Ascending and descending pathways Flashcards
Ascending pathways are sensory / motor ?
Sensory
Sensory information travels to which part of the brain?
Primary somatosensory cortex
Where in the brain is sensory information interpreted?
Post central gyrus
How is the primary somatosensory cortex arranged?
By mapping out the body onto the cortex via the somatosensory strip.
- this gives rise to the homunculus
At what location do sensory fibres cross the midline?
In the medulla
- i.e. the left side of the boy is represented on the right side
Name 2 ascending pathways
Dorsal column medial lemniscus (DCML)
Spinothalamic tract
Which sensory pathway conveys fine touch, pressure, vibration and conscious proprioception?
DCML tract
Sensory information travels up the grey matter of the spinal cord. True or false?
False
- white matter
Which sensory pathway conveys pain, temperature, deep pressure signals?
Spinothalamic tract
DCML tract - where does decusation occur?
Medulla
DCML tract - first order neurones
Carry sensory info from the peripheral nerves to the medulla
DCML tract - signals from the upper limb (above T6) travel in the fasciculus GRACILIS / CUNEATUS ?
Fasciculus cuneatus
DCML tract - signals from the lower limb (T6 and below) travel in the fasciculus GRACILIS / CUNEATUS ?
Fasciculus gracilis
DCML tract - second order neurones
Begin in nucleus cuneatus/gracilis in the medulla.
They deliver information to the third order neurones by crossing over to the other side of the CNS.
DCML tract - where are third order neurones located?
In the thalamus
DCML tract -third order neurones transmit sensory signals from the thalamus to the IPSILATERAL/CONTRALATERAL primary somatosensory cortex
Ipsilateral
Spinothalamic tract - where does decusation occur?
Spinal cord level
Spinothalamic tract - first order neurones
Arise from the peripheral sensory receptors and synapse occurs at spinal cord
Spinothalamic tract - second order neurones carry information from spinal cord level to _____
thalamus
Spinothalamic tract - fibres ascend the spinal cord within the IPSILATERAL/CONTRALATERAL tract?
Contralateral
Spinothalamic tract - third order neurones carry signals from the thalamus to the IPSILATERAL/CONTRALATERAL primary somatosensory cortex
Ipsilateral
A spinal cord lesion is likely to be associated with ipsilateral/contralateral signs and symptoms?
Contralateral
Descending pathways are sensory/motor ?
Motor
LMNs directly innervate muscles to produce movement. True or false?
True
Where is the primary motor cortex located?
In the dorsal portion of the frontal lobe
The right motor cortex controls muscles on the right/left side of the body?
Left
Name 4 descending pathways
Corticospinal tract (pyrimidal)
Tectospinal tract
Reticulospinal tract
Vestibulospinal tract
Which pathway is responsible for fine control - fine, precise movements, particular in the distal limb muscles
Corticospinal tract
Corticospinal tract controls voluntary body movements. True or false?
True
Corticospinal tract - decussation of most motor fibres occurs where?
Medullary pyramids
Corticospinal tract - what structures do fibres cross through to get to the spinal cord?
Internal capsule -> midbrain -> spinal cord
Internal capsule occlusion can block the corticospinal tract and cause which movement in the upper limbs?
Spastic paralysis with hyeprflexion
Which 4 tracts make up the extrapyramidal system?
Tectospinal tract
Reticulospinal tract
Rubrospinal tract
Vestibulospinal tract
Tectospinal tract - which region of the spine does it work on?
Cervical region
Tectospinal tract - function
Visual and auditory function
Important in tracking functions
Tectospinal tract only projects to the upper limbs. True or false?
True
Reticulospinal tract - function
Many autonomic functions of the body
Voluntary movement
Vestibulospinal tract - function
Detects movement
Controls balance and posture
Which of the 3 extrapyramidal tracts does not cross over?
Vestibulospinal tract
Sensory travels from the periphery to the primary somatosensory cortex. This information is then interpreted where ?
Post central gyrus
DCML tract - fasciculus gracilus is medial or lateral to fasciculus cuneatus?
Medial
DCML tract - the fibres ascend up the DCML tract of the spinal cord ipsilateral/contralateral to the side they enter?
Ipsilateral
- decussation doesn’t occur until the medulla
DCML tract - first order neurone primary sensory fibres are which 2 of the following: A beta C fibres A delta A alpha
A alpha
A beta
Which vertebral level is the cut off between fasciculus cuneatus and gracilis?
