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ANATOMY, PHYSIOLOGY, AND DISORDERS OF THE AUDITORY SYSTEM - PART 9

Tổ chức lại có nghĩa là các mạch ("lại hệ thống dây điện") của hệ thống thần kinh đã thay đổi. Có hai cách khác nhau mà điều này có thể xảy ra. Một cách là bằng cách mở (unmasking) thường đóng (không hoạt động) khớp thần kinh hoặc đóng cửa thường mở các khớp thần kinh. | 250 Section III Disorders of the Auditory System and Their Pathophysiology Re-organization means that the circuitry re-wiring of the nervous system has changed. There are two different ways that this can occur. One way is by opening unmasking normally closed dormant synapses or closing normally open synapses. The other way is by forming new connections sprouting of axons and formation of new synapses . Elimination of connections or of cells apoptosis are other ways in which the functional circuitry can change. Connections can be severed or created by sprouting of axons or severing of axons. Connections can also be established by making non-functional synapses functional unmasking of dormant synapses . Furthermore neurons that are normally not activated by their input may become active by alterations in the input such as increase of discharge rate may activate target neurons that are not activated by a lower rate. The excitatory post synaptic potentials EPSP in response to a low rate of incoming nerve impulses may not add up to produce membrane potentials that exceed the firing threshold of the neuron see Fig. A1.1 because of insufficient temporal summation. Changes in synaptic efficacy or increased temporal integration may make it possible for an incoming train of nerve impulses to activate a target neuron. Changes in discharge pattern for example from a regular pattern to burst pattern may make it possible to exceeded the threshold of the target synapse which was not exceeded by the same average rate of discharges and thereby open new connections. Reorganization may have different extents and may change the wiring of local structures such as the cerebral cortex or it may redirect information to population of neurons that have not normally received such input by opening dormant synapses. A third way that the function of the nervous system can change is by altering enhancing protein synthesis in target cells. This means that change from sustained activity to burst .