wei yuanyuan nervous system i. nervous system organization : over 100 billion neuron central nervous...
TRANSCRIPT
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Wei yuanyuan
Nervous system I
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Nervous systemOrganization : over 100 billion neuron
Central nervous systemBrain + spinal cord
Peripheral nervous system :somatic nervous system+vegetal nervous system
The rest of the nervous system(12 cranial nerve and 31 spinal nerve)Carry information between the CNS and other parts of
the body
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Nervous system
31
Enteric nerve
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The nervous tissue is composed of two main cellsNeuron: 1011
Glial cell (in CNS): 1012
AstrocytesOligodendrocytes Microglia Ependymal cells
Nervous system- glial cells
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Nervous system- glial cells
Function of the glial cells in CNS
AstrocytesPhysically support neuronsScaffold during fetal brain developmentconstitute BBBHelp maintaining the proper brain ion concentration and normal
neural excitability by taking up excess K+ from ECF ( epileptic seizures)
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Starlike shape of astrocytes
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Nervous system- glial cells
Function of the glial cells in CNSOligodendrocytes :
form myelin sheaths
Microglia : serve as phagocyte
Ependymal cells : the thin epithelial membrane lining the ventricular system of
the brain and the spinal cord. It is involved in the production of cerebrospinal fluid (CSF).
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Glial cell (in CNS): Astrocytes ;Oligodendrocytes; Microglia Ependymal cell
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Function and type of the glial cells in PNSSchwann cell
Serve as myelin sheathsSatellite cell
Serve as phagocyte
Nervous system- glial cells
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Basic function unit
Definition : individual nerve cell carrying the impulse throughout the body
Nervous system- neuron
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Soma Axon DendritePresynaptic terminals
Nervous system- neuron
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Structure of neuron
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Function of neuronProcessing of information
Soma : integrate the messageAxon : carry the impulse away from the cell
body, transportation of nutrient to the effectorAxon hillock: the place of AP occur
Dendrite : receive the neuron impulsePresynaptic terminals : associate with
another neurons
Nervous system- neuron
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Classification of neuronSensory neuron : from receptorInterneuron: CNS Motor neuron: to effectors
Nervous system- neuron
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Neuron
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Nerve fiber (axon and dendrites) Function
Conducting APNerve impulse
Nervous system- neuron
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Characters of AP conduction on a nerve fiber
The anatomic and physiological integrityNot easy to fatigueConduct in a non-decremental fashion
Nervous system- neuron
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Conduction velocityInfluential factors
DiameterMyelinate or not temperature
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Classification of nerve fibers
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Classification of nerve fibers
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Classification of Sensory fiber
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The former classification method used for efferent fiber
The latter classification method used for afferent fiber
Classification of nerve fibers
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Axoplasmic transportationAnterograde axoplasmic transportationRetrograde axoplasmic transportation
Organelle:Mitochondrial synaptic vesiclesecretory granules
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Axoplasmic transportationAnterograde axoplasmic transportationRetrograde axoplasmic transportation
growth factors certain harmful substances: tetanus toxinHerpesrabies virus
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synapse
Greek "syn-" ("together")
"haptein" ("to clasp").
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Transmission of the information between the neuron
Chemical transmissionClassic synapseNon- synapse chemical transmission
Electrical transmissionGap junction (Astrocytes)
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Chemical Synapse Definition of synapse:
the special site between the two neuron where the information transmit
Structure pre-synaptic membrane:
Calcium channel , synaptic vesicle (neurotransmitter storage)
Synaptic cleftTransmitter diffusion
Post- synaptic membraneK+ , Na+ Channel , receptor
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Pre-synaptic membrane
Pre-synaptic membrane
Synaptic cleft
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Non- synapse chemical transmission
One neuron innervate many effector cells by means of varicosity
Heart the terminal of
sympathetic nerve
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Electrical transmissionGap junction (channel): electric current
movement (quickly and not easy to fatigue)
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Electrical synapse Chemical synapse
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Which one is best for transmission ?
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one-way conduction
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Synaptic transmission
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Synaptic transmissionThe process of synaptic transmission
1. Action potential propagation in presynaptic neuron
2. Ca 2+ entry into synaptic knob3. Release of neurotransmitter by exocytosis4. Binding of neurotransmitter to postsynaptic
receptor5. Opening of specific ion channels in post -
synaptic membrane
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Neurotransmitter
Definition: a chemical substance secreted by presynaptic neuronExcitatory transmitter : Inhibitory transmitter:
Binding with receptor proteinAgonists and antagonists
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Postsynaptic potential (graded potential)Type :
Excitatory postsynaptic potential (EPSP)Inhibitory postsynaptic potential (IPSP)
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EPSP
Postsynaptic membraneMainly permeability to sodiumEPSP: depolarization
Characters (EPSP) :No threshold: local potential or gradient potentialDecreases resting membrane potential.
Closer to threshold.Graded in magnitude.No refractory period.Summation ( temporal summation and spatial summation
)
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Na in>Kout , why ?
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IPSPPostsynaptic membrane
Cl- influx and K+ efflux IPSP : hyperpolarization
CharactersNo threshold.Hyperpolarize postsynaptic membrane.Increase membrane potential( far from TP)No refractory periodSummation
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Summation of EPSP or IPSP
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Integrative function of neuron
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(0.5-1 mSec)
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Characters of AP conduction on a nerve fiber
The anatomic and physiological integrityNot easy to fatigueConduct in a non-decremental fashion
Nervous system- neuron
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Synaptic inhibition
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Postsynaptic inhibition
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Afferent collateral inhibiton( reciprocal inhibition)
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Afferent collateral inhibiton( reciprocal inhibition)Significance : coordination activity of
different nerve centre.
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Recurrent inhibitionNeurons may also inhibit themselves in a negative
feedback fashion.
Interneuron : Renshaw cellsNeurotransmitter :. glycine
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Recurrent inhibition
significance:terminate activity of motor neuron in time.
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Presynaptic inhibition
A
B
C
Neuron A : inhibitory neuron
Neuron B: excitatory neuron
Neuron C : postsynaptic neuron
(+) Neuron B only → Neuron C depolarization 10 mV
(+) Neuron A firstly then
(+) Neuron B → Neuron C depolarization 5 mVReason: Neuron A release inhibitory transmitter which reduce the Neuron B release excitatory transmitter, so ,on Neuron C the EPSP↓
GABA ( gammalon )
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summaryAxoplasmic transportationSynaptic transmissionpost-synaptic potential
IPSPEPSP
Central inhibitionPost-synaptic inhibitionPre-synaptic inhibition