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311 Cards in this Set
- Front
- Back
Function of astrocytes (3)
|
provide nourishment to the neurons
Clean the synapses Have relationships with BVs -> plug up the gaps to prevent them from leaking |
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What are the three types of glial cells in the CNS?
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astrocytes
oligodendrocytes microglia |
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What is the function of the microglia?
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They're the macros of the CNS -> Clean up debris etc
|
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In which areas of the hippocampus does neurogenesis occur?
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Subventricular and subgranular zones
|
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Do we get neurogenesis in adults?
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Yes!
|
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What is the impact of anti-depressants on stem cells involved in neurogensis?
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increase their survival -> increased neurogenesis
|
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What is the impact of stress on neurogenesis?
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Stress decreases the amount of neurogenesis
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What % of the total cardiac output does the brain use?
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20%
|
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Are O2 and glucose stored by neurons?
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NO!
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What are the two sites where the endothelium is leaky?
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Choroid plexus
Area postrema |
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Do women or men have larger corpus callosum's
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Women
|
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What's the left side of the brain involved in?
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Language (in 95% of us)
Maths and Logic (Remember - Left -> Language and Logic) |
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What's the right side of teh brain involved in?
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Right -> spatial, music, facial recognition, visual imagery etc
|
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What are the two types of motor cells?
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alpha and gamma
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Which are bigger - the alpha or the gamma motor cells?
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Alpha are bigger!
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What do alpha motor cells innervate?
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The motor end plates
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What do the gamma motor cells innervate?
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Neuromuscular spindles
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What fibre type are tactile fibres?
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Type II fibres
Aka A-beta fibres |
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What are the four types of tactile receptors / corpuscles?
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Pacinian
Meissner's Merkel cells / discs Ruffini Organ |
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are tactile fibres myelinated ?
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Yes
|
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What fibre types carry proprioception information?
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Ia, Ib and II
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What fibre types carry pain and temp information?
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III and IV
III aka'd A-delta IV aka'd C |
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What are the two different types of pain carrying fibres? And how do they differ in the type of information they carry?
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Pain --> III (A-delta) and IV (C) fibres
III - mapped -> can localise the pain. They're myelinated --> fast transmission IV - not mapped --> dull and diffuse pain. they're unmyelinated -> slow transmission |
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Which pain (and temp) fibres are unmyelinated?
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The IV (aka C) fibres
-> slow transmission |
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Which pain (and temp) fibres are mapped?
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III (aka A-delta)
|
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Which pain (and temp) fibres are not mapped?
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IV (aka C) -> dull and diffuse pain
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What type of fibres carry the info from Pacinian Corpuscles?
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Type II fibres (aka A-beta fibres)
|
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What do Pacinian Corpuscles respond to?
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Deep pressure and vibration
|
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Where are Pacinian Corpuscles located?
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Deep skin, ligaments and joints
|
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What sort of response to Pacinian Corpuscles have to their stimulus?
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It's a phasic response - ie get response when stimulus is applied and removed (but not for the duration of the stimulus)
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What's the size of Pacinian Corpuscles' receptive field?
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They have LARGE receptive field
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Are the fibres travelling back from Pacinian Corpuscles myelinated?
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Yes. All tactile fibres are myelinated
|
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What do Meissner's Corpuscles respond to?
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Fine touch, pressure and vibration
|
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Where are Meissner's Corpuscles located?
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Only in GLABOROUS (ie hairless) skin
|
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Do Meissner's Corpuscles have large or small receptive fields?
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Small
|
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What is the response of Meissner's Corpuscles to their stimulus?
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Only get a response when the stimulus is applied
|
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Do all four sensory corpuscles have the same diameter fibres?
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YES
|
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Do all four sensory corpuscles have the same conduction velocities?
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YES
(They're all myelinated -> all transmit information very quickly) |
|
What do Merkel cells/discs respond to?
|
Fine touch
|
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Do Merkel cells/discs have small or large receptive fields?
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Small
|
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What do Merkel cells/discs and Meissner's have in common?
|
They both have small receptive fields.
|
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Where are Merkel cells/discs located?
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In all skin and hair follicles
|
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What is the response of Merkel cells/discs to their stimulus?
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It's TONIC - ie throughout the whole duration of the stimulus
|
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Which tactile receptor / corpuscle responds throughout the whole duration of the stimulus?
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Merkel cells/discs
|
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Which tactile R / corpuscle responds to deep touch?
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Pacinian
|
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Which tactile R / corpuscle has a large receptive field?
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Pacinian
|
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Which tactile R / corpuscle is only located in glaborous (ie hairless) skin?
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Meissner's
|
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Which tactile R / corpuscle responds to stretch of skin?
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Ruffini organs
|
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What do Ruffini Organs respond to?
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Stretch of skin
|
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Where are Ruffini Organs located?
|
Located in all skin
|
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What do free nerve endings respond to ?
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Pain and temperature
|
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Which tactile Rs/ corpuscles allow you to accurately discriminate locations?
|
The two Ms have small receptive fields!
