physiology 2-cortex
TRANSCRIPT
Total surfacesquare
Thick-ness
Total volume
Neurons number
Glyal cells
2200 сm2 1,3 to 4,5 mm
600сm3 109 - 1010 Total number unknown
6 LAYERS OF CORTEX
I - Molecular(плексиформный) II – External stellatum III – External pyramidal IV - Internal stellatum V –Internal pyramidal VI – Layer of physiformic cells
METHODS OF CEREBRUM FUNCTIONS STUDIES
A. StimulationB. ExstirpationC. Electrophysiological proseduresD. Method of conditioned reflexesE. Method of clinical observation
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)
Registration of single neurons activity
Registration of caused potentials
Electroencephalography
Electroencephalography Method of registration ofvelectrical
potential from the skin of the head Hanse Berger proposed this in 1929 -
1938.
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.
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
I - α - waves
II - β - waves
III - θ (theta) - waves
IV - Δ (delta) - waves
V - epileptic dischanges
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.
Synchronization - occurs at anonimous impulsation to the cortex, at closed eyes.
Desynchronization – occurs at different multiply active impulsation to the cortex, at opened eyes
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).
Modern view on function localization in the cortex.
MOTOR AREA Heterotypical agranular zonesМоtоr zone - precentral gyrus(pyramidal tract, voluntarily movements) HomotypicalAssociative areas – parietal & temporal
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
Sensory specific zones of cortex
AII AI
nucleus
Nucleus – monomodal neurons
A I & A II– associative zones – polymodal neurons
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.
INFLUENCE OF RETICULAR FORMATION ON CEREBRUM
Sleep centers.Suprachyasmatic nuclei of hypothalamus
Nuclei rhaffe in brain stem (Hess center)
Serotonin
Slow sleep Inhibition of painIn spinal cord
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%
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
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
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
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