Exam 3
Functionally, what is the purpose of rods and what is the purpose of cones?
Cones are for detailed vision and acuity specialized for daylight vision
What types of cells does the olfactory epithelium contain?
1. Olfactory sensory neurons 2. Basal cells 3. Supporting cells
Genetically and behaviorally, what is the difference b/t a non-taster and a taster/supertaster? Anatomically, what is the difference b/t a taster and a super-taster? What has cross-modality matching told us about taster status? What are some health consequences of taster status?
1. Supertatser- more fungiform. can taste things are more butter. Dom. TT. doesn't perceive fats to taste as pleasant butt hat means less heart problems. 2. Tatser- Dom Tt, may avoid veggies or alc/tabacco 3.Nontatser- Recessive tt, more likley to smoke and drink. Genetically: needs at least one dominant gene. Behaviorally: T & ST taste bitter things as even more bitter. Avoid veggies and alcohol/tobacco. NT more likely to drink/smoke. Cross modality- has told us that different people perceive the intensity of something with the same concentration, by comparing it to a different sensation of equivalent intensity. Supertasters = sound of a fire engine Nontatsters= sound of a clock Some health concerns with taster status: Nontasters tend to be more depressed. Supertasters & tasters are less likely to drink/smoke BUT might avoid vegetables. Nontasters are more likely to drink/smoke.
What cranial nerves are involved?
2 (optic "sense of sight") and 3 (oculomotor "eye movement, lid elevation, pupil contraction, sense shape")
What is accommodation & how is it accomplished?
Accommodation is the process by which the eye changes its focus; in which the lens gets fatter as faze us directed toward nearer objects. It is accomplished through contraction of the ciliary muscle. The lens is attached to the ciliary muscle through tiny fivers known as the "zones of Zinn."
What is adaptation? Physiologically speaking, why does it occur? Is there a psychological effect on adaptation?
Adaptation- is when you stop perceiving an odor due to continuous exposure (~10 mins) •This happens physiologically to help us to filter out background odors.because could you imagine fricken smelling someone who cooked stir fry all damn day???? •a psychological effect occurs when people are put in a room and half are told its healthy and the other half hazardous the hazardous group smells it for a longer period
What are adaptation and cross-adaptation? What did the essay on water tastes teach you?
Adaptation: Loss of taste with constant stimulation. This is why saliva doesn't taste salty. Cross Adaptation: Reduced response to one primary taste after exposure to another. Ex. Brush teeth+OJ= dead. Essay teaches us that taste is subjective. What we taste now is what we were just tasting.
Know the disorders of taste. Also know the terms aguesia, hypogeusia and dysguesia. Why can altered taste perception be so bad for overall health?
Aguesia: Total loss of taste. Hypoguesia: Decrease in taste of all or specific primaries/tastants Dysguesia: Distorted taste Xerostamia: Drymouth due to dysfunction of salivatory glands. Burning Mouth: Burning pain, usually affecting tongue, hard palate, and lips. Phantaguesia: Lingering, often unpleasant taste with nothing in the mouth. Initiated by strong tastes (coffee, garlic) Early satiety: Feeling full before eating adequate calories.
What is anosmia, and what can cause it? What is specific anosmia, and what is its most common cause?
Anosmia-is the total absence of a sense of smell or inability to smell at all. •It is caused by cribriform plate being moved (head trauma) and slicing the olfactory axons. Specific Anosmia-refers to the inability to detect one specific compound (odor) so it should be called odor specific anosmia, but everything else works fine. •The most common cause is usually genetically based.
What is an astigmatism?
Astigmatism is a visual defect caused by the unequal curving of one or more of the refractive surfaces of the eye, usually the cornea
Refracted
Bent; this happens when the surface is translucent.
What are the different types of bipolar cells?
Bipolar cell- a retinal cell that synapses with either rods or cones (not both) and with horizontal cells, and then passes the signals on to ganglion cells Diffuse bipolar cell- a bipolar retinal cell whose processes are spread out to receive input from multiple cones (Rods) Midget bipolar cell- a small bipolar cell in the central retina that receives input from a single cone (Cones) Project to the Parvocellular layers of the LGN (Thalamus) ON bipolar cell- a bipolar cell that responds to an increase in light captured by the cones OFF bipolar cell- a bipolar cell that responds to a decrease in light captured by the cones
Bitter: usually means poisonous, but what is an example of a built-in system that helps us eat bitter things even though they don't taste great? How many genes for bitter receptors are there and what does that tell us? Do we differentiate b/t bitters? Why or why not? How do bitter and sweet interact with each other? How does the perception of bitter change across the lifespan of women?
