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Neurophysiology

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Neurophysiology

  1. 1. Neurophysiology By: Dr. Osman Sadig
  2. 2. <ul><li>Motor system </li></ul><ul><li>Consists of: </li></ul><ul><li>1- Pyramidal OR Corticospinal system </li></ul><ul><li>(UMN) </li></ul><ul><li>2- Lower motor neurone (LMN) </li></ul><ul><li>3- Extra pyramidal system </li></ul><ul><li>4- Cerebellum . </li></ul>
  3. 3. <ul><li>Corticospinal (pyramidal) </li></ul><ul><li>system---(UMN) </li></ul><ul><li>Composed of: </li></ul><ul><li>1- Motor cortex </li></ul><ul><li>2- Corticospinal tracts . </li></ul><ul><li>1- Motor cortex: </li></ul><ul><li>- Occupies za pre central gyrus </li></ul><ul><li>- The body is represented upside down, </li></ul><ul><li>the area represented depends on the </li></ul><ul><li>functional importance </li></ul><ul><li>- Controls za opposite side of za body </li></ul>
  4. 4. <ul><li>2- Pyramidal tracts (C/S) </li></ul><ul><li>- It passes downwards from motor cortex </li></ul><ul><li>as za corona radiata to za internal capsul </li></ul><ul><li>occupying the posterior 2/3 of za post. limb, descends downwards to occupy za peduncles of mid brain & passes through za pons to form za pyramids of za medulla. In za medulla za majority of C/S tracts decussate wz those of za opposite side and course down in za spinal cord in the lateral column as indirect C/S tracts </li></ul>
  5. 7. <ul><li>and terminate in za LMN. The undecussated C/S fibres descend in </li></ul><ul><li>the anterior column as direct C/S tracts </li></ul><ul><li>decussate at segmental level & terminate </li></ul><ul><li>in za LMN. </li></ul><ul><li>- At different levels of CNS, The C/S </li></ul><ul><li>tracts give fibres to za brain stem nuclei </li></ul><ul><li>and za LMN in za anterior horn of the </li></ul><ul><li>spinal cord. </li></ul>
  6. 8. <ul><li>Function of C/S: </li></ul><ul><li>- Motor cortex is responsible for programming & initiation of skilled motor acts, specially fine distal movements, and is influenced by </li></ul><ul><li>connection from other parts of motor </li></ul><ul><li>system that controls muscle tone & body </li></ul><ul><li>posture. </li></ul><ul><li>- Accurately targeted & coordinated actions require intact functioning </li></ul><ul><li>cerebellum. </li></ul>
  7. 9. <ul><li>- Lesions of C/S system above za level of </li></ul><ul><li>decussation cause contra lateral signs, </li></ul><ul><li>while below that cause ipsi lateral signs. </li></ul><ul><li>Signs of UMNL: </li></ul><ul><li>1- Muscle weakness . </li></ul><ul><li>2- Hypertonia resulting in spasticity. </li></ul><ul><li>3- Hyper- reflexia (increased tendon reflex) +/- clonus. </li></ul><ul><li>4- Extensor planter reflex </li></ul><ul><li>5-Absent abdominal & cremasteric reflexes </li></ul><ul><li>6- In long standing cases there is wasting . </li></ul>
  8. 10. <ul><li>Localization of level of UMNL </li></ul><ul><li>1- Cortical lesions localized loss of fn e.g. </li></ul><ul><li>monoplegia, aphasia, apraxia </li></ul><ul><li>2- Internal capsule hemiplegia </li></ul><ul><li>3- Brain stem lesions crossed hemiplegia </li></ul><ul><li>4- Spinal cord lesions Ipsi lateral weakness. </li></ul><ul><li>The nature of za lesion in </li></ul><ul><li>the nervous system </li></ul><ul><li>1- Trauma & vascular lesions= acute onset </li></ul><ul><li>2- Infections= sub acute onset. </li></ul><ul><li>3- Tumours & degenerative lesions= gradu </li></ul><ul><li>onset & progressive course. </li></ul>
