Vertebrates 17 - Sense Organs

Question 1

General properties for sensing

Answer 1

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

Question 2

Receptor types

Answer 2

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

Question 3

Receptor properties

Answer 3

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

Question 4

Adaptation

Answer 4

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

Question 5

Phasic and tonic

Answer 5

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

Question 6

Taste receptors (gustation)

Answer 6

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

Question 7

Taste bud location

Answer 7

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

Question 8

5 tastes

Answer 8

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)

Question 9

Taste mechanisms: Salt

Answer 9

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

Question 10

Taste mechanisms: Sour

Answer 10

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

Question 11

Taste mechanisms: Sweet, Bitter, Umami

Answer 11

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)

Question 12

Taste receptors in aquatic animals

Answer 12

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.

Question 13

Minnow taste receptors

Answer 13

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

Question 14

Barbels

Answer 14

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

Question 15

Evolution of taste

Answer 15

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

Question 16

Taste receptors in birds

Answer 16

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.

Question 17

Taste: short or long distance?

Answer 17

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

Question 18

Olfactory receptors

Answer 18

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

Question 19

Nasal epithelia

Answer 19

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

Question 20

Turbinate bones in different vertebrates.

Answer 20

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.

Question 21

Odorant receptor proteins

Answer 21

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

Question 22

Transduction mechanism

Answer 22

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.

Question 23

Difference b/w taste and smell

Answer 23

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

Question 24

Smell transmitted to brain pathway

Answer 24

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.

Question 25

Odor and memory

Answer 25

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.

Question 26

Odor and aquatic vertebrates

Answer 26

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

Question 27

Nares of shark

Answer 27

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

Question 28

Snake smell

Answer 28

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

Question 29

Pheromones

Answer 29

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.

Question 30

Flehmen response

Answer 30

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

Question 31

Innervation of pheromones

Answer 31

Separate from normal olfactory, processes in accessory olfactory bulb.

Question 32

Birds and smell

Answer 32

Minimal, not very useful since they are generally far away so there are less olfactory trails. Exception is the vulture. They look for dead food, which is generally smelly. Able to find hidden dead animals (but that’s hard to study in natural environment!)

Question 33

T-Rex and smell

Answer 33

Olfactory bulb was very large (from fossilized brain case made into brain cast). Possible that T-Rex was a scavenger and was able to smell decay.

Question 34

Arterial chemoreceptors

Answer 34

Carotid and aortic bodies (innervated by carotid sinus and the vagus nerves), and medullary receptors. Sense changes in O2, CO2, pH in blood. They control respiration.