senses

Question 1

what are the senses?

Answer 1

• vision
• auditory
• olfactory
• gustatory
• equillibrium

Question 2

the eye

Answer 2

• delicate organ

- eyebrows function in preventing perspiration from entering the eye

Question 3

how is the eye protected

Answer 3

• most of the eye is hidden and protected by a cushion of fat and the bony orbit
• eyelids protect the eye anteriorly, eyelashes contain nerve endings of follicles to initiate reflex blinking
• lacrimal gland produces tears
• 6 extrinsic eye muscles originate from the bony orbit and both enable the eye to follow moving objects and maintain shape of eyeball

Question 4

lens

Answer 4

• separates eyeball into anterior and posterior segments
• biconvex, transparent, flexible, elastic and avascular structure which allows focusing of light on retina
• becomes less elastic and more dense with age and cataracts

Question 5

sclera

Answer 5

• whites of the eye which protects and shaped the eyeball, and anchors extrinsic eye muscles
• transparent anterior portion that bends light is the cornea which contributes to tar reflexes and blinking

Question 6

uvea

Answer 6

• middle vascular pigmented layer
• choroid - brown pigmented most posterior portion that supplies blood to all layers of the eyeball
• cillary body - a ring of smooth muscle and ligaments surrounding the lens that control lens shape and position
• iris - coloured part and the pupil is the opening that regulates the amount of light entering

Question 7

retina

Answer 7

• inner sensory layer, a delicate, richly vascularised two layered membrane
• outer pigmented area stores vitamin A and absorbs light
• inner neural layer consists of multiple cells that transmit and process impulses
• optic disc (blind spot) lacks photoreceptors and is the site where the optic nerve leaves the eye

Question 8

photoreceptors

Answer 8

• rods and cones are highly specialised sensory receptor cells which respond to electromagnetic radiation (light)
• rods are numerous at the periphery of the retina, operate in dim light/nigh vision, and provide indistinct, fuzzy, non colour peripheral vision (black and white)
• cones are found in the macula lutea, operate in bright light and provide high-acuity colour vision and fine focus

Question 9

pathway of light entering the eye

Answer 9

cornea - aqueous humor - lens - vitreous humor - neural layer of retina - photoreceptors
- light is refracted at the cornea as is enters the lens and as it exits the lens