NeuBeh 502
Module 1
Terms
undefined, object
copy deck
- Optical power of the eye is provided by the _______... there is a greater difference in the refractive index here
- cornea
- ____ does not provide much optical power; main function instead is to maintain sharp focus on both near and far objects
- Lens
- _______ fibers are critical to the function of the lens:
- Zonular
- Photoreceptors release _______ - no action potentials!
- glutamate
- Rods - generally for low light conditions
- • Very sensitive • Saturate in moderate-bright light • Poor acuity • No color vision
- Cones - generally for daylight vision; very dense in the fovea
- • Not very sensitive • Never saturate • Good acuity • Provide color vision (3 pigments: red, blue, green)
- What is the first cell to use action potentials in the eye?
- Retinal ganglion cells, after rods/cones and bipolar cells, which do not have action potentials
- Bipolar cells: "On" cell is ________ by glutamate, "off" is _________ by glutamate
- inhibited; excited
- What type of cell do rods synapse on?
- Amacrine cell, which is excited by light, and subsequently outputs to ON and OFF midgets.
- Retinal ganglion cells have ______-______ ______ fields, the size of which are ________
- center-surround receptive; not uniform (ie small in fovea, large in periphery)
- The five types of retinal ganglion cells:
- • Midget (~75%) • Parasol (~8%) • Blue-ON cells (~8%) • Direction-selective • Melanopsin (can respond even when photoreceptors are destroyed)
- Stages of the Phototransduction Cascade:
- 1. Photon capture, retinal changes conformation 2. Rhodopsin activated, and then activates transducin, 3. PDE cleaves cGMP Second messenger 4. Closing of Na+ channels 5. Change of voltage inside rod/cone 6. Change in NT release ➢ Key points: • Massive amplification of signal • Slow • Output (transmitter release) is graded
- Light adaptation: Mechanisms
- ➢ Rhodopsin bleaches ➢ Low Ca++ causes opening of reserve Na+ channels ➢ Steady light shortens duration of PDE action
- An important feature in color vision is the ________ of absorption curves
- overlap
- Blue cells have ______ receptive fields, thus ___ acuity... there are no blue cones in the fovea!
- large; low
- What is stereopsis?
- incorporating left and right visual fields to understand depth.This can happen because the visual system is completely crossed
- All six layers of the LGN have a ________ map that is distorted due to the ________ __ _____.
- retinotopic; distribution of cones
- All ___ layers of the LGN have a retinotopic map, and all the maps are stacked on top of each other in _________. However, there is no __________ between layers.
- six; alignment; connection
- Name three novel response properties in V1
- ➢ Orientation-selectivity ➢ Motion preference ➢ Binocularity (*binocular neurons are essential for stereopsis)
- Lesions to V1 cause _______ in visual field
- scotoma (blind spot)
- Two kinds of neurons in V1:
- ➢ Simple-geniculate driven, input stage of V1 ➢ Complex-cortically driven (including by simple cells)
- The extrastriate visual cortex has two processing streams. What does the ventral pathway concern?
- Ventral stream: V1 -> V2 & V3 -> V4 -> inferotemporal visual areas -> area 7 • Vision for perception • Visual illusions? • Area LIP - receives input from MT (see below) • Grandmother cells • Inferotemporal Cortex - important for object recognition (we just don't know how yet)
- What information is processed in the dorsal pathway?
- V1 -> V2 & V3 -> MT ->MST and parietal visual areas (most notably LIP) -> area 7 • Vision for action • Motion pathway? • Area MT - responsible for perceiving direction of motion • Most cells require moving stimuli • Most cells are direction selective • Some cells are selective for direction in depth • Some cells are selective for absolute distance of target • Image motion caused by motion of animal itself doesn't cause firing
- The superior colliculus also has _________ organization, and receives input from 3 structures:
- retinotopic •Receives input from retina, parietal cortex and motor cortex
- In the superior colliculus, stimulation to ________ ____ ______, which has no receptive field, causes ________ to where visual field would be
- intermediate deep layer; saccades (Rapid Eye Movements)
- The SC was once thought to only control eye movement, but maybe not. Why?
- owls have huge SC but cannot move eyes at all
- Flavor is derived from a combination of 3 sensory inputs:
- 1. taste, 2. olfactory, 3. somatosensory
- There are 6 tastes. What are the important points about sweet?
- ➢ Sweet (G-Coupled) • Combination of two receptors, T1R2 & T1R3 • Expressed in both circumvallate and foliate papillae
- Carbonated is what kind of receptor?
