Vertebrates 17 - Sense Organs Flashcards Preview

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Flashcards in Vertebrates 17 - Sense Organs Deck (34)
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General properties for sensing

Receptor cells to afferent neurons to CNS. External: olfactory, hair cells, taste buds. photoreceptors; internal: baroreceptors, proprioceptors


Receptor types

Chemical: olfactory, taste; Mechanical: touch, pressure, sound waves; electrical: electric fields; Thermal: temp, infrared; Light: photoreceptors


Receptor properties

Selective:have selective receptor proteins; Sensitive: can respond to very small stimuli; Threshold of detection; receptor potential: latency; amplification; adaptation



Rapid and slow??? stops sending stimulus if it doesn’t change


Phasic and tonic

Phasic respond only when stimulus comes; tonic always fire, but can change with stimulus


Taste receptors (gustation)

taste buds are receptor cells (1-2 wks) and sustentacular cells and basal cells (stem cells). Mucous cells, chemicals dissolve in the mucous


Taste bud location

Papillae: folds containing taste buds. Circumvallate: larger, back of tongue; foliate: side of tongue; fungiform: tip, sparse cells


5 tastes

Sweet, salt, bitter, sour, umami (savoury - MSG - glutamate). ALL regions of tongue respond to same stimuli, only in the regions where there are taste buds (front, back, sides)


Taste mechanisms: Salt

Receptor proteins: sodium channels (not voltage gated!); causes depolarization.


Taste mechanisms: Sour

H from acid blocks potassium channels from flowing out, positive charge builds up, depolarizes


Taste mechanisms: Sweet, Bitter, Umami

Sugar binds to sugar receptor, starts signal transduction, blocks K channels, depolarizes. These are tonic receptors, so signal increases when sugar binds. (Bitter and umami same, just different receptor)


Taste receptors in aquatic animals

Buds less developed in agnathans. In fish that can be found in mouth, pharynx, fins, skin, barbels. Most don’t have good taste of salt. Some have some simple chemoreceptors for chemicals, they can “taste” pollution and avoid that.


Minnow taste receptors

500X grater sensitivity to sweet, 200X less to salt



Found in sturgeon, catfish. Usually in muddier waters, bottom feeders. Taste with barbels then vacuum the fish in.


Evolution of taste

Used to detect what is nutritious and what is toxic. Salt taste in terrestrial animals evolved because we need to consume salt to replenish electrolytes


Taste receptors in birds

Generally many less taste buds (chicken has 25, human has 10000). Birds have fairly particular diets, so it doesn’t have the concern of finding toxic food since they aren’t generalists.


Taste: short or long distance?

Vertebrates use taste as short-distance info. You can’t taste from far away durr


Olfactory receptors

Majority in nasal cavity in turbinates in the nasal epithelia. Long cells to brain with projections with cilia on the outside.


Nasal epithelia

Many mucous cells. Traps particles, warm and humidify air as it passes through. Support cells next to receptor cells secrete GFs, maintain ions around cells, etc. Basal cells = stem cells


Turbinate bones in different vertebrates.

Dogs have more turbinate bones and all is covered in olfactory epithelia. Humans have very small epithelia, weaker smell. Mouse has a bit more than humans.


Odorant receptor proteins

Many types, each cell has one type. 1000s of genes (2-4% genome). Shape fits a certain type of molecule


Transduction mechanism

When odorants bind, they activate a pathway: G protein is phosphorylated, adenylate cyclase converts ATP to cAMP, which open cAMP-gated channels, allow Na in and membrane depolarizes.


Difference b/w taste and smell

Both need chemicals, but smell is more sensitive so it can be used as long-distance info.


Smell transmitted to brain pathway

Info passed to olfactory bulb right above the epithelia for processing. Then sent to cortex regions of brain (olfactory cortex). Some smells can trigger epilepsy in some people.


Odor and memory

Purpose to prevent eating noxious food. Highly associated with memory (remember smell a year later, specific pictures only a few months). LTP stimulated in olfactory cortex, memory stored in prefrontal cortex.


Odor and aquatic vertebrates

Well developed in agnathans. Shark olfactory sacs highly folded, lots of surface area. Dominant sensory apparatus.


Nares of shark

Open to the olfactory sacs. Incurrent and excurrent are the same opening (in eel it enters one and exits another).


Snake smell

Snakes use forked tongue to catch molecules and bring them in to their olfactory epithelia



Detected by mid-ventral part of olfactory epithelia called the vomeronasal organs. Usually detected by only animals of same species. Mostly ungulates, cats, not in aquatic tetrapods, bids, bats, primates.


Flehmen response

In cats. Raise upper lips, look like they are smiling but they are actually opening a small duct in palate into vomeronasal organ.