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anatomy: olfactory taste Flashcards

1
Q

chemical senses

A

gustation (taste) and olfaction (smell)

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2
Q

chemoreceptors of chemical senses respond to chemicals in ____

A

aqueous solution

gustation - dissolved in saliva
olfaction - dissolved in fluids of nasal membranes

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3
Q

olfactory epithelium

A

roof of nasal cavity
contains OLFACTORY RECEPTOR CELLS (olfactory neurons)

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4
Q

olfactory neurons/ olfactory receptor cells

A

replaced every 4-8 weeks (formed from basal stem cells)
- just a few molecules are sufficient to activate an olfactory receptor cell/ olfactory neuron
- respond to thousands of different odor-causing chemicals

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5
Q

olfactory cilia

A

a dendrite is directed downwards towards mucus on olfactory epithelium and branches into olfactory cilia in the mucus

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6
Q

mucus

A

captures airborne ODORANTS (chemicals capable of detection of receptors)

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7
Q

odorants/ odors

A

1000 receptors that differentiate 10,000 odors
- may take many odorant receptors to build an odor
- just a few molecules are sufficient to activate an olfactory receptor cell

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8
Q

G protein coupled activation and amplication of an odorant signal

A
  1. odorant binds to its receptor (on G protein couples olfactory receptor)
  2. receptor activates G protein (Golf) (GDP to GTP)
  3. G protein activates adenylate cyclase which converts ATP into cAMP
  4. cAMP opens cation channel (ligand gated) for Na+ and Ca2+ influx into cilium causing DEPOLARIZATION (Ca2+ potential = +140mV)
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9
Q

second messanger cAMP acts as an intracellular ligand to activate _____ to produce ___

A

ligand-gated ion channels
EPSPs

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10
Q

transmission of smell!!!

A

AXONS of olfactory receptor cell ascend up through the bony roof of the NASAL CAVITY via tiny holes in CRIBRIFORM PLATE of the ethmoid bone into the CRANIAL CAVITY

they reach OLFACTORY BULBS and synapse with MITRAL CELLS

the MITRAL CELL AXONS form the olfactory tracts/ nerve

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11
Q

olfactory tracts have 2 destinations

A
  1. olfactory cortex - smell interpreted and identified (inferior frontal lobe)
  2. limbic system - memories and emotions associated with smells are activated

*SMELL is only input that DOES NOT PASS THROUGH THALAMUS

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12
Q

olfactory pathway

A
  1. mitral cell activated
  2. impulses flow from OLFACTORY BULBS via olfactory tracts to PIRIFORM LOBE of OLFACTORY CORTEX
    2 major pathways from olfactory cortex to various parts of brain…
    2a) olfactory tubercle
    2b) olfactory cortex
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13
Q

olfactory cortex and gustatory cortex are in the…

A

insula (both very close to each other in this region)

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14
Q

cerebral activations with TWO odorants

A

main clusters are bilaterally in amygdala and neighbouring cortex and in RIGHT INSULA and orbital gyrus (P < 10-6, corrected)

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15
Q

inorder to be tasted, a chemical must…

A
  • be dissolved in saliva
  • contact gustatory hairs
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16
Q

binding of chemical:

A

DEPOLARIZES taste cell membrane, releasing NT onto SENSORY NEURON

initiates generator potential –> AP in the sensory neuron that is carried back to brainstem

17
Q

branches of cranial nerves

A

carries taste info from TONGUE to BRAIN STEM
- facial nerve VII
- glossopharyngeal nerve

18
Q

facial nerve VII (first nerve)

A

ANTERIOR TWO-THIRDS of tongue
- first nerve is the branch that innervates the BRAIN STEM (from the tongue)

19
Q

glossopharyngeal nerve IX

A

POSTERIOR ONE-THIRD of tongue
- carries together with facial nerve back to brain stem

20
Q

taste organ (successive magnification)

A

10,000 taste buds (sensory organs) are located in PAPILLAE (small rounded protuberance) on tongue

each taste bud has more than 50 epithelial cells of two types:
- GUSTATORY epithelial cells (sensory taste cells)
- BASAL epithelial cells (stem cells)

21
Q

simple receptor

A

olfactory receptor

22
Q

complex receptor

A

gustatory receptor

23
Q

taste reception depends on

A

specialized gustatory receptor cells that detect the taste signal and relay it to gustatory afferent nerve terminals facial and glossopharyngeal

