CONTROL OF MOVEMENT

NERVOUS SYSTEM Ultimate function of the nervous system Brain as the homunculus

SKELETAL MUSCLES Assist in movement Attached to bones Eyes & Abdominal Muscles Flexion Extension

ANATOMY OF MUSCLE FIBERS Two types if Muscle fibers – Extrafusal (alpha motor) & Intrafusal (gamma motor neuron Sensory endings Muscle Fiber: Myofibrils (actin & Myosin)

REFLEXIVE CONTROL OF MOVEMENT Monosynaptic Stretch Reflex Knee tap – Patellar tendon 50 milliseconds Unconscious Utility of an automatic muscle response

GAMMA MOTOR SYSTEM More sensitive to muscle change Less taxing on Brain Conscious movement = Gamma + Alpha motor neurons

POLYSYNAPTIC REFLEXES Many reflexes per spinal connection Interconnected spinal neurons Decerebrate rigidity Clasp-knife reflex

ORGANIZATION OF THE MOTOR CORTEX The “Motor Homonculus” Mapping of the major body areas controlled Graziano and Afalo (2007) Supplementary motor area (SMA)

CORTICAL CONTROL OF MOVEMENT: THE DESCENDING PATHWAY Ventromedial and lateral group Lateral – individual movements Corticospinal tract Lead to pyramidal tracts Then to lateral and ventral corticospinal tracts

PLANNING AND INITIATING MOVEMENTS: ROLE OF THE MOTOR ASSOCIATION CORTEX Supplementary and premotor cortex Planning Executing Ventral What Dorsal Where

THE SUPPLEMENTARY MOTOR AREA Damage to region Difficulty learned sequences Single-unit recording study Shima and Tanji (1998) One hand teaches the other Postier parital cortex Action to move, without thought

THE PREMOTOR CORTEX Involved in learning and executing complex movements Nonarbitrary spatial information Arbitrary spatial information

IMITATING AND COMPREHENDING MOVEMENTS: ROLE OF THE MIRROR NEURON SYSTEMS Mirror Neurons Monkey observations Monkey see, neurons fire, monkey do, neurons fire Inferior parietal cortex Mirror storage Men and women differences

CONTROL OF REACHING AND GRASPING Most actions involve physically manipulating Parietal reach region Pointing and reaching Anterior intraparietal Sulcus Disruption, tough adjustment

DEFICITS OF SKILLED MOVEMENTS: THE APRAXIAS Apraxia Frontal or parietal cortex Without action Paralysis Weakness motor structures

LIMB APRAXIA A type of apraxia discussing limb movement Pantamime Right hemisphere – extrapersonal space Left – one’s own body

CONSTRUCTIONAL APRAXIA Lesions in the right hemisphere Perceive and imagine geometric relations Clock drawing

THE BASAL GANGLIA: ANATOMY AND FUNCTION Important component of the motor system Input from all regions Caudate nucleus Putamen Globus pallidus Ventral anterior muscles Ventrolateral nucleus Subthalamic nucleus

PARKINSON’S DISEASE Muscle rigidity Slowness of movement Resting tremor Postural instability Basal ganglia

HUNTINGTON’S DISEASE Degredation of the caudate nucleus Uncontrollable jerky limb movements Involutary

THE CEREBELLUM Most important part of the motor system 50 BILLION! NEURONS! Flocculonodular lobe Input from vestibular system Vermis Auditory and visual information Fastigial nucleus Interposed nuclei Pontine nucleus

THE RETICULAR FORMATION Large number of nuclei Mesencephalic locomotor region Cat pacing movemets Locomotion Specific motions