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strech reflex physiology

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  1. 1. ReflexDr Raghuveer choudhary
  2. 2. Reflexes Reflex - Rapid, involuntary MotorResponse to Stimulus Reflexes may:– Inborn (Intrinsic) or Learned (Acquired)– Involve only Peripheral Nerves & Spinal Cord– Involve Higher Brain Centers as Well
  3. 3. Reflex Arc 5 Components of Reflex Arc– Receptor – Site of Stimulus– Sensory Neuron – Transmits Afferent Impulse toCNS– Integration Center – Monosynaptic or PolysynapticRegion within CNS– Motor Neuron – Conducts Efferent Impulses fromIntegration Center to Effector– Effector – Muscle Fiber or Gland that Responds toEfferent Impulse
  4. 4. Reflex Arc
  5. 5. Clasification of reflexes Superficial reflexes ---plantar,abdominal,corneal.conjuctival,cremastric Deep reflexes---- biceps,triceps,knee,ankle jerks Spinal Cranial
  6. 6. Anatomical classification Segmental Intersegmental suprasegmental
  7. 7. physiological Flexor(withdrawal reflex) extensor
  8. 8.  Monosyneptic--- strech reflex Di-syneptic---- Golgi tendon Reflex Polysyneptic---- withdrawal reflex
  9. 9. Stretch & Deep Tendon Reflexes For Skeletal Muscles to Perform Normally:– Golgi Tendon Organs (Proprioceptors) Constantly Inform Brain as to State of Muscle– Muscle Spindles Stretch Reflexes Maintain Healthy Muscle Tone
  10. 10. Muscle Spindles Composed of 3-10 Intrafusal Muscle Fibers– Lack Myofilaments in Central Regions– Non-Contractile– Receptive Surfaces Muscle Spindles Wrapped with 2 Types ofAfferent Endings– Primary Sensory Endings of Type Ia Fibers– Secondary Sensory Endings of Type II Fibers– Innervated by γ Efferent Fibers Contractile Muscle Fibers– Extrafusal Fibers Innervated by α Efferent Fibers
  11. 11. Muscle Spindles
  12. 12. Operation of Muscle Spindles Stretching Muscles– Activates Muscle Spindle– ↑ Rate of Action Potential in Ia Fibers– Contracting Muscle ↓ Tension on MuscleSpindle– ↓ Rate of Action Potential on I Fibers
  13. 13. Operation of Muscle Spindle
  14. 14. Stretch Reflex Stretching Muscle– Activates Muscle Spindle– Excited γ Motor Neurons of Spindle → StretchedMuscle to Contract– Afferent Impulses from Spindle Result inInhibition of Antagonist– Patellar Reflex Tapping Patellar Tendon Stretches Quadriceps StartsReflex Action Quadriceps Contract & Antagonistic Hamstrings Relax
  15. 15. motor neuronsensory neuron interneuronInnervation of a Skeletal MuscleThe arm is commanded to a particular position.
  16. 16. motor neuronsensory neuron interneuronA weight is applied to the arm.
  17. 17. motor neuronsensory neuron interneuronA weight is applied to the arm.
  18. 18. motor neuronsensory neuron interneuronThis weight pushes down the arm which stretches the muscle.
  19. 19. motor neuronsensory neuron interneuronA command to further contract the muscle is sent out thealpha motor neuron.
  20. 20. motor neuronsensory neuron interneuronThe arm is returned to its commanded position.
  21. 21. Muscle ToneMuscle tone can be defined as the resistanceof skeletal muscle to stretch
  22. 22. Muscle Tone Muscle tone is due both to the viscoelasticproperties of the muscles and joints and towhatever degree of alpha motor neuronactivity exists
  23. 23. Abnormal Muscle Tone Abnormally high muscle tone, calledhypertonia, The increased resistance is due to a greater-than-normal level of alpha motor neuron activity, which keeps a muscle contracted despite the individual’s attempt to relax it. Hypertonia is usually found when there are disorders of the descending pathways that result in decreased inhibitory influence exerted by them on the motor neurons.
