Neuronal Pathways

Question 1

Dorsal root are ?

Ventral root are?

Answer 1

Sensory (afferent)

Motor (efferent)

Question 2

Name the ascending tracts

pg 15

Answer 2

1. Ventral Spinothalmic tract
2. Lateral spinothalmic tract
3. Ventral spinocerebellar tract
4. Dorsal spinocerebellar tract
5. Fasciculus cuneatus
6. Fasciculus gracilis

Question 3

Tell me about the Spinothalmic tract 
Origin 
function 
site of decussation 
Damage will result in what symptoms?

Answer 3

Origin: Limbs and Trunk
Function: anterior- detects fine touch. Lateral: detects temp, pain and itch
Site of decussation: from the vertebral body it enters it ascends or descends 1-2 levels before synapsing in the dorsal horn then it decussates that level in the anterior white commissure➡ spinothalamic tract➡ VPL nucleus

Imagine:

• a cave man walking along with a spine in one Shane out I’m front of him (anterior) palpating it with a lite touch. In the other hand he has an itch rash, and is holding a fire so is in pain.
• he walks up a few stairs (ascends 1-2 levels)
• he then has to cross to the other side and in doing so crosses a ranging white river (anterior white commissure)
• he then has to climb up some more stairs past medulla and pons and finally reaches his destination in the thalamus

Damage will result in what symptoms?
Anaesthesia (loss of pain)
Thermos aesthetic (loss of pain and temp)
and loss of simple tactile sensations in contra-lateral side of body
17

Question 4

Ventral Spinocerebellar tract

Answer 4

Origin: From the limbs, muscles, joints, tendons
Function: Whole limb movements and postural adjustments.
-unconscious coordination of motor activity
Decussation:
-ascends contra and ipsilaterally. It decussates twice. 1st when it enters the spinal cord, 2nd at the pons
VENTRAL spinocerebellar tract fibres ascend CONTRA- & IPSILATERALLY to enter cerebellum through SUPERIOR CEREBELLAR PEDUNCLE.

• DORSAL spinocerebellar tract fibres ascend IPSILATERALLY and enter cerebellum through INFERIOR CEREBELLAR PEDUNCLE.
view sketch of info
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Question 5

Dorsal colum-medial lemniscus pathway

21

Answer 5

Function:

• conscious proprioception
• discriminative touch
• provides the parietal lobe with instantaneous body image so we are constantly aware of the body parts

3 chain neuronal pathway:
1st: skin/muscle/joint receptors => nucleus gracilis (lower limb) or cuneatus (upper limb) in caudal medulla (fibres ascend ipsilaterally)
2nd: nucleus graciliis/cuneatus => thalamus
(fibres enter the medial lemniscus and decussate in the caudal medulla)
3rd: thalamus => sensorimotor cortex

Damage to will result in:
Affect sensation in ipsilateral dermatomes at and below the level of the spinal cord lesion.

• Gracie (gracile-lower limb) is holding a cure (cuneate) possum in her arms (upper limb). Palpating it lightly (fine touch and proprioceotion
• she has to take the possum back to the nuclear bomb place were it came from (nucleaus in the medulla)
• after she drops it off there she walks out the door and finds her self in front of the Egyptian pyramids. She walks inter an arc shaped door (internal accurate fibres)
• when she gets in, there are medium sized lemons falling out of the sky (medial lemniscus pathway)
• she then ends her journey at the nuclear bomb warehouse (ventral postereolateral nucleaus) were she plans to bomb the post office (post central gyrus)

Question 6

Corticospinal tract

27

Answer 6

1. Begins In pre central gyrus with 2 nuclei, one for axial muscles and one for the limb muscles
2. Descend into the internal capsule ➡into the brain stem ➡
3. At medulla 90% decussate (these are fibres that innervate the limbs)
   The axial fibres don’t decussate here
4. After leaving the brainstem the 2 fibres will run down the corticospinsl tract (anterior and lateral?
5. When they get to their level, the fibres of the anterior corticospinsl tract decussate through the anterior white commissure, before synapsing info the anterior horn of grey matter

A lesion anywhere between anterior horn and muscles would be a LMN lesion

2 neuron pathway

• Everyone’s drinking (motor) at Pres (pre central gyrus)
• everyone gets into the car (internal capsule)
• they drove for a while but lu (lateral fibres) need to throw up, so she gets out of car and crosses the road and throws up in an Egyptian restaurant (decussation at pyramids). 90% of Lus stomach contexts came out that day (90% fibres decussate)
• the rest of the car keeps driving till they reach their destination. (Corticospinsl tracts)
• when they get there they have to cross the raging white river to get into the bar (anterior white commisure)

Question 7

Rubrospinal tract

28

Answer 7

• originates in red nucleus in the tegmentum of the midbrain
• decussates in the vertebral tegmentum of midbrain
  function: Facilitate contralateral flexor motor neurons and inhibit extensor motor neurons

Ruby red (red nucleus) always dumps her boyfriends straight away (decussated straight away) why? Coz their not buff enough. So they eat flexion arm exercises all the time (flex) so they don’t have flat floppy arms

Question 8

Reticulospinal tract

Answer 8

Slide 29

Question 9

Vestibulospinal tract

Answer 9

Slide 30

Question 10

tectospinal tract

31

Answer 10

-originate in tectum of midbrain (colliculi)
-turns head in response to visual and auditory stimulus
-terminate in anterior motor horn in cervical cord segments
Tectonic plates shifted and created an earthquake which crossed the ocean straight away and made really loud noise. Which made a loud noise and made everyone turn around and look