The excitation and The excitation and inhibition in the central inhibition in the central

nervous systemnervous system

The functional states of neuronThe functional states of neuron1. 1. The state of restThe state of rest excitatory excitatory = = inhibitioninhibition influenceinfluence influencesinfluences

2. 2. The state of excitationof excitationexcitatory inhibition influence influences

3. 3. The state of inhibition of inhibitionexcitatory inhibition influence influences

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The inhibition in the central The inhibition in the central nervous systemnervous system

The inhibition The inhibition – – independent neural process that independent neural process that

is initiated by excitation andis initiated by excitation and

leads to inhibitionleads to inhibition

other of excitationother of excitation

Central inhibition by ICentral inhibition by I..MM.. Sechenov Sechenov

Classification of inhibitionClassification of inhibition

By the localizationBy the localization - presynaptic- presynaptic

- postsynaptic- postsynaptic

By the mechanism the mechanism

- depolar- depolarizizativeative

- hyperpolarizative- hyperpolarizative

By thethe types of neural circuitstypes of neural circuits

- Direct - lateral- Direct - lateral

- Reverse - reciprocal- Reverse - reciprocal

Mechanism of presynaptic inhibitionMechanism of presynaptic inhibitionDistribution of AP to the terminal inhibitory Distribution of AP to the terminal inhibitory

neuron, release inhibitory mediatorneuron, release inhibitory mediator

depolarization of depolarization of presynaptic membrane presynaptic membrane of exciting neuronof exciting neuron

Blockade of Ca-Blockade of Ca-channels of channels of presynaptic presynaptic membrane of exciting membrane of exciting neuronneuron

Reduced input Ca into the terminal of exciting neuronReduced input Ca into the terminal of exciting neuron

Reduced secretion of mediatorReduced secretion of mediator

Reduced Reduced EPSPEPSP

I n h I b I t o r y

The mechanism of postsynaptic The mechanism of postsynaptic inhibitioninhibition

Distribution of AP to the terminal inhibitory neuron, Distribution of AP to the terminal inhibitory neuron, release inhibitory mediator, the mediator interacts release inhibitory mediator, the mediator interacts

with receptors on the postsynaptic membranewith receptors on the postsynaptic membrane

Opening of Opening of ССll-- cchannelshannelsOpening of KOpening of K++ channels channels

Hyperpolarization of the postsynaptic membraneHyperpolarization of the postsynaptic membrane

Increase the threshold depolarizationIncrease the threshold depolarization

Reduced excitabilityReduced excitability

I n h I b I t o r y

KK++ comes out of cells comes out of cells ClCl-- enters in the cell enters in the cell

Classification of reflexesClassification of reflexes By the biological significance:By the biological significance: Food StatokineticFood Statokinetic Protective estimatedProtective estimated Sexual homeostaticSexual homeostatic

By the center: the center: spinal Mesensephalicspinal Mesensephalic bulbar Corticalbulbar Cortical For receptor locations:For receptor locations: interoreceptiveinteroreceptive exteroreceptiveexteroreceptive proprioreceptiveproprioreceptive

Reflex - Reflex - stereotyped reaction to the action of stereotyped reaction to the action of external and internal stimuli, which carried external and internal stimuli, which carried with the central nervous systemwith the central nervous system

By the structure of the centerBy the structure of the center MonosynaptycMonosynaptyc PolysynaptycPolysynaptyc

By the nature of effector responses:By the nature of effector responses: MotorMotor VegetativeVegetative

By origin:By origin: UnconditionalUnconditional LegendLegend

Comparative characteristics of Comparative characteristics of conditioned and unconditioned conditioned and unconditioned

reflexesreflexes unconditioned conditionedunconditioned conditioned

acquired hereditaryacquired hereditary

generic individualgeneric individual

stable unstablestable unstable

turned on the effect of turned on the effect of any stimulusany stimulus

Reflex arc closes at Reflex arc closes atReflex arc closes at Reflex arc closes at lower parts of CNS at the level of the lower parts of CNS at the level of the cerebral cerebral cortexcortex

formed on the formed on the basisbasis unconditionalunconditional

Turned on Turned on the effecteffect of specific adequate stimulus

Reflex arc - Reflex arc - neural circuit that neural circuit that provides the reflexprovides the reflex

1 – the receptor1 – the receptor2 - the afferent 2 - the afferent pathpathwayway3 - the nerve 3 - the nerve center center 4 - the efferent 4 - the efferent pathway pathway 5 - the effector 5 - the effector 6 - the reverse 6 - the reverse afferentiationafferentiation

Peculiarities of excitation along a Peculiarities of excitation along a reflexive arcreflexive arc

The integrity of the reflex arc The integrity of the reflex arc Specificity Specificity Isolation of conductionIsolation of conduction Sidedness of conductionSidedness of conduction Synaptic delaySynaptic delay Synaptic potentialitySynaptic potentiality A reversible afferentiationA reversible afferentiation

Functions of individual Functions of individual components of the reflex arccomponents of the reflex arc

R E C E P R E C E P Т Т O R O R - - a specialized cell or cell a specialized cell or cell part, which distinguishes part, which distinguishes natural stimuli and transmit natural stimuli and transmit information about them to information about them to the CNSthe CNS

