Embryonic origins:A) for NRs of CNS (brain and sp. cord) – are neuroblasts of MANTLE zone of NEURAL TUBE. B) for NRs of PNS (of ganglia) – are neuroblasts of NEURAL CREST.
Crest also give rise to: Satellite cells of ganglia and – to Schwan cells of nerves.
GLIALcells (supporting cells) of Central Nervous System (CNS):
1) PROTOPLASMIC astrocytes. It locate in GRAY matter of CNS.
2) FIBROUS astrocytes. It locate in WHITE matter of CNS. Struct.: both types have many cytoplasmic processes.Funct.: a) support high concentration of K+ ions between neurons; b) form blood-brain barrier; c) form cellular SCAR in damaged rdNR in RA- is MOTOR NR. ( in ventral horn of sp. cord). areas of CNS
3) OLIGODENDROCYTES. Occur in both gray and white matter. Funct.: participate in FORMATION of nerve FIBREs. In MYELINATED nerve FIBRES these cells produce MYELIN SHEATH. Injury of those cs is accompanied by DEmyelinationdisease.
4) EPENDYMAL cells. It line wall of brain VENTRICLES and CENTRAL CANAL of sp. cord. It are cuboidal cells with apical CILIA. Funct.: it participate in secretion and movement of CEREBROSPINAL fluid.
5) MICROGLIAL cells. It originate from MONOCYTes and are macrophages of nervous tissue. Funct.: phagocytosis of damagedneurons.
GLIALcells (supporting cells) of Peripheral Nervous System (PNS).
PNS includes : a) ganglia and b) spinal and cranial nerves rdNR in RA- is MOTOR NR. ( in ventral horn of sp. cord)..
1. SCHWANcells.It locate in peripheralnerves.Funct.: participate in FORMATION of nerve FIBREs. In MYELINATED nerve FIBRES these cells produce MYELIN SHEATH. Injury of those cs is accompanied by DEmyelinationdisease.
2. Satellite cells. It locate in all GANGLIA, surrounding perikaryones of neurons.
NERVOUS TISSUE. part 2. NERVE FIBRES. NERVE ENDINGS.
There are 2 types of NFs: 1)MYELINATED NFs (=MNFs) and 2) UNmyelinated NFs.(=UNFs).
BOTH types of NFs form peripheral NERVEand white matterofCNS..
Structure of MNF on the cross section (from centre to periphery):
MS – is spirally wrapped plasma membrane of SCHWANN cell (in peripheral NERVE) orof OLIGODENDROCYTE (in brain and spinal cord). Chemically MS is composed of phospholipids. Neurilemma– is cytoplasm with nucleus of SCHWANN cell (in PNS) or of OLIGODENDROCYTE. It means: nerve fibre is formed by 2cell types:
1. NEURON gives 1 AXON for fibre,
2. SCHWANN cell or OLIGODENDROCYTE give myelin sheath and neurilemma.
Structure of MNF on the longitudinalsection
Structure of UNF on the cross section (from centre to periphery):
SPs – are specialized junctions between 2 neurons (interneuronal SPs) or between neuron and muscle fibre (myo-neural junction). In SP nerve impulse is presented by chemical messengers named NEUROTRANSMITTERS(=NTs).
SP is composed of: 1) PREsynaptic membrane, 2) Synaptic CLEFT, 3) POSTsynaptic membrane.
Presynaptic membr rdNR in RA- is MOTOR NR. ( in ventral horn of sp. cord).. is formed by axonic terminal of previous neuron. It contains synaptic vesicles with NTs. Examples of NTs: a) ACETYLCHOLINE, b) NORADRENALINE (or norepinephrine). Group of SPs, containing acetylcholine - are CHOLINERGIC SPs. Group of SPs, containing noradrenaline - are ADRENERGIC SPs. Postsynaptic membr. contains RECEPTORs molecules, recognizingNTs. This membr. may be formed by 3 components of following neuron: a) by perikaryon. Type of so SP – is axo-somatic SP; b) by dendrite of next neuron. Type of so SP- is axo-dendritic SP; c) by axon of second neuron. Type of so SP – is axo-axonic SP. (a,b,c – are morphologic types of rdNR in RA- is MOTOR NR. ( in ventral horn of sp. cord). interneuronal SPs).
SP between axon terminal and muscle fibre – is myo-neural junction.It belongs to group of MOTOR nerveendings:a) presynaptic membr. is formed by axonic terminal of neuron, BUT b) postsynaptic membr. is formed by muscle fibre SARCOLEMMA (contains receprors to NTs). Functioning of NTs in synaptic cleft provide CONTRACTION of muscle fibre.
NERVE ENDINGS. (=NEs). Includes 3 groups:
Составитель – доцент В.В. Бондаренко.