The Sensorimotor System

Pregunta	Respuesta
What are the principles of sensorimotor control?	1) Sensorimotor system is hierarchically organized 2) Motor Output is guided by sensory input 3) Learning can change the nature and the locus of sensorimotor control
functional segregation	each one of the sensorimotor system is composed of different units (neural structures), each of which performs different function
sensory feedback	eyes, organs of balance, receptors in the skin, muscles and joints all monitor the body's responses and feed their information back into sensorimotor circuits - important in directing continuation of the responses that produce it
ballistic movements	responses that are normally influenced by sensory feedback - brief all-or-none, high speed movements (swatting a fly)
posterior parietal association cortex	important role in integrating information, in directing behavior by providing spatial information and directing attention
association cortex	receives input from more than one sensory system (visual, auditory, somatosensory systems)
Apraxia	disorder of voluntary movement - difficult with specific movements out of context - can perform such movements under natural conditions when not thinking about them
Contralateral neglect	disturbance of ability to respond to stimuli on the side of the body opposite to the side of the brain lesion, in the absence of simple sensory motor deficits - most of the time, deficits in responding occur for stimuli to the left of their body, referred to as egocentric left
dorsolateral prefrontal association cortex	receives projections from the posterior parietal cortex and sends projections to areas of the secondary motor cortex, primary motor cortex and frontal eye field
secondary motor cortex	receive much of their input from association cortex and send much of their input to primary motor cortex
mirror neurons	neurons that fire when an individual performs a particular goal-directed hand movement or when she or he observes the same goal-oriented movement performed by another
functions of mirror neurons	- provide a possible mechanism for social cognition which would facilitate social understanding, cooperation an imitation - mirror neurons respond to the understanding of the purpose of an action
primary motor cortex	located in the percental gyrus of the frontal lobe and is the major point of convergence of cortical sensorimotor signals and a major point of departure of sensorimotor signals from the cerebral cortex
astereognosia (deficits in stereognosis)	large lesions to the PMC disrupt ability to move one body part independently of others and may reduce speed, accuracy and force of a movement - such lesions do not eliminate voluntary movement because there are parallel ways that descend directly from secondary cortex without passing through primary cortex
dorsolateral corticospinal tract	1 group of axons that descends from primary motor cortex through medullary pyramids
dorsolateral cerebrospinal tract	synapses on the interneurons that synapse on motor neurons that project to the distal muscles of the arms and legs (descends from red nucleus)
ventromedial corticospinal tract	direct ventromedial pathway - axons that descend here branch diffusively and innervate neurons circuits in several different spinal segments on both sides of the spinal grey matter
ventromedial portico-brainstem spinal tract	indirect ventromedial pathway - each side carries signals from both hemispheres and each neuron synapses on interneurons of several different spinal chord segments that control the proximal muscles of trunk and limbs
brain stem structures that with the ventromedial portico-brainstem spinal tract	1) tectum 2) vestibular nucleus 3) reticular formation 4) motor nuclei of carnival nerves that control face muscles
tectum (brain stem structure interaction with the ventromedial cortico-brainstem spinal tract)	receives auditory and visual information about spatial location
vestibular nucleus (brain stem structure interaction with the ventromedial cortico-brainstem spinal tract)	receives information about balance from receptors of inner ear
reticular formation (brain stem structure interaction with the ventromedial cortico-brainstem spinal tract)	contains motor programs that regulate species-typical movements such as walking
motor unit	smallest unit of motor activity, that compromises a single motor neuron and all of the individual skeletal muscle fibers that it innervates
motor unit (functions)	- when motor neuron fires, all muscle fibers of its unit contract - units with fewest fibers permit the highest degree of selective motor control - Acetylcholine activates the motor end-plate
motor end-plate	causes the fibre to contract
motor pool	all of the motor neurons that innervate fibers in a single muscle (fast and slow muscle fibers)
fast muscle fibers (white)	contract and relax quickly, fatigue quickly because they are poorly vascularized (few blood vessels)
slow muscle fibers (red)	slower, weaker, capable of more sustained contraction because they are richly vascularized
flexors	bend or flex a joint (biceps)
extensors	straighten or extend a joint (triceps)
synergistic muscles	muscles whose contraction produce the same movement, be it flexion or extension
antagonistic muscles	those that act in opposite (biceps and triceps)
isometric contraction	when activation of a muscle increases the tension that it exerts on two bones without shortening and pulling them together
dynamic contraction	when activation of a muscle shortens and pulls two bones together
tension in a muscle	can be increased by increasing the number of neurons in its motor pool that are firing, by increasing the firing rates of those already firing or by a combination of both
Golgi tendon organs	embedded in tendons which connect each skeletal muscle to bone
Golgi tendon organs (functions)	- respond to increase in muscle tension - provide the CNS with information about muscle tension - protective function; when contraction is too extreme, they exit inhibitory interneurons in spinal chord that causes the muscle to relax
muscle spindles	embedded in the muscle tissue itself - respond to changes in muscle length
patellar tendon reflex (stretch reflex)	elicited by a sudden external stretching face on a muscle
withdrawal reflex	not monosynaptic; first responses to painful stimulus are recorded in motor neurons of arm flexor in about 1.6ms later, about the time it takes a neural signal to cross two synapses -> the shortest route in the withdrawal route involves one interneuron
reciprocal innervation	antagonistic muscles are innervated in a way that permits a smooth, unimpeded motor response; when one is contracted, the other relaxes
cocontraction	smooth movements that can be stopped with precision by a slight nacres in the contraction of the antagonistic muscles
recurrent collateral inhibition	the inhibition on produced by this (motor neuron) local feedback
Renshaw cells	small inhibitory interneurons that mediate recurrent collateral inhibition
Sensorimotor system comprises a hierarchy of central sensorimotor programs	...?
motor equivalence	the fact that the same basic movement can be carried out in different ways involving different muscles - general programs are stored higher in sensorimotor hierarchy and then are adapted to situation as required
motor equivalence (details)	- conscious perception and sensory control of behavior are separated - Central sensorimotor programs for many species-typical behaviors are established without explicit practice of the behaviors - sensory feedback in operation of central sensorimotor program is important
response chunking	practice combines the central sensorimotor programs that control the individual response into programs that control sequences (chunks) of behavior (eg. in an unpracticed typist, the word is individually triggered, in a skilled typist, the sequel of letters are activated as a unit which is shown in speed and continuity)
response chunking (details)	- control is shifted from higher levels of hierarchy to lower levels of hierarchy which has two advantages 1) frees up higher levels of the system to deal with more esoteric aspects of performance 2) permits great speed because different circuits at lower levels of the hierarchy can act simultaneously, without interfering with each other - the involvement of the cerebellum and association areas diminishes when sequences are well practiced

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	Creado por Linda Lummer hace más de 7 años