Lecture 13 - Spinal Pathways Flashcards
cylindrical cable of pathways to and from the brain and the rest of the body
spinal cord
how long does the spinal cord extend?
from the base of the skull (medulla) to L1-L2 vertebrae
true or false: the meninges cover the spinal cord just like in the brain
true
the spinal cord has cervical and lumbar enlargements called the:
brachial plexus and lumbosacral plexus
the cable of pia mater anchoring the conus medularis to the coccyx
filum terminale
what is the conus medullaris?
the terminal end of the spinal cord at L1-L2
the bundle of nerve roots is located at the lower end of your spinal cord in the lumbosacral spine; nerves send and receive messages to and from your legs, feet, and pelvic organs
cauda equina
how many pairs of spinal nerves are there?
31
from C1-C7 the spinal nerves exit ____ the vertebrae
above
from C8-Co1 the spinal nerves exit _____ the vertabrae
below
why does the spinal cord end so high up in the vertebrae as an adult, even though it extends all the way to the coccyx during fetal development?
spinal cord doesn’t grow as fast as the baby
the dorsal and ventral roots join up to form a ___
spinal nerve
cell bodies of sensory neurons are located in the:
dorsal root ganglion
cell bodies of motor neurons are located in the:
ventral horn of the spinal cord
at any given moment, millions of sensory neurons are delivering information to ____, and millions of motor neurons are ____
processing centres in the CNS, controlling or adjusting the activities of muscles
communication between the CNS, PNS, and peripheral organ systems involves _____ that relay sensory and motor info between the periphery and higher centres
ascending and descending pathways
each ascending (sensory) or descending (motor) pathways that consists of:
a chain of neurons and associated nuclei or ganglia
what are the three major sensory pathways?
1) dorsal column/medial lemniscal pathway
2) spinothalamic (anterolateral) pathway
3) spinocerebellar pathway
what type of sensory information is carried along the dorsal column/medial lemniscal pathway?
conscious proprioception, discriminative touch, and mechanosensation
what type of sensory information is carried along the spinothalamic pathway?
pain and noxious temperature
what type of sensory information is carried along the spinocerebellar pathway?
unconscious proprioception
list the steps for how information is carried along the dorsal column/medial lemniscal (DCML) pathway
1) 1st order neuron enters the spinal cord and ascends through the dorsal columns then synapses at the medulla on the ipsolateral (same) side
2) 2nd order neuron from the medulla crosses contralaterally to the medial lemniscus and synapses at the thalamus
3) 3rd order neuron from the thalamus to the primary sensory cortex
found in the white matter and consists of mechanosensory pathways
dorsal columns
list the steps for how information is carried along the lateral spinothalamic tract
1) 1st order neuron from skin receptors synapses at the dorsal horn of the spinal cord
2) 2nd order neuron from dorsal horn crosses over and ascends on the opposite side of the spinal cord (lateral spinothalamic tract) to the thalamus
3) 3rd order neuron from the thalamus to the primary sensory cortex
list the steps for how information is carried along the spinocerebellar pathway
1) 1st order neuron from receptors in joint capsules, tendons, and muscle spindles synapses at the dorsal horn spinal grey matter
2) 2nd order neuron from the dorsal horn travels to the cerebellum via dorsal spinocerebellar tracts on the ipsolateral (same) side
somatic motor commands effect contraction of:
skeletal muscle
somatic motor pathways involve how many motor neurons?
at least 2
where are the cell bodies for the upper motor neurons found?
the CNS processing centres
where are the cell bodies for the lower motor neurons found?
in the ventral horn of the spinal cord or the motor cranial nerve nucleus in the brainstem
the synapse between the upper motor neuron and the lower motor neuron can be either _____ or _____
excitatory, inhibitory
all the muscles you aren’t currently using are being inhibited by:
the upper motor neuron
what happens to muscle control when there is an upper motor neuron lesion?
dis-inhibition of the lower motor neurons leads to spastic paralysis
what happens to muscle control when there is a lower motor neuron lesion?
no matter whether there is an excitatory or inhibitory synapse, there is no response which leads to flaccid (total) paralysis
conscious motor commands controlling skeletal muscle travel via the _____ or _____ pathways
corticospinal, corticonuclear (corticobulbar)
what muscles are regulated by the corticospinal pathway?
limbs and trunk
what muscles are regulated by the corticonuclear/corticobulbar pathway?
head and neck
list the steps for how information is carried along the corticospinal pathway
1) upper motor neurons (UMNs) in the primary motor cortex travel down the spinal cord
2) the UMNs synapse with the lower motor neurons (LMNs) in the spinal cord
3) motor information is carried to the limbs and trunk
list the steps for how information is carried along the corticonuclear/corticobulbar pathway
1) UMNs in the primary motor cortex travel to the somatic motor nuclei of the brainstem where they synapse with LMNs
2) motor information is carried to the muscles in the head and neck
injuries in the UMNs (such as middle cerebral artery strokes, internal capsule strokes, brainstem lesion, or spinal cord injury) lead to:
no control over LMN, leads to spastic paralysis
injuries in the LMNs (such as a spinal nerve inury) lead to:
flaccid (complete) paralysis
list the four basic steps to voluntary movements
1) identification of localization of targets in space (posterior parietal cortex)
2) formulation of a plan of action (premotor cortex and supplementary motor cortex in the parietal lobe)
3) execution of the movement (primary motor cortex)
4) muscle contraction
subsidary descending pathways that help with movement
extrapyramidal pathways
modulate and modify activity in the corticospinal tract to ensure smooth, coordinated, purposeful movement
basal nuclei and cerebellum
