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phys
somatosensory receptors and somatic sensation
| Question | Answer |
|---|---|
| what kind of somatosensory receptors would be stimulated for visual transduction | g protein coupled photo-receptor. agonist: PHOTONS (light) |
| what kind of somatosensory receptors would be stimulated for olfactory transduction | g protein coupled chemo-receptor. agonist: ODORANTS |
| what kind of somatosensory receptors would be stimulated for gustatory transduction | g protein coupled chemo-receptor, ion channel coupled chemo-receptors. both detect tastants (bitter, sweet, sour, umami) |
| what kind of somatosensory receptors would be stimulated for auditory transduction | mechanoreceptors: detect soundwaves |
| what kind of somatosensory receptors would be stimulated for touch (tactile) | mechanoreceptors (pressure, vibration, itch, tickle) |
| what kind of somatosensory receptors would be stimulated for touch (proprioception) | mechanoreceptors (joint angulation, muscle tension, muscle stretch) |
| what kind of somatosensory receptors would be stimulated for touch (nociception) | chemoreceptors (tissue damage, ischemia, inflammation), thermoreceptors (excessive heat or cold), and mechanoreceptors (stabbing, cutting pressure) |
| what kind of somatosensory receptors would be stimuated for touch (thermoreception) | thermoreceptors, heat, heat-pain, cold, and cold-pain |
| what is a receptor potential? | a change in membrane potential (depolarize or hyperpolarize) that occurs following a sensory stimulus |
| what are two mechanisms by which receptor potentials trigger afferent nerve signals | AP NT release (following increased Ca and vesicle fusion) |
| define adaptation | adaptation is an initial high impulse rate to a sensory stimulus that progressively slows until the response slows to a few impulses or none at all |
| define slow adapting and give some examples of slowly adapting receptors | sensory receptors that continue to transmit impulses as long as the stimulus is present: tonic receptors golgi tendon apparatuses, pain receptors, baroreceptors, and peripheral chemoreceptors |
| define rapidly adapting and give some examples of rapidly adapting receptors | sensory receptors only react strongly when a change in stimulus takes place- rate, mvmt, or phasic receptors hair-end organs, meissners corpuscles, and joint rate receptors |
| why would a sensory receptor be slowly or rapidly adapting? | slow ones are needed when persistent detection of a stimulus is required (pain, steady pressure, etc). fast ones are needed to detect movement or rapid changes in stimuli |
| whats the difference between A and C fibers? | A fibers are faster; myelinated and have larger diameters C fibers are slower; unmyelinated and have smaller diameters |
| what are some sensory receptors that transmit via type A fibers? | hair, pacinians, merkel, meissner |
| what are some sensory receptors that transmit via type C fibers? | nociceptors (chemoreceptor flavor), free nerve endings, thermoreception |
| explain the rationale for why a sensory signal would travel through a Type A fiber vs. a Type C Fiber | signals in which instantaneous info and/or high spatially localized info is required, the signal is more likely to travel through a Type A fiber. if we dont need instant transmission, or high spatial localization is not a priority, Type C fibers will do |
| compare spatial summation vs. temporal summation | spatial: concerns the number of sensory nerves stimulated (the more stimulated, the greater the signal strength) temporal: concerns the frequency of sensory nerve impulses (the greater the frequency, the greater the signal strength) |
| what determines if a zone will be excitatory or facilitory? | if an excitatory zone, glutamate, moves the neuron over threshold and an AP is elicited. if a facilitory zone, the excitatory transmitter, glutamate, moves neuron closer to threshold, but no AP is elicited |
| what determines if a zone will be excitatory or inhibitory? | NT is released and postsynaptic receptor expression pattern determines if a zone is excitatory or inhibitory. a neuronal pool that responds to GABA is an inhibitory zone where as a neuronal pool that responds to glutamate is an excitatory zone |
| compare and contrast convergence and divergence of sensory signals | convergence deals with incoming signals that unite to excite a single neuron; it can be single source or multi-source divergence deals with outgoing signals...it can be amplification (spreading out the info) or multi-tract (send in multiple directions) |
