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

10. Electroencephalography

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.

29. INFLUENCE OF
RETICULAR
FORMATION ON
CEREBRUM

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