Exam 5 Chapter 15 part 1 Flashcards
where is the olfactory epithelium located?
in the root of the nasal cavity
what is olfaction?
the sense of smell
what does olfaction occur in response to?
odors that stimulate sensory receptors
what are basal cells in olfaction?
stem cells that replace dead olfactory neurons
what does olfactory epithelium contain?
10 million olfactory neurons
what projects from a bulb-like olfactory vesicle into the mucus layer?
several cilia (olfactory hairs)
what does the cilia do for olfaction?
increases the receptor membrane surface area
what are odorants?
air-borne chemicals that dissolve in the mucus and bind to odor receptors in the membrane
are all odorants detected with equal sensitivity?
no
what do odorant receptors use as a second messenger?
G proteins and cAMP
what does odorant binding cause?
sodium and calcium channels to open
what happens when sodium and calcium channels open dafter odorant binding?
it creates a depolarization and an action potential in the olfactory neuron
what does the olfactory system distinguish?
about 4000 different smells
what are the 4000 different smells that the olfactory system distinguishes based on?
which odorant receptors are stimulated
what are lost olfactory cells replaced by?
proliferation of basal cells in the olfactory epithelium
what do olfactory receptors show?
adaption and central adaption occurs
what do olfactory neuron axons (cranial nerve I) pass through?
the cribiform plate
where do olfactory neuron axons (cranial nerve I) synapse?
in the olfactory bulb
after the olfactory neuron axons (cranial nerve I) pass through the cribiform plate and synapse in the olfactory bulb what occurs?
they pass through the olfactory tract to the olfactory cortex as well as the hypothalamus, limbic system and frontal lobe
where do a majority of neurons in the olfactory tracts project to?
central olfactory cortex areas in the temporal and frontal lobes of the cerebrum
what areas do the central olfactory cortex include? (3)( PAO)
1) the piriform cortex (in the junction between the temporal and frontal lobes)
2) the amygdala (temporal lobe)
3) oribitofrontal cortex
where do olfactory tract neurons project to which are involved with emotional and autonomic responses to olfactory stimuli?
secondary olfactory areas
what areas are included in secondary olfactory areas?
1) hypothalamus
2) hippocampus
3) limbic system
where do gustatory (taste) receptors occur?
in taste buds on the superior tongue surface
what does the superior surface of the tongue have?
projections called papillae
what does the filiform papillae do?
make the tongue surface rough
what does the fungiform, foliate and vallte papillae have?
recessed taste buds
what is the most numerous papillae on the surface of the tongue?
filiform
what is unique about filiform?
it has no taste buds
what does filiform papillae provide?
a rough surface on the tongue allowing it to manipulate food more easily
which are the largest papillae but least numerous?
vallate papillae
what does taste (gustatory) cells synapse with?
sensory neurons
what extends through a taste (gustatory) pore on the epithelial surface?
taste hairs (microvilli)
what replaces dead taste cells?
basal stem cells
what is a life span of a taste cell?
about 10 days
what is our sense of taste formed in conjunction with?
our sense of smell
what do human primary tastes include? (5) (SSSBU)
1) sweet
2) salty
3) sour
4) bitter
5) umami (broth)
what binds receptor proteins in the taste hair membrane?
dissolved chemicals (tastants)
what do tastants generate?
depolarizations
what do some tastants act on?
some on ion channels others on G proteins and second messengers
are all chemicals detected with equal sensitivity?
no
what is an example of not all chemicals being detected with equal sensitivity?
bitter is detected with more sensitivity than sweet
what does taste receptor depolarization generate?
an action potential in the sensory neuron
where do taste bud sensory neurons travel?
along 3 cranial nerves
where do taste bud sensory neurons synapse?
in the tractus soltarius in the medulla
what 3 cranial nurse do taste bud sensory neurons travel along?
facial (VII), glossopharyngreal (IX) and vagus (X)
where do secondary neurons cross over and synapse?
in the thalamus
what does secondary neurons cross over and synapse in the thalamus with?
