Anatomy of the somatosensory system

Question 1

Name the 4 types of hapsis receptors and what they detect

Answer 1

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

Question 2

which hapsis receptors are slow adapting and which are fast

Answer 2

SLOW = ruffini and merkels 
FAST = meissners and pacinian

Question 3

name three methods of proprioception

Answer 3

muscle spindles, golgi tendon organs, joint receptors

Question 4

describe the 2 types of proprioception fibres + what they detect

Answer 4

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

Question 5

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

Answer 5

1. 1a - non contractile Ab- contractile
2. 1a fire when muscle contracting
   Ab continue to fire as long as stimulus

Question 6

Describe the DCML pathway (leg)

Answer 6

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

Question 7

what does the DCML pathway detect

Answer 7

fine touch and proprioception

Question 8

What does the antrolateral system detect

Answer 8

pain, temp and crude touch

Question 9

describe the spinothalamic tract

Answer 9

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

Question 10

How does the spinoreticular tract differ from the spinothalamic tract

Answer 10

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

Question 11

Roles of the

spinomesencephalic spinohypothalmic and spinotectal tract

Answer 11

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

Question 12

other effects of stimulation of 1st order neurones

Answer 12

the contain neurotransmitters like substance P and CGRP

when these are released they cause vasodilation, bradykinin, histamine + prostaglandin release

Question 13

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

Answer 13

C fibres - dull pain synapse lamina 1 + 11 INDIRECT

Ag fibres - sharp localised pain synapse with lamina I + V DIRECT

Question 14

Describe the spinocerebellar tracts

Answer 14

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

Question 15

Role of the spinocerebellar tracts

Answer 15

Proprioception

Question 16

Thalamus - what do they relay

1. VPA
2. Ant nucleus
3. medial nucleus
4. pulvinar
5. med and lat geniculate body

Answer 16

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

Question 17

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

Answer 17

loss of discriminative touch, proprioception -ipsilateral side

Question 18

what is sensory ataxia

Answer 18

coordination difficulties resulting from loss of proprioceptive sensation

Question 19

What is a positive rhomberg sign a sign of

Answer 19

damage to DCML pathway

Question 20

What is freidrichs ataxia

Answer 20

hereditory disorder - ST and DCML path degenerate.

Question 21

what is thalamic pain syndrome

Answer 21

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