Multiple sclerosis Flashcards
What is MS?
MS is an autoimmune disorder which results in the loss of myelin from neurons of the central nervous system, i.e. the brain and spinal cord
What are the symptoms of MS?
Blurred vision, fatigue, difficulty walking, numbness or tingling (paraesthesia) in different parts of the body, muscle stiffness and spasms
What happens in basic peripheral nerve stimulation?
A sensory neurone synapses a signal with a motor neurone, which sends its signal to the muscle.
How can you activate motor and sensory neurons?
An electrical stimulus of an appropriate intensity to a peripheral nerve can activate sensory and motor axons.
How do you cause a twitch?
The activation of the motor axons can cause action potentials to travel along the nerve to cause muscle contraction, a twitch. This can be recorded with electromyography (EMG).
What is the M wave?
Motor wave - the fast response recorded on EMG.
What happens when the sensory axons are stimulated?
The action potentials can travel along the nerve to the spinal cord. These can then cause the lower motor neurons in the spinal cord to become activated. Action potentials in the motor axons can travel along the motor neuron to the muscle where they cause muscle contraction, a twitch. This is a reflex activation of the muscle.
Which wave demonstrates the reflex action of the muscle?
H-reflex
What happens when you have a large electrical stimulus?
These action potentials travel along the motor nerve to the spinal cord (i.e. in the opposite way to normal). These can then cause the lower motor neurons in the spinal cord to become activated. Action potentials in the motor axons can travel along the motor neuron to the muscle where they cause muscle contraction, a twitch.
ANTIDROMICALLY
What wave arises due to motor-motor stimulation following a large electrical stimulus?
F-wave
Define Orthodromic
Travelling in the normal direction in the nerve fibre
Define Antidromic
Travelling in the opposite directon to that normal in a nerve fibre
What does Transcranial magnetic stimulation do?
Cortical motor stimulation
What causes a motor evoked potential MEP on an EMG?
The activation of the upper motor neurons causes action potentials to travel along the entire motor pathway (upper and lower motor neurons) to cause muscle contraction. This EMG response is known as a motor evoked potential (MEP).
What is the total motor conduction time TMCT?
Total time to conduct impulses from the motor cortex to the muscle.(MEP Latency).
