Neural Control of Movement Chapter 2

CENTRAL NERVOUS SYSTEM Brain Cerebral Cortex/Cerebrum Motor cortex Basal Ganglia/Diencephalon – sensory input Cerebellum – motor control Brain stem – sensory input Spinal Cord

CENTRAL AND PERIPHERAL NERVOUS SYSTEM Central nervous system Peripheral nervous system

PERIPHERAL NERVOUS SYSTEM Somatic Sensory (Afferent) Neuron Motor (Efferent) Neuron Autonomic [FYI] Parasympathetic Sympathetic

SENSORY NEURONS Carry impulse towards the CNS Towards CNS

MOTOR NEURONS Carry impulse away from the CNS (e.g. motor nerves) Stimulatory Inhibitory

Spinal Nerves Cervical spinal nerves (C1 to C8) These nerves (eight pairs) supply the back of the head, the neck and shoulders, the arms and hands, and the diaphragm. Thoracic spinal nerves (T1 to T12) These nerves (12 pairs) supply the chest, some muscles of the back, and parts of upper abdomen. Lumbar spinal nerves (L1 to L5) These nerves (five pairs) supply parts of the lower abdomen and the back. Sacral spinal nerves (S1 to S5) These nerves (five pairs) supply the thighs and parts of lower legs, and the feet.

NEURON ANATOMY Dendrite Cell Body Axon

NEURON ANATOMY Neuron …a single nerve cell Nerve ….a bundle or group of neurons A nerve contains both motor and sensory neurons

Proprioception and Kinesthesis What is kinethesis? …awareness of the position and movement of the body What is proprioception? …ability to regulate posture and movement by responding to stimuli from receptors throughout the body

MUSCLE SPINDLES

MUSCLE SPINDLES Provide proprioception Sense the amount of stretch and the rate of stretch Reflexes involving the muscle spindles is how we ‘feel’ a movement was done correctly Spindles are a part of learning; we develop such reflexes as we practice skills and movements

GOLGI TENDON ORGAN

GOLGI TENDON ORGAN Sensitive to muscle tension and active contraction Protect muscle from excess contraction force Stimulation of GTO an afferent impulse is sent to the central nervous system In turn, efferent impulses are sent to the… …Agonist muscle causing it to relax …Antagonist muscle causing it to contract

Other Receptors Proprioceptors of the joints and skin Examples: Meissner’s corpuscles, Ruffini’s corpuscles, Pacinian corpuscles, Krause’s end-bulbs

NEUROMUSCULAR CONCEPTS

Motor Unit One motor neuron and all the muscle fibers it innervates All-or-none principle

Factors Affecting Muscle Tension The number of motor units activated Type of motor units activated (fast or slow twitch) The frequency of stimulation of the motor units

Factors Affecting Muscle Tension Stimulation Subthreshold stimulus Threshold stimulus Submaximal stimulations Maximal stimulation

Factors Affecting Muscle Tension Twitch Summation Tetanus

Neuromuscular Summary An example from baseball. A pitcher throws a curve ball to Derrek Lee Derek’s eyes see the ball coming towards him and is able to identify the pitch as a curve ball Sensory nerves (afferent) send that information to the CNS In the CNS the sensory nerve synapses with motor nerves The motor nerves in turn stimulates the muscles (deltoid and pectoralis major) required to swing the bat in the proper position to hit the ball

Neuromuscular Summary Inside the fibers of the deltoid and pectoralis major, calcium is released The calcium allows myosin heads to attach to actin When the heads swivel the fibers of the deltoid muscle will shorten The shortening of the fibers will pull on the humerus causing Derrek to swing the bat The muscle spindles “tell” the CNS when the arm is in the correct position If all goes as planned, the deltoid and pectoralis major will move his arms into a position to hit the ball

Neuromuscular Summary An example from weight training. A man is having his muscular strength tested on the bench press For his first lift, 50 pounds is put on the bar He will be using his pectoralis major muscle with has 500 motor units (300 slow twitch and 200 fast twitch) and his triceps muscle His CNS stimulates 280 motor units leading to his pectoralis major muscle (180 slow twitch and 100 fast twitch) Remember, each nerve ending stimulates a separate muscle fiber

Neuromuscular Summary The pectoralis major and triceps muscles shortens and his arm extends outward raising the bar with 50 pounds on it. After a few minutes of rest, 100 pounds is place on the bar This time he stimulates 380 motor units (260 slow twitch and120 fast twitch) The weight is successfully lifted After a few minutes of rest, 150 pounds is place on the bar

Neuromuscular Summary This time he stimulates 460 motor units (280 slow twitch and 180 fast twitch) As the pectoralis major muscle contracts the GTO in the pectoralis major are stimulated They stimulate a sensory nerve leading to the CNS In the CNS, the sensory nerve synapses with a motor nerve that will inhibit (relax) the pectoralis major muscle The man is unable to lift the 150 lb