myelination

first one, in the central nervous system, myelin is formed by the oligodendrocytes. One oligodendrocyte can contribute to the myelin sheath of several axons.

myelination II: in the peripheral nervous system, myelin is formed by Schwann cells. Each Schwann cell associates with only one axon, when forming a myelinated intermode.

vertebrate nervous system

The organization of the vertebrate nervous system is different from invertebrates. Vertebrates have a well-organized hollow dorsal nervous system. The central nervous system included a brain and spinal cord. The peripheral nervous system comprise peripheral nerves extending from spinal cord and peripheral ganglia. nervous

EPSP's and IPSP's

If transmitter opens a cation influx, the resulting depolarization is called an Excitatory Post Synaptic Potential (EPSP). These individual potentials are sub-threshold. If the transmitter opens an anion influx, the resulting hyperpolarization is called an Inhibitory Post synaptic potential (IPSP). All these potentials are additive. ıf some of the synapses are inhibitory in type. The cell produce action potential according to the algebric some of both excitatory and inhibitory synapses. The neurotransmitter GABA causes postsynaptic inhibition because its rceptor gated, postsynaptic membrane channels allow CL-flow.
Repitative stimulation of postsynaptic nerve from single synaptic region can also produce action potential. This kind of summation is called as temporal summation. Sometimes even the cell do not produce action potential, it can be come close to threshold potential , this is called as faciltation. Synaptic depression or fatique occur due to the depletion of synaptic vesicles as a result of repitetive stimulation. Continuous stimulation may led to the decline of postsynaptic potential.