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207 Cards in this Set
- Front
- Back
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types of cell in retina (front to back)
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ganglion cells (form nerve fibers)
amacrine cells bi-polar cells horizontal cells receptor cells (rods and cones) |
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rods
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night vision (low light conditions)
abundant in periphery black and white |
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cones
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color vision
daytime vision (bright light conditions) abundant in fovea |
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transduction
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the conversion of physical energy to an electrochemical pattern in the neurons
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resting state of receptor cells
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- constant influx of Na+
- resting potential of -20 mV - inhibitory synapse inhibits bi-polar cells from firing |
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types of receptor cells
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rods and cones
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state of events when light strikes photoreceptors
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- 11-cis-retinal is transformed to all-trans-retinal
- Na+ channels close, causing hyperpolarization (-70mV) - receptor stops firing inhibitory signals to bi-polar cells - bi-polar cells can fire |
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2 types of cells with on-center off-surround receptive fields
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ganglion and bipolar cells
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Bipolar cells (function)
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Connects photoreceptors to ganglion cells
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ganglion cells
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- fire action potentials in response to light
- only source of output from retina |
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Horizontal Cells
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- Receive input from the photoreceptors and project neurites laterally to influence surrounding bipolar cells and photoreceptors
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Amacrine cells
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- Receive input from bipolar cells and project laterally to influence ganglion cells, bipolar cells, and other amacrine cells
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ganglion and bipolar cells
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similar response properties except ganglion cells fire and bipolar cells only have graded potentials (center surround receptive fields)
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Center- surround receptive fields
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Center (on)- spikes per second increases when stimulus hits it
Surround (off)- spikes per second increases when stimulus is removed |
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Ganglion cells (center surround receptive fields)
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- light hits rod cell, inhibiting it
- leads to less inhibition of bipolar cell - bipolar cell is excited and fires onto ganglion cell - ganglion cell is excited |
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lateral inhibition
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light hits rod (r) and rod (l), inhibiting them. horizontal cells (r and l) are inhibited. horizontal cells fire to rod (m), which cause excitation (increased inhibition onto bipolar cells). Bipolar cells are then inhibited and so are the ganglion cells
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benefit of center surround receptive fields
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contour and edge detection
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types of ganglion cells
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parvocellular and magnocellular (both have on and off receptors
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parvocellular ganglion cells
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smaller cell bodies, small recpetive fields, respond to details, located near fovea, input from cone cells
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magnocellular
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larger cell bodies and receptive fields, respond to transient and moving stimuli, spread throughout retina, input from cone and rod cells
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types of cone cells
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red, green, blue (detect different wavelengths)
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three theories of color vision
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the trichromatic (young-helmholtz) theory, the opponent process theory, the retinex theory
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Trichromatic (Young-Helmholtz) theory
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colors are encoded through the relative activity of three classes of cones (RGB)
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Opponent Process Theory
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We perceive color in terms of paired opposites (R-G, B-Y
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The Retinex Theory
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Color vision in terms of spatial comparison, explains color constancy
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what is color deficiency caused by?
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A missing subset of cones
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chemosensory systems
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olfactory, gustatory, vemeronasal
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Flavor
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a combination of input from taste and smell
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taste recpetors (location)
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located in taste buds, which are located on folds of skin called papillae on the tongue and throat (mostly along sides and back of tongue)
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how many receptors per taste bud
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50
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how many taste buds per papillae
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10 or more
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types of papillae
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Fungiform
vallate (circumvallate) foliate filiform |
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Fungiform
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mushroom shaped, front half of tongue
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vallate/ circumvallate
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back of tongue
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Foliate
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like folds, sides of tongue
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Filiform
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fill in middle of tongue. No tastebuds on these
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parts of a taste bud
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capsule cells, taste pores, sensory receptor cells, basal stem cells, microvilli
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Capsule cells of taste buds
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outer protective layer
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taste pores of taste buds
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surface through which tastants enter
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sensory receptor cells of taste buds
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endode which tastants enter, where transduction occurs
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basal stem cells of taste buds
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create new receptor cells
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microvilli of taste buds
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increase surface area for detecting tastants where transduction occurs
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taste receptor cells
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specialized epithelial cells, innervated with cranial nerves
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what happens if taste buds lose innervation?
