Anatomy of the somatosensory system Flashcards
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
- which proprioception fibre is contractile and which non contractile
- When do they fire
- 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
Proprioception
Thalamus - what do they relay
- VPA
- Ant nucleus
- medial nucleus
- pulvinar
- med and lat geniculate body
- pain and touch
- episodic memory and emotion
- olfaction and pain
- oculomotor movement
- 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
