AQA GCSE Biology: Homeostasis and response — Practice Questions & Answers
How the body keeps internal conditions stable using the nervous and endocrine systems, plus reflexes, the eye, blood glucose control, reproductive hormones and plant responses.
1144 practice questions available for this topic — here are 10 with full answers and explanations.
The regulation of internal conditions to maintain a stable internal environment
The transport of substances around the body in the blood
The breakdown of large molecules into smaller ones
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WhyHomeostasis is the regulation of internal conditions of a cell or organism to maintain optimum conditions for function, in response to internal and external changes.
2Multiple choice · Easy
Which of the following is an internal condition that is controlled by homeostasis in the human body?
Hair colour
Eye colour
Blood glucose concentration
Height
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WhyHomeostasis controls blood glucose concentration, body temperature and water levels. Hair colour is a genetically determined feature, not a regulated internal condition.
3Multiple choice · Easy
In a control system, which component detects a stimulus (a change in the environment)?
Effector
Receptor
Coordination centre
Synapse
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WhyReceptors are cells that detect stimuli (changes in the environment). Coordination centres process information and effectors bring about responses.
4Multiple choice · Medium
Which sequence correctly shows the order of components in an automatic control system?
Stimulus -> coordination centre -> receptor -> effector -> response
Stimulus -> effector -> receptor -> coordination centre -> response
Stimulus -> receptor -> coordination centre -> effector -> response
Stimulus -> receptor -> effector -> coordination centre -> response
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WhyA stimulus is detected by a receptor, which sends information to a coordination centre. The coordination centre then triggers an effector to produce the response.
5Multiple choice · Easy
Which two coordination centres are involved in automatic control systems in the body?
Muscles and glands
The brain and the spinal cord
Receptors and effectors
Neurones and synapses
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WhyCoordination centres, such as the brain, spinal cord and pancreas, receive and process information from receptors. Effectors (muscles and glands) carry out responses.
6Multiple choice · Medium
Effectors bring about responses to restore optimum conditions. Which two structures act as effectors?
Receptors and neurones
Muscles and glands
The brain and spinal cord
Sensory neurones and synapses
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WhyEffectors are muscles (which contract) and glands (which secrete hormones). Both restore optimum levels.
7Multiple choice · Medium
In the human nervous system, which type of neurone carries impulses from receptors to the central nervous system?
Motor neurone
Relay neurone
Sensory neurone
Effector neurone
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WhySensory neurones carry electrical impulses from receptors to the CNS. Motor neurones carry impulses from the CNS to effectors, and relay neurones connect them within the CNS.
8Multiple choice · Hard
At a synapse, how is the nerve impulse transmitted from one neurone to the next?
An electrical impulse jumps directly across the gap between the neurones
A chemical is released that diffuses across the gap and triggers a new impulse in the next neurone
The two neurones fuse together so the impulse passes through
The impulse travels through the blood to reach the next neurone
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WhyAt a synapse a chemical (neurotransmitter) diffuses across the gap and binds to receptors on the next neurone, causing a new electrical impulse to be generated. The signal crosses the gap chemically, not electrically.
9Multiple choice · Hard
Why are reflex actions described as automatic and rapid?
They involve the conscious part of the brain making a quick decision
They do not involve the conscious part of the brain, so the response is faster
They use hormones, which travel quickly in the blood
They only involve sensory neurones and no other neurones
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WhyReflexes do not involve the conscious part of the brain. The impulse passes through the spinal cord (or unconscious brain) via a relay neurone, so no decision-making time is needed, making the response fast and protective.
10Fill in the blank · Medium
The pathway of a reflex arc is: stimulus -> receptor -> neurone -> relay neurone -> neurone -> effector -> response.
Answer:
sensory, motor
WhyIn a reflex arc the sensory neurone carries the impulse to the CNS, a relay neurone passes it on within the CNS, and the motor neurone carries the impulse to the effector.
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Homeostasis: The regulation of an organism's internal conditions, such as temperature, water content and blood glucose, to keep them at the optimum levels needed for cells and enzymes to work properly despite changes inside and outside the body.
Internal environment: The conditions inside the body surrounding the cells, such as temperature, pH, water and glucose levels, which homeostasis works to keep relatively constant.
Optimum conditions: The ideal set of internal conditions at which enzymes and cells function most efficiently, which control systems try to maintain.
Control system: A set of components that detects a change in a condition and brings about a response to restore that condition to its normal level.
Stimulus: A detectable change in the internal or external environment that an organism can respond to, such as light, heat, sound or a chemical.
Receptor: A cell or group of cells that detects a specific stimulus and converts it into an electrical impulse in the nervous system.
Coordination centre: A part of the body, such as the brain, spinal cord or pancreas, that receives and processes information from receptors and decides on a response.
Effector: A muscle or gland that carries out a response when stimulated, either by contracting or by releasing a substance such as a hormone.