神经生物学双语课程思考题.pdfVIP

《神经生物学》双语课程思考题 将下列材料翻译成中文 1． The human visual system is very important in the quantity and quality of information it supplies about the world. A glance is sufficient to describe the location, size, shape, color, and texture of objects and, if the objects are moving, their direction and speed. Equally remarkable is the fact that visual information can be discerned over a wide range of stimulus intensities, from the faint light of stars at night to bright sunlight. 2 ． Despite its peripheral location, the retina or neural portion of the eye, is actually part of the central nervous system. The retina comprises complex neural circuitry that converts the graded electrical activity of photoreceptors into action potentials that travel to the brain via axons in the optic nerve. Although it has the same types of functional elements and neurotransmitters found in other parts of the central nervous system, the retina comprises only a few classes of neurons. There are five types of neurons in the retina: photoreceptors(光感受 器细胞), bipolar cells, ganglion cell, horizontal cells, and amacrine cells . 3 ． The two types of photoreceptors, rods and cones, are distinguished by shape (from which they derive their names), the type of photopigment they contain, distribution across the retina, and pattern of synaptic connections. These properties reflect the fact that the rod and cone systems (the receptors and their connections within the retina) are specialized for different aspects of vision. The rod system has very low spatial resolution but is extremely sensitive to light; it is therefore specialized for sensitivity at the expense of resolution. Conversely, the cone system has very high spatial resolution but is relatively insensitive to light; it is therefore specia