Ascending and Descending Pathways Flashcards
The right somatosensory cortex is responsible for sensation on which side of the body?
Left
The left somatosensory cortex is responsible for sensation on which side of the body?
Right
Sensory information from the peripheries reaches the somatosensory cortex how?
Travelling up the spinal cord
Sensation from which areas of the body do not reach the somatosensory cortex by travelling up the spinal cord?
Face and scalp
White matter occupies a smaller proportion of the spinal cord as you travel in which direction?
Downwards (the further down the spinal cord, the less white matter)
Is the dorsal column-medial lemniscus system ascending or descending?
Ascending
What is the dorsal column-medial lemniscus system responsible for?
Fine touch, conscious proprioception and vibration
In the dorsal column-medial lemniscus system, where do the fibres cross over?
The medulla
In which direction do sensory pathways in the body travel?
Ascending
Ascending and descending pathways in the spinal cord are found within which matter?
White matter
What two areas of spinal cord make up the dorsal column-medial lemniscus system?
Fasciculus gracilis and fasciculus cuneatus
Which is more medial in the spinal cord- the fasciculus gracilis or fasciculus cunneatus?
Fasciculus gracilis
Signals from where travel within the fasciculus gracilis (within the dorsal column-medial lemniscus system)?
Lower limb
Signals from where travel within the fasciculus cuneatus (within the dorsal column-medial lemniscus system)?
Upper limb
The anterior aspect of the spinothalamic tract is responsible for what sensation?
Crude touch and pressure
The lateral aspect of the spinothalamic tract is responsible for what sensation?
Pain and temperature
In the spinothalamic tract, where do the fibres cross over?
In the spinal cord
Is the spinothalamic tract ascending or descending?
Ascending
The right primary somatomotor cortex is responsible for muscles on which side of the body?
Left
The left primary somatomotor cortex is responsible for muscles on which side of the body?
Right
Are motor pathways in the CNS ascending or descending?
Descending
Is the corticospinal tract ascending or descending?
Descending
What can the corticospinal tract also be known as?
The pyramidal tract
There are 2 subsets of corticospinal tract. Fibres which have crossed over form which one?
Lateral
There are 2 subsets of corticospinal tract. Fibres which have not crossed over form which one?
Ventral
Where do pyramidal tracts originate?
Cerebral cortex
What are all types of pyramidal tract responsible for?
Voluntary control of the muscles of the face and body
What is the corticospinal tract responsible for?
Fine, precise movement (particularly of distal limb muscles)
Within descending pathways, are there synapses?
No
At the termination of a descending pathway, the neurones synapse to become what?
A lower motor neurone
Where do most fibres in the corticospinal pathway cross over to form the lateral CST?
Medulla
Where do some fibres in the corticospinal pathway cross over to form the ventral CST?
Spinal cord
A CVA of the internal capsule can result in a lack of descending control of the CST which results in what clinical picture?
Spastic paralysis with hyeprflexion of the upper limbs
Where do extrapyramidal descending tracts originate?
Brainstem
What are all types of extrapyramidal tract responsible for?
Involuntary and autonomic control of all musculature
The tectospinal tract involves input mostly to where?
Cervical segments of the spinal cord
The following describes the function of which pathway: “Though to mediate reflex head and neck movement due to visual stimuli”
Tectospinal tract
In the reticulospinal tract, fibres originating where facilitate extensor muscles and inhibit flexor muscles?
Pons
In the reticulospinal tract, fibres originating where facilitate flexor muscles and inhibit extensor muscles?
Medulla
The following describes the function of which pathway: “Controls balance and posture by innervating anti-gravity muscles via lower motor neurones”
Vestibulospinal tract
Does the vesticulospinal tract cross over?
No
Lesions of the brainstem at the level of the midbrain can result in a lack of descending control of the vestibulospinal tract. What clinical picture does this result in?
Domination of extensor muscles and hyperextended spastic paralysis
Where do the first synapses take place in the DCML system?
In the medulla, in the nucleus gracilis/cuneatus
Where do the second synapses take place in the DCML system?
The thalamus
Once the fibres of the DCML pathway have entered the spinal cord, where do they travel to?
The nucleus gracilis/cuneatus of the medulla
Once the fibres from the DCML pathway have synapsed at the medulla, where do they travel to?
The thalamus
Where do the fibres of the DCML pathway go after the 3rd order neurones exit the thalamus?
They travel via the internal capsule to the ipsilateral somatosensory cortex
What happens after fibres from the periphery enter the spinothalamic tract?
They ascend 1 or 2 spinal levels and then synapse at the tip of the dorsal horn
After passing up the spinal cord, where is the next synapse in the spinothalamic tract?
Thalamus
Where do the fibres of the spinothalamic tract go after the 3rd order neurones exit the thalamus?
They travel via the internal capsule to the ipsilateral somatosensory cortex
Fibres of the vestibulo-spinal tract originate where?
Vestibular nucleus in the pons
Where does the tectospinal tract originate?
The superior colliculus in the midbrain
Where does the reticulospinal tract originate?
The reticular formations in the pons and medulla
What is the function of the pontine reticulospinal tract?
Facilitate voluntary/reflex responses and increase tone
What is the function of the medullary reticulospinal tract?
Inhibit voluntary/reflex responses and decrease tone
Where does the rubrospinal tract originate?
Red nucleus in the midbrain
What is the function of the rubrospinal tract?
Excites flexor muscles and inhibits extensor muscles of the upper body
Fibres in the lateral corticospinal tract mainly supply which muscles?
Distal muscles
Fibres in the anterior/ventral corticospinal tract mainly supply which muscles?
Axial/proximal muscles
What are the two pyramidal tracts known as?
Corticospinal and corticobulbar
What is the function of the corticobulbar tract?
Contains the upper motor neurone of cranial nerves to provide innervation of the head, face and neck
The UMNs found in the corticobulbar tract innervate the cranial nerves bilaterally - what are the exceptions to this?
The hypoglossal nuclei and the lower facial nuclei - these are only innervated contralaterally
What is the clinical picture if there is an upper motor neurone lesion of the facial nerve? What is this known as?
Paralysis of the lower half of the contralateral side of the face, with the forehead muscles unaffected. This is known as central facial palsy
What is the clinical picture if there is a lower motor neurone lesion of the facial nerve? What is this known as?
Paralysis of the ipsilateral half of the face including the forehead. This is known as Bell’s palsy
