Lecture 13 - Spinal Pathways

Question 1

cylindrical cable of pathways to and from the brain and the rest of the body

Answer 1

spinal cord

Question 2

how long does the spinal cord extend?

Answer 2

from the base of the skull (medulla) to L1-L2 vertebrae

Question 3

true or false: the meninges cover the spinal cord just like in the brain

Answer 3

true

Question 4

the spinal cord has cervical and lumbar enlargements called the:

Answer 4

brachial plexus and lumbosacral plexus

Question 5

the cable of pia mater anchoring the conus medularis to the coccyx

Answer 5

filum terminale

Question 6

what is the conus medullaris?

Answer 6

the terminal end of the spinal cord at L1-L2

Question 7

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

Answer 7

cauda equina

Question 8

how many pairs of spinal nerves are there?

Answer 8

31

Question 9

from C1-C7 the spinal nerves exit ____ the vertebrae

Answer 9

above

Question 10

from C8-Co1 the spinal nerves exit _____ the vertabrae

Answer 10

below

Question 11

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?

Answer 11

spinal cord doesn’t grow as fast as the baby

Question 12

the dorsal and ventral roots join up to form a ___

Answer 12

spinal nerve

Question 13

cell bodies of sensory neurons are located in the:

Answer 13

dorsal root ganglion

Question 14

cell bodies of motor neurons are located in the:

Answer 14

ventral horn of the spinal cord

Question 15

at any given moment, millions of sensory neurons are delivering information to ____, and millions of motor neurons are ____

Answer 15

processing centres in the CNS, controlling or adjusting the activities of muscles

Question 16

communication between the CNS, PNS, and peripheral organ systems involves _____ that relay sensory and motor info between the periphery and higher centres

Answer 16

ascending and descending pathways

Question 17

each ascending (sensory) or descending (motor) pathways that consists of:

Answer 17

a chain of neurons and associated nuclei or ganglia

Question 18

what are the three major sensory pathways?

Answer 18

1) dorsal column/medial lemniscal pathway
2) spinothalamic (anterolateral) pathway
3) spinocerebellar pathway

Question 19

what type of sensory information is carried along the dorsal column/medial lemniscal pathway?

Answer 19

conscious proprioception, discriminative touch, and mechanosensation

Question 20

what type of sensory information is carried along the spinothalamic pathway?

Answer 20

pain and noxious temperature

Question 21

what type of sensory information is carried along the spinocerebellar pathway?

Answer 21

unconscious proprioception

Question 22

list the steps for how information is carried along the dorsal column/medial lemniscal (DCML) pathway

Answer 22

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

Question 23

found in the white matter and consists of mechanosensory pathways

Answer 23

dorsal columns

Question 24

list the steps for how information is carried along the lateral spinothalamic tract

Answer 24

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

Question 25

list the steps for how information is carried along the spinocerebellar pathway

Answer 25

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

Question 26

somatic motor commands effect contraction of:

Answer 26

skeletal muscle

Question 27

somatic motor pathways involve how many motor neurons?

Answer 27

at least 2

Question 28

where are the cell bodies for the upper motor neurons found?

Answer 28

the CNS processing centres

Question 29

where are the cell bodies for the lower motor neurons found?

Answer 29

in the ventral horn of the spinal cord or the motor cranial nerve nucleus in the brainstem

Question 30

the synapse between the upper motor neuron and the lower motor neuron can be either _____ or _____

Answer 30

excitatory, inhibitory

Question 31

all the muscles you aren’t currently using are being inhibited by:

Answer 31

the upper motor neuron

Question 32

what happens to muscle control when there is an upper motor neuron lesion?

Answer 32

dis-inhibition of the lower motor neurons leads to spastic paralysis

Question 33

what happens to muscle control when there is a lower motor neuron lesion?

Answer 33

no matter whether there is an excitatory or inhibitory synapse, there is no response which leads to flaccid (total) paralysis

Question 34

conscious motor commands controlling skeletal muscle travel via the _____ or _____ pathways

Answer 34

corticospinal, corticonuclear (corticobulbar)

Question 35

what muscles are regulated by the corticospinal pathway?

Answer 35

limbs and trunk

Question 36

what muscles are regulated by the corticonuclear/corticobulbar pathway?

Answer 36

head and neck

Question 37

list the steps for how information is carried along the corticospinal pathway

Answer 37

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

Question 38

list the steps for how information is carried along the corticonuclear/corticobulbar pathway

Answer 38

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

Question 39

injuries in the UMNs (such as middle cerebral artery strokes, internal capsule strokes, brainstem lesion, or spinal cord injury) lead to:

Answer 39

no control over LMN, leads to spastic paralysis

Question 40

injuries in the LMNs (such as a spinal nerve inury) lead to:

Answer 40

flaccid (complete) paralysis

Question 41

list the four basic steps to voluntary movements

Answer 41

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

Question 42

subsidary descending pathways that help with movement

Answer 42

extrapyramidal pathways

Question 43

modulate and modify activity in the corticospinal tract to ensure smooth, coordinated, purposeful movement

Answer 43

basal nuclei and cerebellum