24
Q

taste sensations:

A

sweet (sugars, saccharin, alcohol, some a.a.)
salty (metal ions)
sour (hydrogen ions)
bitter (alkaloids like quinine and nicotine)
umami (elicited by AMINO ACIDS and glutamate)
- savory: meats, cheese, protien foods, heartiness

25
Q

taste receptors - transduction pathways for the 5 taste receptors: SALTY

A

direct ion channel for Na+ influx

26
Q

taste receptors - transduction pathways for the 5 taste receptors: SOUR

A

direct ion channel for Na+ influx and K+ efflux, mediated by H+

27
Q

taste receptors - transduction pathways for the 5 taste receptors: BITTER, SWEET, UMAMI

A

transduction with G proteins (opens Cl- or nonspecific channels)

28
Q

the tongue also has…

A

somatosensory receptors: touch, thermal, etc…

29
Q

Gustatory cells - TASTE CELLS (where receptors are found)

A
  • microvillae (gustatory hairs) that extend through taste pore into saliva to detect chemicals
  • gustatory hairs have membrane receptors for gustatory chemicals
  • gustatory receptor cells are replaced every 7 days (8 times FASTER THAN OLFACTORY NEURON)
  • taistant (equivalant to odorant) binds to specialized receptors on gustatory hairs and graded potentials that cause release of NT which activates gustatory afferent fibers
30
Q

taste buds

A

most of 10,000 are on tongue
in PAPILLAE (BUMPS) ON TONGUE

31
Q

structure of taste bud

A

gourd shape with 3 major cell types
1. SUPPORTING CELLS (insulate receptor)
2. BASAL CELLS - dynamic stem cells (reproduce taste cells)
3. GUSTATORY CELLS - taste cells

32
Q

gustatory afferents

A

nerve endings that receive inputs from from gustatory cells and project to brain stem

each receives input from several gustatory cells

33
Q

taste transduction: stimulus energy of taste is converted into a nerve impulse by:

A
  • Na+ influx in salty tastes
  • H+ in sour tastes (opening cation channels to directly enter or block K+ channels)
  • gustducin is involved in G protein coupled receptors for sweet and bitter tastes
34
Q

gustatory pathway

A

CN VII and IX carry impulses from taste buds to SOLITARY NUCLEUS OF MEDULLA

these impulses travel to the THALAMUS and branch to:
1. gustatory cortex (taste)
2. hypothalamus and limbic system (taste appreciation)

35
Q

influence of other sensations on taste

A
  • taste is 80% SMELL
  • THERMORECEPTORS, MECHANORECEPTORS, NOCICEPTORS influence tastes
  • TEMP and TEXTURE enhance or reduce taste
36
Q

taste pathway

A

afferent fibers are in:
1. Facial nerve VII (anterior 2/3rds)
2. Glossopharyngeal nerve IX (posterior 1/3rd)
3. impulses from epiglottis and lower pharynx are conducted also by Vagus nerve X

all cranial nerves project to SOLITARY NUCLEUS OF MEDULLA (brain stem)

CROSS MIDLINE AT MEDULLA and innervate THALAMUS

thalamic neurons project to GUSTATORY CORTEX IN INSULA

there are also projections to HYPOTHALAMUS and LIMBIC SYSTEM for taste APPRECIATION

37
Q

taste pathway

A

afferent fibers are in:
1. Facial nerve VII (anterior 2/3rds)
2. Glossopharyngeal nerve IX (posterior 1/3rd)
3. impulses from epiglottis and lower pharynx are conducted also by Vagus nerve X

all cranial nerves project to SOLITARY NUCLEUS OF MEDULLA (brain stem)

CROSS MIDLINE AT MEDULLA and innervate THALAMUS

thalamic neurons project to GUSTATORY CORTEX IN INSULA

there are also projections to HYPOTHALAMUS and LIMBIC SYSTEM for taste APPRECIATION

38
Q

taste is also important for development of dietary habits

A
  • mutations in panda T1R1 gene involved in G protein umami pathway
  • panda cannot taste meat now so they eat bamboo
39
Q

umami

A
  • taste associated with AMINO ACIDS and common in protein heavy foods like MEAT
  • sensed through T1R gene family in carnivores
  • pandas have mutation of T1R gene so the T1R1 gene is inactivated and they can no longer taste meat and they are VEGAN

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