- ➢ Carbonated (Ionotropic), same receptor as sour
- Sour:
- ➢ Sour (Ionotropic) • Sour taste channel is composed of two related channel subunits, PKD1L3 & PKD2L1. • Expressed in circumvallate and foliate papillae involve permeation of blockade of channels K+ H+
- What type of receptor is salty?
- ➢ Salty (Ionotropic) Transduced at least in part by diffusion of Na+ ions
- Bitter:
- ➢ Bitter (G-Coupled & Ionotropic) • T2Rs - different T2Rs detect different bitter tastants • Expressed in all three papillae
- Umami:
- ➢ Umami/ "savory" (G-Coupled) • Combination of two receptors, T1R1 & T1R3 • Expressed in fungiform papillae
- _______ are detected by receptor cells in taste buds in taste _______
- Tastants; papillae
- The three types of taste buds and their locations:
- ➢ Circumvallate (back of tongue, 100s buds/papilla) ➢ Foliate (sides of tongue, 100s buds/papilla) ➢ Fungiform papilla (anterior 2/3s of tongue, 1-5 buds)
- Taste cell diagram. How does it relate to labeled line?
- Labeled line model: different taste cells are dedicated to different taste modalities (see image right)
- Taste Pathway:
- Taste cells die every ____ ____; another similar must replace it. _______ fiber must specify what kind of cell should form!
- few weeks; Afferent
- G-Coupled Receptors ⇨
- ATP
- Sweet, bitter and umami use different _________ but converge onto the same _________ pathway
- G-proteins; signaling
- The amplification through G-coupled receptors allows you to _______ _____ ______ of these tastants... evolutionarily relevant
- detect small amounts
- Ionotropic Receptors ⇨
- 5-HT
- Name the 5 steps in the taste process up to action potentials being sent to the brain:
- 1. Ligands activate taste cell 2. Intracellular pathways are activated 3. Ca2+ signal in the cytoplasm triggers exocytosis or ATP formation 4. Neurotransmitter or ATP is released 5. Primary sensory neurons fire and action potentials are sent to the brain (taste cortex)
- Where else does taste occur besides in the mouth?
- gut and airways
- Olfactory pathway:
- Olfactory epithelium (with olfactory receptor cells) ⇨ Cranial Nerve I ⇨ Olfactory bulb ⇨ Olfactory tract ⇨ Olfactory cortex. From there it goes to the cerebral cortex and limbic system
- Additional olfactory path image:
- Olfactory Bulb image
- Olfactory cells image:
- Olfactory cells in the olfactory epithelium live only about two months. They are replaced by new cells whose axons must find their way to the olfactory bulb.
- Olfactory neurons: Each sensory axon terminates in a single _________, forming synapses with the dendrites of __________ interneurons and _____ & ______ relay neurons. The primary dendrite of each mitral and tufted cell enters a single glomerulus, where it __________ extensively.
- glomerulus; periglomular; mitral and tufted; arborizes
- Mitral and tufted cells also extend secondary _______ into the external ________ layer, where granule cell interneurons make reciprocal synapses with these secondary dendrites. The output of the bulb is carried by the mitral & tufted cells, whose axons project in the ______ olfactory tract.
- dendrites; plexiform; lateral
- Within each glomerulus periglomular cells form ________ contacts with ______ cells that receive input in nearby glomeruli. The secondary dendrites of mitral & tufted cells form ________ synapses on the dendrites of _______ cell interneurons, which form inhibitory synapses on numerous secondary dendrites
- inhibitory; mitral; excitatory; granule
- These _________ connections may provide a curtain of inhibition that must be penetrated by the peaks of excitation generated by _______ stimuli. They may also serve to ____ or _____ sensory information prior to transmission to the olfactory cortex.
- inhibitory; odorant; sharpen or refine
- • Axons of neurons with the same olfactory receptor converge in ________ - clusters of dendrites - in olfactory bulb
- glomeruli
- The two relay neurons leaving olfactory bulb are:
- -Tufted cell relay neuron -Mitral cell relay neuron - projects to cortex directly
- Each Olfactory Sensory Neuron expresses only one __________ ______ _____
- olfactory receptor (OR) gene
- Though we only have a few ________ ORs, we can detect ______ odors
- hundred; 5,000+
- Some complex odorants can bind to _________ (the more complex the odorant molecule, the more ORs it could potentially "fit")
- multiple ORs
- Four touch receptor endings in skin:
- ➢ Ruffini corpuscle: Type III SA, Small RF; pulls collagen fibers when activated ➢ Pacinian corpuscle: RA, Large RF; "vibration detectors" ➢ Meissner corpuscle: RA, Small RF ➢ Merkel receptor: Type I SA, Small RF
- Acuity in somatosensory system is related to receptor ________.
