Spinal Cord And Periphery Flashcards
Which fibres enter through the dorsal root into the dorsal horn of grey matter
Axons of sensory fibres
Which neurons have their cell bodies in the ventral horn
Motor neurons
Which pathways are sensory and which are motor (ascending or descending)
Ascending = sensory
Descending = motor
How to know whether a tract is descending or ascending from name
Ends in spinal = generally descending
Starts in spinal = starts in spinal cord and goes elsewhere
What is role of the corticospinal/pyramidal tract
Carries motor impulses from motor cortex to skeletal muscles (voluntary movement)
What is the role of the posterior/dorsal column
Carries touch, tactile localisation, vibration sense, proprioception
What is the role of the lateral spinothalamic tract
Pain and temperature (sensations that have to be responded to quickly)
Where does the pathway for the corticospinal/pyramidal tract begin
Motor cortex (area 4)
What does decussation mean? (What is the decussation of pyramids)
Decussation = fibres crossing from one side of the other
Decussation of pyramids is in the medulla oblongata and is where the motor fibres pass to the contralateral side
Where in the brain do motor fibres pass through (bottleneck)
They are projection fibres as they go down passing through the internal capsule bottleneck
At what point does the UMN become the LMN
When the UMN synapses to the ventral horn at the desired spinal nerve level it becomes the LMN (LMN are found in the ventral horn for the full length of the spinal cord)
Which part of the midbrain do motor fibres pass through
Front part of the midbrain
Where does the 1st order neuron end in the posterior/dorsal column
1st order neuron picks up information from action potentials and ends by synapsing with the cell body of the 2nd neuron in the lower part of the medulla
What is the 2nd order neuron in the posterior/dorsal column called once it decussates in the medulla
Tract is now called the medial lemniscus
Where does the medial lemniscus go (2nd order neuron of posterior/dorsal column)?
Passes through the medulla, pons and midbrain to reach the thalamus
Where does the 2nd order neuron of the posterior/dorsal column end and where does the 3rd order begin
2nd order synapses in the thalamus, 3rd order picks up these signals and its axons pass through the IC and radiate to the post-central gyrus
What happens to the 1st neuron as it reaches the grey matter in the spinal cord of the lateral spinothalamic tract
1st order neuron doesnt go through the dorsal column, enters the grey matter and at the same level synapses and becomes 2nd order neuron
What happens to the 2nd order neurons of the lateral spinothalamic tract?
The decussate at the level of entry to reach the lateral column in the spinal cord (now called lateral spinothalamic tract)
2nd order neuron ends in the thalamus
What happens to the 3rd order neuron of the lateral spinothalamic tract once 2nd order ends in the thalamus
3rd order neuron passes through the IC, radiation to reach the post central gyrus
What is the difference between the lateral spinothalamic tract and dorsal column in terms of where their neurons decussate
Lateral spinothalamic tract = neurons decussate at the same level they come into the spinal cord
Dorsal colum = neurons decussate in the medulla
Which motor neurons (UMN or LMN) mediate reflexes
LMN
What is the role of LMN mediating reflexes
Maintains the tone of the muscle
What happens to reflexes if there is an upper motor neuron lesion
The reflex will still function as the LMN controls the reflex (e.g. patient may not be able to move thumb as pathway is damaged but will have functioning reflex)
What happens to the reflex and tone if there is a LMN lesion
There is not reflex and no tone
What happens to the tone of a muscle in an UMN lesion and LMN lesion
UMN = increased tone (spasticity)
LMN = flaccidity
What would happen if there is a Left UMN lesion at the IC of the corticospinal/pyramidal tract (see photo) (3)
R sided paralysis (as above the level of decussation therefore contralateral paralysis)
Hyper-reflexia
Increased tone
What would happen if there is a Left UMN lesion at the upper cervical spinal cord of the corticospinal/pyramidal tract (see photo) (3)
L sided paralysis (as at the level of the decussation therefore not contralateral paralysis)
Absent reflexes
Flaccid
What would happen if there is a Left LMN of the corticospinal/pyramidal tract (see photo) (3)
L sided paralysis (below level of decussation)
Absent reflexes
Flaccid
What motor neurons does motor neuron disease affect
MND is characterised by combination of progressive UMN and LMN signs and symptoms
LMN in the ventral horn of the spinal cord - progressive and incurable
What happens if a lesion is above the level of decussation (signs and symptoms)
above decussation = UMN
Signs and symptoms are contralateral
What happens if a lesion is below the level of decussation (signs and symptoms)
Below decussation = LMN
Signs and symptoms are ipsilateral (same side)
What is hypertonia/spasticity
Increased tone (rigid muscles) following UMN lesion
(Muscles will be stiff and difficult to move)
What is hypotonia/flaccidity
Decreased muscle tone following a LMN lesion
Leads to muscle atrophy