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they disappear but can regenerate with new innervation and stem cell differentiation
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taste bud innervation
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innervated by cranial nerves VII, IX, and X
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facial nerve innervation
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anterior tongue
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glossopharyngeal nerve innervation
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posterior tongue
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Vagus nerve
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innervates epiglottis
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how many nerve fibers innervate each taste bud
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approx. 50
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Sensory System theories
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labelled line, across fiber pattern
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Labelled line Theory
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each receptor responds to a limited range of stimuli with a direct line to the brain
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Across- Fiber Pattern Theory
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each receptor responds to a range of stimuli that contribute to the perception of each of them (context of responses)
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taste qualities
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sweet, salty, bitter, sour, umami
different parts of the tongue respond to all taste qualities |
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fiber innervation and taste quality
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fibers can respond to more than one taste quality, but each responds best to one specific quality
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taste fiber responses
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across-fiber pattern is dominant form of response, but labelled line is a component as well because there is no cross-adaptation
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Adaptation
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if a receptor is exposed to a particular taste quality for an extended period of time, it will lose its sensitivity and the taste will not be as strong
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cross-adaptation
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if a receptor is exposed to a particular taste quality for an extended period of time, it will lose its sensitivity to other taste qualities and they will also be less strong (DOES NOT OCCUR IN HUMANS)
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substances that modify taste qualities
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Miracle fruit, toothpaste
caused by different transduction methods |
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salty taste interpretation
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availability of salts, essential to life
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sweet taste interpretation
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substances that are safe to eat and provide energy
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bitter taste interpretation
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poisons (like alkaloids in plants)
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sour taste interpretation
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acidic substances, characteristic of spoiled foods
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taste pathways
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-Cranial nerves VII, IX, X
-solitary tract -nucleus of the solitary tract (NTS) in medulla -Discrimination pathway OR motivation and emotion pathway |
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Discrimination Pathway of taste
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-Ventral Posterior Medial Nucleus (VPM) in thalamus
-Primary gustatory cortex (near somatosensory) -Secondary Gustatory Cortex (insular cortex) |
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Motivation and Emotion Pathway of taste
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Limbic System
-lateral hypothalamus -Central Nucleus of the Amygdala |
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what is the taste discrimination pathway
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goes through a thalamic relay nucleus before reaching cortex
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what do the motivational and emotional pathways mean
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involved with emotional associations
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taste reflex pathway
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goes to brainstem for gagging responses
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olfaction (definition)
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the detection of odorants (volatile chemicals) through specialized epithelium in the nose
some detection is through the trigeminal nerve (ammonia) |
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Components of olfactory epithelium
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olfactory knobs
microvilli mucus layer supporting cells bipolar neuron (receptor cells) basal stem cell bowmans gland |
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Bipolar neurons (of olfactory system)
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receptor cells with cilia that contain receptor proteins for detecting odorants
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basal stem cells
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capable of continuously generating new neurons
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supporting cells
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provide nourishment for receptor cells, produce some mucus
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what happens if cribiform plate breaks?
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Can still recover
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what happens if all neurons are removed?
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it becomes difficult to find the correct targets so sense of smell never fully recovers
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olfactory transduction
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-odorant binding proteins carry odorants to receptors
-bind to receptors -G protein (Golf) releases 2nd messenger -2nd messenger causes ion channels to open |
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Taste transduction
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different for different tastes
Uses G protein gustducin |
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Olfactory bulb
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receptor axons synapse directly onto the olfactory bulbs
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components of olfactory bulb
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-glomeruli
-perglomerular cells -mitral cells -granual cells |
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function of Glomeruli
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where the receptors synapse
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function of peroglomerular cells
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connect different glomeruli
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function of mitral cells
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send info out of olfactory bulb
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function of granual cells
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modulate processing and can be regenerated
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Olfactory bulb mapping
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each type of odorant receptor projects to the same glomerulus
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Olfactory pathways
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-olfactory receptor neurons (Cranial never I)
- olfactory bulb -discrimination pathway OR endocrine and emotional pathway (both lead to hypothalamus) |
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Discrimination pathway of olfactory system
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-primary olfactory cortex (ventral frontal lobe)
-Dorsal medial thalamus OR hypothalamus -Association olfactory cortex (orbitofrontal cortex) |
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Endocrine and Emotional Pathway (taste)
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Limbic System
-Central nucleus of the Amygdala -Lateral Hypothalamus |
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What is the discrimination pathway for olfaction?
