HNN PBL2 Flashcards
(38 cards)
What is spinal shock?
the loss of all neurological activity below the level of injury
What does the loss of neurological activity from spinal shock include?
motor, sensory, reflex and autonomic function
What are the clinical features of spinal shock?
- Loss of pain (nociception)
- Loss of proprioception
- Sympathetic dysfunction (bowel & bladder)
- Loss of thermoregulation
What are the 4 phases of spinal shock?
- Areflexia
- Initial reflex return
- hyperreflexia
- hyperreflexia- spacicity
What is the usual timescale for Phase 1 of spinal shock?
0-1d
What is the usual timescale for Phase 2 of spinal shock?
1-3d
What is the usual timescale for Phase 3 of spinal shock?
1-4w
What is the usual timescale for Phase 4 of spinal shock?
1-12m
What is the underlying physiology of Phase 1 of spinal shock?
Loss of descending facilitation - Neurones involved in various reflex arcs lose the basal level of excitatory stimulation they normally receive from the brain
What is the underlying physiology of Phase 2 of spinal shock?
Denervation super sensitivity - reflexes return due to the hypersensitivity of reflex muscles following denervation → more receptors for neurotransmitters are expressed and muscles therefore are easier to stimulate
What is the underlying physiology of Phase 3 of spinal shock?
Axon-supported synapse growth - Interneurones and lower motor neurons below the transection begin sprouting, attempting to reestablish synapses
first synapses to form are from shorter axons (usually from interneurones)
What is the underlying physiology of Phase 4 of spinal shock?
soma-supported synapse growth - Interneurones and lower motor neurons below the transection begin sprouting, attempting to reestablish synapses
takes longer since synapse formation is soma-mediated (takes longer for axonal transport to push growth factors and proteins from soma to the end of the axon)
Why do reflexes return a bit?
due to the hypersensitivity of reflex muscles following denervation → more receptors for neurotransmitters are expressed and muscles therefore are easier to stimulate
How can spinal shock be tested for?
Checking the bulbocavernosus reflex
What is the first reflex to return after spinal shock subsides?
Babinski (or plantar) reflex
What can spinal cord injury result from?
Trauma or compression
In somatic motor pathways where is the upper motor neurone?
Cell body lies in the primary motor cortex
In somatic motor pathways where is the lower motor neurone?
cell body lies in the nucleus of brain stem/ spinal cord
how do the upper and lower motor neurones interact?
The upper motor neurone synapses with the lower motor neurone, which in turn innervates a single motor unit in a skeletal muscle. Activity in the upper motor neurone may facilitate or inhibit the lower motor neurone.
What spinal nerves innervate the diaphragm?
C3,4 and 5
What nerves innervate the intercostal muscles?
C6 and 7
what does it mean if there is a lesion below C4 but above C6/7?
Breathing will occur but without the assistance of the respiratory/ accessory muscles
Do lesions below C6/7 affect breathing?
No
What does a lesion at C1-4 cause?
Quadriplegia (paralysis of all 4 limbs)
