends on what?
depends on specialized gustatory receptor cells that detect the taste signal and relay it to gustatory afferent nerve terminals CN VII or CN IX.
What are the differences in gustatory epithelial cells and their thresholds for activation?
- the bitter receptors detect substances present in minute amounts.
- The other receptors are less sensitive.
- Taste receptors adapt rapidly, with partial adaptation in 3–5 seconds and complete adaptation in 1–5 minutes.
The tongue also has _____ receptors
somatosensory
What are gustatory hairs?
Long microvilli project from the tips of all gustatory epithelial cells and extend through a taste pore.
Describe gustatory epithelial cells.
- The gustatory hairs have membrane receptors for gustatory chemicals
- Gustatory receptor cells are replaced every 7 days
What are basal epithelial cells?
- They divide and differentiating into new gustatory epithelial cells