- density
- Touch relay nucleus is layered in the way neurons _________; layers are not visible through staining, etc.
- respond
- Ratio of S1 to total brain size is quite _______ in humans compared to in other mammals
- small
- Four highly ordered areas in S1, all getting direct information from VPL:
- • Area 1: RA; texture • Area 2: Touch receptive fields, shape • Area 3b: gets input from VPL and sends it to other areas
- Somatotopic mapping reflects receptor ________... maps can change (plasticity)
- density
- Layer 4 in the rat brain - barrels, each belonging to one ________
- whisker
- What type of fiber to sharp pain signals travel through? How are they activated?
- • Aβ fiber • Activated by intense mechanical stimulation or high heat
- What type of fiber does Dull (aching, burning) pain travel through? What tissue do these fibers innervate?
- • Type I: polymodal nociceptor, C fiber; Activated by substances released by tissue damage, and/or acid, heat, noxious substances • Type II: polymodal nociceptor, C fiber; activated by substances released by tissue damage, acid, cold, intense mechanical stimulation • Innervates ALL soft tissue except brain and lens of eye, as well as some deep organs
- • Conductance is variable... fine touch receptors conduct ____, sharp and dull pain conduct ____ & ____ ___, respectively
- fast; slow and very slow
- Nociceptors conduct so slowly because ....
- the function of pain is to modify behavior on a slow time scale (minutes, hours, days...)
- What is Congenital analgesia?
- congenital insensitivity to pain
- What is Hyperalgesia?
- intense pain in response to mildly painful stimulus; spread of hyperalgesia is adaptive, forces you to protect yourself
- What is Allodynia?
- pain in response to completely innocuous stimulus
- What is the ascending pathway for touch as it enters the brain?
- •Spinothalamic tract shrinks on ascent to thalamus •Begins at tract of lissauer → trigeminal ganglion •Target of VMpo is insula, cingulate gyrus
- The descending pain modulation system can be activated by:
- • Opium and its derivatives • Stress • Fear • Hunger • Thirst • Fatigue • Prolonged motor activity • Hypnosis
- Endogenous opioid transmitters include:
- endorphins, enkephalins, dynorphins
- What is neuropathic pain?
- pain caused by damage to the system
- What is tic douloureux (trigeminal neuralgia)?
- pressure of cerebellar vessel on trigeminal tract causing stabbing pain to the face
- What is tabes dorsalis?
- a slow degeneration of the sensory neurons that carry afferent info. The degenerating nerves are in the dorsal columns of the spinal cord & carry information that help maintain a person's sense of position (proprioception), vibration, and discriminative touch.
- What is a phantom limb?
- the sensation that an amputated or missing limb is still attached to the body; Approx. 60 to 80% of individuals with an amputation experience phantom sensations in their amputated limb, & the majority of the sensations are painful
- why does phantom limb pain happen?
- It occurs because of rearrangement of the somatotopic map. Pain is the perceptual correlate of cortical reorganization
- Important anatomical areas to the descending pain pathway:
- Sound is a travelling pressure wave with what important parameters? parameters?
- Frequency Amplitude/Intensity Source
- What are the important components of frequency?
- • Pure tones have single frequency • Fourier transformation can describe component frequencies of complex sounds
- What are the important components of amplitude?
- • Perceptual range • Units: decibels
- What are the important components of source localization?
- speed, wavelength and shadows • Speed depends on medium • Directionality defined by origin & wavelength
- Auditory processing schematic
- Important auditory structures of the outer ear:
- What structures of the outer ear provide resonance amplification & directionality cues?
- • Cartilaginous flange (pinna) • Resonant cavity (concha) • Ear canal (external auditory meatus) • Ear drum (tympanic membrane)
- Important structures of the middle ear:
- How does the middle ear aid the transduction of sound?
- ➢Middle Ear = transformer; couples sound energy from drum (air) to cochlea (water) - •Impedance = sound pressure/particle velocity •Energy transfer by middle ear partially alleviates impedance match •Middle ear reflex - muscles connect to malleus and stapes; contraction stiffens bones and reduces transmission at low frequencies
- Purpose of the inner ear:
- Inner ear is a coiled tube that transduces sound and performs a biological Fourier transformation
- Important structures of the cochlea:
- How long is the cochlea?
