Chapter 17: Lecture Midterm II Flashcards
On each side of the nose, there are 40 or so bundles of axons of
olfactory sensory neurons from the right and left olfactory (I) nerves
the olfactory nerves pass through the
cribriform foramina of the cribriform plate of the ethmoid bone
where do olfactory nerves extend to?
parts of the brain known as olfactory bulbs, which contain glomeruli
where do the second order neurons synapse with the olfactory nerves
at the glomerulus (second order neurons called; mitral cells)
Each glomerulus of the olfactory pathway recieves input from
only one type of olfactory sensory neuron
the axons of mitral cells form
the olfactory tract
where does conscious awareness of smell occur
olfactory cortex in the temporal lobe of the cerebrum
olfactory sensations are the only sensations that
reach the cerebral cortex without synapsing in the thalamus
where does out emotional responses to odours occur
some axons of the olfactory tract project to the limbic system
what type of sense is smell
chemical
the olfactory epithelium covers the…
inferior surface of the cribriform plate and extends along the superior nasal concha
extending from the dendrite of an olfactory sensory neuron are several nonmotile
olfactory cilia,
olfactory cilia are the site of
olfactory transduction
within the plasma membranes of the olfactory cilia are
olfactory receptor proteins that detect inhaled chemicals
Odorants:
chemicals that bind to and stimulate olfactory sensory neurons in the olfactory cilia
Supporting epithelial cells:
columnar epithelial cells of the mucous membrane lining the nose
- they provide physical support, nourishment and electrical insulation for the olfactory sensory neurons and help detoxify chemicals that they come in contact with
Basal epithelial cells
- stem cells located between the bases of the supporting epithelial cells
- they continue to undergo cell division to product new olfactory sensory neurons, which live for only about 2 months before being replaced
Olfactory glands (Bowman’s glands)
- within the connective tissue that supports the olfactory epithelium
- produce mucus that is carried to the surface of the epithelium by ducts
Olfactory transduction
binding of an odorant molecule to an olfactory receptor protein
Chemical reactions involving cyclic AMP (cAMP) cause
depolariztion
Neural pathway for olfaction
- action potential travels to the primary olfactory area
- impulses travel to the frontal lobe (orbitofrontal area) for odor identification
taste is a
chemical sense
taste buds contain
receptors for the sensation of taste
where are taste buds found
tongue, soft palate, pharynx, epitlottis
What kind of epithelial cells do tastebuds contain
- supporting cells
- gustatory receptor cells
- basal stem cells
Where on the tongue are taste buds located
on elevations called papillae
What are the three types of papillae on the tongue
- vallate papillae
- fungiform papillae
- foliate papillae
Vallate papillae
about 12 that contain 100-300 taste buds
Fungiform papillae:
Scattered over the tongue with about 5 taste buds each
Filiform papillae:
- cover the entire surface of the tongue
- increased friction to make it easier for the tongue to move food within the mouth
- contain tactile receptors but no taste buds
MOST ABUNDANT ON TONGUE
What are the 5 primary tastes
- sour
- sweet
- bitter
- salt
- umami (meaty)
Chemicals that stimulate gustatory epithelial cells are known as
tastants
Once a tastant is dissolved in saliva…
it can make contact with the plasma membranes of gustatory microvilli
gustatory microvilli are the sites of
Taste transduction
After there is contact with gustatory microvilli,
it results in depolarizing receptor potential which stimulates exocytosis of synaptic vesicles
After there is depolarization in the gustatory pathways…
neutrotransmitter molecyles trigger a graded potential which produces nerve impulses in the first order sensory neurons
an individual gustatory epithelial cell responds to only
one type of tastant because each cell has either ion channels or receptors for only on of the primary tastes
each taste bud contains
gustatory epithelial cells for each tupe of tastant to allow dfferent tastes to be detected in different parts of the tongue
A bitter cell cannot respond to
a sour or sweet cell and vice versa
what three cranial nerves contain axons of the first-order gustatory neurons that innervate taste buds
- facial nerve (VII)
- glossopharyngeal (IX)
- vagus (X)
The facial nerves serves taste buds on
anterior 2/3rds of the tongue
the glossopharyngeal nerves serve taste buds on
posterior 1/3rd of tongue
the vagus nerve serves taste buds in the
throat and epiglottis
from the gustatory epithelial cells in taste buds, nerve impulses propagate along cranial nerves to…
the gustatory nucleus in the medulla
from the medulla, some axons carrying taste signals project to…
the limbic system and hypothalamus, others project to the thalamus
Taste signals that go to the thalamus then go to..
gustatory cortex in the insula of the cerebrum