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Unformatted text preview: Lecture 14 SmartSite: Lecture 14 Notes Review Motor Control I Announcements: None Motor Control II Reading (Recommended): Relevant por<ons of Chapters 5 & 8 1 REV: Motor Control I Soma<c efferent division of PNS consists of Motor output can range from simple reflex to complex movement A reflex is a stereotyped response to a fixed s<mulus Elements of a reflex: Simplest reflex is stretch reflex, we discussed others sensor, afferent path, integra<on, efferent path, effector Muscle spindle Golgi tendon organ (GTO) Joint receptor axons of motor neurons from spinal cord or brain stem and to skeletal muscle Skeletal muscle regula<on uses 3 kinds of receptors: Muscle spindle contains both: afferent receptors to sense muscle length (stretch) efferent fibers to maintain sensi<vity 2 Locomo<on Rhythmic contrac<on of flexor-extensor muscle pairs produced at the level of the spinal cord Generator ac<vity modified by the brain stem Locomotor command center (LMC) LMC Locomotor paXern generators (LPG) LPG LeY Leg Right Leg 3 Motor Efferent CNS Motor efferents subserve three func<ons: Ini<a<on of movement Adjustment of posture (level extensor excita<on) Coordina<on of muscles Upper motor neurons distributed in 2 pathways: Lower motor neurons of PNS Alpha () motor neurons Gamma () motor neurons Pyramidal fibers from motor cortex to spinal cord Extrapyramidal fibers from motor cortex to brainstem to spinal cord 4 Motor System Regula<on Feedback regula<on Components of CNS Spinal Cord Brain Stem Basal Ganglia Thalamus Cerebellum Cortex (motor, premotor, supplemental) 5 Nega<ve Feedback Regula<on Set Point Controller (CNS) Error Signal Controlled System (Muscle) Nega<ve Feedback Sensor (Muscle spindle) (GTO) (Joint Receptor) Regulated Variables (Length) (Tension) (Posi<on) 6 Primary Motor Cortex Control of fine / voluntary movement Anatomy Located next to and anterior to (in front of) sensory cortex Somatotopically organized 6 cell layer structure Two descending pathways (pyramidal & extrapyramidal) Linked to somatosensory cortex (feedback) Planning (Set Point) 7 Motor Cortex Primary Motor Cortex Located anterior of the central sulcus of each hemisphere Contains a Motor Homunculus Coordina<on and planning of complex motor movements Addi<onal Motor Cortex Fig. 5-9a, pg. 147; Fig. 5-10c, pg. 148 8 The Corticospinal Tracts Neurons project from the primary motor cortex The axons project down through the ipsilateral (same) side of the CNS The fibers cross over in different regions In the medulla In the spinal cord The fibers then synapse upon their contralateral (opposite) side targets Fig. 5-28b, pg. 175 9 Cerebellum Planning & coordina<on of skilled voluntary movement Maintenance of balance & posture Enhancement of muscle tone Many inputs Cortex, somatosensory, muscle, visual, auditory, ves<bular Receives feedback Coordinate, smooth & predict movement Pathology (rough, jerky, uncoordinated movements) Inten<on tremors Overshoot Movement decomposi<on 10 Cerebellum SET POINT (Planned Movement) ERROR SIGNAL CONTROLLER SENSORY INFORMATION FEEDBACK Fig. 5-19b, pg. 166 11 Basal Ganglia Ganglia located in white maXer of brain Putamen Caudate Globus pallidus Func<on Planning of movement - select/maintain purposeful movement Inhibi<on of muscle tone Coordina<on of slow sustained movements Posture monitor & coordinate slow/sustained motor ac<vity Suppress unwanted movements Caudate & Putamen receive input from: Cortex Thalamus Substan<a Nigra (Dopamine; loss of which causes Parkinsons) 12 Basal Ganglia & Thalamus Fig. 5-14a, pg. 154 13 Basal Ganglia Globus pallidus provides output to: Cortex via thalamus Modula<on of descending motor signals Substan<a nigra Res<ng tremor Rigidity (increased tone) Poverty of movement Dyskinesias hard to ini<ate spontaneous repeated inappropriate movements Pathology 14 Thalamus Sensory relay ganglia to the cortex Sensory Filter Preliminary synap<c integra<on Posi<ve reinforcement of voluntary motor control 15 Cerebellum vs. Basal Ganglia Similari<es Monitor and adjust motor ac<vity commands from cortex No direct synapses on lower motor neurons Subconscious coordina<on of voluntary motor ac<vity Differences Cerebellum: maintains balance, coordinates smooth fast motor ac<vity, increases muscle tone acts as the controller in the motor program feedback pathway Basal Ganglia: maintains posture & support (tension), coordinates slow motor ac<vity, inhibits muscle tone acts as set point in the motor program feedback pathway 16 Brain Stem Regula<on of muscle reflexes involved in posture and equilibrium Regula<on and integra<on of synap<c input from Spinal Cord Primary Pathways Ventromedial Path Lateral Re<culospinal Path Muscle tone Ves<bulospinal Path Postural reflexes Fig. 5-19a, pg. 166 17 Summary of Motor Control Fig. 8-23, pg. 286 18 The End (of the nervous system) (Tomorrow we start Muscle) 19 ...
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This note was uploaded on 04/28/2010 for the course NPB 101 taught by Professor Fuller,charles/goldberg,jack during the Spring '08 term at UC Davis.
- Spring '08