spinal cord Flashcards
what grooves are the spinal cord divided left and right into?
anterior median fissure and posterior median sulcus
what is gray matter composed of mainly in the internal spinal cord?
neuron cell bodies
what is white matter composed of mainly in the internal spinal cord?
myelinated axons
what is the central canal or the spinal cord filled with?
cerebrospinal fluid
what is the gray commissure the site of?
axons cross from one side of CNS to other
what type of nuclei does the posterior gray horns contain?
sensory nuclei
what type of nuclei does the lateral gray horns contain?
autonomic motor nuclei
what type of nuclei does the anterior gray horns contain?
somatic motor nuclei
what do cell bodies of interneurons in the posterior gray horns receive and process?
incoming sensory input
what do the sensory nuclei of the posterior gray horns contain?
cell bodies of spinal cord interneurons
what do the cell bodies of the lower motor neurons located in the anterior gray horns send?
somatic motor output towards skeletal muscles
what does the somatic motor nuclei of the anterior gray horns contain?
cell bodies of lower motor neurons
what does the autonomic motor nuclei of the lateral gray horns contain?
cell bodies of preganglioic neurons
what do the cell bodies of preganglionic neurons located in the lateral gray horns send?
autonomic motor output towards glands, cardiac and smooth muscles
what is anterior white commissure the site of?
where axons cross from one side of CNS to other
what is white matter in the spinal cord subdivided into?
white columns
what do white columns contain
ascending and descending spinal cord tracts= bundles of axons
what do ascending tracts conduct?
sensory input to brain
what do descending tracts conduct?
motor output away from the brain
what does the tract name often reveal?
origin, destination and white matter location
what are the posterior white columns?
- fasciculus gracilis
- fasciculus cuneatus
what sensory info does fasciculus gracilis/cuneatus tracts conduct?
- fine touch
- vibration
- pressure
- proprioception (conscious)
what are the lateral white columns?
- lateral spinothalamic
- anterior and posterior spinocerebellar
- lateral corticospinal
what sensory info does the lateral spinothalamic tract conduct?
pain and temp
what sensory info does the anterior and posterior spinocerebellar tracts conduct?
proprioception (unconscious)
where are the anterior and posterior spinocerebellar tracts located?
lateral white columns
what are the anterior white columns?
- anterior corticospinal
- anterior spinothalamic
what sensory info does the lateral corticospinal tract conduct?
-somatic motor output that controls the skeletal muscles of the limbs
is the lateral corticospinal tract an ascending or descending tract?
descending
what sensory info does the anterior corticospinal tract conduct?
somatic motor output that controls the skeletal muscles of the axial skeleton (neck and trunk)
is the anterior corticospinal tract an ascending or descending tract?
descending
are the anterior and posterior spinocerebellar ascending or descending?
ascending
what ascending tract is responsible for crude touch and pressure?
anterior spinothalamic tract
what do sensory pathways connect?
receptors to brain
what do motor pathways connect?
brain to skeletal muscles
what do somatosensory pathways conduct?
general sensory input from receptors to brain
how many relay neurons are involved in the somatosensory pathways?
3
what 3 relay neurons are involved in the somatosensory pathways?
first/second/third-order neurons
what are the three main somatosensory pathways?
- spinothalamic pathway
- posterior column pathway
- spinocerebellar pathway
what does the spinothalamic pathway conduct?
sensations of crude touch, pressure, pain and temp
where do the first-order neurons of the spinothalamic pathway conduct sensory input from receptors into?
posterior gray horns
where do the second-order neurons of the spinothalamic pathway conduct sensory input to?
thalamus
how does sensory info ascend the spinal cord in the spinothalamic pathway?
- anterior spinothalamic tract
- lateral spinothalamic tract
where does the third-order neurons of the spinothalamic pathway conduct sensory input?
to the primary somatosensory cortex
what does the posterior column pathway conduct?
sensations of fine touch, pressure, vibration and proprioception
where do first-order neurons conduct sensory input into in the posterior column pathway?
into the posterior gray horns and up to the medulla oblongata
what tracts does sensory input ascend in the first-order neurons of the posterior column pathway?
-fasciculus gracilis or cuneatus tracts
where do first-order neurons synapse with second-order neurons in the posterior column pathway?
medulla oblongata
where does sensory input get conducted in second-order neurons of the posterior column pathway?
thalamus
where do third-order neurons of the posterior column pathway conduct sensory input?
primary somatosensory cortex
what does the spinocerebellar pathway conduct?
sensations of proprioception
where does the first-order neurons of the spinocerebellar pathway conduct sensory input to?
into the posterior gray horns
where do the first-order neurons of the spinocerebellar pathway synapse with second-order neurons?
within a sensory nucleus
where do second-order neurons of the spinocerebellar pathway conduct sensory input?
cerebellum
what tracts does sensory input ascend in the second-order neurons of the spinocerebellar pathway?
anterior or posterior spinocerebellar tract
what do the somatic motor pathways conduct?
somatic motor output from the primary cortex to a skeletal muscle
how many relay neurons does the somatic pathways involve?
