Tracts/Pathways Flashcards
How many sensory pathways are there?
Five
What are the five sensory pathways?
Spinothalamic pathway Dorsal column medial leminiscal pathway Spinal tract V Chief sensory Tract Spinocerebellar tract
What pathways receive information from the body?
Spinothalamic
Dorsal Column medial leminiscal
Spinocerebellar
What pathways receive information from the head?
Spinal tract V
Chief sensory tract
What are some of the nerve endings that actually receive sensory information?
Free Nerve Endings Merkels Discs Pacinian corpuscles Messiners corpuscles Ruffini end-organs
Muscle spindle fibres
Golgi tendon organs
What are the two ways the brain selectively chooses the sensory information we consciously are aware of?
Accomodation
Selective awareness
What is accommodation?
When the brain NO LONGER feels certain sensory inputs that have been present for a long while
What is selective awareness?
When the brain chooses TO RECEIVE certain sensory inputs (cocktail party phenomenon)
What type of sensory input does the spinothalamic tract receive?
Crude touch/pressure, Pain, Temperature
What type of sensory input does the dorsal column medial leminiscus tract receive?
Discriminative touch/vibration, proprioception
What type of input does spinal tract V receive?
Crude touch/pressure, pain, temperature
What type of input does The chief sensory nucleus V receive?
Discriminative touch/vibration and proprioception
What pathway do both Spinal tract V and The chief sensory tract travel in?
The trigemino-thalamic tract (TTT)
What cranial nerves contribute to spinal tract V?
Trigeminal (main), Facial, Glossopharyngeal and Vagus
What cranial nerves contribute to the chief sensory tract?
Only the trigeminal
Where do The spinothalamic and dorsal column medial leminiscal tracts and spinal tract V and chief sensory nucleus tract synapse in the thalamus?
The spinothalamic and dorsal column both synapse in the VPL as they come from the body
Spinal tract V and the chief sensory nucleus synapse in teh VPM as they come from the head
What is different about the spino-cerebellar tract to all the other sensory tracts?
It gives it’s input ipsilaterally
What kind of input does the spinocerebellar tract give?
Proprioception of muscles to co-ordinate posture and balance
Where does the spinocerebellar tract synapse (eventually)?
The cerebellum
What are the two different types of motor pathways?
Voluntary - Pyramidal
Involuntary - extra-pyramidal
What are the two pyramidal motor pathways? Whats the difference between them?
Corticospinal - body and limbs
Corticobulbar - Head
What type of neurones do the extrapyramidal motor pathways act on?
Gamma Lower motor neurones
What kinds of actions are extrapyramidal motor pathways involved in?
Inhibition of muscles:
- Reflexes
- Posture
Where are the UMN cell bodies located in the cortico-spinal tract?
Mostly in the primary motor cortex, but also importantly in the:
Association motor cortex AND sensory cortex
UMN of the cortico-spinal tract that originate in the primary sensory cortex synapse where, what is their use?
Synapse on the Dorsal medial leminiscal pathway and are involved in the proprioceptive functions of muscle
What are the differences in the lateral and the anterior corticospinal tracts?
The Lateral corticospinal tract (90% of fibres):
- Cross at the decussation point
- Descend on the contralateral side
- Distal muscles and fine motor control
The Anterior corticospinal tract:
- Do not cross
- Descend on the ipsilateral side
- Axial Muscles (around spine) and posture/balance
What is the route from the UMN of the lateral corticospinal tract?
UMN passes through the internal capsule
Pass down into the brainstem and through the crus cerebri, through the pons to the medulla where they form the pyramids
Cross at the decussation point and descend in the lateral funiculus
Then go to ventral horn of grey matter and then onto a mixed spinal nerve
What route from the UMN will the anterior corticospinal tract take?
UMN passes through the internal capsule
Pass down into the brainstem and through the crus cerebri, through the pons to the medulla where they form the pyramids
Will not cross but will continue down the anterior funiculus
Will then cross at the anterior white commisure
If there is a lesion to the corticospinal tract at the level of the brain where will the effects be seen
Contralateral side (assume it is the lateral corticospinal tract).
What is spinal shock?
Occurs when there is damage to the spinal cord and all spinal functions stop for a period of time after the trauma.
Classic signs of UMN lesion?
Spastic paralysis (pen-knife response)
Clonus (rythmic contractions)
Hypereflexia/hypertonia (extrapyramidal damage)
Positive babinski’s sign
Classic signs of a LMN lesion?
Flaccid paralysis - weakness/reduced tone
Positive atrophy (permanent)
Fasciculations
Hyporeflexia
What path does the corticobulbar pathway take?
UMN is in cortex and then synapses onto interneurone and then onto a cranial nerve
What does damage to the corticobulbar tract usually cause?
Exceptions?
Usually causes slight weakness (palsy) not full blown as there is usually bilateral innervation
CNVII and CNXII do not give out bilateral innervation.
If there is a lesion to the corticobulbar pathway to the hypoglossal nerve affecting the UMN what will the effects be?
Tongue will deviate to the opposite side
If there is a lesion to the corticobulbar pathway to the hypoglossal nerve affecting the LMN what will the effects be?
Tongue will deviate to the same side
Damage to the corticobulbar pathway to the facial nerve will cause what?
Paralysis on the lower part of one side of the face.