Built in system:A compound (AMP) inhibits some bitter sensations and is naturally present in mother's milk. 25 bitter receptors on 3 different chromosomes. Tells us that DIFFERENT GENETIC MAKE-UP means that you and I might have different bitter experiences.Yes, because the sense of bitter taste is so important for survival, as ingesting a bitter compound may lead to injury or death. We want some, like coffee, or vegetables. t's hard to distinguish between bitters. Bitter an Sweet interact by inhibiting each other For a women Sensitivity to bitter INTENSIFIES with PREGNANCY & DIMINISHES after MENOPAUSE.
What are cataracts? What causes them? How do they affect vision?
Cataracts are opacities in the lens caused by irregularity in the crystalline and they are caused by irregularity of the crystalline. They are packed together very densely and therefore are very regular, and anything that interferes with the regularity of the crystalline will result in loss of transparency. Congenital cataracts are relatively rare and are present at birth.
What is cognitive habituation? What 3 factors probably work together to cause it?
Cognitive Habituation- The psychological process by which one can no longer smell an odor or has very diminished ability after long term exposure ex. Your house. The three factors are: 1) receptors taking longer to emerge after internalization 2) continuous odorant exposure results in it being in your bloodstream so receptors are constantly adapted 3) cognitive/emotional factors
Illuminance
Energy from source to object; the amount of light falling onto patch of unit surface area.
Radiance
Energy from source; intensity of a light beam.
What does the "visual spectrum" refer to? Even if we can't see it, is there other electromagnetic radiation that we somehow respond to? Know an example of an animal that uses more of the electromagnetic spectrum.
FYI: # of photons = perception of intensity; wavelength = perception of color. The visual spectrum refers to the light we can physically see (380-760 nm). As the wavelength changes, the color we see changes as well. The human eye cannot see infrared radiation, however we use it for night vision devices such as thermal imaging. Also, our tissue can be damaged by ultraviolet rays that cause a sunburn. Most snakes can "see" infrared radiation through their facial pit, such as the pit viper or rattlesnake. This helps them capture prey by the warmth of their blood.
What about to see far away?
Flat to see far way because the Ciliary muscle is relaxed.
What is flavor? How does the brain differentiate b/t tasting or smelling something?
Flavor= combo of taste and odor receptors. Brain knows that something is in your mouth. Brain knows where odorant is coming from not the mouth.
What are the arguments for and against umami being a primary taste?
For: Signals protein, therefore plays important role in nutrition. Hot spot for it in insula. (also hot spots for 4 other tastes) Against: Imperceptible in many protein-rich foods.
What is the fundus?
Fundus is the back layer of the retina-- what the eye doctor sees through an ophtalmoscope
What are the different types of ganglion cells?
Ganglion cell- a retinal cell that receives visual information from photoreceptors via two intermediate neuron types (bipolar cells and amacrine cells) and transmits information to the brain and midbrain P ganglion cell- a small ganglion cell that receives excitatory input from single midget bipolar cells in the central retina and feeds the parvocellular layer of the lateral geniculate nucleus (Cones) Project to the Parvocellular layers of the LGN (Thalamus) M ganglion cell- a ganglion cell resembling a little umbrella that receives excitatory input from diffuse bipolar cells and feeds the magnocellular layer of the lateral geniculate nucleus (Rods) Project to the Magnocellular layers of the LGN
Glomeruli?
Glomeruli- simply put it is a cluster of synapses Clusters of dendrites of mitral/tufted cells within the olfactory bulb where axons from olfactory receptor cells synapse. Each OSN converges on 2 glomeruli Topographic organization in OB: similarly smelling chemicals recognized by neighboring parts of OB. Mitral cells send axons to ipsilateral cortex; efferent pathway of tufted cells unclear. Glomerulus pair: 1 medial and 1 lateral. Each of these in each olfactory bulb...projections from nostril to bulb to cortex largely ipsilateral. Brain knows from what glomerulus axons have traveled, which helps brain determine smell (like labeled-line, right?) But an odorant activates a pattern of OSNs so pattern of glomeruli (so really cross-fiber patterning) Glomeruli pattern of activation differs based on experience & preference for the odorant
How do we perceive proteins and fat? What is the importance of the gut? How do we choose foods?
