The Spinal Cord and Periphery Flashcards
What is the travel of an upper motor neurone in the corticospinal / pyramidal tract?
Upper motor neurone travels from the motor cortex of the cerebral hemisphere into the internal capsule, then continues to the midbrain, and forms the cerebral peduncle (contains pyramidal fibres). At the decussation of the pyramids (in medulla), the fibres either continue as lateral corticospinal tract or anterior corticospinal tract.
(Lower motor neurone in spinal cord ro cranial nerve nucleus)
Where does the upper motor neurone synaps with the lower motor neurone?
Ventral portion of the grey matter of the spinal cord
Where do ascending spinal tracts travel to?
Travel to the cerebral cortex and cerebellum
How many neurones are present in ascending pathways?
3 neurones between peripheral receptor and cortex
Where do ascending pathways synapse and where do they cross the spinal tract?
Enter CNS via the dorsal root / cranial nerve ganglion
Synapse 1: Grey matter of spinal cord (if pain and temperature) or nucleus in the medulla if touch sensation (upper part - cuneate nucleus or gracile)
Crosses over to the contralateral side in the spinal cord or the medulla
Synapse 2: Nucleus in contralateral thalamus
3rd order neurone then travels to the contralateral parietal cortex
What part of the medulls do the first order neurones in the dorsal column travel to?
Gracile and the cuneate nuclei (these are present in the medulla, caudal part)
What forms the medial lemniscus? (found in the pons)
Fibres that have synapsed and crossed over
Indicates the start of the third order neurone
What is the thalamus described as?
Sensory relay station
All sensory information has to synapse first in the thalamus – decides what is important
Which group of the thalamus is responsible for processing sensory information?
•The lateral group are involved in processing sensory information
What fibres are present in the lateral spinothalmic tract?
Pain and temperature fibres
Where do fibres of the lateral spinothalmic tract cross over?
Cross at the level of entry as opposed to the dorsal column pathway that crosses at the upper part of the medulla
Look
Red - motor
Blue - Touch
Green - pain and temperature
Where are the axons of sensory fibres and the nuclei of motor fibres on the cross section of a spinal cord?
The axons of sensory fibres enter through the dorsal root into the dorsal horn of grey matter.
Motor neurons have their cell bodies in the ventral horn.
What is motor neurone disease?
•Group of diseases affecting the motor neuron in the ventral horn of spinal cord. (This neuron is called as the Lower Motor Neuron.)
What are the 3 ascending columns?
The white matter is arranged as 3 columns – posterior,lateral & anterior. Each column has in it various tracts.
What is the posterior dorsal column responsilbe for?
Fine touch, tactile localisation, vibration sense, proprioception
What is the travel of corticobulbar fibres?
Go to contralateral cranial nerve nuclei - responsible for the motor function of non-occulomotor nerve motor funciton
Where do corticospinal tracts cross?
- Corticospinal fibres mostly cross in decussation of pyramids (Lateral corticospinal tract).
- (Anterior corticospinal tract is only 10-15% of fibres)
What are the features of an upper motor neurone lesion?
Hyper reflexia, spastic paralysis
What are the features of an lower motor neurone lesion?
Paralysis, decrease tone and absent reflexes
What is the lower motor neurone responsible for?
Responsible for muscle tone and reflexes
If the upper motor neuron (UMN) is damaged with LMN intact, then reflexes and tone are exaggerated
What is a reflex?
A reflex is an involuntary stereotyped pattern of response brought about by a sensory stimulus.
Which refexes are polysynaptic and monosynaptic?
Monosynaptic: Stretch reflex
Polysynaptic: Flexor reflex
How many neurones are present in the pathway of the ANS?
2
What is the outflow of the sympathetic tract vs the parasympathetic tract?
Sympathetic: Thoracolumbar (T1 - T12, L1 and L2)
Parasympathetic: Craniisacral (CN 3,7,9 and 10, S2, 3 and 4)
Where are the pregagniolnic fibres in the sympathetic and parasympathetic nervous system?
Sympathetic: Near spinal cord
Parasympathetic: Near target organ