- 34 mm in humans
- Organ of Corti covered by ________ membrane
- tectorial
- Movement of Organ of Corti stimulates ______ _____ ____, initiating action potentials to CNS
- Inner Hair Cells;
- Traveling waves distribute frequency specific excitation along cochlear ________
- epithelia
- How does the cochlea exhibit frequency specific excitation?
- Hair cell length varies over cochlear tract ➢High frequency is picked up at the base by shorter hair cells ➢Low frequency is picked up at the apex by longer hair cells ➢Basilar membrane displacement increases from base to apex
- What is the function of outer hair cells?
- Outer hair cells amplify displacement of basilar membrane (i.e., cochlear amplifier)
- How do outer hair cells relate to inner hair cells?
- ➢Activity increases sensitivity of adjacent IHC ➢No neural connection between IHC and OHC
- What is the function of inner hair cells?
- Inner hair cells transform frequency-specific mechanical activity into electrical activity (auditory encoding based on place coding), which is an active process
- Important structures seen in a cochlea cross section:
- Important factors in sound transduction in cochlea:
- ➢Frequency-specific following place code of cochlea ➢Requires metabolic energy ➢Depends on endolymphatic cochlear battery ➢Requires prestin
- In regard to hair cells, what does sound transduction depend on?
- •Sound transduction depends on intact, actin-filled stereociliary bundles, displaced toward tallest ST.
- What connects ST bundles?
- •ST bundles are connected by stiff tip-links containing Cdh23 and Pcdh15
- Transduction channels at ST tip are mechanically gated by ________ __________.
- bundle displacement ➢Largest current at top of SC ➢~100 channels per hair cell
- HC depolarization gives rapid, secure release of multi-quanta from _______ ______ onto afferent neurons
- ribbon synapses
- Ribbon synapses provide finely ______, high frequency responses to environmental stimuli; are present in:
- graded; rods/cones, bipolar cells of retina and cochlear hair cells
- Adaptation of bundle displacement depends on:
- Ca++ influx
- Sensory adaptation refers to:
- ➢Decay of response to sustained stimulus, which reflects importance of change/novel input ➢Provides high-pass filter attenuating responses below a certain frequency
- Hair cells: Receptor vs. Effector
- Process of sound transduction:
- •Auditory (8th) Nerve ➢95% of AN fibers are from Type I ______ ganglion cells ➢Auditory information is encoded as action potentials in _______ fibers of spiral ganglia/AN ➢Single AN axon carries information from _____
- spiral; afferent; 1 IHC
- What is the dynamic range of a single AN fiber?
- Dynamic range of single fiber is ~40 dB
- What is the overall auditory sensory range?
- Sensory range is ~120 dB
- Mechanism for intensity coding:
- •Use high threshold fibers •Spread excitation to adjacent fibers... may work for pure tones, not for complex signals •Efferent system shifts threshold/saturation 10 dB up •Middle ear reflex (low frequencies reduced 10dB)
- Important structures of the auditory pathway:
- Auditory Information Coding: ______ AN fibers carry info from _____ IHC
- 50,000; 3,000
- AN fibers are tuned to a Best or ________ _______; reflecting the hair cell innervated
- Characteristic Frequency (CF)
- Low threshold fibers have high ________ rates; _____ threshold have low spontaneous rates
- spontaneous; high
- Spike frequency _______ so Intensity can be coded using multiple strategies
- saturates;
- Complex sounds have unique/complex ______ that are detected by neurons in auditory cortex
- spectra
- 3 important functions of the Olivocochlear bundle
- •Allows for better signal discrimination •Protects from noise damage •Can modulate mechanical state of Basilar Membrane
- In the central auditory system ________ is maintained cochlea to cortex
- tonotopy
- Paired cochlea contain slightly more than _______ receptor cells
- 30,000
- Sound consists of alternating ________ & ________ propagating through an elastic medium: air.