Glutamate and fat receptors found in the gut because they are too big to be sensed by receptors in the tongue. Gut: Gut signals brain to prefer the foods with fat. Important for survival. However....... how we choose food is based on: 1) Hard-wired taste preferences based on evolutionary needs. (2) Learned responses to food flavors (signals from gut due to important nutrients)
What are the roles of the insular cortex and the orbitofrontal cortex?
INSULAR: Gustotopic in mammals with "hot spots" for each primary taste cortex ORBITOFRONTAL: Temperature, touch, smell, taste, etc. (Flavor too)
What is the fovea?
Is a small pit, near the center of the macula, that contains the highest concentration of cones, and no rods. It is the portion of the retina that produces the highest visual acuity and serves as the point of fixation.
What aspects of taste are probably coded using labeled-line and which ones are probably coded using cross-fiber patterning?
Labeled-Line: Salty, sweet, and bitter (for identification of primary taste) Cross-fiber: More nuanced experience - Milk chocolate vs. Dark Chocolate (for identification of type within a primary taste)
What is shape-pattern theory?
Lock (receptor) and key (odorant) Odorant molecules have different shapes Olfactory receptors have different shapes Different scents (as a function of odorant shape & OR-shape fit) activate different arrays of olfactory receptors in the epithelium Various arrays produce specific firing patterns of neurons in OB (a pattern is generated across the glomeruli), which determines what scent we perceive
What is the accessory olfactory bulb (AOB)?
MOB= Main olfactory bulb •Added on the back of the MOB (no connection) that's activated by the VNO. Humans don't have this. •It is encompassed inside a bony or cartilaginous capsule which opens into the base of the nasal cavity. The vomeronasal receptor neurons possess axons which travel from the VNO to the accessory olfactory bulb (AOB) or, as it's also known, the vomeronasal bulb. •SO accessory olfactory bulb= vomeronasal bulb.
Salt: what can affect salt preference and perception?
Preference is affected by early learning. Cl- or Na+ deficiency in infancy = increased preference in adulthood. Infants fed salty foods increased salt preference. Perception: Low Na+ diet = increase in perceived intensity of saltiness
What makes something an odorant?
Odarant- chemicals that activate odor receptors Must elicit a smell by following the 3 criteria: 1. Volatile (can float thru air) 2. Small (<5.8x10-22 g) 3. Hydrophobic •If the above criteria is not satisfied, technically we shouldn't be able to smell it. oEx: natural gas (methane)
What is the function of olfaction?
Olfaction- detection of chemicals dissolved in the air •To detect chemicals in the environment and take in certain substances and avoid others. In addition to a social role (pheromones).
Inside the OE:
Olfactory sensory neurons: 1.They are small neurons w/ cilia 2. Receptor proteins are on the cilia Each OSN expresses 1 type of receptor protein The receptor proteins are metabotropic: This means that a 2nd messenger opens channels that flux Na+ & Ca2+ ; also open a Cl- channel (lots of Cl- inside these cells) so part of depolarization caused by Cl- efflux. 3. The olfactory sensory neurons are projected through the cribriform plate to glomeruli (clusters of neurons) in olfactory bulb These axons constitute the olfactory nerve (CNI). All projection for olfaction is Ipsilateral.
What types of somatosensory info do we get from the mouth that is relevant to the entire taste experience? What cranial nerve carries that info?
Pain, Texture, and Temperature. TRIGEMINAL NERVE (CN 5)
Understand the anatomy of the taste system: know the names of the different types of papillae; what/where are the taste buds, and taste cells; what is the taste pore; where do fibers of the taste cranial nerves synapse w/ taste cells
Papillae- ridges in the tongue w/ taste buds embedded. 1.Fungiform- most abundant; like a mushroom with the tastebud inside. 2.Foliate- found on the sides (lateral surface) of the tongue, taste buds arranged in the folds. 3. Circumvallate- larger papillae found in back of tongue. like an island surrounded by a mote and the mote has taste buds in it. Nontatse: filloform- found in cats, meant for gripping and grooming. tatsebuds: bud like clusters of receptors (multiple on each papillae) that have an opening (tastes pore) that leads to microvilli which contains the receptors stimulated by tastants. Taste cell: located inside tastebud Taste Pore: opening of taste bud, where chemicals go in and reach microvilli. Fibers of the taste cranial nerve synapse with taste cells on axons of the CN. not all receptor cells synapse on the nerve fiber, some branch so 1 cell per fiber and 1 fiber per cell.
