GCSE Combined Science revision · Biology: homeostasis, inheritance and ecology
The nervous system lets humans react to their surroundings. Receptors detect a stimulus; impulses travel along sensory neurones to the central nervous system (brain and spinal cord), then along motor neurones to effectors. Reflex actions are automatic and rapid, without involving the conscious brain: receptor → sensory neurone → relay neurone → motor neurone → effector. Synapses are gaps between neurones crossed by chemicals.
Watch out In a reflex, the conscious brain is not involved, which makes it faster.
Explain how a nerve impulse crosses a synapse.
Answer A chemical diffuses across the gap and starts an impulse in the next neurone
Which neurone carries impulses from the central nervous system to an effector?
Why are reflex actions fast?
A student's reaction times were 0.24 s, 0.28 s and 0.26 s. What is the mean reaction time in seconds?
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