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Lecture_14 - Lecture 14 •  SmartSite: – ...

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Unformatted text preview: Lecture 14 •  SmartSite: –  Lecture 14 Notes –  Midterm 1: •  Review •  Announcements: •  Motor Control II –  Reflex •  25 Mul9ple Choice ques9ons •  Covers lectures through Friday (Star9ng Mon, lectures on Midterm 2) •  Requires students to bring and use SCANTRON 2000 (blue) •  Will be in 2 rooms –  3 Keiber (Last Name A ­G) –  123 Sci Lec (Last Name H ­Z) •  Reading (Recommended): –  Relevant por9ons of Chapters 5 & 8 REV: Reflex •  Soma9c 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 s9mulus •  Elements of a reflex: –  Simplest reflex is stretch reflex, we discussed others –  sensor, afferent path, integra9on, efferent path, effector –  Muscle spindle, Golgi tendon organ (GTO), Joint receptor –  afferent receptor to sense muscle length (stretch) –  efferent fibers to maintain sensi9vity –  axons of motor neurons from spinal cord or brain stem and to skeletal muscle •  Skeletal muscle regula9on uses 3 kinds of receptors: •  Muscle spindle contains both: Locomo9on •  Rhythmic contrac9on of flexor ­extensor muscle pairs produced at the level of the spinal cord •  Generator ac9vity modified by the brain stem –  Locomotor command center (LMC) LMC –  Locomotor pa_ern generators (LPG) LPG Le` Leg Right Leg Motor Efferent •  CNS Motor efferents subserve three func9ons: –  Ini9a9on of movement –  Adjustment of posture (level extensor excita9on) –  Coordina9on of muscles •  Upper motor neurons distributed in 2 pathways: •  Lower motor neurons of PNS –  Alpha (α) motor neurons –  Gamma (γ) motor neurons –  Pyramidal fibers from motor cortex to spinal cord –  Extrapyramidal fibers from motor cortex to brainstem to spinal cord Motor System Regula9on •  Feedback regula9on •  Components of CNS –  Spinal Cord –  Brain Stem –  Basal Ganglia –  Thalamus –  Cerebellum –  Cortex (motor, premotor, supplemental) Nega9ve Feedback Regula9on Set Point Controller (CNS) Error Signal Controlled System (Muscle) Nega9ve Feedback Sensor (Muscle spindle) (GTO) (Joint Receptor) Regulated Variables (Length) (Tension) (Posi9on) 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) Motor Cortex •  Primary Motor Cortex –  Located anterior of the central sulcus of each hemisphere –  Contains a Motor Homunculus –  Coordina9on and planning of complex motor movements •  Addi9onal Motor Cortex Fig. 5 ­9a, pg. 147; Fig. 5 ­10c, pg. 148 The Corticospinal Tracts •  Neurons project from the primary motor cortex •  The axons project down through the ipsilateral side of the CNS •  The fibers cross over in different regions –  In the medulla –  In the spinal cord •  The fibers then synapse upon their targets Fig. 5 ­28b, pg. 175 Cerebellum •  Planning, coordina9on & posture •  Many inputs –  Cortex, somatosensory, muscle, visual, auditory, ves9bular •  Coordinate, smooth & predict movement –  Receives feedback •  Pathology (rough, jerky, uncoordinated movements) –  Inten9on tremors –  Overshoot –  Movement decomposi9on Cerebellum SET POINT (Planned Movement) ERROR SIGNAL CONTROLLER SENSORY INFORMATION FEEDBACK Fig. 5 ­19b, pg. 166 Basal Ganglia •  Ganglia located in white ma_er of brain –  Putamen –  Caudate –  Globus pallidus •  Func9on •  Caudate & Putamen receive input from: –  Planning of movement  ­ select/maintain purposeful movement –  Decrease muscle tone –  Posture – monitor & coordinate slow/sustained motor ac9vity –  Cortex –  Thalamus –  Substan9a Nigra (Dopamine; loss of which causes Parkinsons) Basal Ganglia & Thalamus Fig. 5 ­14a, pg. 154 Basal Ganglia •  Globus pallidus provides output to: –  Cortex via thalamus –  Modula9on of descending motor signals –  Substan9a nigra –  Res9ng tremor –  Rigidity (increased tone) –  Poverty of movement –  Dyskinesias •  hard to ini9ate •  spontaneous repeated inappropriate movements •  Pathology Thalamus •  •  •  •  Sensory relay ganglia to the cortex Filter Preliminary synap9c integra9on Posi9ve reinforcement of voluntary motor contol Cerebellum vs. Basal Ganglia •  Similari9es –  Monitor and adjust motor ac9vity commands from cortex –  No direct synapses on lower motor neurons –  Subconscious coordina9on of voluntary motor ac9vity •  Differences –  Cerebellum: maintains balance, coordinates smooth fast motor ac9vity, increases muscle tone •  acts as the controller in the motor program feedback pathway –  Basal Ganglia: maintains posture & support (tone), coordinates slow motor ac9vity, inhibits muscle tone •  acts as set point in the motor program feedback pathway Brain Stem •  Control of posture and spinal cord •  Primary Pathways –  Ventromedial Path –  Lateral Re9culospinal Path •  Muscle tone –  Ves9bulospinal Path •  Postural reflexes Fig. 5 ­19a, pg. 166 Summary of Motor Control Fig. 8 ­23, pg. 286 ...
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