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AQA GCSE Biology paper 2 summary notes
Summary notes for AQA GCSE Biology paper 2(year 11 content). Includes diagrams and exam style focused explanations
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HOMEOSTASIS AND RESPONSE RP 7: Reaction timeAim
HOMEOSTASIS
- Investigate the effect of a factor on human reaction time
Homeostasis = regulation of the internal body conditions in
response to internal and external changes Equipment
- Maintains optimum conditions for enzyme action and all cell - Metre ruler
functions - Chair
- Table
Automatic control system
- Receptors = detect stimuli (changes in the environment) Method
- Coordination centres = receive and process information from 1. Person 1 sits down and place non-dominant arm on the
receptors table with their hand overhanging the edge
- Effectors (muscles or glands) = bring responses 2. Person 2 hold ruler with the bottom end in between person
1’s fingers
3. Person 2 drops the ruler without telling person 1 (at a
THE HUMAN NERVOUS SYSTEM
random time)
4. Person 1 catches the ruler with thumb and first finger as
Structure and function quickly as possible
5. Record the measurement on the ruler at the top of person
The nervous system enables humans to react to their surroundings
1’s thumb
and to coordinate their behaviour.
6. Repeat 5 times and calculate the mean
the central nervous system (CNS) = consists of the brain and spinal
7. Use conversion table to convert the ruler measurements
cord
into reaction time
Variables
Independent Dependent Control
1. Receptors detect stimulus
2. Neurones send electrical impulse to the CNS Person having the Measurement on Initial distance
3. CNS coordinates the response and send signal to effectors reaction time tested the ruler / reaction between the thumb
4. Effectors bring responses time and the first finger
Practice
• Reflex arc Always measure at
Dominant or non- the top of the thumb
1. Stimulus detected by receptor
dominant hand
2. Electrical impulse sent from receptor to sensory neurone
Keep the conditions
3. The impulse reaches a synapse. This releases Caffeine (or other of the room the
neurotransmitter (a chemical) which causes an impulse chemicals) same
to be sent along the relay neurone
4. Same thing happens as the impulse reach another synapse
5. The impulse travel along the motor neurone to the effector
The brain
Cerebral cortex = highly folded outer part, responsible for language,
memory and consciousness
Cerebellum = balance and movement coordination
Medulla = unconscious activities, including heart / breathing rate
Reflex actions are automatic and rapid as they don’t involve
the conscious part of the brain
• Difficulties of investigating brain & treating brain damage /
disease
- It’s protected by the skull so it’s difficult to access
- Complex
- Very delicate and easy to damage
, • How to investigate the brain Short sightedness (myopia)
- Study patients with brain damage - Lens too thick / long eyeball
- Electrically stimulate the brain - Can be corrected with concave glasses
- MRI scanning techniques
The eye
The eye is a sense organ containing receptors sensitive to light
intensity and colour
• Treatments for vision defects
pros cons
Glasses No surgical operation Not permanent
• Functions Some people don’t
Retina = contains receptors for light (rods and cones) like the look
Optic nerve = carries impulses from the receptors on retina to Hard/soft No surgical operation Not permanent
contact lenses Almost invisible Can cause eye
the brain
irritation
Sclera = protects the eye
Laser surgery Permanent Expensive
Cornea = refracts light into the eye
General medical risk
Iris = control the size of the pupil Artificial lenses The surgeon can Higher risk (potential
Ciliary muscles & suspensory ligaments = control the shape of precisely control how risk of retina
the lens much tissue to take off damage)
Can completely
• Adaptation to dim light correct the vision
1. Light receptors in retina detects the low amount of light
entering the eye
2. Electrical impulse is sent to the brain Control of body temperature
3. Brain sends impulses to muscles in the iris
4. Muscles contract -> larger pupil -> more light Body temperature is monitored and controlled by the
thermoregulatory centre in the brain
Accommodation = process of changing the shape of the lens to - The thermoregulatory centre contains receptors sensitive to
focus on near or distant objects the temperature of the blood
• Focusing on a near object - The skin also contains temperature receptors
1. Ciliary muscles contract
2. Suspensory ligaments loosen • If the body temperature is too high
3. Lens become thicker and refracts light rays more strongly
- Sweat produced from the sweat glands
• Focusing on a distant object Sweat is evaporated & transfer energy to the
1. Ciliary muscles relax surrounding
2. Suspensory ligaments pulled tight - Vasodilation
3. Lens pulled thin and only slightly refracts light rays 1. Arterials dilate
2. More blood flows through the surface capillaries
• Vision defects 3. Heat transfers out of the blood
Long sightedness (hyperopia) 4. Cooled blood flows back to the body and cools the body
- Lens not thick enough / short eyeball down
- Can be corrected with convex lens
• If the body temperature is too low
- Sweating stops
- Skeletal muscles contract (shiver)
Increased respiration to release energy needed and this
releases heat
- Vasoconstriction
1. Arterials constrict
2. Less blood flows through the surface capillaries
3. Less heat lost
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