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91 Cards in this Set
- Front
- Back
Frequency
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number of cycles per second of air pressure chane passing a point in space. Measured in Hertz
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The higher the frequency...
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the higher the perceived pitch. Doubling frequency raises the sound an octive.
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pinna
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external part of the ear, helps collect sound and is more sensitive to sounds from ahead than behind. The convolutions help localize sound
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Tympanic membrane
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the "eardrum", fluctuations in the air pressure cause the membrane to vibrate, vibrations match the frequency of the sound
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3 ossicles
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"ear bones"; they transmit vibrations from the eardrum to the oval window membrane
they amplify the sound |
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attenuation reflex
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the onset of a high intensity sound causes muscles around the ossicles to contract reducing the movement of the ossicles. Helps prevent loud sounds from saturating the auditory receptor cells in the inner ear
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oval window
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the membrane covered hole on the wall of the coclea
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cochlea
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the part of the inner ear concerned with hearing. Ossicle induced movements in the oval window move fluids in the cochlea which trigger auditory transduction
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3 cochlear chambers with fluid:
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scala media between Reissner's membrane and the basilar membrane.
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Place coding
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the location of the resonating membrane (on the cochlea) informs the brain of the sound frequency
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Shaft vs apex
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higher frequency is closer to the shaft where it is stiff. Lower frequency is at the apex where the basiler membrane is wide and floppy
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Auditory transduction cascade
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at rest, sterocilia stand vertically and channels are partially open. When movements in the basilar membrane cause the longest row of sterocilia to move away from others, the tip links are stretched and pill the channels wider open. When the logest row of stereocilia bends toward the others, tension on the tip links is reduced and the channels close
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inner hair cells vs. outer hair cells
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the inner hair cells account for 95 percent of the spriral ganglion cells, the outter only 5 percent.
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Amplification of low intensity sounds
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comes from the outer hair cells. the motor proteins on the outer hair cells compress during a depolarization which leads to the inner hair cells sterocilia bending more--> greater depolarization
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Perceived intensity of sound depends on:
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1. the rate of spiral ganglion cell firing (amount of NT released)
2. the number of spiral ganglion cells that are firing |
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characteristic frequency
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the frequency to which the auditory neuron is most sensitive
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tonotpic mapping or tonotopy
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the systematic relationship between location and chaaracteristic frequency is perserved in subsequent stages along the auditory pathway
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phase locking
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the consistent firing of spiral ganglion cells at the same phase of a sound wave, arising from the presynaptic hair cells membrane potential that follows the oscillations in sound pressure
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Primary pathway from cochlear nuclei to cortex:
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each ventral cochlear nucleus sends axons to both superior olives. The superior olive localizes sounds in the horizontal plane.
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Superior olive
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first structure in the auditory pathway with binaural neurons, which localize the sounds in the horizontal plane
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interaural time delay
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sound coming from one side of the body will reach the ear on that side before reaching the other ear. Only works for frequencies with wavelengths wider than the width of the head (ie low frequencies)
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Delay line
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some birds have delay lines so that the spike from the two ears arrive at the same time and summate for a larger EPSP
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Interaural intesity difference
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the head casts a sound shadow such that the ear in the shadow detects a lower intensity sound
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EE cells
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neurons in the superior olive that are moderately excited by sound from either ear, and maximally excited when both ears are stimulated (aka respond best to sound on midline).