| design a simple reciprocal inhibition circuit | an incoming signal diverges to generate one excitatory output and one inhibitory output- think about the stretch reflex in the spinal cord as an example |
| design a reverberatory circuit. include inputs for facilitation and inhibition | this is a mechanism of positive feedback for excitatory output from a neuronal circuit that can take many different forms |
| what are some examples of rapidly adapting tactile receptors? | hair, free nerve endings, meissner corpuscles, pacinian corpuscles |
| what are some examples of slowly adapting tactile receptors? | merkel's disks, ruffini's endings, |
| how does hair detect initial contact and movement of objects on the skin? | have a hair-end organ with a basal nerve fiber |
| what kind of fibers do hair-end organs use? | they use A-beta...also, they are rapidly adapting |
| where are free nerve endings found? | throughout the body |
| what do they detect? what kind of fibers do they use? | light touch and pressure (A-gamma), and tickle and itch (type C) |
| where are meissners corpuscles found? | in the fingertips, lips, and no-hairy skin |
| what do they detect and what kind of fibers do they use? | they detect movement of objects over the skin surface and low-frequency vibrations. use A-beta fibers |
| where are pacinian corpuscles found? | in the subcutaneous tissues |
| what do they detect and what kind of fibers do they use? | they detect local compression and vibration, and they use A-beta fibers |
| what are the two kinds of slowly adapting tactile receptors? | merkel's disks, and ruffini's endings |
| where are merkel's disks found? | they are found in hairy and non-hairy skin |
| what do they detect, and what kind of fibers do they use? | they detect steady pressure of objects touching the skin- they use A-beta...this is like holding a cup in your hands |
| where are ruffini's endings found? | they are in the deeper skin and joint capsules |
| what do they detect, and what kind of fibers do they use? | they detect continuous, heavy pressure, and degrees of joint rotation |
| what three things determine the spatial discrimination of tactile sensations? | 1) receptive field size- the smaller the field, the higher the spatial resolution 2) receptor density- the greater the density, the higher the spatial resolution 3) lateral inhibition of afferent signals (so the integrity of the original signal stays) |
| how would a tonic cold receptor respond to a drop or increase in temperature? | as temperature becomes colder, impulse frequency increases. impulse frequency changes as the temperature changes, but never completely adapts. impulse frequency drops below tonic levels if temp increases enough |
| I am a tactile receptor in subcutaneous tissue that detects rapid local compression and vibration to which I adapt very rapidly. I transmit my afferent sensory signals via Type A-beta sensory nerve fibers | pacinian corpuscle |
| I am a tactile receptor abundant in the fingertips, lips, and non-hairy skin that detects movement of objects over the skin and low-frequency vibrations, to which I adapt rapidly. I transmit my afferent sensory signals via Type A-beta | meissner corpuscle |
| I am a tactile receptor abundant throughout the body’s skin. I detect tickle and itch sensations to which I adapt rapidly. I transmit my afferent sensory signals via Type C fibers | free nerve ending |
| I am a tactile receptor located in deep skin and joint capsules that detects continuous heavy pressure and degrees of joint rotation. I adapt very slowly to these signals, and I transmit my afferent sensory signals via Type A-beta | ruffini ending |
| I am a tactile receptor located at the base of hair cells. I detect initial contact and movement of objects on the skin, to which I adapt rapidly. I transmit my afferent sensory signals via Type A-beta | hair-ending |
| I am a tactile receptor located in both hairy and non-hairy skin. I detect steady pressure of objects on the skin to which I adapt slowly. I transmit my afferent sensory signals via Type A=beta | merkel disc |
| As sensory receptor density increases, the spatial resolution of a tactile signal.... | INCREASES |
| As a receptive field size increases, the spatial resolution of a tactile signal.... | DECREASE |
