Physiology of Cortex
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The document summarizes key information about the structure and function of the human cerebral cortex. It discusses the layers of the cortex, methods used to study cortical functions including stimulation and electrophysiological procedures like EEG. Specific topics covered include sensory and motor areas of the cortex, sleep centers and stages of sleep, and the influence of the reticular formation on cortical activity.
Physiology of Cortex
- 2. Total surface square Thick- ness Total volume Neurons number Glyal cells 2200 сm2 1,3 to 4,5 mm 600сm3 109 - 1010 Total number unknown
- 4. 6 LAYERS OF CORTEX I - Molecular(плексиформный) II – External stellatum III – External pyramidal IV - Internal stellatum V –Internal pyramidal VI – Layer of physiformic cells
- 5. Sponsored Medical Lecture Notes – All Subjects USMLE Exam (America) – Practice
- 6. METHODS OF CEREBRUM FUNCTIONS STUDIES A. Stimulation B. Exstirpation C. Electrophysiological prosedures D. Method of conditioned reflexes E. Method of clinical observation
- 7. Electrophysiological methods Registration of electrical activity of a group of neurons (macroelectrodes) Registration of electrical activity of single neurons (microelectrodes) EEG, electrocorticograme Caused potentials (stimulated by light or sound cortex response)
- 8. Registration of single neurons activity
- 9. Registration of caused potentials
- 11. Electroencephalography Method of registration ofvelectrical potential from the skin of the head Hanse Berger proposed this in 1929 - 1938.
- 12. EEG origin Sum of EPSPs & IPSPs Duration of EPSPs & IPSPs is from 30 tо 150 msec Amplitude depends on the frequency & synchronisation of EPSPs & IPSPs Frequency is formed by rhythmic activity of cortex neurons. Rhythmicity is due to the influence of RF of midbrain & thalamic nuclei.
- 13. EEG rhythms Аlfa – α-rhythm - 8-13 Hz - 50-100 mcV Rhythm of synchronization. Registered at the state of peaceful awakefulness at closed eyes mainly in occipital & parieto-temporal zonez. Betha – β- rhythm - 14-30 Hz - 10-30 mcV. Rhythm of desynchronization. Registered at the state of active rest with opened eyes
- 14. I - α - waves II - β - waves III - θ (theta) - waves IV - Δ (delta) - waves V - epileptic dischanges
- 15. EEG rhythms Тhеtа- θ-rhythm - 4-7 Hz - 100-150mcV Rhythm of synchronization. Registered at the state of peaceful awakefulness at closed eyes mainly in children, during sleep in adults, may be a sign of brain hypoxia. Deltа – Δ- rhythm - 0,5-4,5 Hz 150-200 mcV Rhythm of synchronization. Registered at the state of deep sleep, narcosis, at pathological states.
- 16. Synchronization - occurs at anonimous impulsation to the cortex, at closed eyes. Desynchronization – occurs at different multiply active impulsation to the cortex, at opened eyes
- 18. CLINICAL IMPORTANCE OF EEG Epilepsy diagnostics (caused potentials are preferable nowadays). Tumors localization. Cranium traumas & chronic meningitis & encephalitis Evaluation of narcosis depth (Δ rhythm at deep narcosis). To determine the state of death in some cases ( «flat» EEG).
- 19. Modern view on function localization in the cortex.
- 21. MOTOR AREA Heterotypical agranular zones Моtоr zone - precentral gyrus (pyramidal tract, voluntarily movements) Homotypical Associative areas – parietal & temporal
- 23. Сенсорно- специфические области Гетеротипические гранулярные зоны коры Зрительные – затылочная область, шпорная борозда Слуховые – височная область, извилина Гешле Соматосенсорная – постцентральная извилина - кожная чувствительность, проприоцептивная, висцеральная, чувство равновесия, вкус
- 24. Sensory specific zones of cortex AII AI nucleus Nucleus – monomodal neurons A I & A II– associative zones – polymodal neurons
- 28. Sensory zones are topically organized – receptive fields are represented in proportion to the number of afferent neurons, which form these fields, not to the square taken by the receptive field.
- 33. Sleep centers. Suprachyasmatic nuclei of hypothalamus Nuclei rhaffe in brain stem (Hess center) Serotonin Slow sleep Inhibition of pain In spinal cord
- 34. Stages of sleep Stage 0 (awake) – from lying down to falling asleep, 1-2% of sleep time, α – waves at closed eyes, β – waves at opened Stage 1 (dozing) - θ (theta) – waves on to[p of α, eye movements reduced, neck muscles relaxed, 3-6%
- 36. Stages of sleep Stage 2 (unequivocal sleep) - θ (theta) – waves with spindles, K complexes can be evoked on sensory stimulation, little eye movements , easily arrosable, 40-50% of sleep time
- 37. Stages of sleep Stage 3 (deep sleep transition)- θ (theta) – waves, Δ (delta) – waves and spindle activity, K complexes can be evoked on strong stimulation, few eye movements , not easily arrousable, 5-8% of sleep time
- 39. Stages of sleep Stage 4 (cerebral sleep)- Δ (delta) – waves predominate, K complexes can’t be evoked, fixed eyes , difficult to arrouse, 10-20% of sleep time. Night terror may occur at this time
- 40. During stages 2,3,4 heart rate and respiration are steady and muscles are relaxed Stages 3 and 4 are called slow wave sleep (SWS) REM-sleep (paradoxical)- EEG waves of all frequency, K complexes can’t be evoked, dreams and nightmares, HR and BP fluctuate, respiration is irregular, muscles are relaxed, but irregular body movements can occur occasionally Normally stages 0 to 4 and REM occur in succession over a period of 80-100 min, they are repeated cyclically