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EI cells
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maximal response when sound comes from the excitatory side and minimal response from the inhibitory side
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Localization of sound in the vertical plane
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uses the convolutions of the pinna to assess elevation of sound. Doesnt require both ears
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A1
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primary auditory cortex
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isofrequency bands
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strips of neurons with similar characteristic frequencies
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A1 output
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to higher auditory cortical areas that process very complex sounds (aka Wernickes area)
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Lateral Line system
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lateral line receptors are hair cells with cilia embedded in a gelatinous material (cupula). When the cupula moves, the cilia are bent and trigger a depolarizing response
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cupula
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gelatinos material in the lateral line receptors. The cilia of the hair cells are embeded in the cupula
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Vestibular system
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monitors the position and movement of the head and communicates thaat position to motor centers in the brain. helps maintain body balance
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Vestibular labyrinth in the inner ear
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connected to the cochlea and fulled with the same endolymph
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Otolith organs detect:
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changes in head angle and linear acceleration
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Uticle
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layer of hair cells (macula) parallel to the ground while the person is standing (in otolith organs)
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Saccule
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macula perpindicular to the ground while the person is standin (in otolith organs)
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macula
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hair cells in the otolith organs
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Otoliths
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ear stones in the gelatinous cap of the otolith organs
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transductin cascade for vestibular hair cells:
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each mechanically gated K channel on a sterocilium is connected by an elastic top link to the channel adjacent. Sterocilia straight up: channels partially open. etc
K enters the endolymh--> depolarization |
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Macular orientation of hair cells
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each hair cell selects for a specific deirection of head movement. The entire population of hair cells covers all possible direction of linear movement.
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Hair cells in the semiciruclar canals:
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filled with endolymph, stereocilia project into the gelatinous capula. Upon head rotation canal wall rotates but endolymph initially stays still causing fluid motion opposite to head motion. The capula moves with the fluid and bends th ehair cells sterocilia.
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Response to velocity change in teh vestibular hair cells:
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1. if velocity remains constant, then the otliths and the cupula return to resting potentials
2. the hair cells also adapt to the sustained stimuli (never return fully to their resting potential) |
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Central vestibular pathway
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hair cells release excitatory NT onto the dendrites of the Scarpa's ganglion cells whose axons form the vestibular nerve. the vestibular nerve projects to the cerebellum which coordinates motor activites and to the vestibular nuclei
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vestibular nuclei project to:
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spinal cord motor neurons to control muscles in the legs, also motor neurons in trunk and neck that orient head, motor neurons that move eyes, and thalamus which projects to the primary somatosensory cortex and the primary motor cortex
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vestibule-ocular reflex
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enables you to keep your eyes fixed on a point even when your head is moving. Works in complete darkness
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soma
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the body of an organism
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somatic sensations
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all the sensation that are not the five sense. Aka sensations of our skin, muscles, joints, and internal organs; touch, pain, and temperature
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touch transduction by mechanoreceptors
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mechanical deformation of cell membrane--> channels open--> depolarization--> action potential
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Mechanoreceptors nerve endings
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unmyelinated and encapsulated by special non-neural tissues which determine types of tactile stimuli each cell type is sensitive to
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Mechanoreceptor channels
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gated cation channels which probably include TRP channels
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Somatic sensory receptors
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cell bodies in the dorsal root ganglia, they are pseudo-unipolar. The axons of these are called primary afferents. The proximal side of these axons enters the dorsal side of the spinal cord
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receptive field size increases with...
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depth of skin
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dermatome
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area of skin innervated by each spinal nerve
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touch pathway
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alpha and beta axons carrying touch information enter the dorsal horn of the spinal cord:
one branch goes deeper into the dorsal horn to initiate or modify reflexes. the other branch follows the dorsal column to go to the brain. |
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projection to the cortex through the dorsal column-medial lemniscal pathway:
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primary afferents ascend ipsilaterally in forsal column and synpase on to second order neruons in the brain. Second order neurons cross over in the brain stem then project to the ventral posterior lateral nucleus of the thalamus.
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S1 also called:
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brodmanns area 3b
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S1 organization
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neocortex with 6 layers: thalamus to layer IV, layers II and III to orther cortical areas, layers V and VI to subcortical areas
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columnar organization of S1
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by receptor type and location: rapidly adapting neurons and slowly adapting neurons aligned in columns
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somatotopy
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the orderly projection of body parts onto a somatosensory nucleus or cortical area
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Experiments that show somatotopy
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1. electronically stimulating across s1 and observing what area of the body feels a touch sensation
2. also stimulating the body and recording neural activity in s1 |
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homunculus:
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illustrated the relative body representation in the somatosensory cortex. there is over representation of body parts with high densities of receptors
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lateral inhibition does what for the s1 neurons?