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Goes directly to the primary cortex before the thalamus and then further processing in the cortex
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What does the endocrine and emotional pathway mean (olfaction)?
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Amygdala processes emotions
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Pheromones (definition)
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chemicals that are released by a member of a species which have behavioral or physiological affects on a different member of the same species
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detection of pheromones
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through olfactory or vomeronasal system
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hypothalamus and pheromones
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connections to the hypothalamus mediate endocrine effects produced by pheromone stimulation
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Vomeronasal system
(found in most terrestrial vertebrates except birds and old world primates) |
-specialized behaviors bring chemicals into mouth
-receptor neurons on roof of mouth -chemicals are brought into receptors through suction |
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Vomeronasal system and olfactory system
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-vomeronasal neurons can be generated through lifelike olfactory receptor neurons
-separate from olfactory neurons -mediate different behaviors |
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Vomeronasal system higher functioning
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-labelled line
-no adaptation -no primary cortex -no conscious perception is thought to occur |
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Vomernasal behaviour in rodents
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-Lee-Boot effect
-Whitten Effect -Vandenbergh Effect -Bruce effect |
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Lee-Boot Effect
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Groups of female rodents housed together cause the estrous (reproductive) cycles of the females to slow down and eventually stop.
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Whitten Effect
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Groups of non-cycling females exposed to a male odor begin to cycle again and become synchronized.
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Vandenbergh Effect
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Male odors accelerate the onset of puberty in female rodents.
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Bruce Effect
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If a pregnant female encounters a male (or his odor) that is different from her mate, she will spontaneously abort.
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pathway from eye to brain
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-eye
-retina -optic nerve -optic chiasm -lateral geniculate Nucleus (LGN) in thalamus -superior colliculi -Visual cortex (V1) in occipital lobe |
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visual field in retina
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-each eye processes both right and left visual field (backward)
-ex. right visual field is on the left side of each eye -the left visual field is on the right side of each eye |
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optic chiasm
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-info from right side of the left eye (LEFT VISUAL FIELD) crosses
-info from left side of right eye (RIGHT VISUAL FIELD) crosses -"nasal nerves" cross |
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mapping of visual fields in cortex
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-left visual field is on the right side of the brain
-right visual field is on the left side of the brain |
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optic radiations
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neurons that lead from LGN to V1
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function of LGN
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-relay station towards cortex, helps process both magno and parvo info
-center surround receptive fields |
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structure of LGN
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-6 layers (4 parvo, 2 magno)
-forms retinotopic map (2 neighboring neurons will have neighboring receptive fields) -each neuron receives info from 1 or more ganglion cell and sends an axon to V1 (optic radiations) |
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magno
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motion, dynamic events
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parvo
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details, static events
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LGN oddity
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-80% of afferent neurons to LGN are NOT from retina, unknown source
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Structure of V1
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-has 6 layers
-when stained it looks dark because layer IV is densely packed with neurons because it receives input |
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Layer IV of V1
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-axons from LGN connect to layer IV
-info comes in -Layer IV connects to layers II and III |
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Layer II and III
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-send info to layer V, which sends it back
-sends info to V2 |
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Layer V and VI
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sends info to subcortical structures
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Retinotopic map in V1
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-Map is vastly distorted, with most of the map covering the fovea
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retinotopic map and fovea
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-high resolution from the fovea
-almost 1:1 correspondence between receptor cells and ganglion cells -HUGE part of ganglions come from fovea |
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do we notice that we don't see periphery?
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No, because we compensate by moving our eyes a lot (about 3x per sec!)
