2022 AQA GCSE Biology Paper 2

What is homeostasis? - Answer - Homeostasis is the maintenance of a constant internal environment in order to maintain optimum conditions for enzyme and cellular function. Give examples of conditions maintained by homeostasis in the body - Answer - ● Blood glucose concentration ● Body temperature ● Water levels What two types of responses are used in body control systems? - Answer - Nervous and chemical What three components do all control systems have? - Answer - ● Receptors ● Coordination centres ● Effectors What is the function of a receptor? - Answer - Receptors detect changes in the environment (stimuli). What is the function of a coordination centre? - Answer - Coordination centres obtain and process information from receptors. What is the function of an effector? - Answer - Effectors (muscles or glands) bring about responses to stimuli. What is the function of the nervous system? - Answer - The nervous system allows the body to react to its surroundings and coordinate an appropriate response. How does a stimulus lead to a response being carried out by the body? - Answer - ● Stimulus is converted into an electrical impulse by the receptors. ● The electrical impulse passes along sensory neurones to the central nervous system (CNS). ● The CNS coordinates an appropriate response and an electrical impulse is sent along motor neurones to the effector, which carries out the response. What sequence of events describes how the nervous system works? - Answer - Stimulus → receptor → coordinator → effector → response What is a reflex action? - Answer - A reflex action is an automatic and rapid response which does not involve any conscious input from the brain. Why are reflex actions important? - Answer - Reflex actions aid survival by preventing harm to the body. Describe how a reflex action occurs via a reflex arc - Answer - ● The stimulus is detected by a receptor. ● An electrical impulse passes along a sensory neurone to the spinal cord (part of the CNS). ● At a synapse between a sensory neurone and a relay neurone, a chemical diffuses across the gap and stimulates a new impulse which passes along the relay neurone. ● The same process occurs at a synapse between a relay neurone and a motor neur