| what does lateral inhibition do to the spatial resolution of a tactile signal? | INCREASES it |
| Name one location of the body other than fingertips where you would expect two-point discrimination within 5 mm, and explain why it is possible | lips |
| Name any location where two-point discrimination within 5 mm is not possible and then explain why it is not possible | forearm, abdomen...why? cause low receptor density, large receptor fields, and lesser degree of lateral inhibition |
| what kind of receptors are sensing where are body parts are in space? | skin tactile receptors, and joint receptors |
| what kind of receptors detect dynamic movements? | joint receptors, muscle spindles (length), and golgi tendon (tension) |
| what are the two somatosensory pathways up the spinal cord? | dorsal column/medial lemniscal pathway anterolateral system |
| what kinds of fibers do the dorsal column/medial lemniscal pathway use? what kind of info is this better for? | they use FAST A-beta fibers- better for spatial orientation |
| what kinds of fibers do the ALS use? | slower, type A-delta and type C fibers- better for more diffuse orientation |
| what are some highly localized touch sensations? | vibration, movements of objects on the skin, joint positions, and localized pressure sensation |
| what are some diffuse orientations? | more for pain, temp, crude pressure, sensations, itch, tickle, sex |
| trace the transmission of info for the dorsal/medial lemniscal pathway | entry via dorsal root of spinal cord--> flows, uninterrupted to the dorsal column nuclei in medulla--> crosses--> flows through the medial lemniscus to the ventrobasal complex of thalamus--> somatosensory area of cortex |
| what would be the expected outcome of brain damage to somatosensory area | loss of precise localization of tactile information, inability to judge pressure, weight of objects, shapes or textures |
| trace the transmission of info for the ALS | entry via dorsal roots--> signal crosses to the opposite side of the cord to the anterior and lateral white columns--> goes up--> terminates in multiple reticular nuclei of the brainstem, or the PAG, or the intralaminar nuclei of thalamas |
| what would be the expected outcome of brain damage to the reticular nuclei of the medulla, pons, mesencephalon, and PAG? | difficulties sensing and/or localizing pain, temperature changes, tickle or itch sensations, crude pressure sensations, or loss of sexual sensations |
| name three signals that nociceptors can detect | chemical signals (inflammatory signals, tissue damage, ischemia), temperature (extreme heat), and mechanical signals (stabbing, cutting pressure) |
| do nociceptors have free nerve endings? do they adapt? | yes- all nociceptors ARE free nerve endings...they have little to NO adaptations- they are tonic! |
| describe the process of sensing pain following a burn on your forearm. include chemical signals that would be expected to occur; compare and contrast the 2 afferent pathways that would be used to transmit the pain signal to the CNS | extreme hear: highly localized signal via fast-sharp pain pathway (NEOSPINALTHALAMIC TRACT) via type A-beta...use glutamate tissue damage: chemical signals stimulate the slow chronic pain pathways (PALEOSPINOTHALAMIC) via type C...use glu and substance P |
| what are the direct chemical signals that elicit pain? | bradykinin, histamine, serotonin, K and H, prostaglandins |
| what are the indirect chemical signals that elicit pain? | substance P (released by the free nerve ending that senses pain) |
| what are the two kinds of anterolateral pain pathways? | neospinalthalamic--the fast-sharp pathway paleospinothalamic-- the slow-chronic pathway |
| what sets off the neospinalthalamic tract? what kind of NT is used? | mechanical or thermal sensors- they use A-beta fibers. it uses glutamate and the sensation of pain is highly localized |
| what sets off the paleospinothalamic tract? what kind of NT is used | chemical sensors- they use type C fibers, and use glutamate and substance P. sensation of pain is more diffuse |
| why is the paleospinothalamic tract more diffuse? | cause of the fibers, and cause it unloads the signal along the way to the thalamus to various structures |
| describe two mechanisms by which the body modulates nociception | endogenous opioid peptides stimulate analgesic pathways also, we can stimulate low-threshold mechanoreceptors (activated by massage, rubbing, acupuncture) |
