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Block 5; Week 2 > Chemical Senses-Von > Flashcards

Chemical Senses-Von Flashcards

1
Q

About how many olfactory cells do dogs have?

A

1 billion or more

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2
Q

Which is longer: the olfactory nerves or the olfactory tract?

A

the olfactory tract is much longer

the olfactory nerve is short, comes from the olfactory bulb & pierces thru the cribriform plate.

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3
Q

T/F It is easy to rupture olfactory nerves.

A

True. It is…if that happens you could get leakage of CSF into the olfactory cavity. It can look like nasal secretions, but really it is CSF & then you have to be concerned about bacteria that can get into the brain.

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4
Q

Past the cribriform plate there are receptor cells. What do these look like?

A

these are bipolar cells. They have cilia extending into the mucus. They have olfactory knobs near the cilia.

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5
Q

What makes the mucus past the cribriform plate? What is its fcn?

A

the Bowman’s gland

mucus has a protective function, immunoglobulins are found there…

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6
Q

T/F the cilia are actively motile in the nose.

A

False. They just extend into the mucus.

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7
Q

Which cell types are found in the olfactory epithelium?

A

stem cells, basal cells, receptor cells, supporting cells, Bowman’s glands

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8
Q

Are the axons of the olfactory nerves myelinated?

A

No. They are unmyelinated, b/c they are short & they don’t need to be.

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9
Q

How do you stimulate the olfactory receptor cells?

A

the odorants bind to the cilia on the olfactory receptor cells.
they will NOT bind to the body of the receptor. This causes polarization.

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10
Q

What percent of mammalian genes are devoted to odorant receptors?

A

3-5 percent

Note: these odorant receptors on cilia are transmembrane.

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11
Q

Describe what happens when an odorant binds a transmembrane receptor on the cilia of a receptor cell.

A

Odorant molecule binds receptor protein.
G protein activated.
Golf has GTP bound & activates adenylate cyclase.
ATP–>cAMP
cAMP activates the Na+/Ca++ channel. Na+ & Ca++ flow thru.
Ca++ binds CAM and activates the Ca++ gated Cl- channel.
Cl- leaves the cell.
Ca++ also activates the Na+/Ca++ exchanger.

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12
Q

What’s the deal behind combinatorial receptor codes for odors?

A

have maybe 100 odorant receptors that are specific to different types of odors.
can distinguish b/w like 10,000 odors b/c different combinations of activation–>different odors.

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13
Q

What are the layers of the olfactory bulb?

A

Glomeruli (closest to the cribriform plate)
External Plexiform Layer
Mitral Cell Layer
Granule Cell Layer

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14
Q

What do you find in the glomeruli of the olfactory bulb?

A

a small cluster of nerve fibers from the olfactory nerve, filae
here they synapse with dendrites of mitral cells and tufted cells

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15
Q

Where do you find dendrites in the layers of the olfactory bulb?

A

dendrites are found in the mitral cell layer

they end up synapsing with filae in the glomeruli of the olfactory bulb

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16
Q

What are the interneurons that are found in the retina?

A

horizontal cell
amacrine cell
**these connect receptor, bipolar, & ganglion cells

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17
Q

What are the interneurons that are found in the olfactory bulb?

A

periglomerular & granule cells

**these connect receptor & mitral cells

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18
Q

What do the periglomerular cells connect?

A

they are found in the olfactory bulb & they connect the glomeruli!

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19
Q

Where do the mitral & tufted cells extend?

A

they project into the olfactory cortex

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20
Q

T/F The mitral cells synapse in the thalamus before extending into the olfactory cortex.

A

False. They are second order neurons & they don’t synapse in the thalamus, but go directly to the olfactory cortex.

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21
Q

When the olfactory projections go to the cortex, where do they go?

A

they go the uncus (a part of the pyriform cortex)

there are also projection to another part of the pyriform, the amygdala.

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22
Q

The pyriform cortex is a medial projection of which lobe?

A

the temporal lobe.

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23
Q

T/F Olfactory bulb projects directly into the cortex.

A

True.

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24
Q

T/F Olfactory sensitivity decreases with age.

A

True.

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25
Q

What is anosmia? Which syndrome is this seen in?

A

loss of smell

Kallmann syndrome

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26
Q

Aside from anosmia, what else is seen in Kallmann syndrome?

A

this is a genetic condition which consists of not starting puberty.
Includes hypogonadism.

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27
Q

What is hyposmia?

A

reduction in smell

28
Q

What are some possible causes of hyposmia?

A 
viral
sinus infection
head trauma
decreases with age
alteration in pregnancy
smoking
29
Q

What are the 3 CN that mediate taste? Where do they synapse?

A

CN 7, 9, 10
they synapse in the gustatory nucleus in the nucleus solitariis tract.
they also synapse in the ventral posterior medial nucleus of the thalamus.

30
Q

The lateral geniculate nucleus is a part of the ______ pathway. The medial geniculate nucleus is a part of the _____ pathway.

A

Lateral Geniculate Nucleus: visual pathway

Medial Geniculate Nucleus: auditory pathway

31
Q

The part of the cortex that receives tongue info is medial/lateral relative to other structures.

A

It is pretty lateral.

32
Q

The gustatory fibers project to 2 places after they are found in the thalamus at the VPM. What are these 2 places?

