Biology · AQA Paper 2
Homeostasis and the Nervous System
How the body keeps its internal conditions steady with receptors, coordination centres and effectors, how the nervous system and reflex arcs produce fast responses, the required practical on reaction time, and for separate Biology the brain, the eye and the control of body temperature. Matches AQA topic 4.5.1 (homeostasis) and 4.5.2 (the human nervous system). The first three lessons are for both Combined Science and separate Biology. The brain, the eye and the control of body temperature (4.5.2.2 to 4.5.2.4) are for separate Biology only, and some of what they cover is for the Higher tier only.
Lessons
Ticks are remembered on this device only.
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1
Homeostasis and Control Systems
Your cells work properly only when the conditions around them are kept steady. This lesson explains what homeostasis is, why a constant internal environment…
8 terms -
2
Neurones and the Nervous System
Your nervous system detects changes around you and inside you and produces a fast, coordinated response. This lesson covers the path stimulus, receptor…
8 terms -
3
Reflex Arcs
A reflex is a very fast, automatic response that protects the body. This lesson explains how the structure of a reflex arc is related to its function, how a…
8 terms -
4
The Brain
The brain controls almost everything that you do. This lesson is for separate Biology. It covers the structure and functions of the main regions of the brain…
6 terms -
5
The Eye
The eye is the sense organ that detects light. This lesson is for separate Biology. It covers the main structures of the eye and what they do, how the eye…
11 terms -
6
Control of Body Temperature
Humans keep their body temperature at about 37 °C however hot or cold it is outside. This lesson is for separate Biology. It covers how the thermoregulatory…
8 terms
Key terms in this chapter
All 49, gathered from every lesson.
- Homeostasis
- The regulation of the internal conditions of a cell or organism to maintain optimum conditions for function.
- Internal environment
- The conditions inside the body, such as the blood and tissue fluid.
- Receptor
- A cell or organ that detects a change.
- Coordination centre
- A part of the body, such as the brain, that decides the response.
- Effector
- A muscle or gland that carries out the response.
- Negative feedback
- A response that reverses a change and returns a condition to normal (Higher tier).
- Metabolic reaction
- A chemical reaction in a cell, controlled by an enzyme.
- Optimum
- The conditions in which an enzyme works best.
- Neurone
- A nerve cell that carries electrical impulses.
- Stimulus
- A change in the surroundings that can be detected.
- Receptor
- A cell that detects a stimulus and starts an impulse.
- Effector
- A muscle or a gland that carries out a response.
- Central nervous system
- The brain and the spinal cord.
- Synapse
- The gap between two neurones, which neurotransmitters cross.
- Myelin sheath
- A fatty layer round an axon that speeds up the impulse.
- Neurotransmitter
- A chemical that carries the signal across a synapse.
- Reflex action
- A rapid, automatic response that protects the body.
- Reflex arc
- The pathway of neurones involved in a reflex action.
- Relay neurone
- A neurone in the central nervous system that links a sensory and a motor neurone.
- Synapse
- The gap between two neurones.
- Neurotransmitter
- A chemical that crosses a synapse and starts a new impulse.
- Voluntary action
- An action that you choose to do, which involves the brain.
- Reaction time
- The time taken to respond to a stimulus.
- Spinal cord
- A column of nervous tissue that runs inside the backbone.
- Cerebral cortex
- The largest part of the brain, which controls thought, memory, language and voluntary movement.
- Cerebellum
- The part of the brain that coordinates movement and balance.
- Medulla
- The part of the brain that controls the heart rate and breathing.
- Case study
- A detailed study of one person or a small group.
- MRI scan
- A scan that shows which regions of the brain are active.
- Spinal cord
- The column of nervous tissue that joins the brain to the body.
- Cornea
- The transparent front of the eye that refracts light.
- Sclera
- The tough, white outer layer of the eye.
- Iris
- The ring of muscle that controls the size of the pupil.
- Pupil
- The hole in the iris through which light enters.
- Lens
- The flexible structure that focuses light on the retina.
- Retina
- The layer at the back of the eye with the light receptor cells.
- Accommodation
- The change in the shape of the lens to focus on near or distant objects.
- Myopia
- Short-sightedness: light from distant objects focuses in front of the retina.
- Hyperopia
- Long-sightedness: light from near objects focuses behind the retina.
- Ciliary muscles
- The muscles that change the shape of the lens.
- Suspensory ligaments
- The fibres that hold the lens and are slack or taut as the ciliary muscles change.
- Thermoregulatory centre
- The part of the brain that monitors and controls body temperature.
- Sweat gland
- A gland in the skin that produces sweat.
- Vasodilation
- The widening of the blood vessels in the skin, so that more energy is transferred to the environment.
- Vasoconstriction
- The narrowing of the blood vessels in the skin, so that less energy is transferred to the environment.
- Shivering
- Rapid contractions of the skeletal muscles, which release energy.
- Evaporation
- The change from liquid to gas, which takes energy from the surface.
- Dilate
- To get wider.
- Constrict
- To get narrower.