T6
- above T6 = cuneatus
- T6 and below = gracilis
DCML - up until the brainstem, information coming from the body is ipsilateral/contralateral?
Ipsilateral
DCML - after decusation in the brainstem, information is represented ipsilaterally/contralaterally ?
Contralaterally
DCML - how does information from the 3rd order neurone get from the thalamus -> primary somatosensory cortex?
Via posterior internal capsule
Sensory information from which part of the body does not travel via the DCML pathway?
Anterior head
DCML pathway : which side is most lateral and which side is most medial:
Cervical -> thoracic -> lumbar -> sacral
Cervical = lateral Sacral = medial
As we ascend the spinal cord, the ratio of white:grey matter increases/decreases?
Increases
Spinothalamic tract - first order neurone primary sensory fibres are which 2 of the following: A beta C fibres A delta A alpha
A delta
C fibres
Spinothalamic tract - location of the tract?
Anterolateral
Spinothalamic tract - carries information from the opposite side of the body. True or false?
True
Which pathway provides unconscious proprioceptive information to the cerebellum (and is therefore important in motor co-ordination)?
Spinocerebellar pathway
Spinocerebellar pathway - information is transmitted to the ipsilateral/contralateral cerebellum?
Ipsilateral
Both DCML and spinothalamic tracts transmit information to the contralateral somatosensory cortex. True or false?
True
Name the 3 spinocerebellar tracts
Dorsal spinocerebellar tract
Ventral cerebellar tract
Cuneocerebellar tract
Which spinocerebellar tract carries unconscious proprioceptive information from the upper limbs?
Cuneocerebellar tract
Which spinocerebellar tract carries unconscious proprioceptive information from the lower limbs?
Dorsal spinocerebellar tract
Which spinocerebellar tract decussates twice?
Ventral spinocerebellar tract
Trigeminal system - where does the synapse occur for general tactile information of the anterior head ?
In the main sensory nucleus
Trigeminal system - where does the synapse occur for pain, temperature information of the anterior head?
Spinal nucleus
Where do descending spinal tracts arise from?
Cerebral cortex and brain stem
Descending pathways - name 2 lateral pathways
Lateral corticospinal tract
Rubrospinal tract
Descending pathways - lateral pathways are under control from the cerebral cortex / brainstem ?
Cerebral cortex
Descending pathway - lateral pathway is important for voluntary control of distal musculature. True or false?
True
Descending pathways - name 3 ventromedial tracts
Pontine (medial) reticulospinal tract
Medullary (lateral) reticulospinal tract
Lateral vestibulospinal tract
Lateral corticospinal tract contain decusated fibres. True or false?
True
Vental corticospinal tract contain decusated fibres. True or false?
False
- undecusated
Lateral corticospinal tract supplies more proximal/distal limbs ?
Distal
In the corticospinal tract, the upper limb fibres are more MEDIAL/LATERAL and the lower limb fibres are more MEDIAL/LATERAL
Upper limb fibres - medial
Lower limb fibres - lateral
What tract contains the UMN of the cranial nerves to provide innervation of the face, head and neck ?
Corticobulbar tract
Corticobulbar tracts innervate cranial motor nuclei unilaterally/bilaterally?
Bilaterally
- there are exceptions (hypoglossal nuclei and lower facial nuclei which are innervated contra laterally only)
UMN lesion of facial nerve will cause paralysis where?
Lower half of one side of the face only and the forehead muscles remain unaffected
LMN lesion of facial nerve will cause paralysis where?
Paralysis of the ipsilateral one half of the face including the forehead (Bell’s palsy)
Function of the rubrospinal tract?
Excites flexor muscles and inhibits extensor muscles of the upper body
There is no decussation of the vestibulospinal tract. True or false?
True
Cell bodies of the tectospinal tract originate where?
Superior colliculus in the midbrain
Which tract co-ordinates movements of the head due to visual stimuli?
Tectospinal tract
What is the reticular formation?
Mesh of neurone that are located along the length and at the core of the brainstem
Pontine (medial) reticulospinal tract descends ipsilaterally/bilaterally?
Ipsilaterally
Medullary (lateral) reticulospinal tract descends ipsilaterally/bilaterally?
Bilaterally