| what do nerve fibers associated with pain release | endogenous analgesic (opioid) peptides...endorphins and enkephalines...they suppress transmission of pain signals |
| what are some examples of exogenous opioids? | heroin, morphine, and codeine |
| why is pain of a left vent MI often felt in the left shoulder, pec muscles, and arm? | nociceptive info from the left vent is transmitted to the cord at derm T1-5...sensory info from body surface at derm T1-5 enter the cord at the same height (with signals sometimes synapsing on the same neuron)...so, pain from left MI gets mixed with derm |
| compare and contrast the sensation of cold vs heat. at what point will cold or heat be perceived as pain? | cold: 3x as many receptors...type A-delta and C...cold is perceived as pain below 10-15 degrees heat: all type C...perceived as pain above 45 degrees both types of receptors are initially rapidly adapting, but then slowly adapting and TONIC |
| the rest of the questions are true/false | |
| All receptor potentials are depolarizing _________________. | FALSE; some are hyperpolarizing, such as the ones that result from stimulation of photoreceptors by light |
| Mechanoreceptors are only used to detect tactile sensations at the body surface and skin_______________. | FALSE; they are in joints, deep tendons, and arterial walls. more too |
| A receptor potential and an action potential are the same thing _________________. | FALSE. receptor potentials reflect a change in resting membrane potential and can be hyperpolarizing or depolarizing |
| A tactile receptor that adapts slowly will tend to transmit sensory signals as long as the stimulus is present_____________. | TRUE |
| Rapidly adapting tactile receptors always transmit afferent sensory signals via fast Type A-beta fibers | FALSE- itch and tickle sensations (both from rapidly adapting free nerve endings) transmit their signals via type C... |
| Slowly adapting tactile receptors are best for detecting movement of an object across the skin | FALSE- that would be for rapidly adapting receptors |
| Type C fibers are unmyelinated, small, and have a relatively slow conduction velocity | true |
| A region of skin with large receptive fields will be less likely to display 2-point discrimination within 5mm______________ | true |
| The more lateral inhibition occurs with an afferent sensory signal, the lower the spatial resolution of the tactile sensation_____________. | FALSE- that would help sharper the sensory signals to finer spatial resolution |
| The anterolateral pathway transmits somatosensory signals with precise spatial orientation | FALSE- more diffuse (pain and temp) |
| Sensation of back pain will most likely be transmitted via the dorsal column-medial lemniscal pathway____________. | FALSE- goes with ALS with all pain |
| Somatosensory signals that travel via the dorsal column-medial lemniscal pathway terminate in multiple reticular nuclei of the medulla, pons, and mesencephalon______________. | FALSE; they terminate in precise regions of the somatosensory area of the cortex |
| Somatosensory signals that travel via the dorsal column-medial lemniscal pathway will ultimately be transmitted to a specific and appropriate area of the somatosensory area I of the cerebral cortex_____________. | TRUE |
| A patient with bilateral lesions in their Somatosensory Area I of the cerebral cortex will be less likely to sense chronic pain____________. | FALSE- they will have impaired fine, highly localized tactile sensations |
| All pain signals are detected by stimulation of chemoreceptors _________________. | FALSE- mechanoreceptors and thermoreceptors are important for detecting fast pain signals |
| The neospinalthalamic and paleospinothalamic tracts are part of the anterolateral pathway | TRUE |
| Pain signals carried by the neospinalthalamic tract tend to be highly localized _________________. | TRUE |
| Pain signals carried by the paleospinothalamic tract typically result from stimulation of chemoreceptors_______________. | TRUE |
| Pain signals carried by the paleospinothalamic tract are transmitted directly from the spinal cord to the thalamus____________. | FALSE; this describes the neospinalthalamic tract. Paleo signals can terminate in multiple reticular nuclei of the brain stem as well as the thalamus |
| Thermoreceptors transmit their somatosensory signals via fast Type A-beta fibers________________. | FALSE- A-delta or C |
| all thermoreceptors are tonic free nerve endings | true |
Created by:
klwyrick