The Spinal Cord and Periphery Flashcards
afferent/sensory fibres travel through the _____ horn of the spinal cord
dorsal
efferent/motor fibres travel through the _____ horn of the spinal cord
ventral
which horn is anterior
ventral
3 columns of white matter
posterior, lateral and anterior
ascending pathways are (sensory/motor)
sensory
3 most important spinal tracts
- corticospinal/pyramidal
- posterior/dorsal
- lateral spinothalamic
corticospinal carries…
motor impulses from motor cortex to skeletal muscles (hence cortico –> spinal)
posterior column carries…
sensory - touch, localisation, vibration, proprioception
lateral spinothalamic carries…
pain and temperature
where does the corticospinal tract cross over to the contralateral side (mostly)
decussation of medulla pyramids
course of corticospinal
- from primary motor cortex down through the corticospinal tract till the medulla where it crosses sides at the decussation of pyramids.
Travels down spinal cord till synapses with 2nd neuron in ventral horn - leaves through ventral root at same spinal level as synapse
what is a cranial nerve nucleus
an area of grey matter in the brainstem associated with one or more cranial nerves (i.e. where some cranial nerves make synapses)
how many neurons in the two ascending pathways
3.
ascending 1st order neuron
comes in from periphery and enters spinal cord through dorsal horn
crosses at point of entry to spinal cord or at nucleus in medulla
location of ascending 1st order neuron cell body
dorsal root ganglion
lateral spinothalamic 1st order neuron enter through the dorsal root and synapses with the 2nd order in the …
dorsal horn of spinal cord at level of entry
posterior column 1st order neuron
enters through dorsal root and travels up the column. Synapses with the 2nd neuron in a nucleus of the lower part of the medulla (before decussation)
lateral spinothalamic 2nd order neuron
synapses with 1st neuron in dorsal horn at level of entry.
Then crosses the spinal cord to the lateral spinothalamic tract.
It then travels up the spinal cord in this tract to the thalamus where it synapses with 3rd neuron
posterior column 2nd order neuron
synapses with 1st neuron in medulla nucleus.
Crosses medulla into a new tract called medial lemniscus.
Travels up to thalamus to synapse with 3rd neuron
lateral spinothalamic and posterior 3rd neuron
synapses with 2nd in thalamus.
Travel through internal capsule to post-central gyrus in parietal lobe
tract that posterior column 2nd order neuron crosses into
medial lemniscus
lobe of pre-central gyrus
frontal
a medullary lesion below the level of decussation on the left side will effect which tracts and functions
lateral spinothalamic - pain and temp from the right side
posterior - other sensory from the left side
corticospinal - motor to the left side
a lesion below the level of lateral spinothalamic decussation on the left side effects which tracts and functions
all three tracts on the left side - all sensory and motor to that side
what are the two types of reflex
stretch and flexor
process of a stretch reflex response
tendon stretched –> sensory muscle fibres (intrafusal) stimulated –> sensory neuron activated –> synapses with motor on same level back to original muscle –> muscle contracts
–> second axon travels through cord to synapse with interneuron onto a motor neuron for anagonist muscle –> muscle relaxes
process of a flexor reflex response with it’s crossed extensor reflex
pain stimulus –> pain neuron activated –> synapses with an interneuron in spinal cord –> one synapses to motor response on pain side to flex and withdraw, other to the contralateral limb motor for support
purpose of flexor response
to protect from pain
purpose of stretch reflex
control muscle tone and posture
which part of the stretch reflex is monsynaptic
reflex arc from the muscle’s sensory to motor neuron. only 2 neurons, hence monosynapse
what part of the stretch reflex in polysynaptic
the reflex arc to the antagonist muscle. there is an interneuron between the sensory input and motor response
what makes a flexor reflex polysynaptic
sensory input from pain synapses with an interneuron in spinal cord with synapses onto motor for the pain limb and contralateral limb
where does the lower motor neuron go
from the ventral horn of the spinal cord and out through the ventral root
where does the upper motor neuron go
from primary motor cortex down through thalamus and brainstem. Crosses over at decussation. and travels down spinal cord till 2nd neuron at level of exit
effect of UMN lesion on reflexes
exaggerated
which motor neuron mediates refelxes
LMN
which motor neuron lesion increases tone
UMN
summarise the effects of LMN and UMN lesions on reflexes, tone and paralysis
LMN lesion
- reduced/absent reflexes
- loss of tone
- paralysis on side of lesion
UMN lesion
- exaggerated reflexes
- increased tone
- paralysis on same side when below level of decussation
lateral spinothalamic tract in the middle of the spinal cord on the left side is carrying what sensory information
pain and temperature from right side of body
posterior column in middle of spinal cord on the left side is carrying what information
sensory other than pain and temp from the left side of the body
what brain area is the primary motor cortex (aka precentral gyrus)
area 4
what brain area is the primary sensory cortex in (post-central gyrus)
area 3, 1, 2
