Structure and fx of Spinal cord Flashcards
What is at bottom end of Spinal cord?
Narrows at L1 to form conus medullar is, and then caudal equine in lumbar cistern
Where does spinal cord start and end?
Cranial border of atlas to L1
What is the lumbar cistern?
contains auda equina (Lumbar and sacral dorsal and ventral roots)
In Lumbar cistern
What surrounds the spinal cord?
The meninges are continuous, even as spinal cord descends within vertebral column
Why do you do a lumber puncture low down?
below L1 in caudal equine area, so nerves can float out of the way, and spinal cord is not damaged
What are the 4 sections of the spinal cord
Cervical
Thoracis
Lumbar
Sacral
What does the Ventral root of a spinal nerve do?
Ventral root: efferent
How many paired spinal nerves are there?
31
How many cervical nerve pairs are there
8
How many thoracic nerve pairs
12
How many lumbar nerve pairs
5
How many scacral nerve pairs?
5
How many coccygeal nerves?
1
Where do C1 and C8 nerves come out?
C1 nerve comes out ABOVE C1 vertebra, below foramen magnum, C8 comes out below C8
Where are “conus medullaris is” and filum terminale externum”
“conus medullaris” end of spinal cord
hilum terminale externum” end of dural sac?
filum terminale internum: upper three quarters of the filum; covered by the spinal dura and arachnoid meninges. filum terminale externum: lower quarter of the filum; fuses with the investing dura mater and continues inferiorly to attach to the dorsal coccyx
The filum terminale (FT) is a fibrous band that extends from the conus medullaris to the periosteum of the coccyx, and its functions are to fixate, stabilize, and buffer the distal spinal cord from normal and abnormal cephalic and caudal traction.
What does the Ventral root of a spinal nerve do?
Ventral root: efferent
What are the spinal nerves for?
Connect periphery and spinal cord
What is the dorsal column pathway? (overview)
Describes how a sensation passes up the spinal cord, crosses in the medulla and then connects to somatosensory centre in the cortex via 3 neurons and various junctions
What is the internal structure of the spinal cord?
Inner core, grey matter
- Neuronal cell bodies
- H shaped
- Ventral, lateral and dorsal horns
Outer, white matter
- Myelinated axons
- White columns/tracts/funiculi
Where in the spinal cord is grey matter expanded?
Note expanded grey matter at levels that supply the limbs
What does the dorsal root of a spinal nerve do?
Dorsal root: afferent
How is the grey matter organised in the dorsal horn?
Dorsal horn - Neurons receiving sensory input
How is the grey matter organised in the lateral horn?
Lateral horn - Preganglionic sympathetic neurons
How is the grey matter organised in the ventral horn?
ventral horn - Motor neurons
(Also interneurons between/within levels)
what are laminae?
Layers of neurons in grey matter are called laminae
How is white matter organised in the spinal cord?
Myelinated axons
Run in bundles in specific tracts
Many tracts are named according to cell body of origin and where the axon terminates
Helps to aid learning of the different tracts
What does the Ventral root of a spinal nerve do?
Ventral root: efferent
How is sensations carried to brain?
Sensation is carried to the brain: afferent tracts
How are sensations carried?
Sensation is carried to the brain: afferent tracts
Tracts to and from the brain are crossed:
R side of brain controls L side of body
How are motor commands carried?
Motor commands come from the brain: efferent tracts
Tracts to and from the brain are crossed:
R side of brain controls L side of body
Which columns carry ascending and descending tracts?
Dorsal:
Lateral:
Ventral:
Dorsal column contains ascending tracts
Lateral column contains descending and ascending tracts
Ventral column contains mainly descending tracts
Which columns carry ascending and descending tracts?
Dorsal:
Lateral:
Ventral:
Dorsal column contains ascending tracts
Lateral column contains descending and ascending tracts
Ventral column contains mainly descending tracts
Do messages go all the way to brain directly from body?
ascending tract nerves run in 3 order circuits
What is “proprioceptive?”
Information from within the body: proprioceptive
what is exteroceptive?
Information from outside the body: exteroceptive
What do ascending tracts do?
Carry sensory information from periphery to brain
What do Dorsal columns carry?
a pain
b temperature
c light touch
d proprioception?
Dorsal columns: proprioception/light touch
What do spinocerebellar tracts carry?
a pain
b temperature
c light touch
d proprioception?
Spinocerebellar tracts: proprioception
What do spinothalamic tracts carry?
a pain
b temperature
c light touch
d proprioception?
Spinothalamic tracts: pain/temperature
What structure do nerves from the arm form?
Nerves from arm form cuneate fascilicus (Lateral)
What structure do nerves from leg form?
Nerves from leg form gracile fascilicus (medial)
(Dorsal column) what is the gracile fascilicus?
is it medial or lateral?
Nerves from leg form gracile fascilicus (medial)
what is the gracile fascilicus?
is it medial or lateral?
Nerves from leg form gracile fascilicus (medial)
In the dorsal column first order neuron enters spinal cord through _______?
First order neuron enters spinal cord through dorsal root (tract of Lissauer)
In dorsal columns, Myelinated axons ascend ______ (opposite/same) side of cord?
Myelinated axons ascend same side of cord
Describe the three neuron “steps” of the dorsal column pathway?
