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A2 · Practice questions · Nervous and endocrine systems

Blood or wire.

Six original Cambridge-style questions on the two coordination systems, the structure of neurones and how a receptor cell starts an impulse.

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

Gland, neurone, receptor.

01
Recall
[3 marks]

Name the endocrine gland that secretes each of ADH, insulin and glucagon, and give one target cell for each.

  • ADH: posterior pituitary gland; target: cells of the collecting duct (and distal convoluted tubule) in the kidney. ✓
  • Insulin: beta cells of the islets of Langerhans in the pancreas; target: liver / muscle / fat cells. ✓
  • Glucagon: alpha cells of the islets of Langerhans in the pancreas; target: liver cells. ✓
02
Explain
[4 marks]

Compare the ways the nervous system and the endocrine system transmit information.

  • Nervous: electrical impulses along neurones (and chemical neurotransmitter across synapses); endocrine: chemical hormones. ✓
  • Nervous signals go along specific neurones to one effector; hormones are carried in the blood to the whole body. ✓
  • Nervous transmission is fast (milliseconds); hormonal is slower. ✓
  • Nervous effects are short-lived and localised; hormonal effects are often long-lasting and widespread (any cell with receptors). ✓
03
Recall
[4 marks]

Describe the structure of a motor neurone and state how it differs from a sensory neurone.

  • Cell body (with nucleus, many mitochondria and rough ER) in the CNS, with many dendrites. ✓
  • Long axon, usually myelinated by Schwann cells with nodes of Ranvier, ending in motor end plates on an effector. ✓
  • A sensory neurone has a long dendron carrying impulses from a receptor to its cell body. ✓
  • Its cell body is in a ganglion to one side, outside the CNS, and a short axon carries impulses into the CNS. ✓
04
Explain
[5 marks]

Describe the sequence of events by which salt on the tongue leads to an action potential in a sensory neurone.

  • Na+ ions from the salt reach the microvilli of a chemoreceptor cell in a taste bud. ✓
  • Na+ diffuses into the receptor cell through Na+ channels, down the electrochemical gradient. ✓
  • The membrane depolarises, producing a receptor potential. ✓
  • This opens voltage-gated Ca2+ channels; Ca2+ enters and causes vesicles to release neurotransmitter by exocytosis. ✓
  • Neurotransmitter binds to receptors on the sensory neurone and depolarises it; if threshold is reached, an action potential is set up. ✓
05
Analysis
[2 marks]

A hormone circulates in the blood and reaches every organ, but only cells in the liver respond to it. Suggest why.

  • Only liver cells have receptors (on the cell surface membrane) with a shape complementary to the hormone. ✓
  • Other cells lack the receptor, so the hormone cannot bind and no response is triggered. ✓
06
Explain
[3 marks]

Explain why a very weak stimulus on a receptor cell may produce no action potential at all in the sensory neurone.

  • A weak stimulus gives only a small receptor potential (the receptor potential is graded). ✓
  • Little or no neurotransmitter is released, so the sensory neurone is depolarised only slightly. ✓
  • Threshold is not reached, so no action potential is set up (all-or-nothing). ✓

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.