11b chemoreception Flashcards
chemoreception
is the sensory response to a chemical stimulus.
most ancient of all sensory systems.
The medulla which sends signals to the muscles involved in breathing, and the pons which controls the rate of breathing.
interoreceptors
receive stimuli from inside the body
exteroreceptors
receive stimuli from outside the body
minute ventilation
volume (L) of air breathed in one minute.
controlled by the respiratory center in the brainstem
define respiratory center
is made up of three major respiratory groups of neurons, two in the medulla and one in the pons.
In the medulla they are the dorsal respiratory group, and the ventral respiratory group.
ventral respiratory group
controls voluntary forced exhalation and acts to increase the force of inspiration.
pons
dorsal respiratory group
(nucleus tractus solitarius) controls mostly inspiratory movements and their timing.
medulla oblongata
aortic and carotid body receptors
small clusters of chemoreceptors that are part of the major peripheral sensory input
convert the hypoxic signals into an increased neural activity to produce reflex responses in the respiratory and cardiovascular systems.
The respiratory center receives
sensory and peripheral input
If fluid pH changes, the respiratory center triggers a reflex that either
increases respiration rate or
decreases respiration rate
… to keep CO2 partial pressure within normal limits.
2 types of Chemoreceptive exteroreceptor systems can be
olfactory system (smell ) gustatory system (taste )
olfaction
occurs in specialized structures
(e.g., antennae; nose)
usually (not always) located in or on the head
airborne stimuli (molecules) must be dissolved in aqueous solution before they can bind to receptors
gustation
is mediated by specialized organs
usually (not always) located in or near the mouth.
stimuli (molecules) must be dissolved in aqueous solution before they can bind to receptors.
water vs terrestrial gustation and olfaction
In water, stimulus molecules are already dissolved and present in the medium.
This means that taste and smell should be less distinct from each other.
Still, aquatic animals have receptors separated in different body regions.
Labeled lines permit discrimination between chemical stimuli.
Chemical stimuli in terrestrial environments are more distinct than in water.
aquatic fishes gustation and olfaction include
taste receptors both in mouth and on skin
separate olfactory and gustatory systems.
terrestrial gustation and olfaction
Animals must
physically collect stimulus molecules
dissolve them in aqueous fluid
…before the molecules can elicit a receptor potential.
Insect gustatory receptor neurons (GRNs) are located within
bristles or sensilla similar to a mechanosensory sensilla.
bristles? a short stiff hair, typically one of those on an animal’s skin, a man’s face, or a plant.
taste sensillum contains
dendrites of up to four chemoreceptor cells
in some cases, dendrites of one mechanoreceptor
The deterrent cell responds to
[very high salt] and noxious alkaloids.
responds to quinine (a bitter crystalline compound present in cinchona bark, used as a tonic and formerly as an antimalarial drug
tonic = gradually strengtens
Higher stimulus concentration elicits
higher RP frequency.
Each chemoreceptor cell is sensitive to the same or different class of stimulus?
One cell responds to a range of sugar concentrations.
One cell responds to a range of salt concentrations.
One cell responds to plain water (with just enough salt to allow conduction).
Taste sensilla for insects may be located on
the tarsus (terminal segment of the leg; the “foot”)
the proboscis or other mouthpart
antennae
When an insect steps on positive stimulus molecules (e.g., sugars)
receptors trigger mouthpart/proboscis extension reflex
insect automatically samples the potential food source
when an insect steps on negative stimulus molecules (e.g., toxic alkaloid)
- receptors trigger mouthpart/proboscis retraction reflex
- insect automatically avoids dangerous substance
- although one bug’s trash is another bug’s treasure
Flies detect tastants (taste molecules) via gustatory receptor neurons (GRNs) in sensilla on the
labellum (each of a pair of lobes at the tip of the proboscis mouth parts in some insects.)
tarsae ((terminal segment of the leg; the “foot”))
wing margins.
Food inside the mouth is tested by GRNs that are located where?
the taste pegs on the inner labellum and pharynx.
labeled line system
helps to determine which are Attractive responses and aversive responses
from link: The LL model claims in its extreme form that a stimulus identity is encoded by a distinct set of neurons, serves one function, and is conveyed unprocessed from periphery to behavior.
supported by molecular biological studies of the peripheral taste system of mammals and insects by the expression of functionally different receptor proteins in separate populations of taste receptor cells
what type of sensory cells do Vertebrate gustatory receptors have>? also define the word
epithelial sensory cells
each olfactory neuron has how many receptors?
it has a receptor for only one type of smell
glomerulus
bunch of nerve fibers that tranfers info from nose goes to the brain to integrate the stimuli
mitral cells
relay info to the brain and identifies the volatile smell coming from the brain
taste buds
Mammalian taste cells are grouped together
papillae
small swellings on the tongue.