What parts of cortex get olfactory info? Where else in the brain does olfactory information go, and what are the roles of each of those regions?
Piriform Cortex which is the prmary olfactory corext and first process the infro. Then if goes to the Amygdala (emotional memory/approach or avoidance behavior) and the parahippocampal gyrus, and orbitofrontal cortex and interacts closely with the Enthorthinal Cortex and hippocampus (memory) • Aka Limbic System Other areas such as: • orbitofrontal cortex (assigns value/flavor), • and hypothalamus (hormones/feelings/reproduction) Unlike the other senses, olfactory neurons do not go to directly to the thalamus. It directly interacts with areas of the brain involved with emotion and memories. Beyond the OB: OB (mitral cells) projects directly to: entorhinal cortex and piriform cortex= Primary olfactory cortext amygdala (3) piriform cortex (4) amygdala (medial nuclei), (5) periamygdaloid cortex, (6) parahippocampal gyrus/ entorhinal cortex 3, 5 and 6 constitute primary olfactory cortex Olfactory cortex to PFC (directly & via thalamus) hippocampus hypothalamus back to olfactory bulb
What is presbyopia & what causes it?
Presbyopia is "old sight." By the time most people are 40-50 years, they can no longer accommodate the 2.5 diopters or so needed to see clearly at 40 cm. This is inevitable. The lens become sclerotic, or harder, and the capsule that encircles the lens loses its elasticity.
What are the cell layers in the retina (know them from the back of the eye to the front), and understand from which direction light comes in and in what direction the neural impulse travels.
Receptor cells (rods & cones) Horizontal cells (Integrate signals between photoreceptors) Bipolar cells (receptor to ganglion cells) Amacrine cells (Integrate signals between bipolars, amacrines, ganglion cells) Ganglion cells send action potentials to the brain Light passes through the ganglion, bipolar, horizontal, and amacrine cells before making contact with the photoreceptors. When the photoreceptors sense light, they can stimulate neurons in the intermediate layers, which then connect with the frontmost layer of the retina whose axons pass through the optic nerve to the brain
Why does "red eye" occur in photographs?
Red eye occurs in photographs because in dim light, the pupil is dilated. Too much light, it's reflected back from the fundus, through the choroid which gives the reflection and red appearance.
In what way are rods and cones unequally distributed in the retina?
Rods are completely absent from the center of the fovea and cones are most concentrated in the center of the fovea
Understand the physiology of the taste receptors: how do salty, sweet, sour and bitter substances each lead to action potentials in the taste nerves?
Salty: Na+ enters through channel on microvilli -> Depolarization allows Na+ and Calcium in through voltage-gated channels -> Neurotransmitter release -> AP in taste nerve Sour: Acids in water have a free hydrogen proton. H+ enters cell through ion channel and blocks K+ channel -> K+ can't leave -> depolarization -> Na+ and Calcium into cell through voltage-gated channels -> Neurotransmitter release -> AP in taste nerve. Bitter, Sweet, and umami: Tastant molecule binds to metabotropic receptor -> G-protein activated -> Calcium let into cell through membrane, Na+ channels opened; potassium channels blocked -> Neurotransmitter release -> AP in taste nerve.
For what primary tastes do humans show "specific hungers"? What is some evidence for these? What is necessary for something to be able to cause a specific hunger?
Sweet & Salty. "Body wisdom" The need for a nutrient causes the body to crave it. Insulin injections increase craving for sweets. Nutrient needs to be associated with a sensory cue, it won't work if nutrient doesn't have a taste. (Vitamins)
Sweet: What do you know about the receptors for sweet tastes and their relationship to artificial sweeteners? Can we differentiate b/t real sugars and artificial sweeteners, and if so, how?
