Olfaction and Gustation Flashcards
Anosmia
Reversible hyposmia
Hyperosmia
X smell
common reason is from cold
thickened mucus blocks odorants to bind
migraine, psychotic states, pregnancy (increased smell)
Aguesia
X Taste
Tastants
chemical compounds binding to taste receptors for taste
Odorants
Chemical compounds that bind to odorant receptors for odors
5 primary tastes
sweet, sour, salty, bitter, umami
how taste buds send signal to
Taste buds are specialized epithelial cells
APICAL: taste receptors, the chemosensory transduction
(microvilli, taste receptors, voltage gated, TRP R)
BASOLATERAL: neurotransmitter release (serotonin, ATP)
—–> Primary Sensory Neuron to the brain
Salt, or acid (sour) molecule binds to what
flows into ion channel—-> influx of Positive ions—> depolarization—-> increase Ca+ as Na+ flows into the cell
(voltage gated Ca+)
Ca+ = helps vesicles of neurotransmitters bind and release on the basolateral PM
SEROTONIN
sweet, bitter, umami moelcule binds to what
binds to G-coupled PR—-> second messengers —-> depolarization —–> increase Ca+ as Na+ flows in to the cell (voltage gated Ca+)
Ca+ = helps vesicles of neurotransmitters bind and release on the basolateral PM
ATP
SOUR (acid) Receptor and NT
they are H+ Ions flowing through the ion channel
serotonin
SWEET Receptor and NT
Sugars binding to GPCRs
ATP
BITTER Receptor and NT
Various compounds binding to GPCR
ATP
SALTY Receptor and NT
Na+ Ions binding to the ENsC ion channel for Na+
Serotonin
UMAMI Receptor and NT
Glutamate binds to mGluR4 GPCR
ATP
Humans have how many Odorant Receptor Neurons
350 different ones
12 million total
very sensitive to odors
Olfactory cells are and release
bipolar neurons
Glutamate (BASOLATERAL) released on axons to go to the brain
have basal cells support cells inside
1 ODORANT
can stimulate many odorant receptors (we have 350)
the combination of the receptors stimulated by that odorant cause a unique signature for that odor
How does concentration of an odor change how it smells and binds
the more concentration the more receptors it binds to (we have 350) and the smell can be completely different/
LOW: maybe 1 receptor, flowers
HIGH: maybe 8 receptors and smells bad
Sensory Transduction Cascade in the ORN
- Odorant diffused into the mucus of nasal cavity
- binds to the OR proteins (GPCRs) = Golf on olfactory cilia (Olfactory cell is activated= ORN activaed)
- secondmessenger cAMP
- Cyclic- nucleotide gated channels open (CNGC) Ex: cAMP opens it
- Na+ and Ca+2 influx
- some Depolarization
- Ca+2 gated Cl- channels open (cl- leaves) (from step 5 Ca+2 influx binding)
- Ca+2 gated Na+ channels open (Na+ enters) (from Ca+2 from step5)
- more real depolarization for action potential to happen
Olfactory Adaptation
- cAMP is broken down by enzymes when it sticks around for a while
- Ca+ binds to calmodulin —> lowers CNGC affinity to cAMP
- odorant receptor (Golf) gets phosphorylated –> lowers sensitivity to odorant
Bitter receptors and how they function
their GPCRs are very sensitive to very low levels of tastant and innately dont like it
TO AVOID POISONOUS COMPUNDS
you can learn to tolorate this taste (coffee, green leafy veggies, citric fruits) to overcome this
Sweet receptors
signal presence of carbs for energy source
you like this when you need energy
Salty receptors
signal to control Na+ intake for body water balance and BP, blood circulation
Umami receptors
signals a foods protein content, good for us
Sour receptors
signals to dietary acids (H+), can be aversive (you dont like) to maintain acid-base balance in body
Also, spoiled food is often acidic
Age related Gustatory sensitivity decline
(around 60yo)
taste buds decline
remaining taste buds shrink
less saliva made= affects taste
OTHER FACTORS: medication, disease, smoking, pollution, toxins
Age related Olfactory sensitivity decline
(around 70yo)
ORN fibers and receptors decline
nasal mucus declines
OTHER FACTORS: medication, disease, smoking, pollution, toxins
sensitivity decline by age health problems
loss of taste and smell= more flavoring of salt and spices and sugar added to foods
HTN, and DM, and bad health effects
can also cause loss of appetite and depression, impaired immunity
when does the smell and taste start
in utero
to prepare the fetus fro future food and environment by tasting the amniotic fluid
also primes them to want breastmilk
Newborns respond to what taste
SWEET tastes
they can act as an analgesic for them
can cause rapid calming effect and decrease some moderate to mild pain short-term
