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IB Biology HL B3.3.4 Hl Motor Units Questions

Practise tracing a motor-neuron signal from acetylcholine release at the motor end plate to sarcolemma excitation, calcium release from the sarcoplasmic reticulum and muscle contraction.

Syllabus
First assessment 2025
Course
Biology HL
Level
HL

Exam points

  • Identify a motor unit as a motor neuron and the skeletal muscle fibres it controls, joined at neuromuscular junctions.
  • Explain that acetylcholine released at the motor end plate after a motor-neuron action potential excites the muscle-fibre sarcolemma.
  • Trace excitation from the motor end plate to calcium-ion release from the sarcoplasmic reticulum, initiating skeletal-muscle contraction.

IB Biology HL B3.3.4 Hl Motor Units Questions question 1

[Maximum number: 1]

What happens when an action potential reaches motor end plates?

A

Calcium ions are absorbed by the muscle fibres.

B

The sarcomeres relax.

C

Neurotransmitter is released.

D

Action potential is passed to the neuron.

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