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enhances spactial contrast between second order neurons and neighboring neurons. This enhancment in spatial contrast improves two point discrimination
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area 1
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texture
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area 2
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size and shape
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beyond s1 the stimuli that neurons perfer becomes...
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more complex. Rf are larger and some cells are direction selective
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areas 5 and 7
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posterior parietal cortex: integrates tactile inpu, proprioceptive input, and visual information to identify objects. also sends sensory info to motor cortex for movement
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sensory cortical plasticity:
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if the input to a cortical area is underused or removed, surrounding areas of cortex may take over that region. If the input is frequently activated then the rfs may expand over time
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nocioception
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sensory transduction process that provides the signals that tigger pain
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nocioceptors:
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DRG cells with free, branching, unmyelinated nerve endings
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hyperalgesia:
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increased sensitivity to pain stimuli. caused by chemicals released or synthesized when tissues are damaged. chemicals include bradykinin, prostoglandins, and substance P which induces histamine relasese
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Nocioceptor input into the spinal cord
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nocioceptors signal to the spinal cord through A and C fibers which conduct spikes at different speeds. These primary afferents enter the dorsal horn and branch immediately and quickly synapse on to second order neurons using glutamate and substance P as excitatory transmitters
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pain pathways to the cortex
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second order pain neurons crossover immediately and ascend through the spinothalamic tract. The the thalamus the pain touch pathways ocupy different parts of the VPL nucleus and the pain pathway occupies additional thalamic regions.
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nocioceptors in the face pathway to the cortex
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go through the trigeminal nerve to reach second order cells in the brain stem which corssover immediately and ascend to the VPM and other thalamic regions
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afferent regulation:
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pain evoked by nociceptors can sometiems be reduced by simultaneous activation of touch receptors. this is why rubbing the skin around an injury can reduce the pain
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gate theory of pain
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an interneuron serves as a gate that can permit or block signal transmission from the c fibers to second order neurons
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reducing pain perception via descending regulation
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certain emotional and behavioral states activate periaqueductal gray matter neurons, which activate a descending pathway that uses serotonin and endorphins t osuppress the activity of nociceptive neruons in the dorsal horns
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reducing pain pereption via endorphins
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endorphins are endogenous morphine like substance that activate opioid receptors. Activated opioid recpeotrs depress the activity of neurons in the pain pathway by supressing the release of glutamate from presynaptic terminals and hyperpolarizing the postsynaptic neurons
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thermoreceptive nerve endings
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free unmyelinated nerve endings
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TRP channels
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30 have been identified and all are cation channels with six transmembrane domains
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adaptation in thermoreceptors
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the response amplitude of thermoreceptors is highest during and shortly after temperature changes. The temperature pathway is virtually identical to the pain pathway however the two are parallel pathways so info is kept seperate
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electroreception
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process of sensing electric fields
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two kinds of electric field sensing abilities
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1. passive electric sense: can sense an electric field but cannot generate one of their own (sharks)
2. active electric sense: can generate an electric field of their own (electric eel) |
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Electric fields
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generated by seperation of positive and negative charges. to detect an electric field there must be current and flow of charges
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Electric organ discharge (EOD)
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readily observable electrical signal generated by the excitable cells of an electric organ. Behavioral significance: electrolocation, electrocommunication, and stunning prey/warding off predators
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ampullary organs:
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low frequency sensitive receptors. all electric fish have them and they detect weak electric fields. its a jelly lumen with high K+
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ampullae of lorenzini
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can detect the earth's magnetic field
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tuberous organs
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high frequency sensitive receptors. used for electrolocation and electrocommunication.
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Electric organ discharge (EOD)
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readily observable electrical signal generated by the excitable cells of an electric organ. Behavioral significance: electrolocation, electrocommunication, and stunning prey/warding off predators
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ampullary organs:
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low frequency sensitive receptors. all electric fish have them and they detect weak electric fields. its a jelly lumen with high K+
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ampullae of lorenzini
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can detect the earth's magnetic field
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tuberous organs
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high frequency sensitive receptors. used for electrolocation and electrocommunication.
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