IE Meissner's and Merkel cells/discs |
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What do type II fibres carry?
|
Proprioceptive information
|
|
What do type III fibres carry?
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Pain and temp
III is mapped and myelinated |
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What do type IV fibres carry?
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Pain and temp
IV are not mapped and they're unmyelinated |
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What times of receptors are responsible for detecting proprioceptive information? (3)
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Muscle spindles
Joint receptors Golgi tendon organs |
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What sort of information does the spinothalamic tract carry?
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Pain and temperature
+ some light touch |
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What fibre types are carried in the StT?
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III (A-delta) and IV (C)
|
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Where do StT fibres synapse AND cross?
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- Synapse in the dorsal horn
- Then they cross within 2-3 segments of where they came in. |
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Where do StT fibres terminate?
|
Some terminate in the BRF
OThers in the thalamus -> ventroposterior nucleus or medial dorsal intralaminar nucleus |
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In which nuclei of the thalamus do the StT fibres terminate?
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Ventral posterior nuc
Medial dorsal intralaminar nucleus |
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Spinothalamic tract: what's different between the anterior and lateral parts of it?
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Anterior - carries light touch
Lateral - carries pain and temp information |
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What's the difference in location of the StT fibres carrying light touch compared to those carrying pain and temp info?
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Pain and temp - carried in the lateral part of the StT
Light touch -> anterior StT |
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What does the lateral part of the spinothalamic tract carry?
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Pain and temp information
|
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What are the two divisions of teh lateral spinothalamic tract? And what's the differences between the two?
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Neospinothalamic -> carries gp III fibres --> mapped - precise localisation. Get info from skin and superficial. Myelinated -> fast transmission
Paleospinothalamic - carries gp IV fibres - not mapped -> diffuse information (not localised). Comes from deeper structures (viscera, muscles) and unmyelinated -> slower transmission |
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What information is carried int eh neospinothalamic tract?
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III fibres -> pain and temp information from the skin and superficial structures
|
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What info is carried in the paleospinothalamic tract?
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IV fibres -> pain and temp information from the deep sturctures (viscera, muscles) - dull and diffuse information (not mapped)
|
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Which part of the StT provides mapped information?
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Neospinothalamic
|
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Which part of the StT provides more diffuse / less well localised pain/temp information?
|
THe paleospinothalamic tract
|
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Which part of the StT carries the pain/temp information from deep viscera?
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Paleospinothalamic
|
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What will be the effect of a hemi-lesion of the spinal cord on the spinothalamic tract?
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Lose pain and temp information. CONTRAlateral (because the fibres have crossed over just above where they entered)
|
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What information does the anterior spinothalamic tract carry?
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Light touch
|
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What information does the DCT carry?
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Tactile touch
And conscious proprioception |
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What is the journey of the tactile touch fibres in DCT?
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Cell bodies located in DRG -> they come into the spinal cord, don't synapse, travel up on the same side and synapse in the gracile and cuneate nuclei in the brainstem (ipsilateral still)
Then they cross over = sensory decussation and then travel in the medial lemniscus to the ventral posterior nuclues of thalamus. From here -> cortex |
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Where do tactile touch fibres cross over?
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In the brainstem
|
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What part of the thalamus do tactile touch fibres go to?
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Ventral posterior nucleus
|
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Does medial lemniscus carry ipsi or contralateral tactile touch information ?
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CONTRAlateral - the fibres cross in sensory decussation and then enter the medial lemniscus
|
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Gracile tract carries what ?
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Sensory and conscious proprioceptive information from the lower limb
|
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What info does the cuneate tract carry?
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Sensory and conscious proprioceptive information from the upper limb
|
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Which is more MEDIAL in the spinal cord - gracile or cuneate tracts?
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Gracile is more medial (just as legs are more medial to arms)
|
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What's the effect of a hemilesion to the spinal cord on the dorsal column tract?
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IPSIlateral loss of tactile touch and conscious proprioception
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What fibre types carry conscious proprioception info?
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I(a,b) and II
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What fibre types are in the DCT?
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Tactile touch -> II.
Conscious proprioception -> I (a and b) and II |
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What's the journey of conscious proprioception fibres?
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Same as tactile fibres in the DCT - cell bodies in the DRG, come into spinal cord, don't cross in spinal cord, synapse in the cuneate and gracile nuclei, then cross and then travel in the medial lemniscus to ventral posterior nucleus in the thalamus
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What information is carried in the spinocerebellar tract?
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Unconscious proprioception
|
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Which fibre types carry unconscious proprioception info?
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I (a,b) and II
|
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What's the journey of unconscious proprioceptive info?
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Cell bodies in the DRG, fibres come in and synapse in the dorsal horn, then travel up in the spinocerebellar tract (don't cross) and goes itno ipsilateral cerebellum
No projections to the cortex |
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What happens if you have a hemi-section to the spinocerebellar tract?
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Ipsilateral loss of unconscious proprioception
|
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What are the four descending tracts discussed in the lecture?
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- Vestibulospinal
- Reticulospinal - CST - Rubrospinal |
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What are three ascending tracts discussed in teh lecture?
