ascending pathways

Question 1

draw a diagram of major ascending and descending pathways

Answer 1

see page 26 of control notes

Question 2

what sensations are involved in the spinothalamic pathway

Answer 2

pain, temperature, crude touch, pressure

Question 3

what sensations are involved in dorsal column pathway

Answer 3

fine touch, vibration, pressure and position

Question 4

where do the spinothalamic and dorsal column pathways terminate

Answer 4

primary somatosensory cortex

Question 5

what is the role of general sensory pathways

Answer 5

skin, mucous membranes, joints and muscles send info to the brain

Question 6

what is a dermatome and what is an example disease which follows these rules

Answer 6

region of skin innervated by sneezy fibres of a single segmented spinal nerve

herpes zoster hits dorsal root ganglia and shingles present in dermatomes

Question 7

describe the 3 neuron chain in general sensory pathways

Answer 7

1st neurone - pseudo unipolar - cell body in sensory ganglion (DRG or CN ganglion)

2nd neurone - axon crosses midline (in spinal cord), ascends to ventral posterior thalamus

3rd neurone - axon projects to post central gyrus (parietal lobe)

Question 8

what is convergence and divergence

Answer 8

many to one

one to many

Question 9

describe the route of the spinothaalmic tract

Answer 9

through dorsal root into dorsal horn - either travels up cord slightly (lissauers tracts) or connects with secondary neuron in dorsal grey horn

axon 2 crosses midline in ventral white commissure

ascend from spinal lemiscus in the brain stem and enter the VPL of thalamus then via 3rd neurone to primary somatosensory cortex

Question 10

what are the different sensations using lissauers tract in the spinothalamic pathway

Answer 10

pain and temp synapse in substantial gelatinosa and don’t use tract

crude touch ascend lissauers tract before synapsing in SC - allows differentiation

Question 11

how are the areas in the spinothalamic tract organised

Answer 11

somatotopically

arm is medial
trunk is central
leg is lateral

Question 12

describe a brief summary of the dorsal column pathway

Answer 12

through dorsal root into dorsal horn
2nd neurone axons cross midline (internal arcuate fibres) which then ascend in medial menisnus
enter VPL of thalamus and then to primary somatosensory fibres via end neurone fibres

Question 13

in the DCML pathway what is the difference in travel routes above and below T6

Answer 13

below T6 - primary neurone from leg enters gracilis fascicle

above T6 - primary sensory neurone enters cuneate fascicle

Question 14

what’s the difference between the anterior STT and the lateral

Answer 14

anterior is crude touch and pressure

lateral is temperature and pain

Question 15

at what level in the dorsal column pathway does the primary neurones synapse to secondary

Answer 15

closed medulla and cross midline into medial leminscus

Question 16

what is the somatotopic organisation in the dorsal column pathway

Answer 16

fibres ascending the medial leincus

arm in ventral, trunk is central leg is dorsal

Question 17

general sensation in the head is carried by which cranial nerves

Answer 17

5
7
9
10

Question 18

what are the somatic sensation roles for cranial nerve 5, 7, 9, 10

Answer 18

5 - trigeminal - face nose scalp dura

7 - facial - external ear

9 - glossopharnegela - posterior 1/3 tongue, pharynx middle ear

10 - vagus - auditory canals larynx and oesophagus

Question 19

general sensation from their respected areas of cranial nerve, 5, 7, 9, 10 travel through which pathway

Answer 19

trigeminal sensory pathway

Question 20

in the trigeminal nuclei what are the sensory nuclei divided into

Answer 20

mesencephalic - proprioception

pontine (chief sensory) - discriminative touch

spinal nucleus - simple touch pressure, pain and temp

Question 21

describe the process of pain and temperature pathway of trigeminal pathway

Answer 21

1 neurone cell bodies in trigeminal ganglion which then run in spinal tract of trigeminal
synapse with 2 neurone in caudal spinal nucleus
2 neuron axon crossed midline and ascends in the trigeminothelamic tract (trigeminal leminscus) to VPM of thalamus

Question 22

describe the process of crude touch and pressure pathway in the trigeminal nuclei

Answer 22

1 neurones cell bodies sin trigeminal ganglion - run in spinal tract of trigeminal

synapse with 2 neurone more rostrally in the spinal nucleus - axon crosses midline and ascends in trigeminothalamic tract
to VPM of thalamus

Question 23

what what a lesion to the lateral medulla on either side cause

Answer 23

affet sensation
of the face on the ipsilateral side
but of the body from the contralateral side

Question 24

describe the trigeminal pathway of discriminatory touch via the pons (chief sensory)

Answer 24

1 neuone cell bodies in the trigeminal ganglion

synapses with 2 neurones in the pontine nucleus
these axons then cross the midline in the pons and ascend in the trigeminothalamiac tract to the VPM of thet thalamus

Question 25

describe the route and pathway of the proprioception sensation

Answer 25

exception to having the general first order cell bodie sin the peripheral ganglia

afferent primary axons have their cell bodie sin the mesencephalic nucleus (not trigeminal) they then synapse adjacent to the mesencephalic nucleus

2 neurons crosses and ascend to the thalamus in the trigeminothaalmic tract to the VPM thalamus

(some fibres skip the mesencephalic and synapse with the trigeminal motor nucleus for the jaw jerk reflex)