PHYSIOLOGY OF

CENTRAL NERVOUS SYSSTEM

AND

HIGHER NERVOUS

FUNCTIONS

BRAIN- FACTS AND FIGURES

Most of the neurons in the brain are upon birth, since then we lose them

Apoptosis – programmed cell deth – enables functional specialization

Most of the neural connections are formed between 2nd and10th year of life,

Then we lose them (synaptolysis) on behalf of functional specialization

Weight approximately 1500 gramms = 2% of body weight

Brain metabolism comprises 15% of total BM,

Brain consumes 20% of total body oxygen consumption

Brain houses 100 billions of neurons that is 10% of all cells

Within the CNS

90% of CNS cells is glia – supporting cells

Neurones are larger, therefore make 50% of CNS volume

Most of the neurons are interneurones - 90% (integrative function)

Parallels:- Electric currentaction potentials

- Cable networkneuronal network

weight: 1,3 kg

volume 1,3 l

Number of neurons:

10 až 100 billion

Daily losts:

10000 neurons

(age ethanol)

In our 20-ies our brain

Own 160 000 km of

Myelinated axons

One having connections to

5000 other neurons

BRAINHUMAN THINKING HARDWARE

SIGNIFICANT

STIMULUSSELFREGULATORY PROCESSES

LIFE EXPERIENCES – ADEQUATE REACTIONS

a) Principle of hierarchy

b) Principle of excercise/usage

c) Principle of interconnections (feedback – feedforward)

CENTRAL NERVOUS SYSTEM

• Sensory system (senses, afferent fibres)

• Motor (effector) system (muscles and endocrine glands)

• Integration centre (brain)

• Feedback machanisms at different levels of the central nervous system check the outputs:

• Brain stem (breathing, blood pressure)

• Midbrain structures (eating and drinking, sleep and wakefulness)

• Brain cortex (conscious reactions, memory – the highest level of improvement on the base of the experience)

Michelangelo

Creation Of Adam

...larger image encompassing God is compatible with a brain. Michelangelo portrays that what

God is giving to Adam is the intellect, and thus man is able to “plan the best and highest”and

to “try all things received”.

(An Interpretation Of Michelangelo’s Creation Of Adam Based On Neuroanatomy by

Frank Lynn Meshberger, MD)

Sistine Chapelis the best-known chapel in the

Apostolic Palace, the official

residence of the Pope with

Michelangelo´s frescoes

DEVELOPMENTY

OF BRAIN STRUCTURES

NEUROGENESIS

The presence of extra material enormously increases the options.But only by removing the extra maerial the unique art is created.

Genes –environment

Production of cells that will become nervous tissue

ProliferationCell reproduction (mitosis)

MigrationLocation of cells in appropriate brain areas

DifferentiationDevelopment of neurons into particular type

SynaptogenesisFormation of appropriate synaptic connections

Selective cell deathElimination of mislocated cells and cells that failed

to form the proper synaptic connectionsFunctional validation

Strengthening of synapses in use, weakening of unused synapses

DEVELOPMENT OF HUMAN BRAIN

VÝVIN CNS

Maslow, A.H.(1943). A theory of human motivation. Psychological Review 50 (4)

370–96. Retrieved from http://psychclassics.yorku.ca/Maslow/motivation.htm

Maslow's hierarchy of needs

SPIRITUALITY – the top of the pyramid

COGNITIVE BRAIN

(brain of Homo Sapiens)

EMOTIONAL BRAIN

(brain of a horse)

REFLEXIVE BRAIN

(brain of a reptile)

CENTRAL NERVOUS HIERARCHY

OUTLINE

PROLIFERATION – governed by genes

- 3rd week i.u. 250 000 / minute- finished in the 5th month i.u. 1010-1011 neurons

1) Some neurons migrate by following the long

fibers of cells called radial glia. These

fibers extend from the inner layers to the

outer layers of the brain. Neurons glide

along the fibers until they reach their

destination.

2) Neurons also travel by using chemical

signals. Scientists have found special

molecules on the surface of neurons --

adhesion molecules -- that bind with similar

molecules on nearby glial cells or nerve

axons. These chemical signals guide the

neuron to its final location.