- compression & rarefaction
- The _______ ear is not uniformly effective for capturing sounds from any direction; the auricle's corrugated surface collects sounds of different _________ best when they originate at different, but specific, positions with respect to the head
- external; frequencies
- Uppermost fluid filled compartment of cochlea:
- scala vestibuli
- Lowermost fluid filled compartment of cochlea:
- scala tympani (has the round window at the end)
- The _____ _____ or cochlear duct separates the other two compartments along most of their length
- scala media
- The _______ ______, which forms the partition between the scala media and the subjacent scala tympani, is a complex structure upon which _______ transduction occurs
- Basliar membrane; auditory
- ________ is a transmembrane protein that mechanically contracts and elongates leading to __________ of outer hair cells (OHC). Eletromotility is the driving force behind the somatic motor of the cochlear amplifier
- Prestin; electromotility
- ________ is released in a quantal manner from inner hair cells onto ______ ______ cells
- Glutamate; spiral ganglion
- Relatively few cochlear ganglion cells innervate _____ hair cells, and each such ganglion cell extends branching terminals to ________ outer hair cells. Because there are so few, it is unknown if these cells even contribute significantly in hearing.
- outer; numerous
- Ventral cochlear nuclei contain two cell types, with two separate functions:
- Stellate cell: encodes frequencies present in auditory input Bushy cell: provide accurate information about timing of cells
- The ____ performs sound localizations by examining information about auditory delay between the two ears.
- MSO
- The _____ is also involved in sound localization, but uses _______ cues to calculate where a sound originated
- LSO; intensity
- The ____ includes many neurons responsive to low frequency inputs, while the ____ includes many neurons responsive to high frequency stimuli.
- MSO; LSO
- Tip link tension and adaptation to sustained stimuli to hair cells is thought to be regulated through
- Special myosin molecules that systematically adjust tension of tip links by migrating, and pulling the insertion with them
- Hair cells that respond to low frequency have the _______ bundles
- longest
- What type of cell accomplishes the task of creating the surround in center-surround receptive fields?
- Horizontal cells
- The parasol cell is_____
- sensitive to low contrast borders, & processes no color
- Image of RGC cell sizes:
- LSO/MSO auditory pathway
- Cartoon of photo transduction
- Cell types in the CN
- CN divisions illustration:
- Visual pathway through extrastriate cortex illustration:
- Area ___ is a general purpose motion analyzer that informs about direction of motion and speed. It can dtermine direction of stimuli when as little as 7% of dots are moving in the same direction
- MT
- Superficial layers of the SC deal with ______, while the deeper layers are related to _____
- visual responses; motor behavior
- The somatosensory system performs three distinct tasks
- 1) Fine touch. Serves to inform you about objects and the environment immediately around you. 2) Proprioception. Provides information from your muscles and joints that is critical both for maintaining a stable position, and for making accurate movements. 3) Pain. Pain serves to protect you from damage
- Fine touch receptors are all ______ and their cell bodes reside in the _____ ____
- cutaneous; dorsal root
- Cutaneous receptors in non-hairy skin of the hand illustration:
- 1) RA type 1 = Meissner corpuscle 2) RA type 2 = Pacinian corpuscle 3) SA type 1 = Merkel disk receptor 4) SA type 2 = Ruffini corpuscle
- Receptors that mediate fine touch are known as __ ____ receptors
- A beta
- Discriminating between different RA receptors - ________ ________ respond to lower stimulus frequencies than do ________ _______, which are generally considered to be vibration detectors
- Meissner corpuscles; Pacinian corpuscles (Meissner corpuscles also have much smaller and more sharply-defined receptive fields)
- The two kinds of SA receptor can be distinguished by their spontaneous firing rates. ______ ____ receptors have no spontaneous activity, while _______ ______ have a regular discharge, and by their receptive field size: (who is larger?)
- Merkel disk; Ruffini endings (Ruffini endings have large receptive fields)
- When a ________ corpuscle was activated, the subjects felt vibration, with perceived intensity increasing as stimulus frequency increased up to ~200-300 Hz. When a ______ disk receptor was activated, the subjects felt pure pressure.
- Pacinian; Merkel
- In the case of the _______ ______, the branches of the fine unmyelinated process are intertwined among a bundle of collagen fibers that run the length of the capsule
- Ruffini ending; (When the skin is stretched, the collagen fibers are squeezed together, pinching and deforming the neural processes)
- In the hand, _______ corpuscles (RA type 1) have their highest density in the finger tips, with their density dropping as you move toward the palm. The densities of _____ ____ receptors and ________ corpuscles fall off less dramatically, while the density of Ruffini endings appears to be uniform.
- Meissner; Merkel disk; Pacinian
- _________ receptors as a population display a full range of adaptation rates: some are SA, and some are RA. Many are also direction selective, giving a sustained response to slow deflections of a whisker in, for example, an upward rostral direction, and no response to deflection in the opposite direction.
