Which prioprioceptors are activated by skin deformation?
What are the possible ways in which the CNS would use the information provided by the proprioceptors?
Maintain central excitability
On-line correction of errors/ servocontrol by negative feedback
Learning – improvement of future movements
Tell CNS about present status of muscles and body parts – essential of pre-programming/ feedforward
Explain corrective control.
execution: sending signals to the muscle to activate them in an appropriate way.
CLOSED LOOP: corrective control
For slower movements you can have feedback during the execution of the movement and add changes to the planning stage to improve the movement. Posture stability is also important in making a movement . Therefore skilled movements are usually superimposed on posture regulation; to assure the maintenance of a steady base for the movement to be carried out.
Explain feed-back (open loop) contol.
Generation of motor programs needs information about current body statusAnticipatory control – detection of imminent perturbations, requires past experience
Explain negative feedback control
In negative feedback control, signals from sensors are compared to a desired state, represented by the command (reference) signal. The difference, or error signal, is used to adjust the output.
comparator (probably a neurone) : compares desired and actual states and this generates an error signal to the controller, producing adjustments in the movement.
How do feed forward and feed-back control combine?
1. Feedforward anticipates perturbation of ball striking hand and limits displacement of hand
2. Feedback corrects any unwanted displacement of hand
How would we find evidence for proprioceptive guidance of movement?
Two main approaches – observe effects upon movements of:-
1. removal of proprioceptive (sensory) information (with motor innervation preserved)
(a) surgical (e.g. section of dorsal roots or purely sensory nerves)
(b) anaesthesia of sensory roots/ nerves
(c) patients with (purely) sensory neuropathy
2. experimental stimulation of proprioceptors/ sensory nerves (to see how movement progression is altered)
(a) natural stimulation
(b) electrical stimulation
What sensory organ can help to compensate for the loss of proprioceptors?