This question is about neuromuscular coordination and motor control.
Autonomic reflexes are critical for homeostatic survival, but their coordination must be integrated centrally.
State the region of the brainstem that is primarily responsible for coordinating autonomic functions such as heart rate and ventilation.
Muscle contraction is controlled by motor units. A motor unit consists of a single motor neurone and all the muscle fibres it stimulates.
The table below displays typical data for motor units in two different muscles of the body:
| Muscle | Average number of muscle fibres per motor neurone | Primary function |
|---|---|---|
| Laryngeal muscle (controls vocal cords) | 121212 | Precise, rapid adjustments of vocal cord tension for speech |
| Quadriceps femoris (thigh muscle) | 150015001500 | Large, powerful contractions for running and jumping |
Explain how the central nervous system can vary the strength of a contraction in a muscle such as the quadriceps femoris.
With reference to the data in the table, explain why the recruitment of motor units in the laryngeal muscle allows for much finer control over movement than in the quadriceps femoris.
39 exam-style questions on OCR GCSE Biology 3.1 Coordination and control – the nervous system, covering 3.1.1 Structure of the nervous system, 3.1.2 Coordinated response, 3.1.3 The reflex arc, 3.1.4 Structure of the eye, 3.1.5 Defects of the eye, 3.1.6 Structure and function of the brain, 3.1.7 Difficulties of investigating brain function, and 3.1.8 Limitations in treating nervous system damage. Each one has a worked solution and a mark scheme showing where the marks go.