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CNS PHYSIOLOGY

CNS PHYSIOLOGY. Why studying neurosciences?. Neurological symptoms account for high % of consultation in general practice. Accounts for 20% of acute admissions to hospitals, trauma, critical illness, anesthesia & surgery. Dx. is primarily clinical, based on history and physical exam.

christopherhughes
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CNS PHYSIOLOGY

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  1. CNS PHYSIOLOGY

  2. Why studying neurosciences? • Neurological symptoms account for high % of consultation in general practice. • Accounts for 20% of acute admissions to hospitals, trauma, critical illness, anesthesia & surgery. • Dx. is primarily clinical, based on history and physical exam. • Any investigations can only supplement but never replace the process of clinical assessment.

  3. The brain • The brain weighs 2 % of body weight. • The brain utilizes 20% of total energy expenditure. • It contains about 100 billion neurons. • Each neuron has about 10000 (200 – 200000) input. • Single output (axon) • brain is one of the most complex systems

  4. The brain Dinosaur 1600 KgBW, 0.07 Kg brain weight 0.004% Human 70KgBW, 1.4Kg Brain weight 2%

  5. The Symptomatology of a nervous disease 1. Negative symptoms; • Lesion to a center in the CNS may diminish or abolish the function of that center. 2. Positive symptoms; Produced by; • Centers are liberated from the control of a damaged center. • or their activities intensified to compensate for the missing function • or because of unbalanced activities.

  6. The Symptomatology of a nervous disease • Negative symptoms; paralysis blindness, deafness…. 2. Positive symptoms; epileptic focus, spasticity, Babinski sign, rigidity, parasthesia and ataxia.

  7. Babiniski Reflex

  8. BABINSKI http://medicine.ucsd.edu/clinicalmed/neuro3.htm http://www.gen.umn.edu/courses/1135/lab/reflexlab/corticospinaltract.html

  9. Dx. Of Neurological Diseases • Anatomical factors; It determines signs, symptoms and localization of the lesion. • Non-anatomical factors; It helps to determine the etiology of the disease.

  10. Non – Anatomical factors include; 1. The speed of development of signs and symptoms (Acute, subacute or chronic) 2. The course of the signs and symptoms; (progressive, fluctuating) 3. The outcome.

  11. The disturbance of function involves first; • The most recently acquired task. e.g. native language versus acquired language. • The most complex features. e.g. writing, speaking, playing musical instruments versus grasp reflex.

  12. Signals within the CNS Action potential Electrotonic potential

  13. http://fulton.edzone.net/cites/winkler-science/team1/chap8.htmlhttp://fulton.edzone.net/cites/winkler-science/team1/chap8.html http://www.neuro.wustl.edu/neuromuscular/pathol/nervenl.htm

  14. Compound Action Potential, CAP Stimulus Strength http://www.unmc.edu/Physiology/Mann/mann12.html

  15. CAP: Conduction Velocity • Conduction velocities: ~0.2m/s to >100m/s • Give indication on health of nerve fiber • Demyelination decreases velocity Haines, Fundamental Neuroscience, Elsevier, Fig 3-11

  16. Electroneurography(ENG( Definition: • ENG is the measurement of the speed of conduction of impulses down a peripheral nerve. also known as • nerve conduction studies (NCS( • nerve conduction velocity (NCV(

  17. EMG machine

  18. Compound Motor Action Potential:CMAP Motor nerve is stimulated and muscle response is calculated. Latency includes synaptic transmission etc. By subtracting the two latencies, the conduction velocity can be calculated. http://www.mmi.mcgill.ca/Dev/chalk/lect72p2.htm

  19. SNAP: Sensory Nerve Action Potential Figure 2 Median orthodromic sensory study. The index finger digital nerves are stimulated via ring electrodes and the response recorded over the median nerve at the wrist. Mallik, A et al. J Neurol Neurosurg Psychiatry 2005;76:ii23-31ii

  20. NCV disorders • Demyelination is indicated if conduction velocities have fallen below 50 % of normal. • Even significant loss of axons commonly reduces conduction velocities by only about 30% based on a loss of the fastest conducting fibers.

  21. How do I approach a patient with muscle weakness? • Muscle • Nerve • Root • Spinal Cord • Brainstem • Brain

  22. What is your Dx.?

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