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Goal-Directed Behavior and Reflexive Behavior

Goal-Directed Behavior and Reflexive Behavior

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Goal-Directed Behavior and Reflexive Behavior

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  1. Goal-Directed Behavior and Reflexive Behavior

  2. Goal-Directed Behaviors Require: • Goal selection and prioritization • Resistance to distracters -Cross-modal Sensory integration • Perception of target • Awareness of location of movable body part • Ability to aim movement of body part • Ability to detect errors and re-adjust, (use feedback) • Ability to use feedback to control movement of body part

  3. Sensory-Motor Integration in the frontal lobes

  4. THE DLPFC: “The conductor” Integrates cross modal input- may initiate goal-directed behaviors Lesions of the dorsolateral frontal areas results in a number of “executive” motor impairments. These include perseveration, incoordination, motor impersistence, apraxias and hypokinesia. http://www.youtube.com/watch?v=p_uhP1vDfoo

  5. The premotor and supplementary motor ctx: “The sections” Stimulation= complex sequences of behavior (aimless behavior)

  6. Damage to the secondary Motor Cortex? • Ideomotor Apraxia • This apraxia is associated with great difficulty in the sequencing and execution of movements. A common test of apraxia is to request the patient to demonstrate the use of a tool or household implement (e.g., "Show me how to cut with scissors"). Difficulties are apparent when the patient moves the hand randomly in space or uses the hand as the object itself, such as using the forefinger and middle finger as blades of the scissors. They have additional trouble sequencing the correct series of movements and make errors in orienting their limbs in space consistent with the desired action. Imitation of the movements of others will usually improve performance but it is still usually defective. • Memories for skilled acts are probably stored in the angular gyrus of the parietal lobe in the left hemisphere. • http://www.youtube.com/watch?v=gewP1T7GYcc

  7. The primary motor cortex; “the instrument” Stimulation = relatively simple fragments of behavior

  8. TWO MAJOR DESCENDING PATHWAYS FROM THE PRIMARY MOTOR CORTEX: The Dorsolateral pathway

  9. And the VM Path. • The VM pathway does not discretely decussate, but does branch and innervate contra lateral segments in the spinal cord.

  10. Dorsolateral Decussates at medullary pyramids Distal muscle groups More direct More volitional control Higher resolution of control Ventromedial Does not cross Medial muscle groups Gives off spinal collaterals Yoking Lower resolution of control DL vs VM descending motor paths

  11. Other Motor Pathways • In addition there are other motor paths that have relays in the brainstem • These other paths innervate nuclei of the RAS, cranial nerve nuclei, etc…

  12. Descending paths get additional inputs

  13. Both pathways terminate in spinal cord segments

  14. According to part of the body they control

  15. On lower motor neurons (alpha motor neurons)

  16. Amyotropic lateral sclerosis (ALS)disease of the alpha motor neurons

  17. ALS

  18. Alpha motor neurons project to form part of spinal nerve pairs

  19. Terminate on muscle fibers

  20. At each spinal segment

  21. Muscle groups are complex; attach bone to bone via tendons and ligaments

  22. A muscle group has many fibers

  23. The motor unit helps us understand “resolution”

  24. The motor unit: If ratio is high=low resolution

  25. The Neuromuscular junction (NMJ): The receptive portion of muscle-the motor end-plate

  26. The NMJ ( sometimes called the motor end-plate)

  27. nACHr

  28. End-plate potential • Larger • Longer • Leads to Ca+ influx in sarcolema of muscle • Ca+ causes muscle contraction

  29. muscle fibers encase myofibrils. The casing is called the sarcolema Muscle group myofibril Muscle fiber

  30. End-plate potential causes ca+ influx into sarcolemma

  31. Myofibrils in turn contain “Actin and Myosin” filaments

  32. When the NMJ is activated Actin-myosin interact to shorten the length of a muscle fiber

  33. Sliding filament model of muscular contraction

  34. Muscle shortens=work

  35. Disease of the NMJ? MG

  36. MG

  37. MG

  38. Goal-directed Complex Higher levels of control Plastic Numerous reflexive behaviors are involved Reflexive Simple Automatic inplastic Cortical vs Spinal control of behavior

  39. Spinal reflex ARCs • Monosynaptic • stretch • Polysynaptic • Withdrawal • Antagonist muscle groups • Synergistic muscle groups • Polysegmental relexes • Cross-spinal reflexes

  40. A “monosynaptic” spinal reflex arc- the Stretch reflex

  41. The stretch reflex involves neuromuscular “spindles”

  42. Stretch reflex regulates muscle tension in every muscle group

  43. The polysynaptic part of stretch reflexes: inhibition of Antagonist muscles

  44. Spinal inhibition of antagonist muscles require inhibitory interneurons

  45. The “withdrawal reflex arc” a polysynaptic spinal reflex

  46. Also involves interneurons

  47. And may involve more than one spinal cord segment