SUCROSE given in hospitals
How does sweet-solution analgesia work
- brain arousal suppressed when distracted from procedure
- rewarding effect= lowers stress and promote calm
- Anit-nociceptive: SUCROSE activats RF and PAG in rats and activates beta-endorphins release (in infants) which acts to activate the endogenous opioid system
sweet preference during adulthood
declines
high during childhood due to evolutionary sweet = energy and nutrients needed for growth
however, modern world has many sweet foods with no nutrients causing future unknown effects
how to block and mask bitter tastes, from medicine, or coffee and alcohol
Salt: suppress bitter taste at the bitter taste receptors (mono-sodium glutamate and sodium gluconate)
Sweet: suppress bitter taste by having more activation sites in the brain, so masks the bitter signals
nerve pathway for gustation
taste bud–> solitary nucleus —-> (as central tegmental tract) VPM nucleus of thalamus—-> through internal capsule to GUSTATORY CORTEX
three regions of the gustatory cortex
- Postcentral gyrus
- Frontal Operculum
- Insula
somatosensory input to taste
disliking texture of food
CN7 CN9 CN 10 taste —>
- Nucleus tractus solitarius
- VMP of thalamus —> Gustatory cortex –> orbitofrontal cortex, amygdala, and hypothalamus
- Hypothalamus
- Amygdala
CN 10
epiglottis taste, and visceral activity
CN 9
posterior 1/3 taste
CN 7
anterior 2/3 taste
VMP
discriminative taste begins, relay station
Gustatory Cortex
discriminative aspects of taste
Orbitofrontal cortex
integrates visual, somatosensory from mouth, and olfaction and gustation combined
Amygdala
gets info from Gustatory cortex
emotional context and memories to eating
together with nucleus tractus solitarius
Hypothalamus
gets info from Gustatory cortex
homeostatic mechanisms of eating= hunger working together with nucleus tractus solitarius
Limbic System = amygdala and hypothalamus
eating and calming effects of food = reward and limbic system
Medullary Reflex Arcs
for swallowing, salivating, mimetic responses to food happening in the nucleus tractus soitarius
1 olfactory neuron has
many of the same odorant receptors
same odorant receptor on all its cilia
many of the same odorant receptors go through the cribiform plate to converge into the same glomerulus (inside the olfactory bulb)
input to glomeruli
to a mitral/tufted cell in the mitral layer —-> lateral olfactory tract going to the brain
olfactory buld
(GLOMERULUS)
mitral cells—> brain
granule cells (interneuron that release GABA to increase specificity of signal)
periglomerular cells (interneuron that release GABA to increase specificity of signal)
NT released from Olfactory neurons —-> glomeruli (mitral cells)
NT released from mitral neurons—–> (as lateral olfactory tract) Brain Primary Olfactory cortex
GLUTAMATE
GLUTAMATE ?
Primary Olfactory Cortex, is different how
does not go through the thalamus
6 parts of the Primary Olfactory Nucleus
- Anterior Olfactory Nucleus–> SAME + OPPOSITE COTICIES of the BULB (relay station)
- Olfactory tubercle
- PIRIFORM CORTEX —> Hypothalamus (control appetite, hunger)
- —> thalamus (integrate taste, smell, and sight, to appreciate food flavor) - Anterior Cortical Amygdaloid Nucleus— >hypothalamus (emotional learning, olfactory fear conditioning)
- Periamygdaloid cortex—> hypothalamus (interegrational of emotion to food from SMELL)
- Lateral Entorhinal cortex—> hippocampus (memory formation, connects to limbic system and entroichinal cortex for memory of ODOR experience
Anterior Olfactory Nucleus–>
- Anterior Olfactory Nucleus–> SAME + OPPOSITE COTICIES of the BULB (relay station)
PIRIFORM CORTEX —>
PIRIFORM CORTEX —> Hypothalamus (control appetite, hunger)
—-> thalamus (integrate taste, smell, and sight, to appreciate food flavor)
Anterior Cortical Amygdaloid Nucleus— >
Anterior Cortical Amygdaloid Nucleus— >hypothalamus (emotional learning, olfactory fear conditioning)
Periamygdaloid cortex—>
Periamygdaloid cortex—> hypothalamus (interegrational of emotion to food from SMELL)
Lateral Entorhinal cortex—>
Lateral Entorhinal cortex—> hippocampus (memory formation, connects to limbic system and entroichinal cortex for memory of ODOR experience
neurogenesis happens where
olfactory bulb and dentate gyrus of hippocampus
loss of smell can indicate what in the future
even early loss of smell is the first indicator for someone to develop parkinsons later int he future or other neurodegenrative diseases can be linked
