AP 2 3.3 Olfactory and Gustatory Systems Flashcards
olfaction
Smell (olfaction) is a special sense and is one of the chemical senses. Olfactory receptors are activated by airborne chemical substances dissolved in fluid on the surface of nasal mucous membranes.
Olfactory nerves
Olfactory nerves (CN 1) are bipolar receptor cells found in the olfactory epithelium on the roof of the nasal cavity. The olfactory nerves travel through the ethmoid bone in a location called the cribriform plate. The dendrites extend from the cell body to the surface of the epithelium where it terminates in the olfactory bulbs, which are paired masses of gray matter
olfactory bulbs,
The dendrites extend from the cell body to the surface of the epithelium where it terminates in the olfactory bulbs, which are paired masses of gray matter In the olfactory bulbs, olfactory nerve axons synapse with other cell bodies of the olfactory pathway.
olfactory tracts
In the olfactory bulbs, olfactory nerve axons synapse with other cell bodies of the olfactory pathway. The axons then travel together from the olfactory bulbs to form the olfactory tracts, which carry information to the temporal lobes. Here, the signals are interpreted in the primary olfaction area as smell.
seven primary odors
Generally, odors can be isolated to seven primary odors: floral (roses), ethereal (dry-cleaning fluid), camphorates (mothballs), musky (perfumes), peppermint (mint gum), pungent (vinegar) and putrid (rotten eggs).
odor interpreted by the brain
Any odor interpreted by the brain is due to a combination of many different chemical substances.
Smell
Smell is defined as a combination of a limited number of primary odors that are detectable by the brain. Animals, such as dogs, have a much wider range of detectable smells and, therefore, have a larger amount of brain space dedicated to smell interpretation. Generally, odors can be isolated to seven primary odors: floral (roses), ethereal (dry-cleaning fluid), camphorates (mothballs), musky (perfumes), peppermint (mint gum), pungent (vinegar) and putrid (rotten eggs).
Gustatory System
The gustatory system is responsible for the special sense of taste. Taste (gustation) is one of the chemical senses because its receptors are activated by chemical substances dissolved in saliva. Taste receptors are inside taste buds mostly on the tongue but are also throughout the mouth and throat.
tongue
The tongue is responsible for gripping food and repositioning it between the teeth, forming it into a compact mass called a bolus. The tongue pushes the bolus back to the pharynx to begin the process of swallowing.
root of the tongue
the root of the tongue is attached to the floor of the posterior surface of the mouth.
apex of the tongue
The apex of the tongue is located anteriorly,
frenulum
The frenulum is located on the inferior surface of the tongue along the midline
papillae
The tongue contains papillae, which are raised bumps on the tongue. There are three types of papillae that help to grip food on the tongue: circumvallate, fungiform, and filiform. Circumvallate and fungiform papillae both contain taste buds
Taste buds
contain chemical receptors that are stimulated by the chemical composition of food. Taste buds are found primarily on the tongue as well as on the surface of the mouth and wall of the pharynx. Taste buds are formed from gustatory cells and supporting cells.
Gustatory cells
are the chemoreceptor cells inside the taste buds. Each gustatory cell terminates in a gustatory hair, which projects into the saliva to detect dissolved chemicals.
Supporting cells
form the bulk of the taste bud and separate the taste receptors cells from one another
Basal cells
serve as stem cells, which divide and differentiate into new supporting cells that then form new gustatory cells.
mouth also contains nociceptors (pain receptors) and thermoreceptors
The mouth also contains nociceptors (pain receptors) and thermoreceptors (temperature receptors) that also contribute to the taste experience of foods. Both temperature (such as hot tea) and spice (such as hot peppers) impact how taste is perceived by the brain.
taste pathway begins
The taste pathway begins as food chemicals contact the gustatory hairs, which generate an action potential in dendrites that are wrapped around the gustatory cells. The nerve impulse is carried by afferent fibers through two cranial nerve pairs, the facial nerves, and the glossopharyngeal nerves, which transmit the impulse to the thalamus and ultimately to the parietal lobe to be interpreted as taste. The facial nerve carries information from the anterior two-thirds of the tongue, while the glossopharyngeal nerve carries information from the posterior one-third of the tongue.
Anosmia
Pathology of Olfactory and Gustatory Special Sensory Systems
Anosmia is the loss of smell. It is common to have anosmia after a traumatic brain injury. Anosmia from a TBI can be temporary or permanent depending on the severity of the injury and what part of the pathway was damaged. Anosmia can also happen gradually, such as in the case of a growing brain tumor that blocks the olfactory pathway.
five primary tastes
There are five primary tastes: sweet, salty, sour, bitter, and savory (also called umami). The sweet taste is produced by many compounds, including sugars and some amino acids. The salty taste is produced by many metal salts, especially NaCl. The sour taste is produced by acids like acetic acid (in vinegar). The bitter taste is produced by many drugs like aspirin. The savory taste is due to certain amino acids and is found in many foods like fish, ripe tomatoes, aged cheeses, and soy sauce.
Ageusia
Pathology of Olfactory and Gustatory Special Sensory Systems
Ageusia is the loss of the sensation of taste. Stimulation of olfactory receptors has a great effect on the sensation of taste in addition to taste bud stimulation. When the olfactory receptors are obstructed by nasal congestion or other factors, the sensation of taste is dulled or completely lost. Other factors, such as TBI or a brain tumor inside the brain, can also cause ageusia if the taste pathway is damaged.