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function of V1
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basic visual analysis including movement and oriented contours
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Receptive fields in V1
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-receptive fields are elongated rectangles
-simple and complex cells |
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Simple receptive field
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-sub-regions with on and off regions
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complex cells
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-anywhere in receptive field can get on or off response
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simple cell functioning
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-tells us what the contour is
-on and off cancel each other out -if the bar is in a certain place and has a certain orientation the cell will not fire -population code |
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population code
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-functions through a large number of different types of cells
-true for almost EVERY function in the brain |
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Tuning curve
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a graph that shows us the orientation of a contour and the fire rate of a receptive field at each orientation
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Complex cell functioning
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-makes up for simple cell
-can detect the bar anywhere because there are on and off cells everywhere |
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hypercomplex cell
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-if the bar is too long, the firing rate can be reduced or even stop altogether
-explained by cell curvature |
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columnar organization (vision)
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Columns are grouped together by function
-ex. cells within the same column respond best to a single orientation |
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hemianopia
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type of V1 lesion
causes cortical blindness |
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Where/ How Pathway (Mainly magno)
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V1, V2, MST/MT, PPC, Motor Cortex
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MST/MT
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Process depth and motion
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PPC
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-Posterior Parietal Cortex
-motor intent -object localization -spatial attention -decision making |
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What pathway (mainly parvo)
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V1, V2, V4, IT
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IT
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-Infero Temporal Complex
-object recognition -cells respond to complex objects (faces, scenes) -lesions lead to visual agnosia and prosopagnosia |
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fMRI
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-functional MRI
-measures neural activity |
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monkey brain vs. human brain (for vision)
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-humans have a much smaller visual cortex in order to make room for other functions
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Illusory contours
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-Occurs in V2
-V2 responds as if there is a contour even when there is not, which creates the illusion that there is |
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Motion selectivity
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-Occurs in MT
-Cells respond to direction and speed of motion -lesions lead to motion blindness |
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hemineglect
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-caused by lesions to PPC
-if there is a lesion on the right side, person will neglect everything in the left visual field |
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Color selectivity
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-V4
-cells respond to color and exhibit color constancy |
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depth perception, shape from shading
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-occurs in V1, V4, and MT
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mechanical senses
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-cutaneous senses
-senses about body movement and position |
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cutaneous senses
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-touch
-temperature -pain |
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senses about body movement and position
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-proprioception
-vestibular sense |
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general rule 1 for somatosensory system
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somatosensory systems are organized somatotopically
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general rule 2 for somatosensory system
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primary sensory neurons are located outside the CNS (in a ganglion)
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general rule 3 for somatosensory system
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information from one side of the body crosses the midline to the contralateral thalamus and somatosensory cortex
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sensory info from body
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-travels through dorsal root ganglion neurons
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sensory info from head and neck
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-travels through cranial nerves
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skin receptors
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many types
separate into: -touch/pressure/vibration -temperature/pain |
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Corpuscles
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-process vibration and pressure
-include: -meissner's corpuscles -pacinian corpuscles |
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Meissner's corpuscles
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low-frequency vibrations
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Pacinian corpuscles
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high frequency vibrations
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Merkel's disks
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light pressure
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transduction in skin receptors
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-bend membranes which opens Na+ channels
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Dorsal Column pathway
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-carries info from body to brain
-also called Medial Lemniscal Pathway |
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Trigeminal nerve
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carries information from head
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spinal cord pathways
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-ipsilateral for touch
-contralateral side for pain |
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function of dorsal column pathway
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-processes fine, tactile discrimination
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order of dorsal column pathway
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-ascend to medulla on ipsilateral side of spinal cord
-info crosses in medulla -synapses in ventral posterior lateral nucleus (VPL) in thalamus -goes to primary somatosensory cortex |
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Somatotopic organization
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-dorsal root ganglion organized by dermatome
-somatosensory map in VPL and S1 |
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Nocioception means
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pain
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pain is subjective
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-measured by withdrawal response
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skin receptors- pain
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-free nerve ending
