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Flashcards in Anatomy of the somatosensory system Deck (21)
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Name the 4 types of hapsis receptors and what they detect

Meissners corpsules - light touch
pacinian corpscules - vibration + textures
ruffini corspules - skin stretch and finger position
merkets corpscules - pressure


which hapsis receptors are slow adapting and which are fast

SLOW = ruffini and merkels
FAST = meissners and pacinian


name three methods of proprioception

muscle spindles, golgi tendon organs, joint receptors


describe the 2 types of proprioception fibres + what they detect

1a- wraps around muscle and detects changes in muscle length.
Ab- sensory, detects where muscle is


1. which proprioception fibre is contractile and which non contractile
2. When do they fire

1. 1a - non contractile Ab- contractile
1a fire when muscle contracting
Ab continue to fire as long as stimulus


Describe the DCML pathway (leg)

1st order sensory to brainstem (ascends via fasciculus gracilis ) CB - DRG
2nd order to thalamus. CB - nucleus gracilis
3rd order to primary somatosensory cortex. CB - VPN


what does the DCML pathway detect

fine touch and proprioception


What does the antrolateral system detect

pain, temp and crude touch


describe the spinothalamic tract

ST - 1st order to Dorsal horn. CB DRG
2nd order to Thalamus (VPN) CB dorsal horn
(ant and lat ascending tracts)
3rd order to primary somatosensory cortex CB VPN


How does the spinoreticular tract differ from the spinothalamic tract

INDIRECT - only one 2nd order neurone and can transmit to other tracts / multiple synapses in the reticular formation
3rd CB in the interlamina nuclei


Roles of the
spinomesencephalic spinohypothalmic and spinotectal tract

SM - emotional component of pain
SH - autonomic reflex response to pain
ST - orients head and eyes to pain


other effects of stimulation of 1st order neurones

the contain neurotransmitters like substance P and CGRP
when these are released they cause vasodilation, bradykinin, histamine + prostaglandin release


Name the two types of pain fibres, what pain they detect and where they synapse

C fibres - dull pain synapse lamina 1 + 11 INDIRECT
Ag fibres - sharp localised pain synapse with lamina I + V DIRECT


Describe the spinocerebellar tracts

POST + ANT tract - from the legs. synapse at the dorsal nucleus of clark. ant deccusates twice post stays same side --> cortex
cuneocerebellar - from the arms (enters spinal cord ascends to cuneate nucleus where it synapses) --> cerebellum


Role of the spinocerebellar tracts



Thalamus - what do they relay
1. VPA
2. Ant nucleus
3. medial nucleus
4. pulvinar
5. med and lat geniculate body

1. pain and touch
2. episodic memory and emotion
3. olfaction and pain
4. oculomotor movement
5. med = auditory. lat = visual


damage to the DMCL or peripheral neuropathy would lead to what and on which side of the lesion

loss of discriminative touch, proprioception -ipsilateral side


what is sensory ataxia

coordination difficulties resulting from loss of proprioceptive sensation


What is a positive rhomberg sign a sign of

damage to DCML pathway


What is freidrichs ataxia

hereditory disorder - ST and DCML path degenerate.


what is thalamic pain syndrome

damage to thalamus - loss of touch pain temp from contralat side - PAINFUL