Peripheral NS Injury and Repair Flashcards
what are upper motor neurons?
Neurons in the cerebral cortex and
brainstem that govern the activity of
lower motor neurons in the brainstem and spinal cord
what are gamma motor neurons?
LMNs that innervate
intrafusal muscle fibres
(muscle spindles)
what are alpha motor neurons?
LMNs that innervate
extrafusal muscle fibres
for muscle contraction
where do cranial nerve LMNs originate?
brainstem
where are the cell bodies of somatic motor LMNs located?
anterior horn
what is a motor unit?
The alpha motor neuron
and the skeletal muscle
fibres it innervates
what sections of the spinal cord have englargements?
cervical and lumbosacral
why do the cervical and lumbosacral parts of the spinal cord have enlargements?
to accommodate extra motor
units
what are spinal nerves made up of?
posterior (dorsal) and anterior (ventral) roots
what do spinal nerve split to become?
anterior and posterior rami
what are the terminal branches of the brachial plexus?
peripheral nerves
anterior hand posterior root combine to make what?
mixed spinal nerve
how many cervical spinal nerves are there?
8
how many thoracic spinal nerves are there?
12
how many lumbar and sacral spinal nerves are there?
5
how many spinal nerves are for the coccyx?
1-2
what is a dermatome?
an area of skin that is mainly supplied
by afferent nerve fibres from
the dorsal root of a spinal nerve
are peripheral nerve motor or sensory?
mixed!
are cranial nerves also peripheral nerves?
yes
what is upper motor neuron syndrome?
Damage to the descending tract before the anterior horn of the spinal cord
what is lower motor neurone syndrome?
Damage to alpha motor neuron at or distal to the anterior horn
is a stroke an upper or lower motor neurone injury?
upper
what are signs of a stroke as an UMN injury?
usually they have some paresis
+ babinski/Hoffmans
hyperreflexia
hypertonia
what is primarily affected in a spinal cord injury?
primarily UMN
if you have a c spine SCI, it is likely what presentation?
UMN
if you have a l spine SCI, it is likely what presentation?
LMN
is weakness after a SCI unilateral or bilateral?
often bilateral
where is weakness after a SCI?
below level of lesion
people who’ve had a SCI have Hyper or hypo reflexia and tonia?
hyper
what neurons are affected by ALS?
both UMN and LMN
what is the ethology for ALS?
unknown
what happens to the number of motor units when you have ALS?
it decreases
is sensation involved in an alpha motor neuron injury?
no sensory involvement
what happens when you have peripheral severe injury?
weakness and sensory loss
what does Guillan barre syndrome cause?
Destruction of myelin sheath with axonal damage
Rapidly progressing motor and sensory impairments
what is the least severe axon injury?
neuropraxia (axon intact)
what is the most severe axon injury?
neurotmesis (complete nerve lacaeration)
what is axonotmesis?
Injury to axon and myelin but supporting connective tissue intact
when does Wallerian degeneration occur?
when a nerve fiber is cut or crushed
(axonotmesis or neurotmesis) and part of the distal axon degenerates
what is amplitude?
of axons being stimulated
what is latency most affected by?
demyelination
what is latency?
time between stimulation and M wave
what is conduction velocity affected by?
axonal loss and demyelination
what does axonal loss result in?
lower amplitude
what does demyelination result in?
prolonged latency
m wave is spread because only some neurons affected
slow conductor velocity
what is motor unit potential?
Summation of electrical activity of the
muscle fibres of the motor unit
what can needle MEG be used to distinguish?
between LMN, UMN, and myopathies
what are the 2 types of peripheral nerve recovery?
axonal repair and regrowth
collateral sprouting
where is axon regeneration faster?
closer to the injury site and slower further away
what are the 2 key players in axonal regrowth?
macrophages and Schwann cells
what is the purpose of macrophages?
they clear away the degenerating parts
what is the purpose of the Schwann cells?
they act as a guide and simulate regrowth
how do Schwann cells support axon regrowth?
a growth cone extends to search for target
provides a framework to guide growing axons
secretes neurotrophic signals to promote axon growth
does a crush injury (axonotmesis always result in wallerian degernation?
no
is axon recovery more rapid and complete in crush or cut nerve injuries?
crush
is a nerve is cut, it can be surgically reattached within what time frame?
within 3 months
what causes outcomes to be poor with axonal regrowth?
if the injury is severe and distal end is not available for reapposition
what nerve did Henry hEEAD TRANSECT ON HIMSELF?
Radial nerve
what can healthy aging and diseases cause?
it can decrease the number of motor units
what is collateral sprouting?
motor unit size increases
