NEURO 129 Spinal Cord Compression Flashcards
Through what structure does the sensory input enter the spinal cord?
Dorsal root
Through what structure does the efferent response leave the spinal cord?
Ventral root
What are three musculoskeletal sensory receptors?
Muscle spindles, Golgi tendon organ and joint receptors
What does the muscle spindle detect?
Stretch in the muscle
How is the muscle spindle kept under tension and why?
by gamma motor fibres which keep it tense as without tension it would be unable to detect any changes in stretch
What is the purpose of the golgi tendon organ?
To provide inhibitory feedback “inverse myotatic reflex”
What activates the golgi tendon organ and what is the response?
Prolonged contraction or stretch producing muscle inhibition - prevents tendon damage
Describe the basic spinal reflex - the knee jerk reaction
Tapping patellar ligament, stretches quadriceps muscle, activates 1a afferent nerve –> synapses with alpha motor neurone = subsequent muscle contraction
This has an excitatory synapse with an inhibitory interneurone which inhibits the alpha motor neurone causing muscle relaxation
What are Renshaw cells?
Inhibitory interneurones
What do Renshaw cells do?
Release glycine back onto the alpha motor neurone to inhibit it
Where do instructions for voluntary movement lie in the brain?
In the motor cortex - the motor homonculus
What is most of the motor homonculus devoted to?
Hands, face and tongue
What is the main descending motor pathway in the CNS?
The corticospinal tract
Where does the corticospinal tract originate?
Pyramidal cells of the motor cortex
Where does the corticospinal tract cross over?
The pyramids of the medulla
What are the 4 other areas, besides the motor cortex, that the corticospinal tract arises from?
Primary somatosensory receiving area, premotor cortex, supplementary area and posterior parietal cortex
What is apraxia?
An inability to produce a specific motor act even though sensory and motor pathways remain intact
What are the two main ascending tracts to the CNS?
Spinothalamic and the Dorsal Columns
What does the spinothalamic tract carry sensory information about?
Pain, tempterature, touch and pressure
What does the dorsal column carry sensory information about?
Joint position and fine discriminatory touch
Where does the spinothalamic tract deccusate?
At the level it enters the spinal cord
Where do the dorsal columns decussate?
In the medulla
What are the main signs of an UMN lesion?
Paralysis/weakness of movement of affected muscles
HyPERreflexia
HyPERtonia
Why is there Hypertonia/reflexia in an UMN lesion?
Due to lack of inhibition
What are the main signs of a LMN lesion?
HyPOreflexia
Fasiculations
HyPOtonia
Muscle atrophy and denervation
What is Cauda Equina Syndrome due to?
Compression of the lumbar and sacral nerve roots within the cauda equina
What is motor neurone disease due to?
Disease of the anterior horn cells of the spinal cord
What is Myasthesia gravis?
Acquired autoimmune disease against the acetylcholine receptor at the NMJ
What is the main the clinical feature of myasthesia gravis?
Muscle weakness and fatiguability
What is a muscular dystrophy and give an example
Inherited disorder of muscle e.g. Duchennes
What happens in muscular dystrophy?
There is progressive muscle wasting and weakness with proximal muscles being affected worse than distal ones
What is a radiculopathy?
A Nerve root compression
What is Brown-Sequard syndrome?
A lesion in one half of the spinal cord - hemisection
from trauma or disc hernia or compressive tumour
What is a syringomelia
Expanded central canal in cervical region
In UMN lesion what is pyramidal weakness?
Where the flexors of the lower limb and extensors of the upper limb are stronger than the opposite
