1Listen to the audio lecture while viewing these slides1Psychology 372Physiological PsychologySteven E. Meier, Ph.D.Voluntary MovementBrain and Spinal Systems2Psyc 372 – Physiological PsychologyMotor Control• Is organized hierarchically and in parallel• Lower – Reflexes and rhythmic motor patterns• Higher – Give commands without having to specify the details of the motor system.• Lots of overlap3Psyc 372 – Physiological PsychologyHave Three Levels of Control•Cortex•Highest • Primary Mot or Cort ex (Area 4)• Lateral Premotor area (Area 6)• Supplementary Motor area (Also part of Area 6) •Brain Stem•Spinal Cord• Other structures• Cerebellum• Basal Ganglia4Psyc 372 – Physiological PsychologyCortex• Precentral Gyrus (Primary Motor Cortex) • Premotor area (Superior and Middle Frontal Gyrus)• Supplementary Motor area (Superior Frontal Gyrus)• Tertiary Motor Areas (Middle and Inferior Frontal Gyrus)• Issues commands that act on lower levels5Psyc 372 – Physiological PsychologyCortex6Psyc 372 – Physiological PsychologyPrecentral GyrusBroadman’s Area 4• Is the Primary Motor Cortex• Controls the major systems that control body movement.27Psyc 372 – Physiological PsychologyPrecentral GyrusBroadman’s Area 4• Motor cortex is somatotopicallyorganized (motor homunculus).• Most is taken up with the neck, mouth, face and hands.8Psyc 372 – Physiological PsychologyPrecentral GyrusReceives Input From• Premotor cortex• Supplemental motor area• Frontal association cortex• Post Central GyrusMovement involves all of these structures9Psyc 372 – Physiological PsychologyPremotor Cortex and Supplementary Motor Cortex• Broadman’s areas 6 and 8• Help coordinate and plan complex sequences of movement.• Receives information from posterior and prefrontal association areas 10Psyc 372 – Physiological PsychologyTertiary Motor Area• Broadman’s Areas 9, 10 11, 45, 46, 47• More planning and thinking of movement• 45, 46, 47 Involved with speech11Psyc 372 – Physiological PsychologyCortex Motor AreasThalamusBGCerebellumBrain StemSpinal CordMuscleContraction MovementSensory ReceptorsFeedback LoopCortex Motor Areas12Psyc 372 – Physiological PsychologyDescending Motor Pathways• Axons from Area 4 descend to the spinal cord via two groups• Lateral Group• Ventromedial Group313Psyc 372 – Physiological PsychologyLateral Group• Generally controls independent limb movements• Many Pathways• Corticospinal tract: hand/finger movements• Corticobulbar tract: movements of face, neck, tongue, eye• Rubrospinal tract: fore and hind-limb muscles14Psyc 372 – Physiological PsychologyVentromedial Group• Controls gross limb movements• Vestibulospinal tract: control of posture• Tectospinal tract: coordinate eye and head/trunk movements• Reticulospinal tract: walking, sneezing, muscle tone• Ventral corticospinal tract: muscles of upper leg/trunk15Psyc 372 – Physiological PsychologyCorticospinal Tract• Neurons terminate on motor neurons within the gray matter of the spinal cord• Begins in layer 5 o f primary mo to r co rtex• Axons pass through the cerebral peduncles o f the midbrain• 80% cross over to the opposite side of the body (decussate) at the pyramidal decussationin the m edulla• Becomes the Lateral Corticospinal Tract• 20% remain ips ilatera l• Becomes the Ventral Corticospinal Tract.16Psyc 372 – Physiological PsychologyCorticospinal Tract• Terminate onto internuncial neurons or alpha motor neurons of ventral horn• Final common pathway• Efferent neurons to the muscle group17Psyc 372 – Physiological PsychologyFunction • Controls fine motor movements• Destruction: loss of muscle strength, reduced dexterity of hands and fingers• No effect of corticospinal lesions on posture or use of limbs for reaching• Uses different brain structures (BG, Cerebellum)18Psyc 372 – Physiological PsychologyFinal Common Pathway419Psyc 372 – Physiological PsychologyNeuromuscular Junction • The neuromuscular junction is the synapse formed between an alpha motor neuron and a muscle fiber• Each axon forms synapses with several muscle fibers (forming a motor unit).• The precision of muscle control is related to motor unit size.•Small: precise movements of the hand •Large: movements of the leg20Psyc 372 – Physiological PsychologyACh• Primary NT at the neuromuscular junction• ACH release produces a large endplate potential• Voltage changes open Ca++ channels• Ca++ entry triggers myosin-actininteraction (rowing action)• Movement of myosin bridges shortens muscle fiber• Contraction occurs21Psyc 372 – Physiological PsychologyGolgi Tendon Organ Receptors• Function to prevent over-contraction of striated muscle• Are located within tendons• Sense degree of stretch on muscle• GTO activation inhibits the agonist muscle (via release of glycine onto alpha-motor neuron).22Psyc 372 – Physiological PsychologyOther Brain Structures Involved with Movement• Basal Ganglia• Cerebellum•Spinal