AQA GCSE Biology 4.5.2 The Human Nervous System Exam Questions

About AQA GCSE Biology 4.5.2 The Human Nervous System

The human nervous system is part of AQA Homeostasis and response, examined on Paper 2. All students need the structure of the nervous system, the reflex arc and synapses, plus the required practical on reaction time. GCSE Biology students also study the brain, the eye (including accommodation and vision defects) and the control of body temperature. It links to homeostasis in 4.5.1 and hormones in 4.5.3. Examiners like reflex arc sequences, explaining why reflexes are fast, labelling the eye and brain, and explaining how the body responds when it is too hot or too cold.

What you need to know

• 4.5.2.1 Structure and function Information from receptors passes along cells (neurones) as electrical impulses to the central nervous system (brain and spinal cord), which coordinates the response of effectors. Pathway: stimulus -> receptor -> coordinator -> effector -> response.
• Reflex arcs and synapses Reflex actions are automatic and rapid; they do not involve the conscious part of the brain. Impulse passes from sensory neurone to relay neurone in the CNS to motor neurone. At a synapse a chemical diffuses across the gap to start an impulse in the next neurone.
• Required practical: reaction time Plan and carry out an investigation into the effect of a factor, such as caffeine or practice, on human reaction time, for example with a ruler drop test. Repeat and calculate a mean, controlling variables such as the hand used.
• 4.5.2.2 The brain (Biology only) The cerebral cortex controls consciousness, intelligence, memory and language; the cerebellum coordinates muscular activity; the medulla controls unconscious activities such as heart and breathing rate. Brain damage is hard to treat because the brain is complex and delicate; scans such as MRI help map regions.
• 4.5.2.3 The eye (Biology only) Know the retina, optic nerve, sclera, cornea, iris, ciliary muscles and suspensory ligaments. In accommodation for a near object, ciliary muscles contract, suspensory ligaments slacken and the lens becomes thicker; for a distant object the opposite happens. Myopia and hyperopia are corrected with lenses, laser surgery or replacement lenses.
• 4.5.2.4 Control of body temperature (Biology only) The thermoregulatory centre in the brain has receptors sensitive to blood temperature and receives impulses from skin receptors. If too hot: sweating and vasodilation. If too cold: vasoconstriction, shivering and less sweating.

Common mistakes in 4.5.2 The Human Nervous System

• Saying the impulse jumps across the synapse. A chemical is released and diffuses across the gap to stimulate the next neurone.
• Saying reflexes go through the brain. Reflexes are coordinated by the spinal cord or unconscious parts of the brain.
• Saying blood vessels move closer to or further from the skin. Vasodilation and vasoconstriction change the diameter of arterioles, changing blood flow near the surface.
• Reversing accommodation. For near objects the ciliary muscles contract and the lens becomes thicker, refracting light more strongly.
• Saying the iris focuses light. The cornea and lens refract light; the iris controls how much light enters.

Try three 4.5.2 The Human Nervous System exam-style questions