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- Spinothalamic
- DCT - Spinocerebellar |
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What is the difference between the basic and the skilled descending tracts?
|
Basic - phylogenetically older, less sophisticated. Involved in maintaining posture, locomotion, muscle tone and visceral reflexes
Skilled - newer and more sophisticated. Skilled movements give us quality of life |
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Are the basic descending tracts more lateral or more medial cf the skilled ones?
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Basic = more medial in the spinal cord
|
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What are the two 'basic' descending tracts?
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Vestibulospinal
Reticulospinal |
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What is the role of the vestibulospinal tract?
|
Information comes down from the vestibular nucleus to muscles -> correction of balance based on info from the middle ear etc. Acts on the EXTENSOR muscles to correct balance
|
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What type of muscles are particularly innervated by the vestibulospinal tract?
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Extensors
|
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What happens if you have a lesion to the vestibulospinal tract on one side?
|
Body lateropulsion - ie will collapse to that side of the body because you don't have the extensors to correct your position
|
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Where do fibres in the reticulospinal tract originate?
|
The BRF
|
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What do fibres in the reticulospinal tract innervate?
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Visceral smooth muscle + somatic muscles
|
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What happens if you have a lesion to the reticulospinal tract?
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Not hugely significant. Get loss of visceral control (minor)
|
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What are the two 'skilled' descending tracts?
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CST
Rubrospinal tract |
|
Where does the rubrospinal tract originate from?
|
The red nuclues
|
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Is the rubrospinal tract more developed in humans or rats?
|
rats
|
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What is the function of the rubrospinal tract in humans?
|
It isn't very well developed in humans.
Believed to help the CST, particularly with learned movements |
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What's the journey of fibres in the rubrospinal tract?
|
They start in the red nucleus and then cross over the midline in the ventral tegmental decussation and travel down to synapse with motor cells
|
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Where do fibres in the CST originate from?
|
- Motor cortex
- Frontal- cingulate cortex - Parietal cortex |
|
What's the journey of fibres in the CST?
|
They come down from cortex (motor, frontal-cingulate, parietal), go through the corona radiata, internal capsule, cerebral peduncle, pyramid. Then 80% of the fibres crosses over = motor / pyramidal decussation (these -> lateral CST) -> travels down the contralateral spinal cord and synapses with motor cell
|
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Do all the CST fibres cross over?
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NO. Only 80% do
Those that don't cross over form the anterior / ventral CST |
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Which types of muscles does the CST particularly innervate?
|
The anti-gravity muscles (flexors of the arms and extensors of the limbs)
|
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What's the difference in terms of types of muscles innervated between the CST and the vestibulospinal tract?
|
CST -> distal muscles (particularly fingers)
Vestibulospinal -> proximal / axial muscles |
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Does the internal capsule carry only CST fibres?
|
NO
|
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Do the pyramids carry only CST fibres?
|
YES
|
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Approx how long is the spinal cord?
|
45cm
|
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What are the three layers of meninges? Name them from INSIDE -> OUTSIDE
|
Pia mater
Arachnoid mater Dura mater |
|
T/F - spinal cord is continuous iwth the medulla oblongata?
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True
|
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What's the name of the cone shaped bit at the very end of the spinal cord?
|
Conus medullaris
|
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What's the filum terminale?
|
It's a fibrous band of pia mater that anchors the spinal cord to the sacrum and coccyx
|
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How many segments are there in the human spinal cord?
|
31
|
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How many segments are there in the cervical spinal cord?
|
8
|
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At approx what level does the spinal cord end?
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L1
|
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T/F - the arachnoid mater stays closely adhered to the spinal cord
|
FALSE
it's the pia that's tightly adhered and follows the spinal cord wherever it goes |
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Is the grey matter central or peripheral in the spinal cord?
|
Centra
|
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At what levels do the symp pre-ganglionic neurons come out?
|
C8-L1
|
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Where do the parasymp preganglionic neurons come out?
|
S2-4
|
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What schema do we use to subdivide the grey matter in the spinal cord?
|
The Rexed laminae system
|
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Which Rexed laminae make up the dorsal horn
|
Dorsal horn = Laminae I-V
|
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Which Rexed laminae make up the ventral horn?
|
VIII and IX
|
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Which Rexed laminae make up the intermediate grey?
|
VI, VII and X
|
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Somatic motoneurons are located in which Rexed lamina?
|
Lamina IX
|
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What's the difference between the medial and the lateral motor columns?
|
Medial - present throughout the length of the spinal cord. Contains motoneurons innervating the axial muscles
Lateral - present only in the cervical and lumbar enlargements -> innervates the limbs |
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T/F: damage to the spinal cord -> UMNL only?
|
FALSE. Will get UMNL signs below the level of the lesion. But at the level, ventral horn etc might be damaged --> can have LMNL at that level
|
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In terms of the sensory neurons- do the large diameter myelinated afferents lie medial OR lateral to the smaller diameter unmyelinated afferents?
|
Large = medial to the smaller, unmyelinated ones
|
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What are the three main 'channels of communication' in terms of processing sensory input?
|
1. Reflex channels
2. Cerebellar channels 3. Lemniscal channels |
|
Describe the knee jerk reflex
|
Primary afferent stretch Rs in the patellar tendon synapse directly on motor neurons that innervate the quadriceps femoris muscle
|
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Are the monosynaptic reflexes newer or older (in terms of evolution) than the polysynaptic reflexes?
|
Monosynaptic = newer!
