The Spinal Cord and the Periphery Flashcards
Grey and white matter of the spinal cord
White outside
Grey inside
How do axons of sensory fibres enter though into the spinal cord?
Through the dorsal route into the dorsal horn of grey matter
Where do motor neurones have their cell bodies in the spinal cord?
In the ventral horn
What is white matter made up from?
Tracts
What are tracts?
Axons transmitting information between higher centres in the brain and peripheral nerves = pathways
What type of information do ascending tracts take?
Sensory
What type of information do descending tract take?
Motor
What columns does white matter have?
Posterior
Lateral
Anterior
Function of ascending spinal tracts
Carries sensory information to the brain (cerebral cortex and cerebellum)
Features of ascending spinal tracts
3 neurones between the peripheral receptor and the cortex
Order of features in ascending spinal tracts
- receptor - first order neurone (dorsal root present off this)
- Reaches grey matter of spinal cord or nucleus in medulla
- 2nd order neurone - crosses over to contralateral side in spinal cord or medulla
- Reaches Nucleus in contralateral thalamus
- 3rd order neurone - to contralateral parietal cortex
What does the posterior/dorsal column of ascending tracts carry?
Fine touch
Tactile localisation
Vibration sense
Proprioception
Journey of posterior/dorsal column of ascending tracts
- Gracile and cuneate nuclei in medulla -> 1st order neurone to
- 2nd order neurone -> Crosses over to medial lemniscus in pons to the
- VPL nucleus in thalamus
- 3rd order neurone -> post central gyrus in parietal lobe
What does the lateral spinothalamic tract carry on the right side?
Pain and temp from left side of body
What does the lateral ascending tracts carry?
Pain
Temperature
Journey of Lateral spinothalamic tract
2nd order neurone crosses over at the level of entry to reach lateral column in the spinal cord
VPL nucleus of thalamus
Post central gyrus of parietal lobe
Where do motor/descending tracts of the spinal cord originate?
Within the cerebral cortex and brainstem
Function of descending tracts
Control of movement
Muscle tone
Spinal autonomic fibres
How many neurones do descending tracts have?
2
Features of descending tracts
Motor
2 Neurones in the pathway
They decussate to the opposite side of the brainstem
Function of the corticospinal/pyramidal tract
Control of voluntary skilled movements
What kind of pathway is the corticospinal/pyramidal tract?
Descending
What is the blood supply to the corticospinal/pyramidal tract?
MCA
Where do corticobulbar fibres go?
Go to contralateral cranial nerve nuclei
Where do corticospinal fibres go?
Mostly cross in decussation of pyramids (lateral corticospinal tract)
How much of the fibres does the anterior corticospinal tract have?
10 - 15%
What is the lower motor neurone responsible for?
Muscle tone and reflexes
What is the autonomic nervous system?
Nerve cells within both CNS and PNS concerned with innervation and control of visceral organs, smooth muscle and secretory glands
How many neurones does the basic autonomic efferent pathway have?
2
What nerves does the sympathetic ANS have an effect on?
T1-12
L1 + 2
What nerves does the parasympathetic ANS have an effect on?
III, VII, IX, X
S2-4
What is the outflow of sympathetic fibres taken by?
Thoracolumbar
What is the outflow of parasympathetic fibres taken by?
Craniosacral
What is motor neurone disease?
A group of diseases affecting the motor neurone in the ventral horn of the spinal cord (LMN). The neurone dies and as a result the muscle supplied by it atrophies
Presentation of an UMN lesion
Exaggerated reflexes - hyperflexia
Exaggerated tone - spasticity (spastic paralysis)
Presentation of a herniated disc on the left side of C3 (e.g. brown sequard syndrome)
Left sided paralysis
Left sides loss of touch, vibration and sense
Right sided loss of temp and pain
Reflexes on left side exagerated
What is a reflex?
An involuntary stereotyped pattern of response brought about by a sensory stimulus
Where are many reflexes mediated?
At the level of the spinal cord (spinal reflexes)
Types of reflexes anatomically
Monosynaptic
Polysynaptic
Example of a monosynaptic reflex
Stretch reflexes
Example of a polysynaptic reflex
Flexor reflex
How does a stretch reflex work?
- Tendon stretched
- Intrafusal muscle fibres stimulated
- Sensory neurone activated
- Monosynaptic reflex arc
4b. Polysynaptic reflex arc to inhibitory interneurone - Muscle contraction
5b. Reciprocal innervation
What is the stretch reflex important in?
Control of muscle tone and posture
What is the function of the flexor reflex?
Helps to protect the body from painful stimuli
How does the flexor reflex work?
- pain stimulus
- Sensory neurone activated
- Polysynpatic reflex arc
- Flexion and withdrawal from noxious stimulus
4b. Crossed extensor response to contralateral limb (only in weight bearing limbs)