  9. 11. <ul><li>4- Demyelinating lesions= remission and relapses. </li></ul><ul><li>5- Epilepsy, migraine & TIA= paroxysmal. </li></ul><ul><li>NB: destructive lesion weakness </li></ul><ul><li>irritative lesions seizures </li></ul>
  10. 12. <ul><li>Lower motor neurones </li></ul><ul><li>(LMN) </li></ul><ul><li>LMN consist of: </li></ul><ul><li>1- Anterior horn cells in za spinal cord and </li></ul><ul><li>the homologus motor nuclei in za brain </li></ul><ul><li>stem </li></ul><ul><li>2 Afferent nerve which originate in za ant. </li></ul><ul><li>horn cells and pass via za ant. spinal </li></ul><ul><li>nerve roots in za peripheral nerves to </li></ul><ul><li>the muscles or glands. </li></ul>
  11. 13. <ul><li>* Impulses from supra spinal centres can </li></ul><ul><li>only reach za muscles through intact </li></ul><ul><li>LMN. </li></ul><ul><li>* Muscle movement depends on the </li></ul><ul><li>integrity of za LMN which also connect </li></ul><ul><li>the skeletal muscles wz supra spinal </li></ul><ul><li>centres. </li></ul><ul><li>Signs of LMN lesions </li></ul><ul><li>1- Weakness or paralysis of muscles suppl </li></ul><ul><li>by za affected LMN </li></ul><ul><li>2- Hypotonia </li></ul>
  12. 14. <ul><li>3- Absent tendon reflexes </li></ul><ul><li>4- Fasiculation </li></ul><ul><li>5- Absent or flexor planter response </li></ul><ul><li>6- Muscle wasting. </li></ul>
  13. 15. <ul><li>Extra pyramidal system </li></ul><ul><li>It is a complex systems of neurones and </li></ul><ul><li>fibres wz reciprocal connections with </li></ul><ul><li>cerebral cortex, thalamus, cerebellum, </li></ul><ul><li>brain stem nuclei & anterior horn cells. </li></ul><ul><li>It consist of: </li></ul><ul><li>1-Basal ganglia (caudate nucleus, putamen </li></ul><ul><li>and globus pallidum) </li></ul><ul><li>2- Sub thalamic nuclei </li></ul><ul><li>3- Substantia nigra </li></ul><ul><li>4- Red nucleus. </li></ul><ul><li>5- Reticular formation of za brain stem. </li></ul>
  14. 16. <ul><li>The extra pyramidal system influence on </li></ul><ul><li>the spinal cord indirectly through </li></ul><ul><li>pathways arising in za brain stem. </li></ul><ul><li>Functions of extra pyram syst </li></ul><ul><li>1- Adjustment of fine & fast voluntary </li></ul><ul><li>movement generated in za C/S system </li></ul><ul><li>2- Involuntary adjustment of posture and </li></ul><ul><li>muscle tone </li></ul><ul><li>Signs of extra pyram disorders </li></ul><ul><li>1- Increased muscle tone causing rigidity </li></ul><ul><li>( cog wheel & lead pipe). Hypotonia in </li></ul>
  15. 17. <ul><li>chorea. 2- Akinetic or rest tremors. </li></ul><ul><li>3- Hypokinesia & difficulty wz fine tasks. </li></ul><ul><li>4- Abnormal posture & poverty of movements, shuffling gait. </li></ul><ul><li>5- Chorea </li></ul><ul><li>6- Athetosis </li></ul><ul><li>7- Dystonia </li></ul><ul><li>8- Hemibalismus. </li></ul><ul><li>9-Postural instability falls. </li></ul><ul><li>10- No muscle weakness, normal planter </li></ul><ul><li>response, normal or increased tendon </li></ul><ul><li>reflexes, </li></ul>
  16. 18. <ul><li>The cerebellum </li></ul><ul><li>-The cerebellum modulates muscle tone , </li></ul><ul><li>controls co ordination of voluntary </li></ul><ul><li>movements & is important for maintainanc </li></ul><ul><li>of posture & balance through its connections with the thalamus, basal ganglia, cerebral cortex, vestibular syst and za spinal cord </li></ul><ul><li>- It is closely connected wz za vestibular </li></ul><ul><li>syst & recieves proprioceptive inputs </li></ul><ul><li>from the spinal cord </li></ul><ul><li>- Cerebellar lesions & its connections cause ipsi lateral signs . </li></ul>