MIGRATION OF NEURONS

RADIAL GLIA

VENTRICULAR

ZONE

INTERMEDIATE

ZONE

MARGINAL

ZONE

ventral dorsal

MIGRATION• Not all neurons are successful in their

journey. Scientists think that not allreach their destination. Many either never differentiate, or die and disappear.

• Some neurons survive the trip, but end up where they shouldn’t be. Mutations in the genes that control migration create areas of misplaced or oddly formed neurons that can cause disorders such as childhood epilepsy or intellectual disability. Some researchers suspect that schizophrenia and the learning disorder dyslexia are partly the result of misguided neurons.

• Neuronal positioning is a fundamental process during brain development. Abnormalities in this process cause several types of brain malformations https://www.researchgate.net/publication/283980795

MIGRATION OF NEURONS– GROWTH CONE

Lamellipodia FilopodiaGrowth cone is specialized to identifythe proper pathway for axonal growth

FasciculationChemoaffinity hypothesis (Sperry, 1981)

CAMs = cell-adhesion

molecules

molecules of lamininmolecules of integrins– support for growing

axons

DIFFERENTIATION

Cell differentiation – neuroblasts arrive at

its final place (guided by genes)

- electrical activity of the

neurons changes structure of the brain

(guided by the environment)

APOPTOSIS vs NECROSISApoptosis is a normal, natural

process which is necessary for

the body as it maintains a

balance in the number of cells in

the body. So if apoptosis does

not take place as it should in the

brain, there will be signs of

dysfunction. Necrosis is a

pathological process which is

detrimental to the body. It occurs

when the cells are exposed to

toxins, or on exposure to

extreme conditions These lead to

damage to the wall or membrane

of the cell. The imbalance in the

internal environment of the cell

leads to inflammation and tissue

damage which leads to

accumulation of cellular debris.

SYNAPTOGENESIS

http://www.pnas.org/content/110/Supplement_2/10395/F1.expansion.html

Electric activity influences brain development – „USED IS DEVELOPED“

2 – 10. POSTNATAL YEARS – development of connections

– SYNAPTIC CAPACITY - up to 20 000 synapses per neuron

- SYNAPTIC PLASTICITY

SYNAPTIC PLASTICITY

Lamprecht & LeDoux

Nature Reviews Neuroscience 5, 45-54, 2004

VGCC – voltage gated calcium channels

Neurolignín hrá významnú

úlohu pri vzniku a

vyformovaní špecifického

synaptického spojenia

MODEL SYNAPTOGENÉZY

VEDENIE AXÓNU ADHÉZIA BUNIEK TVORBA SYNAPSY

Axón pontínnej neurolignín

bunky sa blíži granulárnej bunky

ku granulárnej b. a neurexín axónu vytvoria synapsu

http://images.google.com/imgres?imgurl=http://www.cumc.columbia.edu/news/in-vivo/Vol1_Iss1_jan14_02/pictures/model-for-

synaptogenesis.jpg&imgrefurl

DEVELOPMENT OF COGNITIVE FUNCTIONS

NEURONAL AND SYNAPTIC DEATH

Neurones compete with each other for trophic factors (NGF – Nerve Growth Factor, Levi Montalcini, 1940) which

produce target neurons – selective nerve death

SYNAPTIC CAPACITY– NUMBER OF

SYNAPSES ON ONE NEURON – reduction to50% in adulthood

SYNAPTIC ELIMINATION depends on the

activity of neurons during development

„Use it or lose it” –Unused neurons areeliminated after critical

periodduring life span (in humans after the age of 10)situation in visual cortex)

a) Normal healthy cat b) After molecular deprivation

1 and 5 monocular activation, 2,3,4 binocular activation with eye preference in 2 a 4

SYNAPTIC COMPETITION

NEUROGENESIS IN ADULTHOOD

Neurogenesis in adulthood. Comparison between human brain and rat brain.

Neurogenesis was confirmed in two areas of the brain: subventricular zone (SVZ) of lateral

ventricles (where neurones of bulbus olfactorius develope) and gyrus dentatus hippocampi

(area associated with learning and memory). In SVZ progenitor cells migrate into olfactory bulb

where differentiation to neurons occurs.