Part 5: Spinal cord pathways Flashcards
spinal cord is a ____ (descr.)
cylindrical cable of pathways to & from brain and rest of the body
spinal cord extends from ____ to ____
base of the skull (medulla) to L1-L2 vertebrae
spinal cord vs vertebral column
vertebral column extends to coccyx but spinal cord ends at L1-l2 vertebrae
plexus is a ___
collection of nerves
two plexus in spinal cord
-cervical (brachial plexus)
-lumbar (lumbosacral plexus)
what covers the spinal cord?
-meninges
central canal of spinal cord is _____
continuous with ventricles of brain
conus medullaris (def.)
-tapered, lower end of the spinal cord at L1-L2
cauda equina (def.)
spinal nerves continue to branch out diagonally (looks like horse tail)
spinal cord ends at ____
conus medullaris at L1-L2
filum terminale
fibrous tissue downward from the apex of the conus medullaris to coccyx (stabilize lower part)
in spinal cord, grey mater is _____
in the inner layer
dorsal horn is at ___
back
ventral horn is at ____
front
sensory at ___ horn
dorsal
motor at ___ horn
ventral
sympathetic at ___ horn
lateral
cervical part of spinal cord: grey matter vs white matter
equal amounts due to cell bodies and large amounts of axons
thoracic part of spinal cord: grey matter vs white matter
mostly white matter due to limited muscles at thorax
lumbar part of spinal cord: grey matter vs white matter
mostly grey matter (large amounts of cell bodies)
sacral part of spinal cord: grey matter vs white matter
mostly grey matter (large amounts of cell bodies)
___ pairs of spinal nerves
31
____ pairs of cervical nerves
8
____ pairs of thoracic nerves
12
____ pairs of lumbar nerves
5
____ pairs of sacral nerves
5
7 cervical vertebrate but ___ cervical nerves
8
cervical vertebrae nerves come out on top of ____
vertebrae
fetal vs adult development of spinal cord
spinal nerves lines up with vertebrae but all the upper body grows, spinal cord moves up but nerves still come out at original levels so spinal cord ends at L1-L2 but nerves continue past that
spinal cord organization
medulla oblongata -> L1-L2 conus medullaris -> cauda equina -> filum terminale
in spinal cord, white matter is on ___
outer layer
grey matter has two horns: ___
posterior (dorsal/sensory) horn
anterior (ventral/motor) horn
dorsal & ventral horns lead to _____ roots
dorsal & ventral roots
dorsal & ventral roots join up to form _____
spinal nerve
dorsal root ganglion is ____
cell bodies of sensory neurons
below the C7 vertebrae, spinal nerves come out ____
below the vertebrae
ventral root doesn’t contain ____
ganglion only the dorsal root
sensory and motor information between brain, spinal cord and peripheral nerves and organ systems happens how often?
all the time, around the clock
ascending pathways are ____
sensory
descending pathways are ____
motor
ascending and descending pathways are made of _
chain of neurons and associated nuclei/ganglia
synapses are ___
inter-neuronal connections
what varies between pathways?
number of neurons and synapses
number of somatic sensory pathways
3
Three types of major sensory pathways
- Dorsal column/medial leminscal pathway
2.Spinothalamic (anterolateral) pathway - Spinocerebellar pathway
Dorsal column/medial leminscal pathway controls ____
-joint/limb position & motion sense (conscious proprioception) + light touch
Spinothalamic (anterolateral) pathway controls ____
pain, noxious temperature
Spinocerebellar pathway controls _____
unconscious proprioception
Right hemisphere controls _____ and the left half controls ____
-the left side of the body
-the right side of the body
Dorsal column conveys ____ & _____ from ______
-joint position (conscious proprioception) & discriminative touch (3D recognition of objects w/o vision) from
trunk & extremities
Dorsal column pathways involves how many order neurons?
3 (three)
Dorsal column pathways: 1st order neuron
-from skin/joint receptor
-enters the spinal cord and ascends the white matter as the dorsal columns
-synapses at medulla (same side)
Dorsal columns consists of______
the mechanosensory axons
Dorsal column pathways: 2nd order neuron
-from medulla
-crosses to opposite side
-ascends as the medial lemniscus
-synapses at thalamus
Dorsal column pathways: 3rd order neuron
-from thalamus
-goes to primary sensory cortex to thalamocortical projections
thalamus acts as the ___
bouncer directing what goes to the brain from sensory nerves
Dorsal column pathway general image
Lateral Spinothalamic Pathway involves how many order neurons?