More common are the poly-synaptic arcs |
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Whats the eg of the polysynaptic reflex given in the learning topic?
|
Light touch on the shoulder -> dramatic startle response - requires coordination across a large number of spinal segments
|
|
When pain and temp neurons come in and synapse with the second order neurons in the dorsal horn, what laminae are the second order neurons located in?
|
Laminae I or V
|
|
Where do spinothalamic fibres cross the midline?
|
In the spinal cord - usually about 1 or 2 segments above where they came in
|
|
What are 'first order' sensory afferents?
|
They're the neurons with the cell bodies in the periphery
|
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Do primary afferent fibres project directly to the thalamus?
|
NO. They also synapse at least once before getting to the thalamus
|
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What NT is released at the synapse between pre and post ganglionic cells in the autonomic NS?
|
ACh - acts on nicotinic Rs
|
|
At the synapse between pre and post ganglionic cells in the ANS, what NT is released ? and what R type does it act on?
|
ACh is released
Acts on nicotinic Rs = ion channels -> fast acting |
|
What NT does the post ganglionic neuron release onto its target in the PARA NS? And acts on what type of R?
|
ACh
Onto muscarinic Rs |
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What NT does the post ganglionic neuron release onto its target in the SYMP NS? Acts on what R?
|
Noradrenaline
Onto alpha and beta type Rs |
|
What are the two impt exceptions in the symp NS in terms of NT released and R acted on?
|
- Sweat glands -> ACh acts on muscarinic Rs
- Adrenal medulla -> pre releases ACh onto nicotinic R -> adrenal medulla cells act as the post ganglionic neuron |
|
Where are the cell bodies of the symp NS preganglionic neurons located?
|
In the intermediolateral cell column in the thoracolumbar region of the spinal cord
|
|
Pre and post ganglionic neurons in the symp NS - which are myelinated / unmyelinated?
|
The pre = myelinated
Post = unmyelinated |
|
Do the sympathetic preganglionic neurons get modified? If so, what by?
|
YES!
By spinal afferents AND by descending inputs from brainstem / hypothalamus |
|
Spinal afferents coming in and interacting with symp pre-ganglionic neurons -> how does this happen?
|
The incoming information (afferents) can't interact directly with the neuron - needs to first communicate with an interneuron and then the interneuron will communicate with the pre-ganglionic neuron
|
|
How do descending inputs from the brainstem / hypothalamus interact with the sympathetic pre ganglionic neurons?
|
They can interact directly with the neuron!
|
|
T/F: symp pre-ganglionic neurons ONLY get modified / affected by spinal afferents coming in at the same level?
|
False. They are predominately affected by those coming in at the same level, but also get input from those coming in at nearby segments
|
|
What's the cardio-cardiac reflex?
|
Spinal afferents come in from the heart and then synapse in the spinal cord with interneuron that then interacts with the sympathetic preganglionic neuron going back out to the heart
Remember : the afferent can't interact directly with the preganglionic neuron - needs to go via the interneuron! |
|
Symp NS supply to the bladder comes from where in the spinal cord?
|
Lumbar region
|
|
Para NS supply to bladder comes from wehre in the spinal cord?
|
Sacral region
|
|
Which bladder muscles are innervated by ANS (hence involuntary control)?
|
Detrusor muscle
Internal sphincter |
|
Which bladder muscle(s) innervated by somatic motor nerves (hence voluntary control)?
|
External sphincter
|
|
Weeing = para or symp NS ?
|
Weeing -> paraNS dominates
|
|
What is the effect of symp innervation on the bladder?
|
Symp -> don't want to wee
--> Relaxes the detrusor muscle so it can hold more urine And contracts the internal sphincter -> makes it tighter / more closed |
|
Where is the micturition centre located?
|
In the pons
|
|
What's the process of weeing?
|
Sensory afferents from the bladder send info saying that the bladder is getting quite stretched. And the cortex sends signals to the pontine micturition centre
Both these --> get info coming into the sacral spinal cord --> Increased paraNS activity to the bladder AND decreased pudendal nerve activity Para -> contraction of detrusor and relaxation of internal sphincter Decreased pudendal nerve -> external sphincter relaxes |
|
What's the positive feedback loop in urination?
|
Flow through the urethra -> sends signals up to the pontine micturition centre. Also, bladder contraction sends positive signals too.