2
what are the two relay neurons of the somatic motor pathways?
- upper motor neuron
- lower motor neuron
what are the two main somatic motor pathways?
- lateral corticospinal pathway
- anterior corticospinal pathway
what does the lateral corticospinal pathway conduct?
the somatic motor output that controls the skeletal muscles of the limbs
what do the upper motor neurons of the lateral corticospinal pathway conduct?
somatic motor output from the primary motor cortex to an anterior gray horn
what spinal tract does the somatic motor output from the upper motor neurons of the lateral corticospinal pathway descend?
lateral corticospinal tract
where does the upper motor neurons of the lateral corticospinal pathway synapse with lower motor neurons?
in a motor nucleus
what do lower motor neurons of the lateral corticospinal pathway conduct?
somatic motor output to skeletal muscles of the limbs
what does the anterior corticospinal pathway conduct?
somatic motor output that controls the skeletal muscles of the axial skeleton (head, neck, trunk)
what do the upper motor neurons of the anterior corticospinal pathway conduct?
somatic motor output from the primary motor cortex to an anterior gray horn
what spinal tract does the somatic motor output from the upper motor neurons of the anterior corticospinal pathway descend?
anterior corticospinal tract
what do lower motor neurons of the anterior corticospinal pathway conduct?
somatic motor output to skeletal muscles of the neck and trunk
what are spinal reflex arcs?
neural pathways that produce rapid, predictable, involuntary somatic or autonomic reflex response to a stimulus
what do spinal cord injuries result in?
sensory and/or motor losses at or below the level of injury
what does damage to the posterior gray horns or ascending spinal cord tracts lead to?
loss of sensation
what does damage to the anterior gray horns or corticospinal tracts lead to?
spastic or flaccid paralysis
what does a complete transection of the spinal cord result in?
a loss of all sensations and voluntary movement
what does a transection in the cervical region of the spinal cord result in?
quadraplegia
what does a transection in the thoracic or lumbar region of the spinal cord result in?
paraplegia
what is spinal shock?
a transient period of complete sensory and motor loss, and a loss of all reflexes below level of lesion, reflex activity gradually returns
what is spastic paralysis?
- loss of voluntary movement
- reflex activity intact but abnormal
what is flaccid paralysis?
loss of voluntary movement and reflex activity
is flaccid paralysis caused by damage to the upper or lower motor neurons?
lower
is spastic paralysis caused by damage to the upper or lower motor neurons?
upper
approx how long is the spinal cord?
42cm long
approx how wide is the spinal cord?
14mm wide
when does the spinal cord end?
L1-L2 of vertebral column in adults and L4 in infants
what is the cone shaped structure that the spinal cord terminates at?
conus medullaris
what is the spinal cord anchored to the coccyx by?
filum terminale
how many regions are there in the vertebral column?
5
how many segments are there in the vertebral column?
31
how many pairs of cervical nerves are there?
8
how many pairs of thoracic nerves are there?
12
how many pairs of lumbar nerves are there?
5
how many pairs of sacral nerves are there?
5
how many pairs of coccygeal nerves are there?
1
what are the five regions starting from closest to the head down?
- cervical
- thoracic
- lumbar
- sacral
- coccyx
what do spinal nerves branch to form?
peripheral nerves
what type of nerves are spinal nerves?
mixed nerves that contain the axons of sensory and motor (somatic and automatic) neurons
are dorsal roots motor or sensory?
sensory
are ventral roots motor or sensory?
motor
what do dorsal roots contain?
axons of sensory neurons
what do ventral roots contain?
axons of motor neurons (somatic and autonomic)
what do dorsal root ganglion contain?
cell bodies of sensory neurons
what is the collection of roots beyond the conus medullaris called?
cauda equina
how is the spinal cord protected from mechanical forces?
- vertebral column
- CSF
- spinal meninges
what is CSF withdrawn from the spinal cord in a lumbar puncture used for?
diagnostic testing or reducing intracranial pressure
what is a lumbar puncture (spinal tap)?
involves the insertion of a needle into the subarachnoid space beyond L3
how is the outer dura mater separated from the vertebral column?
epidural space
what is the site of anaesthetic administration?
epidural space