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IGCSE · Practice questions · The nervous system

Receptor to effector.

Six original Cambridge-style questions on the parts of the nervous system, the three types of neurone, reflex arcs, reaction-time data and (Extended) how a synapse passes an impulse in one direction.

Original questions All questions on this page are original work, written in the Cambridge IGCSE style. They are not from past papers. They test the same concepts and skills the syllabus rewards.
Keep these straight

Five links, one direction.

01
Recall
[3 marks]

Describe the mammalian nervous system in terms of the central nervous system and the peripheral nervous system, and state its role.

  • The central nervous system (CNS) consists of the brain and the spinal cord. ✓
  • The peripheral nervous system (PNS) consists of the nerves outside the brain and spinal cord. ✓
  • Its role is the coordination and regulation of body functions, using electrical impulses that travel along neurones. ✓
02
Explain
[5 marks]

A person steps on a drawing pin and lifts their foot away. Describe the pathway of the impulse in this reflex arc.

  • Pain (pressure) receptors in the skin of the foot detect the stimulus. ✓
  • An impulse travels along a sensory neurone to the spinal cord. ✓
  • In the spinal cord a relay neurone passes the impulse to a motor neurone. ✓
  • The motor neurone carries the impulse to the effector, a muscle in the leg. ✓
  • The muscle contracts, lifting the foot away from the pin. ✓
03
Analysis
[3 marks]

A diagram shows three neurones. Neurone A has a long fibre that starts at a receptor and its cell body is on a side branch. Neurone B is short and lies entirely inside the spinal cord. Neurone C has its cell body inside the spinal cord and a long axon that ends in a muscle. Identify A, B and C.

  • A: sensory neurone (carries impulses from a receptor to the CNS). ✓
  • B: relay neurone (inside the CNS, links sensory and motor neurones). ✓
  • C: motor neurone (carries impulses from the CNS to an effector). ✓
04
Data
[4 marks]

Students tested their reaction time by catching a falling ruler. The ruler fell further before being caught when the student was tired.

ConditionMean distance fallen / cm
rested14
tired21

(a) Calculate the percentage increase in distance fallen when tired. (b) Catching a ruler is not a reflex action. Suggest why, and state one variable that should be controlled.

  • (a) (21 − 14) ÷ 14 × 100 = 50% increase. ✓
  • (b) The student decides to catch the ruler: the response involves the brain and is a voluntary action, not automatic. ✓
  • It is slower than a reflex because the impulse passes through the brain and more synapses. ✓
  • Control: same ruler, same starting height or hand position, same hand used (also accept same number of practice attempts). ✓
05
Recall
[4 marks]

Extended. Describe the structure of a synapse.

  • A synapse is a junction between two neurones. ✓
  • The ending of the first neurone contains vesicles holding neurotransmitter molecules. ✓
  • There is a narrow synaptic gap between the two neurones. ✓
  • The membrane of the next neurone has receptor proteins that the neurotransmitter binds to. ✓
06
Explain
[5 marks]

Extended. Explain how an impulse passes from one neurone to the next across a synapse, and why it can only travel in one direction.

  • The impulse arriving at the end of the first neurone stimulates vesicles to release neurotransmitter molecules into the synaptic gap. ✓
  • The neurotransmitter molecules diffuse across the gap. ✓
  • They bind with receptor proteins on the membrane of the next neurone. ✓
  • This stimulates an impulse in the next neurone. ✓
  • Only the first neurone has vesicles of neurotransmitter and only the next neurone has receptor proteins, so the impulse can only travel one way. ✓

Mark this once you have attempted all six and checked your working. It records a Practiced badge on the topic and adds a one-time bonus. Revealing the solutions alone does not count.