cerebral cortex tutorial Flashcards
what is MS
MS is an autoimmune disorder which results in loss of myelin from neurons of the central nervous system (i.e. brain and spinal cord)
main symptoms of MS
blurred vision
tingling (paresthesia) or numbness in different parts of the body
difficulty walking
muscle stiffness and spasms
what is peripheral nerve stimulation and what does it do in the body
it is an electrical stimulus to a peripheral nerve.
when this stimulus is of appropriate intensity it can activate sensory and motor axons.
what is the tool used to record peripheral nerve stimulation as waves
electromyography
what are the two types of waves seen in EMG from the same peripheral nerve stiimulation and in what order
M wave first and H reflex (wave) second
what does the M - wave represent
1) stimulation of a motor axon somewhere along its length,
2) activation of this axon leads to action potential travel along the nerve towards the muscle
3) muscle contraction-> twitch
what does an H reflex represent
a reflex activation of muscle:
1) stimulation of sensory axons, activation, action potential travels along nerve to spinal cord
2) activation of motor axons, action potentials travel along lower motor neuron to muscle where they cause
3) muscle contraction - twitch.
what does a stimulus have to be for an F wave?
needs to be a large electrical stimulus
what is unique about an F wave compaired to other 2 peripheral stimulation waves
1) needs bigger stimulation
2) involves antidromic conduction
what does an F wave represent
1) stimulus on motor axon, action potentials travel along motor nerve to spinal cord - antidromic conduction
2) then lower motor neurons in spinal cord become activated and action potential in motor axons travel along motor neuron in muscle where they cause twitch
is an F-wave a reflex?
NO
WHAT IS Antidromic and orthodromic conduction?
antidromic conduction is when a stimulus travels in the opposite direction to that normal in a nerve fibre
orthodromic conduction is travelling the normal way in a nerve fibre
what technique is used to stimulate motor neurones in the cortex ?(cortical motor stimulation)
transcranial magnetic stimulation (TMS)
What happens in the body after TMS?
1) activation of upper motor neurons
2) action potentials travel along upper motor neurons, then lower motor neurons then reach muscle
3) muscle contraction
what is the name of the wave seen in EMG after TMS
motor evoked potential (MEP)
WHAT IS Total Motor Conduction Time, what is another name for it
its the time it takes for an action potential to go from brain to muscle- MEP latency- motor evoked potential latency
what is peripheral motor conduction time (PMCT)
Its the time of action potential going from spinal cord to muscle along motor axon
PMCD calculation formula
(M wave latency + F wave latency -1)/2
WHAT is the role of the -1 in the PMCT formula?
-1 is the approximation of the time it takes for the action potential to turn around once it has reached the lower motor neuron
what is CMCT central motor conduction time calculated
TMCT- PMCT
what neurons is there a problem with in MS?
LOWER MOTOR NEURONS
if there is a longer than usual MEP latency, (wave from brain stimulation) what neurons have a problem?
could be upper motor, could be lower motor, could be both
with what findings can you suspect a problem in the CNS
with prolonged MEP latency from brain stimulation and normal F latency from peripheral nerve stimulation
is MEP longer for hand or leg muscles?
LEG: 26.5 ms, Hand: 19.5 ms
is peripheral motor conduction time or CMCT longer for hand
peripheral 13.6> 5.9
is PMCT or CMCT longer for leg
CMCT. 13.9>12.7
is PMCT longer for leg or hand
hand 13.6> 12.7
is CMCT longer for leg or hand
leg 13.9>5.9