tertiary neurons that reach the taste area in the insula lobe
does receptor and central adaption for taste occur?
yes
what is refraction used for?
to bend light and form an inverted image on the retina
how is a clear, sharp image formed?
by changing the thickness of the lens (focusing or accomodation)
what is an important characteristic of light rays?
that they can bend
what is happening when the lens is thin for far away object?
ciliary muscle is relaxed
what is happening when the lens is thick for close objects?
sphincter-like ciliary muscle contracts
what does pupil restriction do?
reduce the light entering and increases the depth of field
when object come close what must the eyes do?
converge to keep the image on the center of retina (convergence)
what does the neural part of the retina have?
several layers
what does the outer layer of the retina contain?
photoreceptor cells (rods and cones)
what is the middle layer of the retina composed of?
bipolar neurons
what does the inner layer of the retina contain?
ganglion cells whose axons extend out the optic nerve
what are in between the layers of the retina?
synapses in the plexiform layers
what does the pigmented lauyer or pigmented epithelium of the retina consist of?
a single layer of cells filled with the pigment melanin
is pigmentation strictly necessary for vision?
no, people with albinism can see but their visual acuity is reduced because of light scattering
what are the rods and cones (photoreceptors)
modified neurons
what does the inner segment of the eyes photoreceptors synapse with?
a bipolar cell
what does the outer segment of the eye’s photoreceptors contain?
membranes for photoreception
what are rods specialized for?
vision in dim light
what does rods produce?
grays
what does the membrane of rods contain?
rhodopsin
what is rhodopsin?
a protein called opsin + the pigment retinal
what is retinal made from?
vitamin A
what is rhodopsin associated with?
a G protein (transducin) and a cGMP phosphodiestrerase
what does the cGMP phosphodiestrerase do?
converts cGMP into GMP
what happens during darkness?
chemically gated sodium channels in the outer segment are open in the presence of cGMP
what does the open chemically gated sodium channels in the outer segment during darkness cause
a potential of -30mV
as a result of the potential of -30mV what do the photoreceptors release?
the inhibitory neurotransmitter glutamate continually at the synapse
what a photon of light strikes the retinal what happens?
it changes from 11-cis retinal to 11-trans retinal
what dose the changing from 11-cis retinal to 11-trans retinal do?
activates transducin and the cGMP phosphodiesterase that breaks down cGMP
what happens after the transducin and phosphodiesterase that breaks down cGMP is activated? (4) (SMCP)
1) the sodium channels are closed
2) the membrane hyperpolarizes
3) the cell releases glutamate
4) the bipolar cell releases a neurotransmitter
what happens once the bipolar cell releases a neurtransmitter?
the 11-trans retinal is then removed from opsin and enzymatically converted to 11-cis retinal to regenerate photopigment
what are cones for?
specialized color vision and high visual acuity in bright light
what different cones have?
different opsins
what do the different opsins of cones form?
photopigments (RGB) (Red, green, blue)
what do the different photopigments absorb?
different wavelengths of light for color vision
what does the sensitivity of the visual system vary from?
a dark-adapted state (rods) to a light-adapted state (cones)
where are cones located?
they are concentrated near the macula
where are rods located?
more numerous away from the macula
does the retina do any visual processing?
yes, some
what do bipolar cells that monitor rods monitor many rods show?
considerable convergence and produce coarse images in dim light
what do bipolar cells that monitor cones often monitor a single cone show?
little convergence and produce detailed, sharp images in bright light.
where is the optic nerve located?
it leaves the eyes and travels to the optic chiasm
how does the field of view work?
the lateral half of the field of vision crosses over at the optic chiasm
why does the lateral half of the field of vision cross over at the optic chiasm?
so that each visual cortex gets the opposite side of the field of view from both eyes
what does binocular vision allow?
depth perception
where does the optic tract go?
to the lateral geniculate nucleus and then onto the visual cortex
where do collaterals go?
to other locations such asthe superior colliculus
where is the visual cortex located?
in the occipital lobe
