The Eye Flashcards
What happens to the eye in bright light
The circular muscles contract and the radial muscles relax, making the iris widen and therefore making the pupil narrows, limiting the light passing through
What occurs to the eye in dim light
The circular muscles relax and the radial muscles widen the pupil, allowing more light in
How is light accommodated onto the retina from a near object
The ciliary muscles contract, releasing any tension from the eyeball. The lens adopts a fatter shape so that it refracts more light
How is light accommodated onto the retina from a far object
The ciliary muscles relax, transferring pressure to the suspensory ligaments pulling the lens to a thin shape, so light doesn’t converge as much
Where are Rod and Cone cells found
Cones are concentrated at the centre of the retina, whereas rods are mainly found in the periphery of the retina
What is the blind spot
The place where neurones leave the eye so there is an area devoid of receptors
What occurs when light strikes rhodopsin
It breaks down into retinal and opsin, which results in a change of membrane potential, a generator potential
Why are rod cells sensitive
Rhodopsin absorbs light readily and is more easily broken down because retinal convergence enables the input of many rods to be added together
What is a consequence of retinal convergence
The brain cannot distinguish which rod of a group sharing the same optic nerve has been stimulated
What occurs in bright light to rhodopsin
It is entirely bleached, so all the rods because non-functional, dark adaptation
What pigment is found in cone cells
Iodopsin
What is high visual acuity
The brain is able to distinguish between points that are close together
What is the function of skeletal muscle
Movement of parts of the body and locomotion
What is the structure of the skeletal muscle
The nuclei lie beneath the sarcolemma out of the way of the myofibrils, each surrounded in sarcoplasmic reticulum joined transversely by T-tubules
What is the difference between rods and cones in terms of retinal convergence
Many rods synapse with each bipolar neurone and many bipolar cells connect with each neurone at the optic nerve
Cones generally synapse with a singular bipolar neurone and a single neurone at the optic nerve
