Скачать с ютуб Electrical synapse I Gap Junction I Connexins I connexon I Synaptic plasticity I innexons I innexins в хорошем качестве

Electrical synapse I Gap Junction I Connexins I connexon I Synaptic plasticity I innexons I innexins

Synapse is defined as a junction between one or more neurons. The junction between the neuron and muscle is called neuromuscular junction. Neurons except those that are present at electrical synapses are separated from each other by a distance of 20-30 nm. This space that separates neurons from each other is called synaptic cleft. Synaptic transmission: The rapid and transient change, which is either excitatory or inhibitory, exerted by a presynaptic signal, usually the action potential, on the post synaptic cell is called synaptic transmission. Synaptic plasticity: Is defined as an ability of a synaptic actions to change the functional properties of the synapses. Synaptic plasticity is exploited in development, learning, memory etc. Synapses may be Electrical or chemical Excitatory or inhibitory Slow or fast Can mediate the transmission or modulate the synaptic plasticity. Electrical synapses: Are those synapses in which action potential or electric current flows directly from one cell onto the another cell. Electrical synapses lack synaptic delay i.e. time taken by the electric current to move from one cell onto the another cell. Most electrical synapses are bidirectional i.e. current can flow in either direction except rectifying synapses present between lateral giant axon and the giant motor neuron of crayfish in which current flow is unidirectional and are non-polar i.e. there is no concept like pre-and post-synaptic neurons. These are present in regions where speed of conduction and synchronization between multiple cells is essentialTwo cells at electrical synapses are connected through gap junctions in such a way that the two cells are electrically and metabolically coupled. The metabolic coupling is of particular importance to avascular tissues like lens and epidermis of the skin. There is a slight decrease in the intensity of current due to low resistance at gap junctions in electrical synapses. Electrical synapses differ in strength. The strength of synapse is directly proportional to the area of gap junction and vice a versa. The cells in electrical synapse are separated by a small distance of 3.5 nm. These small space is bridged by a regular array of channels called connexons. Each connexon is a hexamer of connexin proteins that make a small 2 nm aqueous pore, called annulus, through which ions and small molecules less 1000 Daltons like cAMP, inositol phosphates, ATP, amino acids, sugar phosphates, coenzymes, Ca++monomers, tracers and dyes pass. There are 21 different connexins that are subdivided into three subfamilies α, β and γ in humans. The molecular weight varies between 26,000 to 60,000. Connexins may be compatible or not. e.g. even though nodal tissues and cardiac myocytes are in physical contact, former has Cx40 while later has Cx43 that are incompatible. As a result, there is no coupling between cardiac myocytes and nodal tissues. Invertebrate protostomes have innexons consisting of innexins that are analogous to connexins of vertebrate gap junctions. Electrical synapses are of particular importance in escape systems of crayfish and neurons that control electric organ of fishes like electric ray, electric eel etc. #electricalsynapses #synapticcleft #synapticdelay #bidirectional #gapjunctions #connexons #connexin #innexin #innexon #electricalcoupling #metaboliccoupling #Cx40 #Cx43 #connexinincompatibility