Lecture 12 - Deafferentation Flashcards
How did Flemish art depict sensation?
Using the Allegory of the Five Senses
What is the Allegory of the Five Senses?
Painting depicting characters demonstrating the five senses
What types of nerves do muscles have?
Muscle and sensory
What is proprioception?
“Muscle sense”
Conscious perception of body position and movement in the absence of vision
How does the proprioceptive pathway work?
Skin/joint/muscle spindle receptors receive info and send it up the spinal cord to the primary and somatic sensory cortex
What are muscle spindles?
Stretch receptors located intramuscularly
How do muscle spindles work?
Firing pattern corresponds with muscle length and changes in muscle length
What is tendon vibration?
Stimulates muscle spindle firing by vibrating at 80-120 Hz to create the illusion of altered position and movement
How can proprioception be measured?
Direction testing and matching testing
What are the pros of direction testing?
A good indicator of whether a pathway is intact
What are the cons of direction testing?
Can’t quantitatively measure acuity or position vs movement sense
What is direction testing?
Movement of joints while the subject responds
What are the pros of matching testing?
Keeps the pathway intact, is a measure of acuity, keeps position/movement possible
What are the cons of matching testing?
Increased cognitive and perceptual demands
What is matching testing?
Establishes target and the subject matches
What is deafferentation?
A disorder where larger fiber sensory neurons no longer function
What is another name for deafferentation?
Sensory neuronopathy
What is the current incidence of deafferentation
Less than 20 known cases in the world
What is the cause of deafferentation?
Selective apoptosis of 1a afferent neurons
What causes apoptosis associated with deafferentation?
The cause is unknown. Possibly viral infection
What are the signs and symptoms of deafferentation?
No sense of movement or touch No tendon tap reflexes No sense of body schema Poor muscle coordination Poor force control Inability to walk Pain and temperature senses intact
What is body schema?
Concept of the body, full body representation of self.
How can deafferentation be simulated?
Ischemic nerve block or dorsal rhizotomy
How do ischemic nerve blocks simulate deafferentation?
By placing a tourniquet to slowly stop blood flow so enough blood allows the motor neurons to work but not the sensory neurons
