GCSE Biology · AQA 8461 · Topic 4.5.2
The human nervous system
Key points
- Pathway: stimulus → receptor → sensory neurone → coordinator (CNS) → motor neurone → effector → response.
- The central nervous system is the brain and spinal cord. Impulses cross the gap between neurones (synapse) by chemicals diffusing across.
- Reflexes are automatic and fast, using a relay neurone in the spinal cord, and protect the body from harm.
- The brain: cerebral cortex (memory, language, consciousness), cerebellum (balance and coordination), medulla (heart and breathing rate). Studying it is hard; scans and studying damage help.
- The eye: the cornea and lens focus light onto the retina; the iris controls pupil size. Ciliary muscles and suspensory ligaments change lens shape (accommodation).
- Short sight (myopia) and long sight (hyperopia) are corrected with lenses, laser surgery or lens replacement.
- Body temperature is monitored by the thermoregulatory centre in the brain; sweating and vasodilation cool the body, shivering and vasoconstriction warm it.
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The nervous system lets you react to your surroundings in a fraction of a second. This sub-topic covers how impulses travel, why reflexes protect you, and the structure of the brain and eye, plus how the brain controls body temperature.
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