Movement

The eyes, the organs of balance, and the receptors in skin, muscles, and joints monitor the body’s responses, and they feed their information back into sensorimotor circuits.

ballistic movements—brief, allornone, highspeed movements, such as swatting a fly,not influenced by sensory feedback

Association cortex is at the top of the sensorimotor hierarchy.

Two major areas of sensorimotor association cortex:

the posterior parietal association cortex

the dorsolateral prefrontal association cortex.

The posterior parietal association cortex directs behavior by providing spatial information, and in directing attention

It receives information from the three sensory systems:

the visual system,

the auditory system

the somatosensory system

The dorsolateral prefrontal association cortex receives projections from the posterior parietal cortex - sends projections to areas of secondary motor cortex -to primary motor cortex - to the frontal eye field.

Areas of secondary motor cortex - receive much of their input from association cortex and send much of their output to primary motor cortex.

Areas of secondary motor cortex are thought to be involved in the programming of specific patterns of movements after taking general instructions from dorsolateral prefrontal cortex.

Mirror neurons - neurons that fire when an individual performs a particular goal directed hand movement or when they observe the same goal directed movement performed by another.

The primary motor cortex - is dedicated to controlling parts of the body that are capable of intricate movements, such as t__he hands and mouth__.

The neurons of the primary motor cortex play a major role in initiating body movements.

The cerebellum and the basal ganglia interact with different levels of the sensorimotor hierarchy and, in so doing, coordinate and modulate its activities

Cerebellum-motor learning, particularly in the learning of sequences of movements.

basal ganglia - habit learning

Neural signals are conducted from the primary motor cortex to the motor neurons of the spinal cord over four different pathways.

Two pathways descend in the dorsolateral region of the spinal cord(dorsolateral motor pathways) and two descend in the ventromedial region of the spinal cord—(ventromedial motor pathways)

The motor neurons activated by the two ventromedial tracts project to proximal muscles of the trunk and limbs (e.g., shoulder muscles), whereas the motor neurons activated by the two dorsolateral tracts project to distal muscles (e.g., finger muscles)

Motor units - the smallest units of motor activity

he primary motor cortex to the motor neurons of the spinal cord over four different pathways.

A skeletal muscle comprises threadlike muscle fibers bound together in a tough membrane and attached to a bone by a tendon.

Golgi tendon organs and muscle spindles-monitor the activity of the activity of skeletal muscles

Acetylcholine - activates the motor end-plate on each muscle fiber and causes the fiber to contract. Released by motor neurons at neuromuscular junctions.

Contraction - method that muscles have for generating force, muscle can generate force in only one direction. All of the motor neurons that innervate the fibers of a single muscle are called its motor pool.

Fast muscle fibers - contract and relax quickly. quick movements such as jumping

Slow muscle fibers - slower and weaker, capable of more sustained contraction. gradual movements such as walking

Each muscle has both fast and slow fibers

Flexors act to bend or flex a joint, and extensors act to straighten or extend it.

Cocontraction - the simultaneous activation of muscles on opposite sides of a joint

Movements produced by cocontraction are smooth, and they can be stopped with precision by a slight increase in the contraction of the antagonistic muscles.

Motor equivalence-same basic movement can be carried out in different ways involving different muscles

Sensorimotor system - fundamentally plastic. General commands to act are issued by cortical circuits, but exactly how an act is actually completed depends on the current situation (e.g., body position). The sensorimotor system maintains the ability to change itself in response to practice.