Lab 3 Discussion Questions Flashcards
What is an EMG?
Electromyography: measures muscle response or electrical activity in response to a nerve’s stimulation of the muscle
What eye movements did we observe when the subject was slowly rotated and the eyes were open?
Eyes jumped ahead in direction of perceived motion
What did we observe when the subject was rotated rapidly followed by an abrupt stop?
Nystagmus
Why was the subject able to control nystagmus when spun slowly, but couldn’t when spun quickly?
Endolymph was moving too rapidly in both directions
Why were we asked to stay quiet during the VOR trials?
Too much noise will override the vestibular input and give you alternate positional info
How did increased voltage at low frequency affect the H and M waves?
- H wave increased, then decreased at higher voltages due to antridromic APs
- M wave increased, then plateaued at higher voltages
Why do the H and M waves first appear at diff voltages? From which neuron does each stem from
- H wave come from afferent neuron –> large diameter = less resistance = easier to stimulate = H wave seen at lower voltage
- M wave comes from efferent neuron –> smaller diameter = more resistance = harder to stimulate = M wave seen at higher voltage
Why do the H and M waves appear at diff distances after the stimulus?
- M wave has a shorter path length = short latency from stimulus
- H wave has a longer path length = long latency from stimulus
In what direction do orthodromic APs travel?
From cell body to axon terminal
In what direction to antidromic APs travel?
Backwards towards the cell body
Are afferent or efferent fibers larger? Significance?
Afferent fibers are larger, so they have lower resistance
What components of a reflex arc does an H wave have? M wave?
- H wave has the whole reflex arc from afferents to effector
- M wave has from efferents to effector
What are the roles of the vestibular system?
- Posture
- Balance
- Control of head
- Eye movements
What are the 3 semicircular canals? What does each sense?
- Superior canal senses rotation front to back (nodding head)
- Horizontal canal senses rotation R to L (shaking head)
- Posterior canal senses rotation in the plane from the L to the R shoulder
What happens to the R and L sides of the VOR system when there is rotations in the counterclockwise direction (to the L)?
- L side gets depolarized b/c stereocilia bent towards kinocilium
- R side gets hyperpolarized b/c stereocilia bent away from kinocilium
