Motor System

The visuomotor delay is approximately 200 250 300 150( 200, 250, 300, 150 ) ms.
The proprioceptive delay is approximately 50 30 80 150( 50, 30, 80, 150 ) ms.

Feedforward (open closed( open, closed )-loop) control:

Because of the delays in the sensorimotor system, open-loop control is used for short long( short, long ) movements.
Disadvantages:
- Inaccuracies Delays Noise( Inaccuracies, Delays, Noise ) cannot be corrected
- Unexpected changes Inaccuracies Noise( Unexpected changes, Inaccuracies, Noise ) will not be taken into account

High Low( High, Low ) gain and high low( high, low ) sensorimotor delay can lead to overcompensation too little compensation( overcompensation, too little compensation ) and instabilities a stable motor command( instabilities, a stable motor command ).

An efference afference( efference, afference ) copy is an internal copy of an outflowing (efferent afferent( efferent, afferent )), movement-producing signal generated by the motor system.

The experiment where you move your eyeball with your hand and the world moves shows that the brain uses motor commands to the eye sensors in the eye muscles( motor commands to the eye, sensors in the eye muscles ) in order to predict the eye's position.

A motor unit consists of a spinal motor neuron a sensory interneuron a pyramidal motor neuron( a spinal motor neuron, a sensory interneuron, a pyramidal motor neuron ) and the muscle fibres that it innervates. the motor neurons it projects to. the disc in the spinal cord it projects( the muscle fibres that it innervates., the motor neurons it projects to., the disc in the spinal cord it projects )

A muscle is typically innervated by a few hundred a few thousand about 50 about 50.000( a few hundred, a few thousand, about 50, about 50.000 ) spinal motor neurons.

Recruitment:

Small Large( Small, Large ) motor neurons are recruited first because of the high low( high, low ) resistance within their axon.
They have a lower higher( lower, higher ) innervation number and therefore produce less more( less, more ) force.

The motor homunculus is most detailed for the primary motor cortex premotor cortex supplementary motor area( primary motor cortex, premotor cortex, supplementary motor area ).

It disappears if you zoom in zoom out( zoom in, zoom out ).

The motor pathway to lateral motorneurons runs contralateral ipsilateral( contralateral, ipsilateral ) and controls mainly distal muscles nearby muscles( distal muscles, nearby muscles ).
It includes the corticospinal tract medial tract( corticospinal tract, medial tract ).

The patway to medial motorneurons runs ipsilateral contralateral( ipsilateral, contralateral ) and controls mainly stance and posture fine movements unconscious movements( stance and posture, fine movements, unconscious movements ).

The corticospinal tract

The connections come from the cortical layer V IV III II I( V, IV, III, II, I ).
Many of these connections terminate on spinal interneurons medial neurons projection neurons( interneurons, medial neurons, projection neurons ).

Only M1 PM SMA( M1, PM, SMA ) contains neurons projecting directly to spinal motor neurons. These cortical neurons are called corticomotorneurons complex neurons( corticomotorneurons, complex neurons ). Those neurons have only one synapse.

The axons of corticomotorneurons terminate on spinal motor neurons the muscle fiber( spinal motor neurons, the muscle fiber ).

The can also influence other muscles via spinal interneurons projection neurons receptors( interneurons, projection neurons, receptors ).

Most of the time the excite agonist muscles and inhibit antagonist ones.

The forward-model is used at the beginning end( beginning, end ) of movements.