- vibrissal
- In humans, axons entering below the belly button run in the medial division of the dorsal columns, the ______ fasciculus. Axons entering above this level run in the lateral division of the dorsal columns, the ______ fasciculus.
- gracile; cuneate
- Illustration of VPL/VPM mapping:
- The 2 RA cutaneous layers differ from each other in that the more superficial one gets input from Pacinian corpuscles and Meissner corpuscles. In the deeper RA layer, _______ information is excluded.
- Pacinian
- To understand the different somatosensory maps, Randolph and Semmes made small lesions restricted to the hand representation of just one area within S1, which resulted in:
- A loss of ability to discriminate by texture - they could no longer discriminate between hard and soft objects, or between rough and smooth ones.
- Lesioning area SII resulted in:
- A lesion of area 2 destroyed their ability to distinguish between shapes, e.g. between a diamond and square, or between convex and concave.
- Lesioning area SIIIB was the most devastating because:
- Monkeys could discriminate neither texture nor form. What happens with lesions of area 3a is unknown.
- All ________ information that reaches the brain is preprocessed in the spinal cord
- nociceptive; These ascending and descending branches may travel up to 4 levels above or below their point of entry, but no farther
- laminae III and IV are together called ________ ______, and lamina II is the _______ _______, a name that you will hear frequently in reference to pain processing.
- nucleus proprius; substantia gelatinosa
- most axons of the ___________ tract do not make it all the way to the thalamus - they stop and synapse somewhere along the way in the brain stem.
- spinothalamic
- The pain/temperature pathway is simpler for the head and face than for the body. Primary sensory neurons have their cell bodies in the _________ ganglion.
- trigeminal
- Medial view of human brain showing regions of high activity in cingulate gyrus found with PET orfMRI scans in two different conditions. Aqua regions were activated by painful heat. Orange region was active when the subject performed the "Stroop" task.
- Lesions of the _______ result in a curious syndrome, pain asymbolia, in which the patient remains aware of painful stimuli and can distinguish sharp from dull pain, but no longer finds pain to be aversive. Thus pain has become disconnected from ________.
- insula; suffering
- What substances excite polymodal nociceptors?
- bradykinin, histamine, prostaglandin, and K+ Other excitatory substances include acids, capsaisin (the active component of chili peppers) and similar components of mustard and black pepper. A large subset of C nociceptors are also activated by intense mechanical stimulation and by heat (> ~45 deg).
- __ _______ nociceptors signal "sharp" pain that is well-localized and of rapid onset. ________ nociceptors give rise to dull aching or burning pain that is more delayed and is poorly localized.
- A delta; Polymodal
- When C fibers are activated, they release substance P, which has 2 effects: It causes ________, and it triggers the release of ________ from mast cells.
- inflamation; histamine
- Nociceptors become increasingly sensitive when stimulated, and may end up responding to mild and quite ________ stimuli
- innocuous
- __ ____ receptors, do not send axons directly to the brain, This arrangement provides an opportunity for _________ of the strength of the pain signal that is sent to the brain.
- A beta; modulation
- The exact mechanism of pain modulation is not known, but we do know that 1) it occurs in the _____ ____ and 2) descending axons from the ______ ____ play a major role in inhibiting nociceptors
- dorsal horn; Brain stem
- Descending pain modulation system illustration:
- Descending pain input illustration:
- What normally activates the descending pain modulation system?
- Stress and fear are potent activators, as well as simple motor activity, at least of large muscle groups
- ➢ Ruffini corpuscle:
- Type III SA, Small RF; pulls collagen fibers when activated
- ➢ Pacinian corpuscle:
- RA, Large RF;"vibration detectors"
- ➢ Meissner corpuscle:
- RA, Small RF
- ➢ Merkel receptor:
- Type I SA, Small RF
- Taste cell illustration
- Sweet, bitter and umami use different G proteins, but converge onto identical signaling pathways mediated by PLCB2
- Taste transduction:
- DIFFERENT TYPES OF TASTANTS ARE DETECTED BY DIFFERENT TASTE CELLS THAT EXPRESS DISTINCT MEMBRANE RECEPTORS OR IONOPHORES
- Chorda tympani & petrosal ganglion?
- Chorda goes to facial for taste (anterior 2/3 of tongue), petrosal goes to glossopharyngeal (posterior 1/3) go to solitary tract of medulla, to thalamus VPM, to gustatory cortex