AQA GCSE Biology - B5

AQA GCSE Biology - B5 What is homeostasis? The regulation of conditions inside the body to maintain a stable internal environment in response to changes in both internal and external conditions What things do automatic control systems regulate? Body temperature, blood glucose level and water content What are the three main components that work together in automatic control systems? Receptors, coordination centres and effectors What does negative feedback do? When the level of something in the body is too high or low, the body uses negative feedback to bring it back to normal How does negative feedback work? Receptor detects a stimulus - level is too high or low. Coordination centre receives and processes the information, then organises a response. Effector produces a response and restores the optimum level. The effectors will continue to produce this response for as long as they are being stimulated by a coordination centre. This sometimes leads to the opposite problem occuring, in which case the negative feedback process starts again What makes up the nervous system? The central nervous system, sensory neurones, motor neurones and effectors What is the central nervous system? The brain and the spinal chord, connected to the body by sensory neurones and motor neurones What are sensory neurones? The neurones that carry information as electrical impulses from the receptors to the CNS What are motor neurones? The neurones that carry electrical impulses from the CNS to effectors What are effectors? Muscles and glands which respond to nervous impulses What are synapses and what do they do? They are the connections between two neurones. The nerve signal is transferred by chemicals (neurotransmitters) which diffuse across the gap and set off a new electrical signal in the next neurone What are reflexes? Rapid, automatic responses to stimuli that don't involve the conscious part of the brain How does a reflex arc work? Stimulus is detected by receptors, causing impulses to be sent along a sensory neurone to a relay neurone in the CNS. Impulses reach a synapse between sensory neurone and relay neurone, causing neurotransmitters to be released, which diffuse across the gap and cause an impulse to be sent down the relay neurone. The same thing happens when the impulses reach a synapse between the relay neurone and the motor neurone. The impulses travel down the motor neurone to the effector, which produces a response How would you investigate reaction times? Ruler drop test or computer test What is the cerebral cortex? The outer layer of the brain which is responsible for concio