First order neuron synapses with 2nd order neuron in nucleus cuneatus (or nucleus gracilis in medulla)
2nd order neuron crosses midline in medulla of brain stem to form medial lemniscus
Ascends to thalamus to synapse with 3rd order neuron
Travels to somatosensory cortex
whats ataxia?
Ataxia is a term for a group of disorders that affect co-ordination, balance and speech. Any part of the body can be affected, but people with ataxia often have difficulties with: balance and walking.
what does the dorsal column do?
The dorsal column, also known as the dorsal column medial lemniscus pathway, deals with the conscious appreciation of fine touch, 2-point discrimination, conscious proprioception, and vibration sensations from the body; sparing the head.
what happens when there is one sided damage to the dorsal column?
Disruption in pathway leads to unilateral loss of proprioception/VS/discriminative touch
if both sides of the dorsal column are damaged what clinical result occurs?
Bilateral dorsal column loss leads to severe ataxia
what diseases can bilaterally damage the dorsal column?
Possible causes: Multiple sclerosis, B12 deficiency
Pt presents with unilateral loss of proprioception
vibration sensation, discriminative touch, what could be the cause?
Disruption in dorsal column pathway leads to unilateral loss of proprioception
vibration sensation, discriminative touch (2 point distinguishing?)
what is discriminative touch?
what carries it?
Dorsal column
Fine touch (or discriminative touch) is a sensory modality that allows a subject to sense and localize touch. The form of touch where localization is not possible is known as crude touch.
What do spinothalamic tracts carry?
Sensory
unconscious proprioception and smooth motor control
nociceptive, temperature, crude touch, and pressure from our skin to the somatosensory area of the thalamus
What is “nociceptive?”
Nociceptors are sensory receptors that detect signals from damaged tissue or the threat of damage and indirectly also respond to chemicals released from the damaged tissue. Nociceptors are free (bare) nerve endings found in the skin muscle, joints, bone and viscera.
How many neurons in the spinothalamic circuit?
2
1st order neuron enters through dorsal root (tract of Lissauer)
Synapses with second order neuron
Crosses midline at level of entry
Myelinated fibres ascend up anterior/lateral spinothalamic tract
do spinothalamic tracts cross at medulla or at level of entry?
Crosses midline at level of entry
what is the tract of lissauer?
What is responsible for the transmission of pain, temperature, and crude touch to the somatosensory region of the thalamus?
spinothalamic tract, an ascending pathway of the spinal cord
What are these two fissures/sulci called?
Anterior (ventral) median fissure
posterior (dorsal) median sulcus
which nerves pass through sacral hiatus?
S5 (x2)
coccygeal
where does hilum terminale attach and what does it do?
It extends from the conus medullaris and descends among the nerve roots of the cauda equina to attach to the dorsum of the coccyx, acting as an anchor for the spinal cord within the vertebral canal.
label these spinal meningeal layers
spinal pia mater
spinal arachnoid mater
spinal dura mater
label:
ventral
dorsal
lateral
What do the descending tracts of the spinal cord do?
Innervate motor neurones
what do dorsal root ganglions at spinal cord carry?
sensory afferent fibres from body organs/muscles
What do ventral roots fo spinal cord carry?
Motor fibres, efferent
What is the central commissure of the spinal cord?
The gray matter is subdivided into the gray commissure, which is the strip connecting the two halves of the spinal cord that surrounds the central canal (“H”)
What are the dorsal and ventral horns?
The “top and bottom” of the “H” of grey matter in spinal cord
What do ventral horns contain?
cell bodies of motor neurons
What do dorsal horns contain?
Dorsal horns contain neuronal cell bodies that process information received from sensory fibers, entering the spinal cord from the dorsal roots and dorsal rootlets
Where are upper motor neurons found?
upper motor neurons are found inside the cerebral cortex and various nuclei of the brainstem,
Where are lower motor neurons found?
lower motor neurons are found inside the brainstem or the ventral horn of the spinal cord
How are muscles of the body innervated?
From the ventral horns, axons from lower motor neurons leave the spinal cord through the ventral roots and travel within peripheral nerves to innervate the skeletal muscles of the body.
How does the corticospinal tract run?
From the primary motor CORTEX to spinal cord, to innervate voluntary movements of trunk and limbs
How do the upper motor neurones run in corticospinal tract?
The cell bodies of the first-order neurons of this pathway lie in the primary motor cortex. The axons then descend via the
-corona radiata, through the -internal capsule, the
-cerebral peduncle of the midbrain, and the
-ventral aspect of the pons to reach the
-ventral aspect of the medulla.
SLIDE 20
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Dorsal columns: light touch/proprioception
Spinothalamic tracts: pain/temperature
Spinocerebellar tracts: unconscious proprioception
Dorsal columns:
Spinothalamic tracts:
Spinocerebellar tracts:
Dorsal columns: light touch/proprioception
Spinothalamic tracts: pain/temperature
Spinocerebellar tracts: unconscious proprioception
What do descending tracts do?
Involved in control of movement
Voluntary control of movement: corticospinal tract=pyramidal tract
Involuntary control of movement:
Extrapyramidal tracts
Are Extrapyramidal tracts for voluntary or involuntary movement?
Involuntary control of movement:
Extrapyramidal tracts
Voluntary control of movement: corticospinal tract=pyramidal tract
