Ascending tracts in the spinal cord

Question 1

where are receptors for pain and temperature found

Answer 1

dermis and epidermis of skin / mucosa

Question 2

where are cell bodies of sensory fibres situated

Answer 2

dorsal root ganglion

Question 3

how do local anaesthetics like lignocaine work

Answer 3

block sodium channels on the axons and nerve conduction

Question 4

what convey the sensation of pain and temperature

Answer 4

small myelinated (Aδ) and myelinated (C) fibres to the dorsal root

Question 5

pathway of axons of pain transmission

Answer 5

enter at all levels and synapse in dorsal horn
cross into contralateral spinal cord via anterior white commissure
ascend through spinal cord and spinothalamic tract

Question 6

where do fibres of the spinothalamic tract terminate

Answer 6

in the ventroposterior lateral nucleus of the thalamus

Question 7

VPL projections

Answer 7

projects axons through the posterior limb of the internal capsule to reach the somatosensory cortex

Question 8

functions of the spinothalamic tract

Answer 8

carries pain and temperature from body
also carries crude touch allowing sensation of touch without localisation

Question 9

role of spinoreticular tract

Answer 9

carries pain and crude touch

Question 10

polysynaptic relays of the spinoreticular tract

Answer 10

relays to the brainstem are in reticular formation
loose network of neurons between nuclei
these in turn projects via the non-specific thalamic nuclei

Question 11

reticular activating system

example

Answer 11

reaches widespread areas of the cortex
required for arousal of higher CNS centres

increased wakefulness as a result of pain

Question 12

what is the dorsal column medial lemniscus system responsible for

Answer 12

fine touch
conscious proprioception and vibratory sense

Question 13

where are receptors for proprioception located

Answer 13

muscles, tendons and joints

Question 14

dorsal column medial lemniscus system fibres
where are their cell bodies located

Answer 14

large, fast conducting fibres (Aβ)
pass towards the spinal cord in the peripheral nerves
dorsal root ganglion

Question 15

fasciculus gracilis

Answer 15

ascending fibres from the legs and lower trunk
in the dorsal column
terminate in the nucleus gracilis in the medulla oblongata

Question 16

fasciculus cuneatus

Answer 16

ascending fibres from the arms and upper trunk
in the dorsal column
terminate in the nucleus cuneatus in the medulla oblongata

Question 17

nucleus gracilis and nucleus cuneatus axons pathways

Answer 17

decussate medulla (cross the contralateral)
ascend through the medulla, pons, and midbrain as the medial lemniscus

Question 18

where do fibres of the medial lemniscus terminate

Answer 18

in the ventroposterior lateral nucleus of the thalamus

Question 19

function of the medial lemniscus

Answer 19

carries fine touch, vibration and proprioception from arms, legs and trunk

Question 20

effect of damage to the dorsal column medial lemniscus pathway

Answer 20

if before the decussation signs will be on the same side
if after the decussation the signs will be on the opposite side of the lesion

Question 21

tabes dorsalis

Answer 21

due to syphilis
caused by demyelination by advanced infection
occurs if the primary infection is left untreated for 10-15 years
ataxia and staggering gait

Question 22

trigeminal nerve afferents carry sensation from three non-overlapping segments of face

Answer 22

ophthalmic (V1)
maxillary (V2)
mandibular (V3)

Question 23

where do axons in the trigeminal nerve terminate

Answer 23

spinal trigeminal nucleus
chief sensory nucleus
mesencephalic nucleus

Question 24

spinal trigeminal nucleus

Answer 24

in the medulla oblongata and cervical spinal cord
receives pain and temperature from face through trigeminal and glossopharyngeal nerves
projects axons that cross contralateral and terminate in the VPM

Question 25

chief sensory nucleus of V

Answer 25

located in pons
receives fine touch and vibration sensation from face via three branches of trigeminal
projects axons that join contralateral medial meniscus and terminate in the VPM

Question 26

mesencephalic nucleus of V

Answer 26

located in the midbrain
contains cell bodies of axons of mandibular branch of trigeminal that carry proprioceptive input
projects axons to neurons of the trigeminal motor nucleus

Question 27

ventroposterior medial nucleus of the thalamus

Answer 27

relays fine touch, pain and temperature input from contralateral face
projects axons through genu of internal capsule to reach somatosensory cortex

Question 28

referred pain

Answer 28

pain sensation arising from a visceral structure can cause pain perception localised to predictable cutaneous regions
pain is referred to dermatomes supplied by the same posterior roots as the organ

Question 29

where is referred pain experienced from:
parietal pleura and diaphragm
appendix
ureters
gallbladder

Answer 29

parietal pleura and diaphragm: shoulder near root of neck
appendix: umbilicus then right iliac fossa
ureters: flank and inguinal area
gallbladder: below the ribs and shoulder

Question 30

neuropathic pain

Answer 30

continuous, intractable and frequently excruciating
burning pain with or without peripheral nerve damage
results from damage to sensory pathways not nociceptor activation

Question 31

phantom limb pain

common causes

Answer 31

pain from limb that no longer exists
stimulus applied anywhere along the nerve fibre experienced as from the skin area supplied by that nerve

fibres at the stump are frequently squeezed by scar tissue
may also result from plasticity changes in the somatosensory cortex

Question 32

gate control theory

Answer 32

small fibres activate posterior horn neurons that transmit pain centrally (open the gate)
large myelinated fibres activate interneurons that inhibit neurons in the posterior horn that transmit pain (close the gate)

Question 33

supraspinal antinociception

Answer 33

periaqueductal grey activates serotonergic neurons in medullary raphe nuclei
project to enkephalin interneurons in dorsal horn and suppresses pain transmission from first to second order neurons