GCSE AQA Triple Biology Higher Tier
Paper 2 Questions and Answers Solved
100% Correct
Homeostasis
The regulation of the internal conditions of a cell or organism in response to
internal or external changes. E.g. the control of: blood glucose
concentration, body temperature, water and ion levels, etc.
Negative Feedback
This is a type of control mechanism:
1) a receptor detects a change in a stimulus.
2) the coordination centre compares the stimulus to a set point.
3) an effector then produces a response to correct any difference from the
set point.
The Thermoregulatory Centre
This is in the brain and it monitors and controls body temperature, blood
temperature via impulses from temperature receptors.
Effects when Body Temperature is too High
- Vasodilation.
- Swear more.
- Transfer of energy form the skin to the environment.
Effects when Body Temperature is too Low
- Vasoconstriction
- Stop sweating
- Piloerection
- Shiver
The Nervous System
This enables humans to react to their surroundings and coordinate their
behaviour. It stimulates a reflex arc.
,Reflex Arc
1) the pain stimulus is detected by receptors.
2) impulses from the receptor pass along a sensory Neurone to the CNS.
3) an impulse then passed through a relay Neurone.
4) a motor neurone carries an impulse to the effector.
5) the effector (muscle or gland) responds
Synapse
The connection between neurones. When an electrical impulse reaches
this, a chemical is released that diffused across the gap. This causes an
electrical impulse to be generated in the second one.
Human Reaction Time Required Practical
1) the experimenter holds a meter rule from the end.
2) the subject had their finger and thumb a small distant apart either side of
the ruler on the 50cm line.
3) the experimenter lets go of the ruler and the subject has to trap it.
4) the distance the ruler travels from the 50cm line is noted.
5) the experiment is repeated on the subjects that have just drunk coffee
and the subjects that have not.
Parts of the brain
- Medulla
- Cerebellum
- Cerebral Cortex
Medulla
controls automatic actions such as heartbeat and breathing.
Cerebellum
coordinates movement and balance
cerebral cortex
responsible for consciousness, intelligence, memory and language.
, - Optic Nerve - carries impulses from the retina to the brain.
- Sclera - forms a tough outer layer.
- Cornea - transport region.
- Iris - controls the size of the pupil and the amount of light reaching the
retina.
- Ciliary Muscles & Suspensory Ligaments - change the shape of the lens
to focus light onto the retina.
Accommodation
The process of changing the shape of the lens to focus on near or distant
objects.
Myopia
Shortsightedness.
Hyperopia
Long sightedness.
The Endocrine System
This is made up of glands that secrete hormones directly into the
bloodstream.
Hormones
Chemical messengers that are carried in the blood.
Pituitary Gland
This is a master gland in the brain that secretes several hormones in
response to body conditions.
Adrenaline
This is produced by the adrenal glands in times of fear or stress to increase
the bodies heart rate.
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