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Neural Signaling · Paper 2 — Free Biology HL Practice Questions
1MasterySAQ-SStructure of neurons5 marksPaper 2~8 min
A researcher studying the nervous system of the squid (Loligo pealeii) measures the diameter of a giant axon and finds it to be . In humans, a typical myelinated motor neuron has an axon diameter of but conducts action potentials at , compared to in the squid giant axon.
(a)
State one structural feature of the squid giant axon that is an adaptation for rapid signal transmission. [1 mark]
(b)
Describe how the structure of a human myelinated axon allows saltatory conduction. [2 marks]
(c)
Evaluate the relative effectiveness of large axon diameter versus myelination as strategies for increasing nerve conduction velocity, using the data provided. [2 marks]
Solutions
2MasterySAQ-SStructure of neurons5 marksPaper 2~8 min
A neurobiologist examines a cross-section of a peripheral nerve under an electron microscope. She observes that some axons are surrounded by multiple layers of Schwann cell membrane forming a myelin sheath, while others have only a single Schwann cell layer without myelin.
(a)
State how the myelin sheath is formed by Schwann cells. [1 mark]
(b)
Describe how the structure of the myelin sheath contributes to the speed of nerve impulse transmission. [2 marks]
(c)
A patient presents with progressive demyelination of peripheral motor neurons. Explain why this condition leads to a reduction in muscle response speed, and predict one additional consequence for normal nerve function. [2 marks]
Solutions
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