Lecture 22 - Short and Long-Loop reflexes and control of sensory feedback Flashcards
How long do short-latency responses take?
20-50ms
How long do long latency responses take?
50-105ms
How long do voluntary responses take?
120+ ms
Where are SLR’s processed?
Spinal cord
Where are LLRs processed?
Brain
Where are voluntary VOLs processed?
Brain
What type of feedback is involved in SLRs?
spinal proprioceptive
What type of feedback is involved in LLRs?
Spinal and cortical propriceptive feeback
What type of feedback is involved in VOLs?
spinal, cortical proprioceptive and visual feedback
What is an example of a SLR?
knee jerk relfex (monosynaptics stretch reflex)
What are 2 properties of SLRs?
- SLR scale with background muscle activity (Henmans size principle)
- SLR scale with rate and amount of muscle stretch (more APS fired with larger stretch of muscle spindle)
Is LLR polysynaptic or monosynaptic?
polysynaptic
What are some other names for LLR?
- long loop
- long latency
- transcortical
What type of feedback look do LLRs involve?
transcortical feedback loops
Which reflex does goal directed processing?
LLR
What do LLRs depend on?
The goal of the task
Behavioural task of keeping hand in target
What is the SLR mostly driven by?
With the exception of the largest target
The rate and amout of motion caused by the perturbation
Behavioural task of keeping hand in target
LLR annd VOL responses the same mechanical perturbation are inversly proportional to what?
Size of the target
Behavioural task of keeping hand in target
Does the larger or smaller target have the smallest stretch response?
largest (lower accuracy demands, don’t need to ‘work as hard’ to keep hand in target
Behavioural task of keeping hand in target
What is the desired state in this example?
To keep arm in a fixed target (goal of the task)
Behavioural task of keeping hand in target
What is the motor plan in this example?
maintaining arm in target
Behavioural task of keeping hand in target
What is the motor command in this example?
Activity in limb motor circuits (cortical or subcortical) to maintain the hand in the target
What is expected state?
intened or planned movement
What is error?
the difference between the expected state and the actual state
What does the error signal do?
Used to adjust ongoing movement
What is the feedback control system?
movement control mechanism that uses sensory feedback to detetc errors and correct voluntary motor actions
What is a comparator? What is the comparorator in the feedback control system?
Comparator compares the actual and expected state of the body
the brain
What is the effector?
the component of the peripheral motor system that generates the desired motor response
Summarize SLRs.
They allow rapid stimulus dependent responses to a mechanical perturbation
Summarize LLRs.
slower, polysynaptic responses that enable rapid, task-dependent control of sensory feedback to support voluntary motor actions
Are SLRs or LLRs faster?
SLRs
