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A Biology IGCSE course > Nervous system and structure of the eye > Flashcards

Nervous system and structure of the eye Flashcards

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1
Q

What is sensibility

A

The ability to detect or sense changes in the environment

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2
Q

What are the two systems that control the body

A

nervous system
endocrine system

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3
Q

What is a stimulus

A

A change in an organism’s surroundings

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4
Q

What is a receptor

A

receptors detect stimuluses and transduce the stimulus’ energy into electrical impulses

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5
Q

What is an effector

A

a muscle or gland that brings about a response to a stimulus

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6
Q

What can the ear detect

A

vibrations, sound, spacial positioning

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7
Q

What can the nose detect

A

chemicals in the air through nose chemoreceptors

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8
Q

what is the function of the nervous system

A

The nervous system uses electrical impulses to bring about fast but short lived responses which enable organisms to react to their surroundings and co-ordinate their behaviour.

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9
Q

what are the parts of the nervous system

A

CNS - central nervous system - brain, spinal cord
PNS - Peripheral nervous system- the rest

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10
Q

What are neurones

A

Specialised cells which carry electrical impulses
There are three types:
* Motor
* Sensor
* autonomic

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11
Q

PRACTICE DRAWING NERVE CELLS MOTOR AND SENSORY

A
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12
Q

What can influence reaction time?

A
  • age
  • sex
  • physical fitness
  • fatigue
  • distraction
  • alcohol
  • whether the stimulus is auditory or visual
  • diet
  • drugs - stimulus or depressant
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13
Q

What is a synapse

A

A gap where two neurones meet

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14
Q

How do impulses travel synapses

A

chemicals called neurotransmitters are released by the first neurone which carries the electrical impulse which diffuses across the gap and makes the next neurone transmit an electrical impulse by attaching to receptors on its surface.

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15
Q

PRACTICE DRAWING SYNAPSES AND NEUROTRANSMITTERS… synaptic vesticle synaptic cleft receptor neurotransmitter molecules nerve impulse

A
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16
Q

PRACTICE STRUCTURE OF THE eye

A
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17
Q

What is the function of the cornea

A

transparent surface, meaning refraction occurs to focus light on retina

18
Q

What is the function of the pupil

A

Hole in centre of iris through which light enters the eye

19
Q

What is the function of the retina

A

Contains light sensitive receptor cells called rods (which respond to low light intensity but not wavelength à black and white) and cones (which respond to different wavelengths but only work in high intensity light à colour). It is dark to absorb as much light as possible.

Reflects light onto the optic nerve

20
Q

What is the function of the optic nerve

A

Carries electrical impulses from the receptors along sensory neurones to the brain

21
Q

Fovea

A

Where most cone cells are found on the retina

22
Q

Ciliary muscle

A

Changing the shape of the lens by contracting which helps focus the light on the retina

23
Q

Suspensory ligaments

A

slacken or become taught changing the shape of the lens

24
Q

lens

A

A curved structure in the eye that bends the light entering the light through refraction and focuses it so that it hits the retina

25
Q

Iris

A

This regulates the amount of light that accesses the back of the eye. This can dilate (expands eye) or constrict so that the right amount of light can be received

26
Q

Sclera

A

This is the supporting wall of the eyeball

27
Q

blind spot

A

This is where the eye cannot see, because the light cannot be reflected by the retina if it hits the nerve.

28
Q

Conjunctiva

A

This is a transparent mucous membrane on the surface of the eyelids, which keeps the surface of the eye:
moist
lubricated
protected from dust
and can generate tears with glands

29
Q

What are reflex actions

A

rapid, automatic and involuntary response of the nervous system which do not involve the brain as they pass through a relay neurone

Undergoes a reflex arc

30
Q

What is the order that impulses travel in a reflex action

A
  1. A stimulus (heat) is received by a receptor
  2. The receptor converts this information into an impulse.
  3. This impulse is transmitted along a sensory neurone
  4. This impulse is transmitted along a relay neurone
  5. The impulse is transmitted along a motor neurone to an effector
  6. Effector (arm muscle) brings about a response by the arm muscle contracting which pulls hand away from flame.
    Also known as reflex arc
31
Q

What are the different types of photoreceptors in the eye

A

On the retina - cones and rods

32
Q

What is the function of cones

A

colour vision - can detect primary colours r g b
located in the fovea
sensitive to high-light intensities

33
Q

What is the function of rods

A

responsible for night vision Sensitive to low light intensities
around the periphery of the retina

34
Q

How can an image be seen

A

light refracts on the cornea and the lens onto the retina where it is reflected. Means image is inverted at first, but the brain flips the image

35
Q

What is accomodation

A

changes in the eye that allows us to see objects at different distances

36
Q

accommodation (near vision)

A

ciliary muscles contract, suspensory ligaments slacken leading to thick lens increasing the refraction of light

37
Q

Accommodation(distant vision)

A

ciliary muscles are relaxed, suspensory ligaments are tense and the lens are thin to allow for less refraction

38
Q

What changes in the eye with different light intensities and why

A

high light intensity → pupil constricts
less light is absorbed to avoid damaging retina

low light intensity → pupil expands
This means that more light can be absorbed

39
Q

How does the pupil constrict/expand

A

pupil expands by zonular fibres tightening and ciliary muscles relaxing
pupil constricts by zonular fibres relaxing and ciliary muscles contracting.
Antagonistic muscles

40
Q

How are nerve cells adapted for their function

A
  1. long
  2. myelin sheath
  3. can make many connections

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