B3.1 The Nervous system - Eye

Question 1

<p>Describe and state the function of the cornea.</p>

Answer 1

<ul> <li>Transparent coating on the front of the eye</li> <li>Protects the eye, refects light entering the eye</li></ul>

Question 2

<p>Describe and state the function of the conjunctiva.</p>

Answer 2

<ul> <li>Protective membrane contiunuous with the eyelids across the front of the visible sclera</li> <li>Protects from infection by stopping pathogens entering the eye</li></ul>

Question 3

<p>Describe and state the function of the pupil.</p>

Answer 3

<ul> <li>Central hole in the iris</li> <li>Allows light to enter the eye</li></ul>

Question 4

<p>Describe and state the function of the iris.</p>

Answer 4

<ul> <li>Coloured ring of muscle</li> <li>Alters pupil size by contracting or relaxing</li></ul>

Question 5

<p>Describe and state the function of the lens.</p>

Answer 5

<ul> <li>Transparent biconvex lens</li> <li>Focuses light clearly onto the retina</li></ul>

Question 6

<p>Describe and state the function of the suspensory ligaments.</p>

Answer 6

<ul> <li>Work together with the cilary body to control the shape of the lens by becoming taught or slack</li> <li>Connect the ciliary body to the lens</li> <li>When ciliary muscles contract the suspensory ligaments relax allowing the lens to go fat</li> <li>When ciliary muscles relax the suspensory ligaments are pulled taught stretching the lens thinner</li></ul>

Question 7

<p>Describe and state the function of the retina.</p>

Answer 7

<ul> <li>Contains two types of photoreceptor cells rods and cones</li> <li>Photoreceptor cells produce a nervous impulse when exposed to light</li></ul>

Question 8

<p>Describe and state the function of the optic nerve.</p>

Answer 8

<ul> <li>Nervous tissue</li> <li>Carries nerve impulse from the retina to the brain</li></ul>

Question 9

<p>Label the parts of the eye</p>

Answer 9

<ol> <li>Sclera – Tough outer wall, ‘white’</li> <li>Conjunctiva – membrane over eye</li> <li>Cornea – transparent outer layer</li> <li>Lens – focuses light</li> <li>Pupil – allows light into eye</li> <li>Aqueous humor -nutrients &pressure</li> <li>Iris – controls diameter of pupil via circular and radial muscles</li> <li>Vitreous humor – pressure and shape.</li> <li>Choroid – nutrients & waste</li> <li>Fovea – blind spot</li> <li>Optic nerve head – nerves exit</li> <li>Optic nerve – impulses to eye</li> <li>Retina – contains rods & cones</li></ol>

Question 10

<p>What is the aqueous humor</p>

Answer 10

<p>A fluidwhich isbetweenthe cornea and lens that provides nutrients for the the lens and cornea that have no blood supply and helps maintainpressure</p>

Question 11

<p>What is the vitreous humor?</p>

Answer 11

<p>A transparent, colourless, gel-like substance that fills the space between the lens and the retina within the eye and helps maintainpressure and shape.</p>

Question 12

<p>Name the two types of photo receptor cell in the eye.</p>

Answer 12

<ol> <li>Rods - respond to light and allow you to see in low light levels</li> <li>Cones - respond to red, blue and green light to allow you to see in different colours</li></ol>

Question 13

<p>Name the cells and their structures.</p>

Answer 13

<p>Cell A: Rod cell</p>

<p>Cell B: Cone cell</p>

<ol> <li>Outer segment</li> <li>Inner segment</li> <li>Synaptic region</li> <li>Disc</li> <li>Connecting cillium</li> <li>Mitochondria</li> <li>Nucleus</li> <li>Synapse</li></ol>

Question 14

<p>How do the circular and radial muscles control the size of the pupil?</p>

Answer 14

<ol> <li>In dim light the radial muscles contract and the circular muscles relax to make the pupil become larger to allow more light to reach the retina.</li> <li>In bright light the radial muscles relax and the circular muscles contract to make the pupil become smaller and protect the retina.</li></ol>

Question 15

<p>How do the suspensory ligaments and cilliarymuscles control the shape of the lens?</p>

Answer 15

<ol> <li>When an object is nearby the cilliarymusclecontracts down towards the lens allowing the suspensory muscles to become slack. This causes the lens to fatten and become more convex, increasing the refraction of the light passing through.</li> <li>When an object is far the cilliarymusclerelaxes away from the lens allowing the pulling the suspensory muscles taut. This causes the lens to be pulled thiner and become less convex, decreasing the refraction of the light passing through.</li></ol>

Question 16

<p>What is the name given to the process of focusing incoming light?</p>

Answer 16

<p>accomodation</p>

Question 17

<p>What is meant by the term myopia?</p>

Answer 17

<ul> <li>Shortsightedness</li> <li>Someone who isshort-sightedcan see near objects clearly, but they cannot focus properly on distant objects.</li></ul>

Question 18

<p>Name the causes of myopia?</p>

Answer 18

<ol> <li>Eyeball elongated = distance the lens to retina too great</li> <li>Lens too thick and curved = light is refracted to much and focuses short</li></ol>

Question 19

<p>How can myopia be corrected?</p>

Answer 19

<p>Myopia is corrected by a concave lens in front of the eye.</p>

Question 20

<p>What is meant by the term hyperopia?</p>

Answer 20

<ul> <li>Longsightedness</li> <li>Someone who islong-sightedcan see distant objects clearly, but they cannot focus properly on near objects.</li></ul>

Question 21

<p>What are the causes ofhyperopia?</p>

Answer 21

<ul> <li>Eyeball too short = distance the lens to retina too small</li> <li>Loss of elasticity in the lens = cannot become thick enough to focus (often age-related)</li></ul>