The document summarizes key aspects of neurophysiology, including the motor system, corticospinal system, lower motor neurons, extrapyramidal system, cerebellum, sensory system, reflex activities, and control of micturition. It describes the components and functions of these systems, as well as signs associated with lesions in different parts of the nervous system.

1. Neurophysiology By: Dr. Osman Sadig

2. Motor system Consists of: 1- Pyramidal OR Corticospinal system (UMN) 2- Lower motor neurone (LMN) 3- Extra pyramidal system 4- Cerebellum .

3. Corticospinal (pyramidal) system---(UMN) Composed of: 1- Motor cortex 2- Corticospinal tracts . 1- Motor cortex: - Occupies za pre central gyrus - The body is represented upside down, the area represented depends on the functional importance - Controls za opposite side of za body

4. 2- Pyramidal tracts (C/S) - It passes downwards from motor cortex as za corona radiata to za internal capsul 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

7. and terminate in za LMN. The undecussated C/S fibres descend in the anterior column as direct C/S tracts decussate at segmental level & terminate in za LMN. - At different levels of CNS, The C/S tracts give fibres to za brain stem nuclei and za LMN in za anterior horn of the spinal cord.

8. Function of C/S: - Motor cortex is responsible for programming & initiation of skilled motor acts, specially fine distal movements, and is influenced by connection from other parts of motor system that controls muscle tone & body posture. - Accurately targeted & coordinated actions require intact functioning cerebellum.

9. - Lesions of C/S system above za level of decussation cause contra lateral signs, while below that cause ipsi lateral signs. Signs of UMNL: 1- Muscle weakness . 2- Hypertonia resulting in spasticity. 3- Hyper- reflexia (increased tendon reflex) +/- clonus. 4- Extensor planter reflex 5-Absent abdominal & cremasteric reflexes 6- In long standing cases there is wasting .

10. Localization of level of UMNL 1- Cortical lesions localized loss of fn e.g. monoplegia, aphasia, apraxia 2- Internal capsule hemiplegia 3- Brain stem lesions crossed hemiplegia 4- Spinal cord lesions Ipsi lateral weakness. The nature of za lesion in the nervous system 1- Trauma & vascular lesions= acute onset 2- Infections= sub acute onset. 3- Tumours & degenerative lesions= gradu onset & progressive course.

11. 4- Demyelinating lesions= remission and relapses. 5- Epilepsy, migraine & TIA= paroxysmal. NB: destructive lesion weakness irritative lesions seizures

12. Lower motor neurones (LMN) LMN consist of: 1- Anterior horn cells in za spinal cord and the homologus motor nuclei in za brain stem 2 Afferent nerve which originate in za ant. horn cells and pass via za ant. spinal nerve roots in za peripheral nerves to the muscles or glands.

13. * Impulses from supra spinal centres can only reach za muscles through intact LMN. * Muscle movement depends on the integrity of za LMN which also connect the skeletal muscles wz supra spinal centres. Signs of LMN lesions 1- Weakness or paralysis of muscles suppl by za affected LMN 2- Hypotonia

14. 3- Absent tendon reflexes 4- Fasiculation 5- Absent or flexor planter response 6- Muscle wasting.

15. Extra pyramidal system It is a complex systems of neurones and fibres wz reciprocal connections with cerebral cortex, thalamus, cerebellum, brain stem nuclei & anterior horn cells. It consist of: 1-Basal ganglia (caudate nucleus, putamen and globus pallidum) 2- Sub thalamic nuclei 3- Substantia nigra 4- Red nucleus. 5- Reticular formation of za brain stem.

16. The extra pyramidal system influence on the spinal cord indirectly through pathways arising in za brain stem. Functions of extra pyram syst 1- Adjustment of fine & fast voluntary movement generated in za C/S system 2- Involuntary adjustment of posture and muscle tone Signs of extra pyram disorders 1- Increased muscle tone causing rigidity ( cog wheel & lead pipe). Hypotonia in

17. chorea. 2- Akinetic or rest tremors. 3- Hypokinesia & difficulty wz fine tasks. 4- Abnormal posture & poverty of movements, shuffling gait. 5- Chorea 6- Athetosis 7- Dystonia 8- Hemibalismus. 9-Postural instability falls. 10- No muscle weakness, normal planter response, normal or increased tendon reflexes,

18. The cerebellum -The cerebellum modulates muscle tone , controls co ordination of voluntary movements & is important for maintainanc of posture & balance through its connections with the thalamus, basal ganglia, cerebral cortex, vestibular syst and za spinal cord - It is closely connected wz za vestibular syst & recieves proprioceptive inputs from the spinal cord - Cerebellar lesions & its connections cause ipsi lateral signs .