3 (three)
Lateral Spinothalamic Pathway: 1st order neuron
-from skin receptors
-synapses at dorsal horn of spinal cord
Lateral Spinothalamic Pathway: 2nd order neuron
-from dorsal horn
-crosses over on opposite side of spinal cord
-synapses at thalamus as lateral spinothalamic tract
Lateral Spinothalamic Pathway: 3rd order neuron
-from thalamus to primary sensory cortex via thalamocortical tract
Unconscious Proprioception (def.)
body knows where each muscle and joint is at all times
Lateral Spinothalamic Pathway general image
Spinocerebellar Pathway carries ____
unconscious proprioception (joint position + vibration sense) from trunk and extremities to cerebellum
Spinocerebellar Pathway involves how many order neurons?
2 (two)
Spinocerebellar Pathway : 1st order neuron
-from receptors in joint capsules, tendons, & muscle spindles
-synapses at dorsal horn spinal grey matter
Spinocerebellar Pathway : 2nd order neuron
-from dorsal horn
-to cerebellum via dorsal spinocerebellar tracts
Spinocerebellar Pathway general image
CNS issues ___ commands that are distributed to body by ___
motor
PNS
somatic motor commands effect contraction of ____ muscle
skeletal
somatic motor pathways involve at least ___ motor neurons
2 (two)
motor neurons involved in somatic motor pathways
-upper motor neuron (UMN)
-lower motor neuron (LMN)
UMN has cell body in ___ and synapses onto ____
CNS processing centres
LMN
LMN has cell body in ___ and synapses onto ____
ventral horn of spinal cord/motor cranial nerve nucleus in brainstem
skeletal muscle
Modulation of Lower Motor Neuron by Upper Motor Neuron (excitatory synapse)
UMN–> excites LMN -> excites muscle (large signal at muscle)
Modulation of Lower Motor Neuron by Upper Motor Neuron (inhibitory synapse)
UMN–> inhibits LMN -> inhibits muscle (small signal at muscle)
Upper Motor Neuron Lesion
UMN –> inhibitory synapse prevented –> LMN –> spastic paralysis (muscles are tight and hard- spasm-always active)
Lower Motor Neuron Lesion
UMN –> excitatory or inhibitory synapse –> no response leads to flaccid paralysis (relaxed and therefore shrink,)
only axon of ___ extends to skeletal muscle
LMN
Conscious motor commands controlling skeletal muscle travel via the ___ pathways
corticospinal or corticonuclear (corticobulbar)
Corticospinal (Pyramidal) pathway
-UMN extend from the cerebral cortex (Cortico) to the spinal cord (Spinal) which houses the LMN
- LMN extend axons to regulate muscles of the limbs + trunk
Corticonuclear (Corticobulbar) pathway
UMN extend from the cerebral cortex (Cortico) to motor
cranial nerve nuclei (LMN) in the brainstem (Nuclear [Bulbar])
- LMN extend axons to regulate muscles of the head + neck
corticospinal + corticonuclear pathway general image
Corticospinal Pathway originates from
pyramidal neurons in the cortex from:
-Primary motor cortex and Premotor cortex
______ regulate distal limb muscles à important for precise, skilled, learned movements (such as playing piano)
Corticospinal Pathway
Corticospinal Pathways path
Primary Motor (& Sensory) Cortex -> Internal Capsule –>Crus Cerebri in Midbrain –> Pyramids in Medulla –> Decussation of the Pyramids (crosses over) -> Lateral Corticospinal Pathway
Upper Motor Neuron Injury in corticospinal pathway
-Middle Cerebral Artery Stroke
-Internal Capsule stroke
-Brainstem Lesion
-Spinal Cord Injury
lower Motor Neuron Injury in corticospinal pathway
Spinal Nerve Injury
Voluntary Movements (summary of previous slide)
- Central Motor Program
1.Identification and localization of targets in space->posterior parietal cortex
2. Formulation of a plan of action –> premotor cortex &
supplementary motor cortex
Execution of the movement à primary motor cortex
Extrapyramidal Pathways (def.) + example
Subsidiary descending pathways that help with movement
- (ie: contract your bicep muscles (pyramidal tract), you need to relax your opposing triceps muscles (extrapyramidal tract)
Basal Nuclei and Cerebellum Modulate and modify_______
activity in the corticospinal tract to ensure smooth, coordinated, purposeful movement
