英国纽卡斯尔大学 生理学课件0019.pptVIP

School of Biomedical Sciences Physiology Module PSC 1001 The Nervous System: Sensation and Motor Control Dr Adrian Rees adrian.rees@ncl.ac.uk Lecture 19 Vision and the eye Objectives At the end of this lecture you should be able to : Describe the anatomy of the eye and the retina Explain how an image is formed on the retina Know what is meant by the fovea and the blind spot Know that there are two types of retinal receptors: rods and cones. Describe how the photoreceptors of the eye respond to light under different conditions Outline the trichromatic theory of colour vision The electromagnetic spectrum Cross section of the eye The eye The cornea Responsible for refracting (bending) light rays to bring them into focus on the retina The lens Responsible for accommodation – changing the refractive properties of the eye with object distance Retina Layer at the back of the eye containing photoreceptors, neurons and nerve fibres Visual field of the eye Role of the lens in accommodation Role of cillary muscles in accommodation: lens rounded for near vision (below), flattened for distant vision The retina Fovea Point of maximum acuity (resolution) Blind spot or optic disk Region where nerve fibres and blood vessels leave the eye No vision in this region Brain “fills in” the missing area Blood vessels Remove the last sheet from the handout. Hold the sheet about 40 cm in front of youClose right eye and fixate cross with your left from distance of about 40 cmBring paper slowly towards you. At a particular distance the white spot will disappear as its image falls on the optic disc, the blind spot.Notice also what happens to the vertical lines Structure of the retina Organisation of the retina Two types of photoreceptors Rods (scotopic vision) most sensitive but only monochromatic (single colour). Only work at low light levels, bleached at high light levels Cones (photopic vision) Three types sensitive to long (red), medium (green) and short (blue) wavelen