PNS Anatomy
Where is the cell body of a motor neuron located?
Ventral (anterior) Horn Cell
What is the Resting Membrane Potential (RMP) of an axon's cell membrane at rest?
-70 to -90 mV.
In Wallerian degeneration, how long does it take to for a distal motor axon to degenerate?
7 days
Define Ohm's law
Current = Voltage/Resistance
In The Legend of Zelda Ocarina of Time, who is Zelda's alter ego?
Shiek
What is an Innervation Ratio (600)?
The amount of muscle fibers belonging to an axon.
Example: Innervation ratio of 600:1 means that there are 600 muscle fibers to 1 axon.
What is the process of propagating a current from one node to another node called?
Saltatory Conduction
In the axonal regrowth process, how far will an axon travel in one day and one month respectively?
One day: 1 millimeter
One month: 1 inch
Give at least one advantage and disadvantage of using a monopolar needle electrode compared to using a standard concentric needle electrode.
--advantages: inexpensive, less painful, larger recording area, records more positive sharp waves.
--disadvantages of a monopolar: requires a separate needle or surface electrode, Have more interference if reference electrode is too far, teflon fraying
Which bear is best?
Black bear
What are the components of a motor unit?
1) anterior horn cell (motor nerve cell body)
2) motor nerve axons and peripheral nerve
3) NMJ
4) muscle fibers
State and describe the 3 components of the neuromuscular junction.
1) Presynaptic Region: area at the axon's terminal zone that contains compartments containing ACh.
2) Synaptic Cleft: space where ACh crosses from the presynaptic region to the receptors on the postsynaptic region. The synaptic cleft contains Acetylcholinesterase which degrades ACh.
3) Postsynaptic Region: membrane lined with ACh receptors.
What are the 3 categories of nerve injury according to the Seddon classification AND which ones are irreversible/reversible?
1) Neuropraxia: Seen in nerve compression injury. Local myelin is injured BUT Axon is INTACT. Recovery seen within 2 weeks.
2) Axonotmesis: Seen in nerve crush injury. Myelin AND axon is disrupted. Recovery is seen within several weeks to months.
3) Neurotmesis: Seen in nerve transection injury. Myelin and axon is disrupted. Recovery is NOT seen.
Define Maximal Stimulus
--Electrical stimulus at an intensity level in which no further increase in an evoked potential will occur from the nerve with added stimulus intensity.
In the Mortal Kombat Series, which earth realm fighter defeats Shao Kahn in the 10th Mortal Kombat tournament?
Liu Kang
What type of fibers do electrodiagnostic studies evaluate?
1A (large myelinated) fibers.
Other types of fibers that electrodiagnostic studies do NOT test include type 1b, 2, 3 and 4 fibers.
What waveform changes you would expect to see in a nerve conduction study if you were to DECREASE the temperature of the tested limb. Please describe changes in the following:
1) Latency
2) Duration
3) Conduction velocity
4) Amplitude
1) Latency: prolonged
2) Duration: increased
3) Conduction velocity: Decreased
4)Amplitude: Increased
Define a conduction block and describe what this would look like on a nerve conduction study.
--Definition: failure of an action potential to propagate past an area of demyelination along axons that are otherwise normally intact.
--On nerve conduction study, it will present as a drop >50% in CMAP amplitude between the proximal and distal stimulation sites across the area of injury.
Define a high frequency (low pass) filter and a low frequency (high pass) filter.
High frequency filter: filter that removes signals with frequencies higher than the cutoff setting.
Low frequency filter:filter that removes signals with frequencies lower than the cutoff setting.
How many legendary men have officially closed the Captains of Crusher #4 Gripper (equivalent to 365 pounds)?
5
Name and define the 3 different kinds/types of nerve connective tissue.
1) Endoneurium: connective tissue surrounding each individual axon and its myelin sheath.
2)Perineurium: connective tissue surrounding fascicles (bundles) of nerve fibers.
3) Epineurium: connective tissue that surrounds the entire nerve and holds all the fascicles together.
Please define rigor mortis AND THEN describe the physiology behind Rigor Mortis.
--Definition: Rigor Mortis is a phenomenon where there is stiffening of the muscles after death.
--In a NORMAL (NOT DEAD) person, Calcium is ACTIVELY PUMPED (requires ATP) from the muscle into the sarcoplasmic reticulum. This allows for Muscle relaxation.
--In a DEAD person, NO ATP is present, THUS calcium CANNOT be pumped into the sarcoplasmic reticulum and the calcium STAYS in the muscle. This causes permanent contraction AKA rigor mortis
Please describe what you would find on nerve conduction study for a demyelinating process. Please comment effects on latency, conduction velocity, temporal dispersion, and amplitude.
Latency: prolonged
Conduction velocity: decreased
Temporal Dispersion: increased
Amplitude: Decreased across the site of injury.
Name at least one contraindication for emg/ncs
--External cardiac pacemakers, Central line catheters, supratherapeutic INR (>3)
During the golden era of bodybuilding in the 1970's, what was Arnold Schwarzenegger's nick name in the bodybuilding community?
The Austrian Oak