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15 Cards in this Set
- Front
- Back
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What are the 4 different regions involved in the pain pathway from the periphery to the brain? |
Site of injury spinal cord brain stem brain |
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Describe the location and response properties of each mechanorecptor and the nociceptor |
Hair follicle receptors: responds to light hair brushes, located in the dermis by the base of hair follicles Meissner Corpuscle: responds to dynamic deformations of the skin (e.g. waving your hand); located between the dermis and epidermis Pacinian Corpuscle: responds to vibrations; located deep in the dermis Merkel's Disc: senses indentation depth (i.e. how far the skin has been displaced); located between dermis and epidermis Ruffini Corpuscle: responds to stretch; located within the dermis Free nerve endings: responds to injurious forces; located near the surface of the skin within the epidermis |
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Describe the three distinct fibre types. What type of information do they respond to? Are they myelinated? What is their diameter? How fast is their conduction velocity? |
A-beta: respond to touch; myelinated; 6-12 um; 35-90 m/s A-delta: respond to pain (thermal and mechanical); myelinated; 1-5 um; 1-40 m/s C-fibers: respond to pain (all types); unmyelinated; 0.2 - 1.5 um; 0.5 - 2 m/s |
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What does adaption rate mean? What is the relative adaptation rate of each of the receptor types? |
Adaptation rate refers to how quickly a receptor can adapt to a stimulus and stop firing APs. HFR, Meisner Corpuscle, Pacinian Corpuscle - fast adaptation rates Merkel's disk, Ruffini Corpuscle - moderate adaptation rates Free nerve endings / nociceptors - slow adaptation rates |
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What does response threshold mean? What is the relative response threshold of each of the receptor types? |
The minimum intensity required to elicit an AP. Mechanorecptors all have lower thresholds compared to the nociceptors. |
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When is the onset firing characteristics of each fibre type to increasing pressure over time? Including timing and amplitude. |
A-beta -> A-delta -> C-fibers in timing and amplitude (A-beta first and highest amplitude) |
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At what point in the pathway does congenital analgesia impact pain perception? |
The site of injury (i.e. the receptors) The axons have their Na channels blocked, making them unable to fire APs. |
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Describe how the spinal cord represents different parts of the body. |
information from a specific part of the body is sent to a specific section of the spinal cord (usually where the spinal cord is the closest) |
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Describe the organization of the cross section of the spinal cord. |
Ventral (motor) and Dorsal (sensory) roots White matter (myelinated) on the outside, grey matter (unmyelinated) on the inside |
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Where do A beta, A delta and C fibres send information that they receive from the periphery? |
A-beta -> dorsal horn-> medulla oblongata -> 2nd neuron -> thalamus - > 3rd neuron -> somatosensory cortex (lemniscal tract) Pain fibers - dorsal horn -> 2nd neuron -> thalamus - > 3rd neuron -> somatosensory cortex (spinothalmic tract) |
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Compare and contrast the details of the lemniscal tract and spinothalmic tract. |
Lemniscal tract - > crosses over at the brain stem Spinothalmic tract - crosses over at the spinal cord |
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Which brain regions are activated by pain? |
S1 & S2 - the somatosensory cortex, the ACC, and the Insula |
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What is the role of the thalamus? |
to relay info. from the brainstem and spinal cord to the cortex (primarily S1) |
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What is the role of the somatosensory cortex? |
Perception, localization, and intensity of pain |
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Where is the location of the sensory homunculus? What role does it play? How are body parts not represented? Does this match the true anatomy? |
reflects the localization of the body within the somatosensory cortex the larger the body part, the more sensitive it is |