they swell due to Hot foods or drinks can burn your taste buds, causing them to swell up. … Eating spicy foods like hot peppers or foods that are very acidic like citrus fruits can irritate your tongue. stress. Being under stress has been linked to many health issues, including swollen, enlarged papillae.
filiform papillae
located on anterior 2/3 of tongue
most numerous type of papilla
no associated taste receptors
contain mechanoreceptors, and sense touch
are responsible for the tongue’s rough texture
connective tissue core is covered by keratin-rich epithelium
very rough tongues (e.g., cat) have even higher concentrations of keratin
what makes the filiform papillae different from the rest?
it does not have any taste receptors
fungiform papillae
associated with taste receptors
located mostly at the tip of the tongue
also scattered among the filliform papillae
relatively few taste buds
taste buds vs taste receptors
Taste buds contain the taste receptor cells, which are also known as gustatory cells
Each bud has 50-150 receptor cells that differ in morphology and function.
diff taste receptors are:
salty, sweet, bitter, sour, and umami
foliate papillae
associated with taste receptors
located on lateral borders and back of tongue
no keratin, so soft in texture
numerous taste buds
these are the ones that become inflamed and swell, causing annoyance!
circumvallate papillae
associated with taste receptors
located at the back of the tongue
each has thousands of taste buds
in humans, 8-12 located on the back of the tongue
taste bud I II and III differs from IV b/c
the first three each mediate different taste qualities.
Type IV (basal cells) give rise to new taste receptor cells that is located at the basal portions near the nerve fibers
pheromones is what type of communication? like is it intra or interspecific attraction?
it is intraspecific because only a male within the same species can recognize the realease of the female within the species
very sensitive nose is needed to dectect the pheromoes from miles away
also function in: sex-attraction trail-marking alarm pheromones colony-recognition
Ionotropic transduction
deals with salty and sour taste receptors
type 1 receptor is salty b/c
the simplest
Salt taste receptor cells depolarize with increasing Na+-influx.
type 3 receptor is sour b/c
is triggered by protons.
protons are primarily responsible for sour taste
protons interact with distinct channels on Type III apical membranes.
This activates proton-gated cation and Cl- channels to trigger RP.
Metabotropic (GPCR) transduction deals with what type of receptors?
bitter sweet and umani
These all occur in different sub-populations of Type II receptor cells.
Cells that sense each taste use different GPCRs that can form dimers.
Taste receptor type 1 membeR 1 (T1R1)
Taste receptor type 1 membeR 2 (T1R2)
Taste receptor type 1 membeR 3 (T1R3)
Sweet activates the T1R2/T1R3 dimer
Umami activates the T1R1/T1R3 dimer
Bitter activates any of a large family of T2R receptor proteins
diff btwn gustation and olfactory sensillum s
Gustatory sensillum: one terminal pore
Olfactory sensillum: entire shaft perforated with pores.
odorants?
a substance giving off a smell, especially one used to give a particular scent or odor to a product.
describe the bipolar neurons that olfactory receptor cells have
Cell bodies are housed in a layer of epithelium
One dendrite reaches the surface to meet the ambient medium
The other dendrite forms a long axon connecting directly to brain
what does the watery mucus do for cells that are coming through our nose
protects the vulnerable nerve cells from toxins
regulates access of chemical odorants to the sensory cell’s membrane receptor sites
enzymatically breaks down spent pheromone molecules
how long do vertebrate olfactory cells last?
30-90 days
anosmia:
Damage to the receptor cells and/or their stem cells
can result in anosmia: the lack of sense of smell.
Anosmia can be transient or permanent.
Glomeruli
All axons of the same receptor type converge at one or two locations in the glomeruli.
Glomeruli are spherical regions in the brain’s olfactory cortex
where sensory receptors synapse onto processing neurons.
Variations in GPCR amino acid sequence
determine which stimulus ligand can bind there.
Each receptor cell has one to a few different types of receptor proteins.
olfactory smell process
- Airborne molecules bind to mucous proteins on the sensory cell membrane.
- The stimulus molecule acts as a ligand,
binding to an olfactory receptor protein (usually GPCR).
Variations in GPCR amino acid sequence
determine which stimulus ligand can bind there. - cascade begins
vomeronasal organ
This includes most mammals, but not humans.
The vomeronasal organ is an odor-specialist.
It detects pheromones and other chemical signals
urinary proteins
lipid secretions
…which are important components of scent markings
do Animals have different ways of delivering molecules to the VNO?
yes!
reptiles, via tongue flicking
in mammals, through the nasopalatine duct
vomeronasal organ (VNO) are helpful because?
They predominantly help mediate responses to pheromones,
which play important roles in a variety of behaviors
defense
recognition of young
mating
aggression
flehmen response
pulls stimulus-laden air into the nasopalatine duct, facilitating detection of pheromones (and other chemical stimuli).
Taste Mutants and Natural Selection for cockroaches
American scientists found that the mutant cockroaches had a “reorganised” sense of taste, making them perceive the glucose used to coat poisoned bait not as sweet but rather as bitter.