Sweet is detected by G Protein-Coupled receptors. In relation to artificial sweeteners: Artificial sweeteners activate the G-Protein-Coupled Receptors. 1 signal from receptor. More so, glucose is the main source of energy for humans and sucrose which is table sugar stimulate receptors as well. Yes, we use ADDITIONAL TASTES (like bitter for some artificial sweeteners)
What is the purpose of each of the 4 primary tastes (ie, what important info do they give us that is necessary for our survival)?
Sweet: Energy Salty: We need ions for proper nerve & muscle function Bitter: Toxic Chemicals Sour: Bacteria/spoiled food
How do the receptors in the VNO differ from those in the olfactory epithelium?
The VNO has fewer receptors than the OE. VNO= Jacobson organ and found in animals
What is the pupillary light reflex?
The pupillary light reflex, otherwise known as Whytt's reflex, is the immediate constriction of the pupil in response to bright light.
What shape do you need your lens (flat or bulging) to see close by?
To see close by= bulge The Ciliary muscle must contract which causes the lens to bulge
What cranial nerves innervate the tongue? What brain regions (in order) get info about taste?
Vagus (10) Circumvallate Glossopheryngeal (9) Filoform Corda Tympani (7) Fungiform 1.Cranial Nerve -->2. Nucleus solitary tract (medulla)--> 3. Thalamus -->4. Primary gustatory Cortex.
Transmitted
When light passes through a transparent object. When light hits a surface it can be transmitted, absorbed, or reflected.
Retina
a light sensitive membrane in the back of the eye that contains rods and cones which relieve the image from the lens and send it to the brain through the optic nerve.
How are gaglion and bipolar cells connected to each other?
amacrine cells
What is hyperopia
farsightedness, a common condition in which light entering the eye is focused behind the retina and accommodation is required in order to see near objects clearly
What is myopia?
nearsightedness, a common condition in which light entering the eye is focused in front of the retina and distant objects cannot be seen sharply
Macula
the central part of the retina that has a high concentration of cones
Iris
the colored part of the eye, consisting of a muscular diaphragm surrounding the pupil and regulating the light entering the eye by expanding and contracting the pupil
What is emmetriopic
the condition in which there is no refractive error, because the refractive power of the eye is perfectly matched to the length of the eyeball
Pupil
the dark, circular opening at the center of the iris in the eye, where light enters the eye
What is the optic disk?
the location where the arteries and veins enter the eye and where the axons of ganglion cells leaves the eye via the optic nerve
Vitreous Humor
the transparent fluid that fills the vitreous chamber in the posterior part of the eye
Optic Nerve
the which nerve that exits the back of the eye & carries visual info to the visual cortex in the brain.
lens
transparent structure located behind the pupil that actively focuses or bends light as it enters the eye (accommodation) so that the light falls on the retina.
Absorbed
when the surface is dark colored. when light hits a surface it can be absorbed, reflected, or transmitted.
Reflected
when the surface is light colored. When light hits a surface it can be reflected, absorbed, or transmitted.
Do we use labeled-line or cross fiber patterning to identify odors? Understand why!
•Olfactory perception is based on cross-fiber patterning! •The overall pattern of activity in the OB and then olfactory cortex determines the odor we perceive.
Are there compounds that should be odorants but we cannot smell?
• Yes, Natural gas (methane) and CO (bi-product of methane) • No natural recptors for them and have never needed to smell them, aside from the fact that they don't meet the criteria in #3.
How/why do olfactory thresholds increase with age?
•A change in the proportion of cell regeneration OR cell death (more die than remade) that continues to increase the older we get. •The more cells, the more you can detect, the easier so the threshold is lower but since there is less, this means the threshold will increase b/c it will take a while before the scent is smelled. •but taste and trigeminal perception do not decline (why old people like spicy/salty food)
What is the olfactory epithelium?
•A secretory mucous membrane in the nose whose function is to detect odorants in inhaled air. •The cribriform plate is above it; Olfactory mucosa below it. •Olfactory sensory neurons die & are replaced ~1x/mo •Basal cell (stem cell) matures into a new OSN in same location & w/ same receptor protein •Axon has to find its way to correct part of OB. •Copy of receptor protein on axon to find correct glomerulus •Replacement of OSNs decreases with age •50% of people at or older than 85 are anosmic
What are turbinates?