-temperature -pain |
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temperature transduction
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-temperature gated ion channels (specialized for different ranges)
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pain transduction
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-tactile
-temperature -chemical (capsaicin) |
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interaction of thermoreceptor and nociceptor
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-at a maximum temperature, activity of thermoreceptor levels off, because it cannot respond any more strongly
-at this point, nociceptors start firing and their activity increases over time if the thermoreceptor is not altered |
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Nociceptors
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2 kinds of pain
-fast pain (pinprick, cut) -slow pain (burning) |
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A-delta fibers
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-small, myelinated fibers
-carry fast pain |
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C fibers
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-unmyelinated
-carry slow pain |
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spinothalamic pathway
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-(anterolateral pathway)
-carry pain and temperature to the brain |
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order of spinothalamic pathway (carries pain and temperature)
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-sensory neurons synapse in dorsal horn of spine
-info immediately crosses to contralateral side -travels to many nuclei in thalamus and other locations -goes to S1 |
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analgesia (definition)
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decreased sensitivity to pain
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types of analgesia
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-opoids
-stress -mating |
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Opiate induced analgesia
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-drugs:morphine, vicodin, heroin
-endogenous opiates: endorphins -FUNCTION BY BLOCKING RELEASE OF SUBSTANCE P (neurotransmitter) |
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stress induced analgesia
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-times of severe stress (war, abuse)
-2 ways: -release of stress hormones increases level of endogenous opiates -release of endogenous cannabinoids in CNS |
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mating induced analgesia
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-during pregnancy and vaginal stimulation
-increased levels of estrogen and progesterone cause release of endogenous opiates |
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referred pain
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-pain receptors are only in skin
-organs signal pain to closest dermatomes |
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phantom limb
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-after amputation, cortex is reorganized to accommodate change, but does not occur immediately
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Proprioception
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-knowing where your body is in space
-(follows dorsal columnpathway w/ other somatosensory info) -2 types of receptors -muscle spindles -golgi tendon organ |
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muscle spindle
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responds to stretch
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Golgi tendon organs
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-respond to increases in muscle tension
-prevent contractions that are too strong |
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Vestibular system (functions)
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-sense of balance
-head movements in all directions |
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location of vestibular system
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-receptors in inner ear
-types of receptors -saccule -utricle -semicircular canals |
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receptor functioning
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-work by displacement of hairs
-info carried by auditory nerve |
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Saccule and Utricle
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-sense head tilt and acceleration
-tilt or acceleration shifts otoliths, which bends hair cells -bending hairs opens or closes K+ channels -confusion between tilt and accerleration |
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Semicircular canals
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-head rotation
-uses differences between the 2 sides to know which direction head is turning -can be fooled (warm h2o, turning toward that side) |
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Nystagmus
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-reflexive eye movement
-counteracts head turn |
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application of nystagmus
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-check to see if vestibular system is functioning correctly
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amplitude
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loudness
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frequency
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pitch
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amplitude measurement
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10-90 dB
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frequency measurement
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number of waves/second 15-20,000 Hz
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pure sound waves
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sound artificial b/c speech is made of multiple frequencies
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purpose of eustcian tube
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adjust for air pressure
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three chambers of cochlea
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scala vestibuli
scala tympani scala media |
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three bones of ear
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hammer
anvil stirrup |
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structure of cochlea
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-oval window where stirrup connects to cochlea
-fluid filled -basilar membrane is covered in specialized hair cells -auditory nerve collects info from hair cells and leaves cochlea |
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function of semicircular canals
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balance and orientation
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function of bones of middle ear
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bones mechanically amplify vibrations from tympanic membrane
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method of transmission in hair cells
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neurotransmitters, no axons
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tectorial membrane
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parallel to basilar membrane, senses movement of hair cells
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trigeminal nerve
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carries sensory information from head
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mechanism of salty taste receptor
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permit sodium ions to cross membrane
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mechanism of sour taste receptor
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H+ ions in, K+ ions out
detects presence of acids |
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mechanism of sweet receptor
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-tastant binds to receptor
-causes release of gustducin -releases 2nd messenger cAMP -closes K+ channel -build up of positive charge causes opening opening of Ca+ channels -release of neurotransmitter |
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mechanism of bitter receptor
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-2nd messenger is IP3
-causes influx of Ca+ |
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mechanism of umami receptor
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-2nd messenger cAMP
-influx of Ca+ |
