The Neural Control of Movement

Introduction The central nervous system consists of the brain and spinal cord The nervous system is involved in sensation, interpretation, and execution

The Neuromuscular System in Exercise Science Nervous system Peripheral nervous system (PNS) Central nervous system (CNS)

Motor neuron causes muscle to contract Whole structure comprised of a single motor neuron and all of the muscle fibers connected to that motor neuron a motor unit

Communication Among Nerve Cells Each connection of two neuron is called a synapse Nerve impulse arrives the end of one neuron, it cause a chemical to be release called neurotransmitters to produce (EPSP or IPSP)

Communication Between Nerve Cells and Muscle The connection between a motor neuron and a muscle fiber, called the neuromuscular junction Impulse in the motor neuron originates in the spinal cord While it travel to the end of the neuron when it causes the release of transmitter called acetylcholine

EMG: Muscle Electrical Activity Measure electrical energy generated by other biological tissues Heart (ECG; EKG) Brain (EEG) Muscle (EMG)

How do we control force generation Control the level of muscular force chiefly through two mechanisms Change the # of motor units activated by the brain Change frequency those motor units are activated More motor units and faster rate of motor unit activity-greater EMG activity that can be recorded

How we balance during normal movement Activates the muscles necessary to maintain balance first, then Activates the muscles needed to perform movement (purposive activity - a movement performed with a clear aim) Can measure priority scheme by EMG methods Brain uses a priority system for the jobs it has to maintain balance and postural stability

Interaction Between Performer and Environment The PNS receives and sends information from the real world to the brain, and the brain has the responsibility of sorting out what’s important and what’s not. The nervous system uses structures called receptors to determine the status of thins in the real world.

Vision Is important for many of the motor skills Visual acuity acuteness or clearness of vision Static VA: the ability of the lens to change shape Dynamic VA: the ability to discriminate objects while they are moving

peripheral vision is a part of vision that occurs outside the very center of gaze. There is a broad set of non-central points in the field of view that is included in the notion of peripheral vision

Depth perception is the visual ability to perceive the world in three dimensions (3D) and the distance of an object. Depth perception is a binocular or stereoscopic skill Is determined from the brain’s ability to combine information received from both eyes

Visual Control of Movement Vision is often called the dominant sense Kids keep their eyes locked on the bouncing as dribble a basketball Skilled ball player seldom needs to look at the ball while dribbling Kinesthetic sense The ability to determine limb and body position in position Allows a skilled dribbler to predict the moment-to-moment position of the ball

Visual Tracking Muscles position the eye in the socket and determine where we focus our vision – smooth pursuit The mechanism of choice for following slowly moving objects Very rapid eye movement are performed using saccades to focus on the new object of interest Visual Saccade 掃視

Kinesthesis The ability to perceived the position of the body and limbs in space

The anatomy and physiology of kinesthesis The most important receptor is called the muscle spindle Detects length change of muscle and sends neural impulses to the rest of the nervous system When the brain gets the information about the current length of the muscle, it can decide how to continue the movement

Joint receptor are located in joints like the knee and hip joints Contains small nerve fibers that are sensitive to a particular joint angle Vestibular system is a series of canals and other small organs in the inner ear Sensitive to changes in motion Small hair cell floating in a specialized fluid snese this motion if accelerate up or down, forward, backward

The Kinesthetic System in Motor Learning Kinesthetic sense can be important when acquiring new motor skills Kinesthetic sense can be improved with practice

The Use of Feedback in Skill Acquisition Motor program A set of instructions for performing a particular task Requires time to send information from the limbs to the brain, and the brain needs time to process the information it receives and send a correction back to the working muscle

Feedforward Control for rapid Movements When the fastest human movements, there may not be enough time to make midcourse corrections Very rapid movements called ballistic movement and are preprogrammed Once the ballistic movement begins, it continues until the motor program plays itself out Control by cerebellum

Movement performed in the absence of feedback are open-loop During rapid movement agonist muscle is activated first, and antagonist muscle is activated to protect the limb from high force (muscle injury) Movement performed in the absence of feedback are open-loop No circuit from the muscle or spinal cord to brain center Movement is too fast to allow any information from the peripheral receptors to be effective

The Neuroscience of Motor Learning The human brain consists of 1013 neurons Habituation as a decrease in an elicited behavior resulting from the repeated presentation of an eliciting stimulus (a simple form of learning). When aplysia learns the stimulus that is not longer a threat B A B A

Memory for the movement is stored in synapse Repeated activation results in a change in the ability of the information to cross the synapse from sensory neuron to motor neuron Synaptic plasticity The ability of the synapse to change

Important areas for motor learning is the cerebellum- contains a dense layer of cells involved in skilled movement, particularly in the outer layer of the cerebellum called cerebellum cortex Purkinje cell in cerebellar cortex has a cell body with a large number of denrites The dendritic spines contain small processes called dendritic spines

Brain Plasticity PET study showed cerebral blood flow in left sensorimotor cortex after 1 hour of practice Neural activation plays in changing muscle fiber characteristics-(Buller & Lewis 1965)

The Time of Motor Activity Reaction time can be defined as the time interval between the stimulus and the initial response Reaction time provides an overall appraisal of the ability to receive and process auditory, visual, kinesthetic, or other types of sensory information, and begin to execute the appropriate movement

Anatomy of a reaction time task Visual stimulus to eyes receptor →brain’s cerebral cortex →motor cortex (movement planning) →motor cortex neurons synapse on motor neurons in spinal cord (activate the responding muscles)

Anticipation Timing Timing of motor activity is important to proper execution A movement too soon or too late and the ball will end up in foul territory Requires players to make judgment about the velocity of the ball, the path the ball is follow etc A continued neural processing, brain has to try to continually update this information

Discussion Could you take a example to explain a use feedback in skill acquisition in a given movement. What is the importance of visual control of movement and kinesthetic sense in sports. How you train these bio-abilities. In your viewpoint, a good balance (equilibrium) during normal movement would reflect a health status in aged people. Why? Could you design a research topics on the neural control of movement.