--> increased detrusor contractoin and increased relaxation of teh internal sphincter |
|
What sort of muscle makes up the internal and external sphincters of the bladdeR?
|
Internal -> smooth muscle
External -> striated muscle |
|
What's the name of the area of smooth muscle at the base of the bladder (below which the bladder opens into the urethra)?
|
Trigone
|
|
Does the detrusor muscle get more para or symp innervation?
|
More para
|
|
What nerve innervates the external sphincter of the bladder?
|
The pudendal nerve
|
|
What are the three levels of CNS control of bladder function?
|
- Lumbar and sacral spinal cord
- Micturition centre in the pons - Supra-pontine centres which influence the micturition centre |
|
What is the process by which we maintain continence? (ie the bladder is filling a little bit, but isn't super full)
|
Detrusor muscle = smooth muscle -> can stretch lots. When it stretches, afferent fibres send info back to the spinal cord re degree of stretch. Increased stretch -> increased activity of these fibres --> two reflexes:
- Inhibition of para innervation to detrusor (so it can relax more and stretch more) - Excitation of the pudendal nerve -> increased contraction of the external sphincter |
|
What impact does contraction of detrusor have on the internal sphincter?
|
Contraction of detrusor -> mechanically pulls open the internal sphincter
|
|
What are the two signals making up the positive feedback loop during urination?
|
Bladder contraction
Flow through the urethra |
|
What happens to the bladder in a LMNL?
|
There's NO REFLEX!!
-> bladder will keep filling and filling until the pressure is so great that it leaks out This is called overflow incontinence They will also have stress incontinence (eg when they laugh or cough) |
|
What happens to the bladder in UMNL?
|
It's hyper-reflexic -> when it fills, will get emptying (can't stop this!)
But they often get detrusor-sphincter - dysynergia -> urinary frequency and urge incontinence They won't have the positive feedback loop up to the pons --> don't get the last 25% of urine out |
|
In which lesion (UMNL vs LMNL) do you get overflow incontinence?
|
Lower motor neuron - no reflex --> will just flow out when it's super full
|
|
In which lesion (U vs L MNL) do you get detrusor-sphincter dys-syngergia? And what's the result of this?
|
Upper motor -> hyper-reflexic --> can get the two muscles acting independently
They get urinary frequency and urge incontinence |
|
What happens to the bladder in spinal shock?
|
There's no innervation -> no reflexes -> overflow incontinence
|
|
What sort of muscle makes up the internal and external anal sphincters?
|
Internal = smooth muscle
External = striated muscle |
|
What nerve innervates the external anal sphincter?
|
Pudendal nerve
|
|
Do symp nerves play signt role in the defecation reflex?
|
No
|
|
What innervates teh smooth muslce in the wall of the rectum?
|
Para NS
|
|
Information re stretch of the rectum is carried back to the spinal cord in which nerve?
|
The pelvic splanchnic nerve
|
|
T/F: Relaxation of the internal anal sphincter is controlled by the para NS?
|
False.
Internal anal sphincter is controlled by enteric nerves (ie intrinsic to the bowel) |
|
Internal anal sphincter is controlled by what nerve?
|
Enteric nerves
|
|
What do we need for defecation to take place? how is this achieved?
|
Increased intra-abdo P
This is achieved by contraction of muscles in the abdo and thoracic walls and subsequent lowering of the diaphragm |
|
What happens to the defecation reflex if you destroy the spinal cord?
|
Reflex is lost
|
|
What happens to defecation if you have a spinal cord lesion above the sacral spinal cord?
|
Will still have the reflex. But this isn't enough to empty -> need increased intra abdo P and you prob don't have the innervation to muscles required to achieve this.
-> Need external compression of the abdomen and/or manual expansion of the external anal sphincter |
|
What's the difference in number of marriages between SCI people and normal population?
|
Fewer marriages in SCI
|
|
What's the difference in number of divorces between SCI people and normal population?
|
More divorces in the SCI people cf normal population
|
|
What's the effect of despondency, grieving and chronic pain on a person's adjustment to spinal injury?
|
Associated with poor adjustment
|
|
What factors are associated with good outcome after SCI?
|
- Young age
- Female sex - Higher education level - The ability to relate well - Confidence in ones mastery over the envt |
|
What are the three main types of pain?
|
Acute
Cancer Chronic non-cancer pain |
|
What's the definition of acute pain
|
Pain that's been present for minutes - weeks
|
|
What's the definition of chronic pain?
|
Present for longer than 3 months
|
|
What's the difference between chronic non-cancer pain and cancer pain?
|
They might be quite similar
But our approach to Tx is very different |
|
What's neuropathic pain?
|
Due to primary lesion or dysfunction of teh NS
|
|
What's nociceptive pain?
|
Arises from actual (or threatened) damage to non-neural tissue. Picked up by nociceptors
|
|
Does our psychological state make a contribution to our experience of pain?
|
YES!
Eg in sport or battle - might not actually be very aware of the pain During times of anxiety, people might show marked pain behaviour with what appears to be a minor injury |
|
Are psychological factors more signt in chronic or acute pain?
|
CHRONIC
|
|
Does neuropathic pain respond well to analgesics?
|
No
|
|
What sort of meds might be used to help treat neuropathic pain?
|
anticonvulsants
antidepressants |
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What do we do in first aid management of a SCI?
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Immobilise the unstable spine
Pay attention to the airways and breathing And any other possible injuries |
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Tetraplegia -> where's the injury?
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Cervical spine
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Quadraplegia -> where's the injury?
