For Teacher

1. B10 The human nervous system
Student Book answers
B10.1 Principles of homeostasis
Question
number
Answer Marks Guidance
1 regulation of internal conditions of cell or organism
to maintain optimum functional conditions
in response to internal and external changes
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2 receptors
cells that detect changes in internal or external environment
may be part of nervous or hormonal control systems
coordination centres
areas that receive and process information from receptors and
coordinate body’s response
may be part of nervous or hormonal control systems
effectors
bring about response to signal from coordination centres
may be muscles or glands
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3 a Any three from:
• temperature increase
• temperature decrease
• levels of sunlight increase
• wind levels increase
• lack of food
3 Any other valid suggestion.
3 b temperature increase – warming body
temperature decrease – cooling body
levels of sunlight increase – burning skin
wind levels increase – increasing cooling from skin surface
lack of food – hunger.
3 Any other valid suggestion. Explanations
must match answers given in 3a.
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2. B10 The human nervous system
Student Book answers
B10.2 The structure and function of the human nervous system
Question
number
Answer Marks Guidance
1 a to take in information from external and internal environment
and coordinate body’s response
so you can react to surroundings
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1 b neurone: single nerve cell;
nerve: bundle of hundreds or thousands of neurones
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1 c sensory neurone: carries impulses from sense organs to central
nervous system (CNS);
motor neurone: carries information from CNS to body’s effector organs
(muscles and glands)
3
2 a eye,
ear,
skin,
nose,
tongue
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2 b eye: light
ear: sound, pressure
skin: touch, pressure, pain, temperature, vibration
nose: smell
tongue: taste
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3 light from fruit detected by sensory receptors in eyes,
impulse travels along sensory neurone to brain,
information processed in brain,
impulse sent along motor neurone
to muscles of arm and hand
so you pick up fruit and put it in mouth
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3. B10 The human nervous system
Student Book answers
B10.3 Reflex actions
Question
number
Answer Marks Guidance
1 a They enable you to avoid damage and danger because they happen
very fast.
They control many vital bodily functions, such as breathing, without
need for conscious thought.
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1 b This would slow process down, making it less effective at preventing
damage. It would be very difficult to consciously control all bodily
functions and still be able to do anything else.
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2 Reflex actions (e.g., breathing, swallowing) need to happen constantly
and operate automatically, even when you are asleep,
so cannot rely on conscious thought processes.
Speaking and eating require coordination of different areas of body
so need to be under conscious control.
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3 stimulus (pinprick) → receptor → sensory neurone (electrical impulse)
→ synapse (chemical impulse) → relay neurone (electrical impulse) →
synapse (chemical impulse) → motor neurone (electrical impulse) →
muscles in leg lift foot
6
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4. B10 The human nervous system
Student Book answers
B10.4 The brain
Question
number
Answer Marks Guidance
1 a millions of interconnected neurones
arranged in different regions
to carry out different functions
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1 b takes in all sensory information
and coordinates responses
as well as allowing conscious thought, intelligence, and emotions
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2 cerebral cortex: consciousness, intelligence, memory, language
cerebellum: coordinating muscular activity and balance
medulla: unconscious activities (e.g., gut movements, breathing)
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3 a Any two from:
• Studying people with brain damage
• Electrically stimulating parts of the brain
• MRI scans
Any four marks for relevant points
• studying people with brain damage allows scientists to match
changes of behavior or memory to the damaged area of the
brain
• this allows scientists predict what function the area normally
carries out.
• scientists can electrically stimulate specific areas of the exposed
brain
• and observe the effect this has on the patient’s behavior.
• MRI scans produce images of brain activity or damage within
live patients,
• This can be linked to observed behaviors.
2
4
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5. B10 The human nervous system
Student Book answers
Question
number
Answer Marks Guidance
3 b Points may include:
benefits
• observe normal function of the brain
• observe live patients
• communicate with patients during the procedure
• MRI is non-invasive
• these techniques are painless.
risks
• brain is complex and fragile,
• function of the brain is not fully understood
• easy to cause unintended damage
• it could be considered unethical to ‘experiment’ on healthy
patients.
3
3
Accept any thoughtful point.
Accept any thoughtful point.
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6. B10 The human nervous system
Student Book answers
B10.5 The eye
Question
number
Answer Marks Guidance
1 a Any three from:
• sclera,
• cornea,
• iris,
• pupil,
• lens,
• suspensory ligaments,
• ciliary muscles,
• retina,
• optic nerve,
• blind spot,
• fovea
3
1 b sclera: white outer layer of eye, relatively tough and strong so eyeball not easy to
damage;
cornea: transparent area at front of eyeball that admits light, curved surface to help
focus light coming into eye on retina;
iris: muscular structure to control size of pupil;
pupil: hole in iris through which light enters eye;
lens: clear disc to help finely focus light onto retina;
suspensory ligaments: attach ciliary muscles to eyeball, involved in changing shape
of lens;
ciliary muscles: contract and relax to change shape of lens and focus light on retina;
retina: layer at back of eye containing light receptor cells,
optic nerve: carries impulses from light‑sensitive cells of retina to brain;
blind spot: where optic nerve leaves eyeball;
fovea: area of cones where light is brought into clear focus on retina.
6 Answer should match components
given in part a. Up to two marks
per component.
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7. B10 The human nervous system
Student Book answers
Question
number
Answer Marks Guidance
2 Longitudinal muscles of iris contract
and circular muscles relax
in dim light, making pupil as large as possible to let in maximum light.
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3 Vision involves much more than lens and retina. Light enters eye through cornea,
which focuses it towards the iris and retina.
Light passes through the iris, then lens.
Lens changes shape to focus light onto retina.
Light‑sensitive cells of retina stimulated by light and send impulses along neurones.
Impulses travel along optic nerve and are translated by brain into visual images.
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8. B10 The human nervous system
Student Book answers
B10.6 Common problems of the eye
Question
number
Answer Marks Guidance
1 When ciliary muscles contract,
suspensory ligaments loosen
and lens becomes thicker.
When ciliary muscles relax,
suspensory ligaments pulled tight
and lens pulled thin.
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2 a close objects:
• ciliary muscles contract,
• suspensory ligaments loosen,
• lens becomes thicker and refracts light rays strongly;
far away objects:
• ciliary muscles relax,
• suspensory ligaments pulled tight,
• lens pulled thin and only slightly refracts light rays
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2 b When doing close work ciliary muscles are contracted
to keep lens thick
and able to focus light from close objects.
When looking at distant objects ciliary muscles relax.
Looking up into distance regularly when doing close work rests ciliary
muscles.
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3 a myopia:
can see close objects in clear focus but distant objects look blurred,
as lens too curved or eyeball too long;
hyperopia:
can focus clearly on distant objects but close objects appear blurred,
as lens too flat and thin or eyeball too short
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