A

gustatory cortex aka frontal operculum

insula gustatory cortex

33
Q

Which part of the tongue does CN7 contribute to taste?

A

the anterior 2/3 of the tongue-taste buds

34
Q

Which part of the tongue does CN9 contribute to taste?

A

posterior 1/3 of the tongue-taste buds

35
Q

Which part of the tongue does CN10 contribute to taste?

A

taste buds of the epiglottis

36
Q

Taste seems to be an emotional experience b/c the insula communicates with which 2 structures? These also communicate w/ the thalamus.

A

hypothalamus

amygdala

37
Q

What is the rough distribution of flavors around the tongue?

A

bitter on the back
sour & salty on the sides
salt near front
sweet near front

38
Q

What are the 3 types of taste buds?

A

Circumvallate papillae
Fungiform papillae
Foliate Papillae

39
Q

Describe the structure & location of circumvallate papillae?

A

there are trenches on both sides w/ taste buds on either side
they are mainly in the back of the tongue
innervated by CN9

40
Q

Describe the structure & location of fungiform papillae?

A

these have their taste buds on the top
CN7
more near the front of the tongue

41
Q

Describe the structure & location of foliate papillae?

A

these are on the back & the side
have serous glands associated with it
taste buds are in its sides/trenches
CN9

42
Q

How many taste cells does each bud have? How often do they need to be replaced?

A

50-150 taste cells

replaced every 2 weeks

43
Q

Which cells in the taste buds replace the old taste cells?

A

the basal cells replace them!

44
Q

Do receptor cells have their own axons?

A

no, they synapse with CN nerves

45
Q

Describe the structure of the taste pores of the taste buds?

A

they have microvilli that extend into the open space

46
Q

Which part of the taste bud makes up the apical domain? Basal domain?

A

The taste pore with its microvilli makes up the apical domain. The basal domain is the body of the taste bud. then you have your gustatory afferent axons.

47
Q

What special things happen at the apical domain of the taste bud?

A

There are ion channels & G-coupled receptors that respond to certain flavors. This activates second messengers & causes a cascade effect.

48
Q

What special things happen at the basal domain of the taste bud?

A

The TRPM5 channel opens up.
Na+ channel opens up to let Na+ in.
K+ channel opens up to let K+ out.
Ca++ channel opens up to let Ca++ in.

49
Q

What happens after the TRPM5 & other channels are opened in the taste bud?

A

then Ca++ enters in the cell from the outside & from the ER.
this allows synaptic vesicles with NT to be released from the taste bud.

50
Q

Once the synaptic vesicles with NT are released from the taste bud…what happens next?

A

they are released
they then activate the primary neurons w/ gustatory afferent axons.
This AP sends info to the ganglion & to the nucleus solitarii tract.

51
Q

What types of flavors affect the ion channels in the apical domain?

A

salt

sour

52
Q

What types of flavors affect the G protein coupled receptors on the apical domain?

A

sweet
bitter
umami
**this activates 2nd messengers!

53
Q

What types of NT are released from taste buds?

A

ATP
Serotonin
GABA

54
Q

What is Ageusia?

A

loss of taste

55
Q

What is hypogeusia?

A

reduction of taste

56
Q

What are possible causes of loss of taste?

A 
smoking
Cystic Fibrosis
Bell's Palsy
Oropharyngeal tumors
Chemotherapy-prevents necessary turnover of taste buds
57
Q

What is cacogeusia?

A

extremely unpleasant taste

58
Q

What can cause cacogeusia?

A

schizophrenia & other psychiatric disorders

59
Q

What are some chemosensitive structures that are innervated by the trigeminal nerve?

A

nose
cornea
tongue
teeth

60
Q

What is the function of chemosensitive structures?

A

alert to harmful stimuli & initiate their removal

61
Q

T/F There are some receptor cells in the tongue that resemble taste receptors that are innervated by the trigeminal nerve.

A

True.

62
Q

The ciliary nerves & ethmoid nerves both come off of the opthalmic division of the trigeminal nerve. What do they innervate?

A

ciliary nerves–>cornea

ethmoid nerves–>nose

63
Q

What does this mean: General rule–>3 neurons to the cortex?

A

usu you have a receptor that may be specialized.
Then there are 3 neurons & you get to the cortex.
1. Bipolar or Ganglion Cell–>Sensory nucleus
2. Sensory Nucleus–Thalamus
3. Thalamus—>Cortex

64
Q

What is an exception to the 3 neurons to the cortex rule?

A

Olfaction.

65
Q

Ascending projections of cochlear nuclei: ____________ prior to thalamus.

A

goes to the superior olivary nucleus before it goes to the thalamus.

66
Q

What does MSO stand for? What does this structure help you do? This can detect differences in inter aural time of ______ microseconds.

A

medial superior olive
helps you to position yourself based on what you hear. Tell which ear the sound is closer to.
10 microseconds!

67
Q

What is the order of events of hearing something closer to your left side?

A
  1. Left ear hears sound.
  2. AP begins traveling toward MSO
  3. Right ear hears sound.
  4. AP begins traveling toward MSO
  5. APs converge on MSO. This is most strong if they converge at the same time.

Block 5; Week 2 (8 decks)

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