  24. 24. upper motor neurondisorders. Clinically, the descending pathways—primarily the corticospinal pathways—and neurons of the motor cortex are often referred to as the ―upper motor neurons‖ (a confusing misnomer because they are not really motor neurons at all). Abnormalities due to their dysfunction are classed, therefore, as upper motor neuron disorders.
  25. 25.  Thus, hypertonia indicates an upper motor neuron disorder. Spasticity is a form of hypertonia in whichthe muscles do not develop increased toneuntil they are stretched a bit, and after abrief increase in tone, the contractionsubsides for a short time. Rigidity is a form of hypertonia in which the increased muscle contraction is continual and the resistance to passivestretch is constant.
  26. 26.  When the muscles are hypertonic, the sequence ofmoderate stretch muscle contraction, strong stretch musclerelaxation is clearly seen. Passive flexion of the elbow, forexample, meets immediate resistance as a result of thestretch reflex in the triceps muscle. Further stretchactivates the inverse stretch reflex. The resistance toflexion suddenly collapses, and the arm flexes. Continuedpassive flexion stretches the muscle again, and thesequence may be repeated. This sequence of resistancefollowed by give when a limb is moved passively is knownas the clasp-knife effect because of its resemblance to theclosing of a pocket knife. It is also known as thelengthening reaction because it is the response of aspastic muscle to lengthening.
  27. 27. Hypotonia Hypotonia is a condition of abnormallylow muscle tone, accompanied byweakness, atrophy (a decrease in musclebulk), and decreased or absent reflexresponses. It more frequently accompanies disorders ofthe alpha motor neurons (―lower motorneurons‖), neuromuscular junctions, or themuscles themselves.
  28. 28. Golgi Tendon Reflex Opposite of Stretch Reflex– Contracting Muscle Activates Golgi TendonOrgans– Afferent Golgi Tendon Neurons Stimulated– Neurons Inhibit Contracting Muscle– Antagonistic Muscle Activated– Contracting Muscle Relaxes– Antagonist Contracts
  29. 29. GTO Rx
  30. 30. Flexor & Crossed Extensor Reflexes Flexor Reflex Initiated by Painful Stimulus(Actual or Perceived) → AutomaticWithdrawal of Threatened Body Part Crossed Extensor Reflex - 2 Parts– Stimulated Side Withdrawn– Contralateral Side Extended
  31. 31. Crossed ExtensorReflex
  32. 32. Flexor & Crossed ExtensorReflexes
  33. 33. Superficial Reflexes Initiated by Gentle Cutaneous Stimulation– Plantar Reflex Initiated by Stimulating LateralAspect of Sole of Foot– Response Downward Flexion of Toes– Indirectly tests for Proper Corticospinal TractFunctioning Babinski’s Sign– Abnormal Plantar Reflex– Corticospinal Damage– Great toe Dorsiflexes Smaller Toes Fan Laterally
  34. 34. Babinski’s Sign
  35. 35. Somatic Reflexes
  36. 36. Motor cotexBasalgangliacerebellumInhibitoryreticularformationFacilitatory reticularformationVestibularnucleus
  37. 37. General Properties ofReflexes Adequate Stimulus The stimulus that triggers a reflex isgenerally very precise. This stimulus iscalled the adequate stimulus for theparticular reflex
  38. 38.  Final Common Path The motor neurons that supply theextrafusal fibers in skeletal muscles are theefferent side of many reflex arcs. All neuralinfluences affecting muscular contractionultimately funnel through them to themuscles, and they are therefore called thefinal common paths.
  39. 39.  Central Excitatory & Inhibitory States the spinal cord also shows prolongedchanges in excitability, possibly because ofactivity in reverberating circuits orprolonged effects of synaptic mediators. When the central excitatory state is marked,excitatory impulses irradiate not only tomany somatic areas of the spinal cord butalso to autonomic areas.
  40. 40.  In chronically paraplegic humans, forexample, a mild noxious stimulus maycause, in addition to prolonged withdrawal-extension patterns in all four limbs,urination, defecation, sweating, and bloodpressure fluctuations (mass reflex).
  41. 41. THANK YOU