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nervous system and the eye Flashcards

1
Q

sensory neurone

A

-receptor neurone
-transmits nerve impulses from the sense organs/receptors to the CNS

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2
Q

relay neurone

A

-intermediate neurone
-transmits nerve impulses from the sensory neurone to the motor neurone

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3
Q

motor neurone

A

-effector neurone
-transmits nerve impulses from the CNS to the effectors

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4
Q

structure of motor neurone

A

-irregular shaped cell body
-long nerve fibre extending from the cell body

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5
Q

structure of sensory neurone

A

-circular cell body
-long nerve fibre extending towards the receptor and a shorter one extending to the relay neurone

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6
Q

synapse

A

-the junction between 2 neurones
-allows nerve impulses to be transmitted when chemicals are released by neurones

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7
Q

spinal nerve

A
  • ‘mixed’ nerve
    -contains both sensory and motor neurones
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8
Q

central nervous system

A

consist of brain and spinal cord

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9
Q

peripheral nervous system

A

consist of cranial nerves [from brain], spinal nerves and sense organs

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10
Q

reflex action [define]

A

the immediate subconscious response to a specific stimuli without conscious control

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11
Q

voluntary action [define]

A

a deliberate action that is done under conscious control

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12
Q

reflex action [touch hot object]

A

-[receptor] heat from the object stimulates the nerve endings in willy’s skin, producing nerve impulses
-[SN] sn transmits nerve impulses across a synapse to rn in the spinal cord
-[RN] rn transmits nerve impulses across a synapse to mn
-[MN] mn transmits nerve impulses across a synapse to bicep muscles
-[effector] bicep muscles contract, withdrawing hand suddenly

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13
Q

reflex arc [define]

A

the shortest pathway by which the nerve impulse travels from the receptor to the effector in a reflex action

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14
Q

cranial reflex

A

-controlled by the brain [not conscious] and usually occur in head region
-e.g. pupil reflex, blinking, salivation

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15
Q

spinal reflex

A

-controlled by spinal cord
-e.g. sudden withdrawal of the hand touching a hot object, knee jerk reflex

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16
Q

characteristics of endocrine control

A

-involves hormones as signals
-hormones are transported to the blood
-usually slow responses
-responses can be short or long lived [eg adrenaline and growth hormone]
-always involuntary
-may affect more than one target organ [effector]
-ductless

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17
Q

characteristics of nervous control

A

-involves nerve impulses as signals
-nerve impulses are transported by neurones
-usually quick responses
-responses are short lived
-can be voluntary or involuntary
-usually localised [affect one particular part of the body]

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18
Q

sclera/sclerotic coat

A

-tough white outer covering of the eyeball which is continuous with cornea
-protects the eye from mechanical damage

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19
Q

conjunctiva

A

-thin transparent membrane covering the sclera
-it is a mucous membrane; secretes mucous to keep the front of the eyeball moist

20
Q

eyelash

A

shield eye from dust particles

21
Q

tear gland

A

-wash away dust particles
-keep cornea moist for atmospheric o2 to dissolve into cornea
-lubricate conjunctiva; reduce friction when eyelids move
-exploited when doing bio

22
Q

eyelids

A

-protect cornea from mechanical damage
-allows squinting; prevents too much light entering eyelid and damaging retina
-allows blinking; spreads tears over cornea and conjunctiva, wipes dust particles off cornea

23
Q

iris

A

-circular sheet of muscles
-controls size of pupil which controls amount of light entering the eye
-contains a pigment that gives the eye its colour

24
Q

pupil

A

-hole in the centre of the iris
-allows light to enter the eye

25
ciliary body
-contains ciliary muscles; control the curvature/thickness of the lens
26
suspensory ligament
-connective tissue that attaches the edge of the lens to the ciliary body
27
cornea
-dome shaped transparent layer continuous with the sclera -refract/bend light rays into the eye -causes the greatest refraction of light into the eye
28
aqueous chamber
-filled with aqueous humour [transparent watery fluid] -aqueous humour keeps the front of the eyeball firm and helps to refract light into the pupil
29
lens
-transparent, circular and biconvex structure -elastic; change its shape/thickness to focus light onto retina
30
retina
-light sensitive layer where images are formed -contains photoreceptors [light sensitive cells] which are connected to nerve endings from optic nerve
31
choroid
-pigmented black; prevent internal reflection of light -contains blood vessels; bring o2 and nutrients to eyeball and remove metabolic waste products
32
vitreous chamber
-filled with vitreous humour [transparent jelly-like substance] -vitreous humour keeps eyeball firm and helps to refract light onto the retina
33
fovea
-small yellow depression in the retina stimulated directly behind the lens -images are focused here -contains the greatest concentration of cones, but no rods -allows people to have detailed colour vision in bright light
34
optic nerve
-transmits nerve impulses to the brain when photoreceptors in the retina are stimulated
35
blind spot
-region where optic nerve leaves the eye -does not contain rods or cones, thus not sensitive to light
36
cones
-found only in fovea -allows us to see colours in bright light
37
rods
-found throughout retina, just not in fovea -more sensitive to light than cones -allows us to see in dim light, but only black and white
38
pupil reflex [bright light]
-circular muscles of the iris contract -radial muscles of the iris relax -pupil becomes smaller and constricts, reducing amount of light entering the eye
39
pupil reflex [dim light]
-circular muscles of the iris relax -radian muscles of the iris contract -pupil enlarges and dilates, increasing amount of light entering the eye
40
benefits of pupil reflex
-automatic, no learning is required -prevents excessive light from entering the eye and damaging the retina -immediate response -allows enough light to enter the light for us to see
41
transmission of nerve impulses for pupil reflex [bright light]
-when bright light is shone into the eyes, photoreceptors in the retina is stimulated -SN in optic nerve transmits nerve impulses across a synapse to RN in the brain -RN in the brain transmits nerve impulses across a synapse to MN -MN transmits nerve impulses across a synapse to iris -circular muscles of iris contract and radial muscles of iris relax, causing pupil to constrict, reducing amount of light entering the eye
42
formation of image on the retina
-light rays are refracted through the cornea and the aqueous humour onto the lens -lens cause further refraction and the rays are brought to a focus on the retina -image on the retina stimulates rods/cones [depend on light intensity]
43
characteristics of the image formed on the retina
-upside down/inverted -laterally inverted -diminished/smaller than actual
44
focusing/accommodation
-the adjustment of the lens of the eye so that clear images of objects at different distances are formed on the retina
45
focusing [distant object]
-ciliary muscles relax, pulling on the suspensory ligaments -suspensory ligaments become taut, pulling on the edge of the lens -lens become thinner and less convex -light rays from the distant object are sharply focused on the retina -photoreceptors are stimulated -nerve impulses are produced and transmitted by the optic nerve to the brain -brain interprets nerve impulses, allowing willy to see the distant object
46
focusing [near object]
-ciliary muscles contract, relaxing pull on the suspensory ligaments -suspensory ligaments slacken, relaxing their pull on the edge of the lens -lens, being elastic, become thicker and more convex -light rays from the near object are sharply focused on the retina -photoreceptors are stimulated -nerve impulses are produced and transmitted by the optic nerve to the brain -brain interprets nerve impulses, allowing willy to see the near object

biology (6 decks)

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