  17. 19. <ul><li>Signs of cerebellar disorders </li></ul><ul><li>1- Ipsi lateral incordination of limbs </li></ul><ul><li>- Dysmetria (past pointing) </li></ul><ul><li>- Intention tremors </li></ul><ul><li>- Dyssenergia (decomposition of mov </li></ul><ul><li>- Dysdiadokinesia (impaired alternate </li></ul><ul><li>movement) </li></ul><ul><li>2- Loss of balance ataxic or broad base </li></ul><ul><li>gait & pt tends to fall towards the </li></ul><ul><li>affected side. </li></ul><ul><li>3- Scanning & explosive speech </li></ul><ul><li>4- Nystagmus </li></ul>
  18. 20. <ul><li>5- Hypotonia </li></ul><ul><li>6- Normal but pendular tendon reflexes </li></ul><ul><li>7- Head tilted to za side of lesion </li></ul><ul><li>8- Titubation. </li></ul>
  19. 21. <ul><li>The sensory system </li></ul><ul><li>-The sensory input reaches za nervous sys </li></ul><ul><li>from specialized receptors in za skin, </li></ul><ul><li>muscles and joints & through za autonomic nervous syst from za internal organs and viscera. </li></ul><ul><li>- The sensory system comprises: </li></ul><ul><li>1- Receptors </li></ul><ul><li>2- Peripheral nerves </li></ul><ul><li>3- Spinothalamic tracts </li></ul><ul><li>4- Posterior column tracts </li></ul>
  20. 22. <ul><li>5- Medial lemniscus </li></ul><ul><li>6- Main sensory nucleus of za thalamus </li></ul><ul><li>7- Sensory cortex in za pre central gyrus </li></ul><ul><li>- Superficial (exteroceptive ) sensations </li></ul><ul><li>include pain, temp & touch </li></ul><ul><li>- Deep (proprioceptive ) sensations include </li></ul><ul><li>deep pain, pressure pain, position and </li></ul><ul><li>vibration sense. </li></ul><ul><li>- Interoceptive sensations arise from the </li></ul><ul><li>internal organs & viscera. </li></ul><ul><li>* All sensory impulses arise in za sensory </li></ul><ul><li>receptors & pass along za 1 st order </li></ul>
  21. 23. <ul><li>neurone to za spinal cord. These neurone </li></ul><ul><li>have their cell bodies in za dorsal root </li></ul><ul><li>ganglia. </li></ul><ul><li>1- Fibres sub serving superficial sensation </li></ul><ul><li>synapse wz za 2 nd order neurone in the </li></ul><ul><li>post. horn of za spinal cord, most of </li></ul><ul><li>which cross to za opposite site to </li></ul><ul><li>ascend in za lateral S/T tract in za dors </li></ul><ul><li>lateral column to za sensory nucleus of </li></ul><ul><li>the thalamus, thence za 3 rd order neuro relays to za sensory cortex. Some ascend in za ipsi lateral S/T tract. </li></ul>
  22. 24. <ul><li>2-Fibres sub serving proprioception ascend </li></ul><ul><li>in za ipsi lateral post. column to synaps </li></ul><ul><li>with za Gracil & Cuneate nuclei in the </li></ul><ul><li>lower part of za medulla, thence za 2 nd </li></ul><ul><li>order neurone cross za mid line and ascend in za contra lateral medial </li></ul><ul><li>lemniscus to za main sensory nucleus of </li></ul><ul><li>the thalamus from which the 3 rd order </li></ul><ul><li>neurone relays in sensory cortex. </li></ul><ul><li>3- Some afferent fibres sub serve spinal </li></ul><ul><li>reflexes </li></ul><ul><li>4- Some fibres arising in za muscle receptors synapse in za post. horn </li></ul>
  23. 27. <ul><li>cells & ascend in za ant. & post. spino - </li></ul><ul><li>cerebellar tracts to za cerebellum </li></ul><ul><li>sub serving proprioception. </li></ul><ul><li>5- Collateral branches from S/T tracts and </li></ul><ul><li>from special sensory pathways to the </li></ul><ul><li>reticular formation of za brain stem </li></ul><ul><li>are important for arousal & maintainanc </li></ul><ul><li>of consciousness. </li></ul><ul><li>6- Non dominent parietal cortex is concerned wz asteriognosis, two point discrimnation and spatial orientation of za body. </li></ul>
