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AQA GCSE Biology · 8461
AQA 8461 · 4.5.2.1 Nervous System Structure Check the specification (PDF) (opens in a new tab)
Explain how the nervous system structure is adapted to coordinate behaviour.
Describe the pathway of information from stimulus to response via the CNS.
Explain the structure and function of a reflex arc.
Interpret data on nervous system function and reaction times.
Plan and carry out an investigation into factors affecting reaction time.
The nervous system helps you react to your surroundings and coordinate what your body does. It links cells that detect a change with cells that can respond. For example, if you notice a pencil being held up, light from it stimulates receptors in your eyes. Seeing it and deciding to reach for it involves information travelling through the nervous system before muscles move your arm.
A detectable change is a stimulus. A receptor detects it and starts an electrical impulse. The impulse travels along a specialised nerve cell called a neurone. This arrangement lets information pass between a receptor, the central nervous system and the part of the body that will respond.
The central nervous system (CNS) consists of the brain and spinal cord. Electrical impulses from receptors travel to it along sensory neurones. The CNS receives and processes the information, then coordinates a suitable response. Impulses travel away from the CNS along motor neurones to effectors. An effector may be a muscle, which contracts, or a gland, which secretes a substance such as a hormone.
The route has an order: the receptor detects the stimulus, the CNS coordinates what happens next, and the effector produces the response. Sensory and motor neurones make this possible by carrying impulses in opposite directions relative to the CNS. In the pencil example, the eyes detect the light, the CNS processes that information, and impulses to arm muscles help bring about the movement.
Information travels to the CNS from receptors; the CNS coordinates impulses to effectors that produce a response.
A sensory neurone carries an electrical impulse from a receptor to the CNS (brain and spinal cord). The CNS processes the information and coordinates a response. A motor neurone carries an impulse from the CNS to an effector. Muscles respond by contracting; glands respond by secreting.
In a pathway question, name the sensory neurone carrying impulses to the CNS and the motor neurone carrying impulses from the CNS to the effector.
Keep the stimulus and response distinct: a change is detected by a receptor; a muscle or gland carries out the response.
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Last updated
Stimulus
A change in the internal or external environment that can be detected.
Receptor
A cell that detects a stimulus.
Neurone
A nerve cell that carries electrical impulses.
Sensory neurone
A neurone that carries electrical impulses from a receptor to the central nervous system.
Central nervous system (CNS)
The brain and spinal cord, which process information and coordinate responses.
Motor neurone
A neurone that carries electrical impulses from the central nervous system to an effector.
Effector
A muscle or gland that carries out a response.
Put your knowledge into practice — try past paper questions for Biology
Stimulus
A change in the internal or external environment that can be detected.
Receptor
A cell that detects a stimulus.
Neurone
A nerve cell that carries electrical impulses.
Sensory neurone
A neurone that carries electrical impulses from a receptor to the central nervous system.
Central nervous system (CNS)
The brain and spinal cord, which process information and coordinate responses.
Motor neurone
A neurone that carries electrical impulses from the central nervous system to an effector.
Effector
A muscle or gland that carries out a response.