8519196
Description
| Question | Answer |
| Role of iris | Regulates size of pupil |
| Role of pupil | Admits light |
| Role of retina | Contains receptors for vision |
| Role of aqueous humor and vitreous humor (2) | Transmits light rays and supports eyeball |
| Role of rods (2) | Black and white vision in dim light |
| Role of cones (2) | Coloured vision in bright light |
| Role of fovea (2) | - Most concentrated zone of cone cells - Vision is has most resolution |
| Role of lens | Focuses light rays |
| Role of sclera | Protects and supports eyeball |
| Role of cornea (2) | - Focuses light - Refracts it to the largest extent |
| Role of choroid | Absorbs stray light |
| Conjunctiva (2) | - Covers sclera and cornea - Keeps eye moist |
| Role of Optic nerve | Transmits impulses to the brain |
| Role of eye lid | Protects the eye |
| Characteristics of blind spot (2) | Zone where ganglion neurones join together to form nerve fibre |
| How does the brain help in sight? (1) | Corrects image, such that the image does not appear upside down |
| Define accommodation (2) | Ability of lens to change shape and focus on objects at different distances |
| Focusing with ciliary muscles sequence (further away from object) (5) | 1. Ciliary muscles relax, pulling on suspensory ligaments 2. Suspensory ligaments become taut and pull on the edge of the lens 3. Lens become thinner, less convex (reject rounded) 4. Light rays concentrated on retina 5. Photoreceptors stimulated, nerve impulses send image to brain |
| Focusing with ciliary muscles sequence (nearer to object) (5) | 1. Ciliary muscles contract, releasing tension on suspensory ligaments 2. Suspensory ligaments slacken and loosen on the edge of the lens 3. Lens become rounder, more convex (reject rounded) 4. Light rays concentrated on retina 5. Photoreceptors stimulated, nerve impulses send image to brain |
| Identify the circular and radial muscles in terms of location (2) | Circular muscles ==> Inner Radial muscles ==> Outer |
| Pupil reflex (Dim light) | 1. Photoreceptor cells in retina detect light intensity 2. Impulses sent through optic nerve to brain 3. Brain sends impulses along a motor neurone to pupil muscles 4. Radial contracts, Circular relaxes (RCCR) |
| Pupil reflex (Bright light) | 1. Photoreceptor cells in retina detect light intensity 2. Impulses sent through optic nerve to brain 3. Brain sends impulses along a motor neurone to pupil muscles 4. Circular contracts, radial relaxes (CCRR) |
| Purpose of pupil reflex (2) | Let less light through pupil, thus protecting photoreceptor cells in retina |
| Comparing rods and cones: sensitivity | - Rods are more sensitive than cones - Able to function well in dim light |
| Comparing rods and cones: Types of rod | - Cones have 3 types of cells, as compared to 1 type of cell for rods - Allows red, blue and yellow vision |
| Comparing rods and cones: Ratio of something ;) | - Rod: Group of rod cells to one nerve fibre - Cones: One cone cell to one nerve fibre |
| Comparing rods and cones: Pigment? | - Rods: Rhodopsin - Cones: Photopsins |
| 1. Which way does light come in contact with the retina? 2. Where is the sensory neurone located? | 1. Light comes in from the left hand side 2. Light shines *on* the sensory neurone, located along the (also) left hand side |
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