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Could be in T or L cord or in the nerve roots within the spinal canal
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What's the definition of the spinal level of injury?
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It's the lowermost neurologically INTACT segment - with normal motor and sensory function
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What's the definition of a complete spinal cord lesion?
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No voluntary motor or sensory function is preserved more than 3 segments below the level of injury
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What happens with high cervical spine lesion?
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Diaphragmatic paralysis (because don't have phrenic nerve innervation)
They require mechanical ventilation |
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What happens with low cervical, high thoracic injuries?
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Paralysis of the intercostal and abdo muscles -> diaphragm is the only muscle of respiration
-> can't do forced inspiration or expiration --> respiratory insufficiency And can't cough |
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What do we need to do about paralytic ileus?
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Naso-gastric aspiration
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When does spinal shock occur?
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Typically after traumatic spinal cord injury
But can also happen after inflammation or interruption of blood supply to the spinal cord |
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What happens in spinal shock?
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Lost the sensory and motor function below level of injury
And there's a loss of reflexes - both somatic and autonomic We say it's an 'areflexic acute flaccid paralysis' |
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Is spinal shock more prominent following abrubt lesions or more gradual lesions?
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Abrupt
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What happens to bladder and bowel in spinal shock?
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They've completely lost all activity and reflexes
-> paralytic ileus = bowel with no activity And flaccid bladder / no tone |
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What happens to the sympathetic tone during spinal shock if injury is above T6?
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Above T6 -> signt loss of sympathetic vascular tone --> decreased vascular resistance --> pooling of blood in extremities --> low BP
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What happens to BP during spinal shock when injury is above the T6 level?
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It falls
(Due to loss of symp innervation of the blood vessels) |
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What happens to HR during spinal shock when injury is above T6 level?
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It's low ie bradycardia
Don't have the symp innervation to the heart to increase HR |
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During spinal shock with injury above T6, how does the skin feel?
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Warm and dry - because have vasodilation in the periphery
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How does spinal shock (above T6) differ from hypovolaemic shock?
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Spinal shock -> low BP, low HR, warm and dry skin
Hypovolaemic shock -> low BP (because low BV), high HR (reflex) and the skin is cold and clammy (because of vasoconstriction) |
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How would someone in spinal shock above T6 present?
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- Low Bp
- Low HR - Warm and dry skin |
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How would someone in hypovolaemic shock present?
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- low Bp
- High HR - Cold and clammy skin |
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How do we treat someone in spinal shock (above T6)
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Do NOT give fluid replacement - their BP isn't low because of low BV - if you give them fluids, might get fluid overload and other problems
-> We usually can leave the low BP untreated. If it's super bad, might give inotropic agents (eg dopamine) to increase pumpin gof the heart |
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How does Tx for hypovolaemic shock and spinal shock differ?
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Hypovolaemic -> give them fluids
Spinal shock -> don't want to give them fluids. Usually just watch and wait (don't treat them) |
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How long does spinal shock last?
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Between several hours and 4 weeks
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Where does the lesion have to be for SCI patient to get autonomic dysreflexia?
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Above T6!
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What's paralytic ileus?
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Complete absence of bowel activity.
Occurs during spinal shock |
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What are some of the theories for what causes spinal shock?
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- lost the tonic descending excitatory influences from the brain -> depression of reflexes
- Increased inhibition - this is due to change in R function at the site of injury and/or because the injury causes a transient increase in the amount of chemicals that dampen down nerve activity |
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Does clonus occur with increased or decreased tone?
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Increased tone -> clonus
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Which spinal roots are you testing when you do the biceps reflex?
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C5(6)
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Which spinal roots are you testing when you do the brachioradialis reflex?
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C6
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Which spinal roots are you testing when you do the triceps reflex?
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C7
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Which spinal roots are you testing when you do the patellar reflex?
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L4
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Which spinal roots are you testing when you do the achilles reflex?
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S1
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What is the scoring for a normal reflex?
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2
(we score from 0-5) |
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What score do you give if the reflex is totally absent?
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0
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What score do you give if the reflex is trace / decreased compared to normal?
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1
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What reflex score do you give if the patient has sustained clonus ?
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5
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What reflex score do you give if the patient has brisk reflexes?
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3 (out of 5, 2 is normal reflex)
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What reflex score do you give if the patient has non-sustained clonus?
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4
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What sort of BP do we see in someone with spinal shock?
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About 80-100 systolic
and 50-60 diastolic |
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Describe the stretch reflex
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Neuromuscular spindles sit parallel to muscle fibres - stretched --> they send signal back to spinal cord (along Ia fibres) and synapse with alpha motor neuron --> innervates the motor endplate -> contraction
Also, the Ia fibre activates inhibitory interneuron - inhibits the antagonist muscles |
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What Rs are involved in the stretch reflex?
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Neuromuscular spindles
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What fibres carry the signal back from the muscle in the stretch reflex?
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Ia fibres
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What's the difference between alpha and gamma motor neurons?