  24. 28. <ul><li>7- The dominant parietal cortex is </li></ul><ul><li>concerned wz reception of speech </li></ul><ul><li>* The body is represented upside down in </li></ul><ul><li>motor cortex. </li></ul><ul><li>* Disorders of sensory syst cause pain, </li></ul><ul><li>paraethesiae, anaethesia, analgesia and </li></ul><ul><li>loss of sensory discrimination. </li></ul>
  25. 29. <ul><li>Signs of sensory dysfunction </li></ul><ul><li>1- Peripheral nerve lesion loss of all </li></ul><ul><li>sensations & spinal reflexes sub served </li></ul><ul><li>by za nerve. </li></ul><ul><li>2- Post. nerve roots Dermatomal loss </li></ul><ul><li>of all sensations & reflexes sub served </li></ul><ul><li>by za nerve root (+ root pain) </li></ul><ul><li>3- Spinothalamic tracts Contra lateral </li></ul><ul><li>loss of pain & temp below za lesion </li></ul><ul><li>4- Post. Columns Ipsi lateral loss of </li></ul><ul><li>vibration & position sense wz sensory </li></ul><ul><li>ataxia & +ve Romberg sign. </li></ul>
  26. 30. <ul><li>5- Brain stem loss of all contra lateral </li></ul><ul><li>sensations. With mid brain lesions the </li></ul><ul><li>face is also involved. Pontine & medulla </li></ul><ul><li>lesions cause ipsi lateral sensory loss. </li></ul><ul><li>6- Thalamic lesions Spontaneous </li></ul><ul><li>unpleasant pain & contra lat loss of all </li></ul><ul><li>sensations. Pain threshold is increased </li></ul><ul><li>7- Internal capsule Contra lat loss of all </li></ul><ul><li>sensations </li></ul><ul><li>8- Sensory cortex Increased threshold </li></ul><ul><li>of sensations, astereognosis, sensory </li></ul><ul><li>inattention (agnosia) & receptive dysphasia </li></ul>
  27. 33. <ul><li>Reflex activities </li></ul><ul><li>Reflex act represents za simplest </li></ul><ul><li>integrated activity of nervous system. </li></ul><ul><li>1- Stretch or tendon reflexes: they are </li></ul><ul><li>mono synaptic postural reflexes e.g. </li></ul><ul><li>knee, ankle, jaw & corneal reflexes. </li></ul><ul><li>2- Superficial reflexes: they are poly </li></ul><ul><li>synaptic protective reflexes e.g. abdom </li></ul><ul><li>cremasteric and planter reflexes. </li></ul>
  28. 34. <ul><li>Control of micturition </li></ul><ul><li>Micturition is controlled by: </li></ul><ul><li>1- Higher centres for voluntary control of </li></ul><ul><li>mict. </li></ul><ul><li>2- Parasympath (S2,3,4) causes contractio </li></ul><ul><li>of detrusal muscles & relaxation of </li></ul><ul><li>internal sphincter. </li></ul><ul><li>3- Sympath (T12 &L1,2 ) causes relaxatio </li></ul><ul><li>of detrusal muscles & contraction of </li></ul><ul><li>internal sphincter, </li></ul><ul><li>4- Pudendal nerve (S1,2,3) controls </li></ul><ul><li>external sphincter. </li></ul>
  29. 35. <ul><li>Bladder dysfunction </li></ul><ul><li>1- Cortical lesions: </li></ul><ul><li>- Post. Central lesions loss of </li></ul><ul><li>awareness of bladder fullness & incont </li></ul><ul><li>- Pre central lesions difficulty in initiation </li></ul><ul><li>of mict & retention of urine. </li></ul><ul><li>- frontal lesions inappropriate mict </li></ul><ul><li>due to social dis inhibition. </li></ul><ul><li>2- Spinal cord lesions: </li></ul><ul><li>- Above mict centre (pyramidal) </li></ul><ul><li>urgency & incontinence (hypertonic) </li></ul><ul><li>3- LMN lesions Atonic bladder retention </li></ul><ul><li>with overflow & later autonomic bladder. </li></ul>

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