•A structure found in the nose which acts as the surface area for the epithelium to rest on. It contains ridges that add turbulence to incoming air to send some thru the olfactory cleft and onto the olfactory epithelium
Olfactory bulb?
•Blueberry sized extension of the brain above the nose which first processes olfactory info. 2 in each brain hemisphere for each nostril. Contains mitral cells and glomeruli.
Cribriform plate?
•Bony structure found in the nose with tiny holes at eyebrow level separating the nose from brain. Axons from OSNs pass through the holes in the plate to enter the brain
Dogs have more olfactory receptor neurons that humans, and rats have more types of olfactory receptors than humans. What are the functional consequences of these differences?
•By mice having more olfactory receptors they are better able to discriminate between smells than we are due to them being more sensitive to odors while dogs are better able to detect smells than us (5% of brain devoted to olfaction) •Amount of olfactory receptors doesn't affect how well someone smells. •It does however, affect sensitivity to certain odorants. •The more olfactory receptors you have = the more sensitive you are to odors •The more intense an odor, = the less pleasant it will be.
Olfactory nerve
•CN 1, axons of OSNs bundle together after passing through cribriform plate to form nerve which conducts impulses from olfactory epithelia in nose to bulb
What is the vomeronasal organ?
•Chemical sensing organ at base of naval cavity, evolved to detect pheromones. not found in humans, it is a secondary olfactory bulb in animals
What evidence points to the hedonic value of odorants (ie, whether or not we find them pleasurable) being innate and what evidence points to it being learned?
•Hedonic is pleasureable so whether we find certain smells pleasurable or not measured by rating an odors pleasantness/familiarity/intensity is the hedonic value of an odorant. Ex. I love FlowerBomb. Learned: • infants don't display preferences for pleasant smells, if exposed to a certain smell in utero display preference for it, cultural differences point to learned, no smell is universal Innate: • animals living in specific habitats with limited food sources have hardwired responses to particular smells that's adaptive. Learned taste aversion is to the smell of food/drink in humans
Do humans have these (#27 and 28)? What is their role?
•Humans have a AOB. Humans also have a very small VNO with few receptors, believed to be vestigial.
What is the projection neuron within the glomerulus that receives info from the olfactory nerve and sends info to the cortex?
•Mitrial cells are the main projective output neurons of the olfactory bulb while tufted cells are a secondary class of output neurons
What do you know about the link between olfaction, emotion and memory?
•Odors are better at eliciting emotional memories as opposed to general memories because the 1st experience determines emotional association of the odor (quickly encoded).
What are the 3 main roles of pheromones?
•Pheromones are chemicals released by an animal that affects behavior of another animal of the same species. •For communicating between animals of the same species about territory, mating, and defense
How can suggestion affect odor perception?
•Suggestion can make people believe that a certain odor smells a certain way. Odors are invisible and disconnected from language so we look for cues anywhere.
What neural substrates underlie the connection between olfaction, emotion and memory?
•The axons from the OB synapse directly in the amygdala (emotional processing)
What is some evidence for pheromonal communication in humans?
•The mcclintock effect (women living together mestrate) •Hormones made in adrenal glands (increase alertness/positive mood for women, decrease positive mood in men. •Woman in intimate relationship has more regular menstrual cycle, men's sweat alters cortisol levels in women. •Technically there shouldn't be anymore b/c no vomeronasal organ (VNO), but have olfactory receptors that closely resemble pheromones
Understand the anatomy of the olfactory receptor cells.
•The olfactory sensory neurons have cilia. •The Olfactory receptor cells are found in the cilia. •This is all going down in the of the olfactory epithelium. •The mucosa (first layer) contains the dendritic portion of the OSN which also contain the cilia (this is where the cilia picks up the odorant molecule). •Once traveling up from the cilia is the axon of the OSN which keeps going all the way up through the cribriform plate as part of olfactory nerve and ends in olfactory bulb. Extra: • The axons then travel through tiny holes in the cribriform plate and converge to form the olfactory nerve from there OSNs that represent the same receptors converge on the same glomeruli in the olfactory bulb where mitral cells receive the info and send it to cortex.
What are some differences between men and women in olfaction?
•Women detect odors more readily than men, responses are stronger, and at lower thresholds. •Women of child bearing period sensitize to odors until they smell them very small while others don't, and odor is more important in choosing partners to women (pharamones).