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Alpha - larger and innervates the motor end plates
Gamma - smaller and innervate the neuromuscular spindles |
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Describe the gamma reflex loop
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Signal comes down from the higher centres - synapses on the gamma motor cell in the spinal cord -> it goes out and activates the neuromuscular spindle (tricks it into thinking the muslce has been stretched) -> info back along Ia fibres to the spinal cord -> activates alpha motor neuron
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Which spinal tracts use the gamma reflex loop? And what's its role?
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The vestibulospinal and reticulospinal tracts
The gamma reflex loop allows the higher centres to control the muscle tone (particuallry of the proximal muscles) |
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Describe the flexor reflex
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Painful stimulus sensed by Rs -> info travels into the spinal cord and activates an excitatory interneuron -> it activates motor neuron --> withdraw limb from the painful stimulus
Get activation of several levels of the spinal cord - need lots of muscles contracting |
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What's the role of the golgi tendon reflex?
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It's teh stop reflex - ie stops muscle contraction
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Describe the golgi tendon reflex
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Muscle is contracted / stretch -> golgi tendon organ sends info back to the spinal cord along Ib fibres -> activates inhibitory interneuron which in time inhibits the alpha motor neuron -> stops contraction
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What happens to the cardiovascular reflex in spinal shock above T5/6?
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Decreased sympathetic outflow --> drop in symp innervation of the BVs --> vasodilation and blood pooling --> dropped BP
Don't have the symp NS to increase the HR -> low HR too |
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What happens to the bladder in spinal shock?
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No reflex urination when it's full
-> need a catheter inserted |
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Within what time period following SCI do we see autonomic dysreflexia
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Within a year
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Where does lesion have to be to get AD?
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Above T5/6
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What happens in AD?
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Painful stimulus (eg full bladder/impacte bowel) activates nociceptors -> this info goes up the spinal cord but gets stopped at the level of the lesion. At this site, the pain signals activate the sympathetic NS (below the level of the lesion) - signals can't get past the lesion! -> in bottom half of the body, have symp acting --> vasoconstriction and increased BP
This is sensed by baroRs -> activate paraNS in the top half of the body -> vasodilation |
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What happens to the BVs in top and bottom of the body in AD?
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Top of body -> parasymp dominates --> vasodilation
Bottom -> symp dominates --> vasoconstriction |
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What symptoms do you get with AD?
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Headached
Sweating flushing Goosebumps Hypertension (can be upwards of 200 = very dangerous!) |
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What are some egs of positive neurological symptoms?
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tingling
pins and needles burning phantoms etc |
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Where is the lesion in an UMNL?
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In the CNS (brain, cerebellum, spinal cord)
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Where is the lesion in a LMNL?
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Peripheral NS - anterior horn cells, nerve roots, brachial or lumbo-sacral plexus, peripheral nerve, NM junction, muscle
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What happens to tone and reflexes in UMNL
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Tone - increased
Reflexes - increased |
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What happens to tone and reflexes in LMNL
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both decreased
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Do you get signt atrophy in U or L MNL?
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Lower -> no innervation to the muscle -> atrophy
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Do you see spasticity in U or L MNL? Why?
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Spasticity = due to hypertonicity ie occurs in UMNL
Flexion in the arms is dominant, and extension in the legs |
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Babinski sign in U or L MNL ?
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UMNL
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Clonus in in U or L MNL ?
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UMNL (due to increased tone)
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Fasciculations in in U or L MNL ?
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LMNL
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Fibrillations in U or L MNL ?
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LMNL
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What happens to bladder reflex in UMNL?
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Still have the reflex, in fact it's hyper-reflexic -> when it's full, bladder will automatically empty (but don't get the positive feedback loop --> won't fully empty the bladder)
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What are the two types of Rs that pick up fibres (name them with letters, not numbers!)
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A-delta (aka III) - they're smaller than C fibres, myelinated (-> fast), and reserved for heat and mechanical stimuli
C fibres (aka IV) - they're unmyelinated and larger than the A delta fibres. Polymodal -> can detect all types of stimuli |
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Which type of pain fibres are polymodal (can detect all types of pain stimuli)
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C fibres (ie IV - the unmyelinated ones)
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Which type of pain fibres are larger?
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C fibres (ie IV)
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What is decart's theory of pain?
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Stimulus -> pain info sent through the spinal cord and up to the brain
Then there's an area in the brain responisble for feeling pain "Push button" theory of pain |
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What's the Cartesian model of pain?
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Same as Decart's theory - pain sensed by R, info sent up spinal cord to brain
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What are the problems with Decart's theory / Cartesian model of pain?
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- Doesn't take into account how much your surrounding envt can affect perception of pain
- Doesn't explain referred pain - Doesn't explain the placebo effect - Doesn't explain how if you cut the nerves can still have pain / amputation pain |
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Who came up with the Gate theory of pain?
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Melzack and Wall
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What is the Gate theory of pain?
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There's modification of the pain messages (both feed forward and feed back):
- Touch -> decreased pain (becuase the big fibres carrying touch information inhibit the incoming pain info in the smaller fibres) - And info coming down from the brain can also modulate pain (increase or decrease) |
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What are the problems with the gate theory of pain?