Receptor functions:Receptor functions:Perception of stimulusPerception of stimulusInitial filtering of informationInitial filtering of informationEncoding of informationEncoding of informationInformation transferInformation transfer

Classification of receptorsClassification of receptors By modality (feeling, formed in humans):By modality (feeling, formed in humans):VisualVisual Hearing HearingOlfactory Olfactory FlavorFlavorThermal Thermal PainPain

By factor that contributes to stimulation of By factor that contributes to stimulation of the receptors:the receptors:

MechanoreceptorsMechanoreceptors ChemoreceptorChemoreceptor

Thermoreceptors Thermoreceptors PhotoreceptorsPhotoreceptors By the nature of the interaction between By the nature of the interaction between

the receptor and the stimulus:the receptor and the stimulus:DistantDistant

ContactContact

By location:By location:ExteroreceptorsExteroreceptors

InteroreceptorsInteroreceptors

ProprioreceptorsProprioreceptors

By the ability to adapt:By the ability to adapt:TonicTonic

PhasePhase

By the mechanism of functioning:By the mechanism of functioning:Initially sensitiveInitially sensitive

Secondary sensitiveSecondary sensitive

The mechanism of excitation of initially The mechanism of excitation of initially sensitivesensitive receptorsreceptors

Effects of stimulusEffects of stimulus

Increased Increased permeability permeability of the of the membrane to membrane to sodium ionssodium ions

The emergence The emergence of the receptor of the receptor potentialpotential

The emergence The emergence of AP, its of AP, its distribution on distribution on the axon to the the axon to the nerve centernerve center

ReceptorReceptor

cellscells

The mechanism of excitation of The mechanism of excitation of secondary sensitive receptorssecondary sensitive receptors

Effects of stimulusEffects of stimulus Excretion a Excretion a

mediator from mediator from the receptor the receptor cellscells

The The emergence emergence of the of the receptor receptor potentialpotential

The emergence of AP, its The emergence of AP, its distribution on the axon to distribution on the axon to the nerve centerthe nerve center

Receptor Receptor

cellcell

The emergence The emergence of generating of generating potentialpotential

SensitiveSensitive

neuronneuron

Types of information that is encoded in the Types of information that is encoded in the receptorsreceptors

The quality of the stimulusThe quality of the stimulus Power stimulusPower stimulus The duration of the stimulusThe duration of the stimulus

Encoding – Encoding – the process of transformation the process of transformation of the receptor potential in a series of of the receptor potential in a series of AP (AP generation series)AP (AP generation series)

Nerve centerNerve center - A collection of nerve - A collection of nerve cells that organize a cells that organize a reflex or regulate reflex or regulate specific physiological specific physiological functionfunction

Properties of the nerve centersProperties of the nerve centers1. 1. TonusTonus

2. 2. SummationSummation

3. 3. Transformation of the rhythmTransformation of the rhythm

4. 4. AftereffectAftereffect

5. 5. FatiguabilityFatiguability

6. 6. High sensitivity to hypoxiaHigh sensitivity to hypoxia

SummationSummation

SpatialSpatial TTemporalemporal

The principles of interaction between nerve The principles of interaction between nerve centerscenters

The principle of localizationThe principle of localization The principle of plasticityThe principle of plasticity The principle of subordinationThe principle of subordination The principle of corticalizationThe principle of corticalization The principle of dominantThe principle of dominant The principle of coordinationThe principle of coordination

The principle of dominantThe principle of dominantDominantDominant – – is the dominant center of excitation is the dominant center of excitation

in CNS, modifying and subordinates in CNS, modifying and subordinates

a work of other centersa work of other centers

Meaning of dominant:Meaning of dominant:1.1. Ensure the formation of behavioral reactionsEnsure the formation of behavioral reactions

2.2. Ensure the formation of emotionsEnsure the formation of emotions

3.3. Participation in the pathogenesis of diseasesParticipation in the pathogenesis of diseases

Properties of dominant:Properties of dominant:1.1. Increased excitabilityIncreased excitability

2.2. Persistence of excitationPersistence of excitation

3.3. Ability to summationAbility to summation

4.4. Ability to brakeAbility to brake

5.5. InertiaInertia

Conditions of formation of Conditions of formation of dominant:dominant:

Influence of environmental stimuliInfluence of environmental stimuli Influence of stimuli of the internal environmentInfluence of stimuli of the internal environment

(level of nutrients, hormones)(level of nutrients, hormones)

Conditions of disappearance of Conditions of disappearance of dominant:dominant:

Meeting the needs for which formed Meeting the needs for which formed dominantdominant

The emergence of a stronger dominantThe emergence of a stronger dominant Secondary braking in dominantSecondary braking in dominant

The principle of coordinationThe principle of coordinationCoordinationCoordination – – harmonization of the activity harmonization of the activity

of of nervous centersnervous centers

CoordinationCoordination

ConvergenceConvergence DivergenceDivergence ReverberatioReverberationn

summationAlleviationOcclusionCommonterminalway

IrradiationGeneralizationInductionReciprocalinteraction

Aftereffect