19. Signs of cerebellar disorders 1- Ipsi lateral incordination of limbs - Dysmetria (past pointing) - Intention tremors - Dyssenergia (decomposition of mov - Dysdiadokinesia (impaired alternate movement) 2- Loss of balance ataxic or broad base gait & pt tends to fall towards the affected side. 3- Scanning & explosive speech 4- Nystagmus

20. 5- Hypotonia 6- Normal but pendular tendon reflexes 7- Head tilted to za side of lesion 8- Titubation.

21. The sensory system -The sensory input reaches za nervous sys from specialized receptors in za skin, muscles and joints & through za autonomic nervous syst from za internal organs and viscera. - The sensory system comprises: 1- Receptors 2- Peripheral nerves 3- Spinothalamic tracts 4- Posterior column tracts

22. 5- Medial lemniscus 6- Main sensory nucleus of za thalamus 7- Sensory cortex in za pre central gyrus - Superficial (exteroceptive ) sensations include pain, temp & touch - Deep (proprioceptive ) sensations include deep pain, pressure pain, position and vibration sense. - Interoceptive sensations arise from the internal organs & viscera. * All sensory impulses arise in za sensory receptors & pass along za 1 st order

23. neurone to za spinal cord. These neurone have their cell bodies in za dorsal root ganglia. 1- Fibres sub serving superficial sensation synapse wz za 2 nd order neurone in the post. horn of za spinal cord, most of which cross to za opposite site to ascend in za lateral S/T tract in za dors lateral column to za sensory nucleus of the thalamus, thence za 3 rd order neuro relays to za sensory cortex. Some ascend in za ipsi lateral S/T tract.

24. 2-Fibres sub serving proprioception ascend in za ipsi lateral post. column to synaps with za Gracil & Cuneate nuclei in the lower part of za medulla, thence za 2 nd order neurone cross za mid line and ascend in za contra lateral medial lemniscus to za main sensory nucleus of the thalamus from which the 3 rd order neurone relays in sensory cortex. 3- Some afferent fibres sub serve spinal reflexes 4- Some fibres arising in za muscle receptors synapse in za post. horn

27. cells & ascend in za ant. & post. spino - cerebellar tracts to za cerebellum sub serving proprioception. 5- Collateral branches from S/T tracts and from special sensory pathways to the reticular formation of za brain stem are important for arousal & maintainanc of consciousness. 6- Non dominent parietal cortex is concerned wz asteriognosis, two point discrimnation and spatial orientation of za body.

28. 7- The dominant parietal cortex is concerned wz reception of speech * The body is represented upside down in motor cortex. * Disorders of sensory syst cause pain, paraethesiae, anaethesia, analgesia and loss of sensory discrimination.

29. Signs of sensory dysfunction 1- Peripheral nerve lesion loss of all sensations & spinal reflexes sub served by za nerve. 2- Post. nerve roots Dermatomal loss of all sensations & reflexes sub served by za nerve root (+ root pain) 3- Spinothalamic tracts Contra lateral loss of pain & temp below za lesion 4- Post. Columns Ipsi lateral loss of vibration & position sense wz sensory ataxia & +ve Romberg sign.

30. 5- Brain stem loss of all contra lateral sensations. With mid brain lesions the face is also involved. Pontine & medulla lesions cause ipsi lateral sensory loss. 6- Thalamic lesions Spontaneous unpleasant pain & contra lat loss of all sensations. Pain threshold is increased 7- Internal capsule Contra lat loss of all sensations 8- Sensory cortex Increased threshold of sensations, astereognosis, sensory inattention (agnosia) & receptive dysphasia

33. Reflex activities Reflex act represents za simplest integrated activity of nervous system. 1- Stretch or tendon reflexes: they are mono synaptic postural reflexes e.g. knee, ankle, jaw & corneal reflexes. 2- Superficial reflexes: they are poly synaptic protective reflexes e.g. abdom cremasteric and planter reflexes.

34. Control of micturition Micturition is controlled by: 1- Higher centres for voluntary control of mict. 2- Parasympath (S2,3,4) causes contractio of detrusal muscles & relaxation of internal sphincter. 3- Sympath (T12 &L1,2 ) causes relaxatio of detrusal muscles & contraction of internal sphincter, 4- Pudendal nerve (S1,2,3) controls external sphincter.

35. Bladder dysfunction 1- Cortical lesions: - Post. Central lesions loss of awareness of bladder fullness & incont - Pre central lesions difficulty in initiation of mict & retention of urine. - frontal lesions inappropriate mict due to social dis inhibition. 2- Spinal cord lesions: - Above mict centre (pyramidal) urgency & incontinence (hypertonic) 3- LMN lesions Atonic bladder retention with overflow & later autonomic bladder.