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Can't explain how you can still have pain even if you're nerves are blocked / severed
-> how is the pain stimulus getting up to the brain !? |
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What does neuropathic pain feel like?
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Shooting
Burning Electric Sharp |
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What is hyperaesthesia and with what condition does it occur?
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Overly sensitive to touch!
Occurs with neuropathic pain |
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What is hyperalgesia?
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Increased response to a normally painful stimulus (eg pin prick)
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What is allodynia?
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Pain in response to a stimulus that wouldn't normally be painful (eg light touch)
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What's time course of onset of neuropathic pain?
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Delayed onset (can be months after the injury)
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What percentage of people with an amputation get some neuropathic pain?
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60-80%
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What percentage of people with herpes zoster get neuropathic pain?
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10-20%
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What % of people with a stroke get neuropathic pain?
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8%
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What % of people with SCI get neuropathic pain
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30-40%
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What is the 'ectopic activity' mechanism (for explaining neuropathic pain)
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Get formation of tissue at the end of the damaged nerve = neuroma. On this neuroma and on the DRG itself, we have increased Na+ channels --> the nerve is more likely to fire (and can even fire spontaneously)
--> Cells in the spinal cord are getting activated all the time (more glutamate - acting on NMDA Rs) -> these cells undergo LT changes - increased responsiveness to incoming signals and they can fire spontaneously too |
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What are the 5 mechanisms mentioned in the lecture to explain neuropathic pain?
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- ectopic activity
- Decreased inhibition - Involvement of glia - Sprouting - Changes in the cortex |
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Why do we get touch being perceived as pain in neuropathic pain!?
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SPROUTING
The C-fibres carrying pain come into superficial layers of the dorsal horn and synapse with cells there. The A fibres (carrying touch) go in and synapse deeper in the horn When the C-fibres die off they release chemical messengers -> the A fibres will grow up (SPROUT) and now communicate with the cells that were previously getting pain information -> when touch info comes in, will synapse with the cells that used to get pain information --> we perceive the touch as pain! |
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What analgesic adjuvants do we use in Tx of neuropathic pain?
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- Tricyclic antidepressants
- Anti-convulsants (stop the random firing of cells in the spinal cord) |
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Prosthesis -> more or less neuropathic pain?
WHY |
Much LESS
The prosthesis prevents the neural plasticity going on |
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What's the social model of disability?
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Disabled people are a minority in society and a lot of their problems stem from the way society treats them
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Who can consent to sterilisation of an adult who is incapable of making the decision for themselves?
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Only the guardianship tribunal can give that consent!
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What level and above = tetraplegia?
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T1 and above
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What's the ratio between tetra and quadraplegia
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1:1 (approx)
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What's the incidence of spinal cord injuries in Aus ( cases p/million people p/year)
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15-17 cases p/million p/year
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In what age brackets are SCI most common?
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There are two peaks:
- 15-24 males - 65-74 (both genders) |
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What % of people who suffer SCI are male?
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82% are male!
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What % of SCI are due to MVAs?
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50%
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What's the highest cause of SCIs? and second highest?
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Highest = MVAs
Second = falls |
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What are the most common sites of SCI ?
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C4-6
and T12-L2 (after the ribs) |
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What happens in an anterior cord syndrome?
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Get the spinothalamic and corticospinal tracts affected
often do to vascular problem or disc prolapse |
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What happens in a central cord syndrome?
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Upper limbs are weaker than the lower limbs
Often due to hyperextension or flexion |
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When you dive into a rock (EG) what type of spinal injury do you do?
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COMPRESSION
|
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What happens with a compression SCI?
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- If the ligaments stay in tact, can be a stable injury
- Can get crush / burst fracture -> boney fragments project into the spinal canal |
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What happens with a hyper-extension injury?
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Central cord syndrome -> upper limb weaker than lower limbs. Likely to be incomplete injury
|
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What happens with a flexion SCI?
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Likely to be a complete injury. If the posterior ligament is disrupted, it's unstable.
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Falling down stairs / car accident -> what type of SCI do you tend to get?
|
Flexion rotation injury
|
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What happens iwth a flexion rotaton SCI ?
|
Likely to be an incomplete injury
Spinal cord likely not to be severely compromised |
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What % of SCI patients develop at least one pressure ulcer?
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50-80%
|
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How do you define AD?
|
Systolic BP that's 20-40 mmHg above their resting BP
|
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How do you treat AD?
|
Sit them up, remove tight clothing
Empty urine bag / make sure not blocked + that bowelisn't blocked Can give them GTN = vasodilator |
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After one episode of AD, what happens to your risk of another one in the next 48 hours?
|
Signtly increased
|
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What's primary prevention of SCI?
|
Stop it from happening n the first place
Eg seat belts, safer roads adn cars, RBTs, Helmet use, workplace safety, falls prevention |
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What's secondary prevention of SCI?
|
Reducing the severity and managing the risk factors
EG improved retrieval, early decompression, specialised care |
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What's tertiary prevention of SCI?
|
Minimising the effects
EG rehabilitation programs, education and self-management, |