Physiology 2-Cortex

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